Conditions Outlook March 27, 2013
Prepared by: Joe Lammers

Period
Day 3 – 5 is Friday, March 29 to Sunday, March 31.
Day 6 – 10 is Monday, April 1 to Friday, April 5.

Snowpack Day 3 – 5 (Friday to Sunday):

Little or no new snow is expected to be added to the snowpack during this period for most areas, and settlement of old storm snow will continue. Cool nightly temperatures will promote surface faceting and surface hoar development, but increasingly intense solar radiation will make the snow surface moist on sun-exposed slopes. This moist snow is likely to form a crust with overnight re-freezes.

At higher elevations, the surface hoar/crust interface from March 9^th / 10^th remains a concern. Human triggering is most likely in the Northwest regions, but should also be considered as a factor in the Columbia Mountains, the north end of the South Coast Inland region as well as the Purcells. Reactivity in these areas seems most likely in large, unsupported terrain with large triggers such as cornice fall. Having said that, recent human involvements suggest we should not disregard the variable and destructive nature of this layer.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Destructive persistent slab releases remain a real possibility in the Northwest, as well as on isolated slopes in the Columbia Mtns, the Purcell Mtn Range and the South Coast Inland areas. A big warm-up forecast for Friday may be the real test for avalanche activity on these layers. Warming is also likely to spark new cornice fall, which would be a likely trigger for avalanches releasing at this interface.

On sun-exposed slopes, solar radiation will likely trigger widespread loose wet avalanches when the sun comes out. There is a possibility these surface release could step down to lower weak layers, pulling out a sizeable slab.

Snowpack Day 6 – 10 (Monday to Friday):

Again, little or no new snow is expected for most areas west of the Continental Divide. A cooling pattern is likely to generate stiff crusts on some previously moist surfaces. Further settlement, surface hoar development and surface faceting are likely on steep, north facing slopes. On the eastern slopes of the Rockies new snowfall is possible.

Avalanche Activity Day 6 – 10 (Monday to Friday):

With forecast cooling the snowpack will gain strength and avalanches will become less likely. The exception may be in the mountains east of the Continental Divide where new snow instabilities may develop.

Conditions Outlook March 20, 2013
Prepared by: James Floyer

Period
Day 3 – 5 is Friday, March 22 to Sunday, March 24.
Day 6 – 10 is Monday, March 25 to Friday March 29.

Snowpack Day 3 – 5 (Friday to Sunday):

Little or no new snow is expected to be added to the snowpack during this period for most areas. Cool air temperatures will preserve dry snow on north aspects, but increasingly intense solar radiation will make the snow surface moist on southerly slopes. This moist snow is likely to form a crust with overnight re-freezes.

At higher elevations, the surface hoar layer from March 9^th / 10^th is likely to remain a concern, especially in more aggressive, steep terrain with convex features. This layer will remain more reactive in the Northwest regions, but should be considered as a factor in all alpine riding areas.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

For the Northwest, concern for human-triggered avalanches on the March 9^th / 10^th layer is heightened. Recent remote-triggered avalanches (from up to 500 m away on 20^th March) and ongoing whumpfing point to an inherently unstable snowpack. The weather will promote only slow healing, and heightened avalanche danger will last through the extended period.

For all regions, concern for human-triggered avalanches on the 9^th / 10^th layer remains in the alpine on steep slopes of all aspects, particularly those with convex terrain features. On south-facing slopes, solar radiation will likely trigger widespread loose wet avalanches if/when the sun comes out. There is a possibility these surface release could step down to the lower weak layer, pulling out a sizeable slab. For north aspects, the bigger danger from warming will likely be the possibility of cornice collapse.

Snowpack Day 6 – 10 (Monday to Friday):

Again, little or no load is expected for most areas. Successive melt-freeze cycles are likely to generate stiff crusts on south aspects. The snow quality on north aspects is likely to deteriorate more slowly. With anticipated light winds, wind slabs are likely to be isolated rather than widespread.

Avalanche Activity Day 6 – 10 (Monday to Friday):

With successive melt-freeze cycles, the snowpack will gradually gain strength. However, this slow gain in strength may be tempered by a gradual rise in air temperature. A low probability of triggering a large avalanche will remain through the period, especially for alpine areas. Cornice collapses and solar-induced avalanches remain likely.

Conditions Outlook: March 13, 2013
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday, March 15 to Sunday, March 17.
Day 6 – 10 is Monday, March 18 to Friday, March 22.

Snowpack Day 3 – 5 (Friday to Sunday):

Temperatures should gradually start to drop through the period. This will likely form a new rain crust below treeline in most southern regions, and possibly extending up to treeline in some areas. The cooling and drying trend should also help to stabilize the March 9-11 surface hoar layer, which is probably down close to 100 cm in most areas. Winds are expected to be light during the period but isolated new wind slabs may form. The South Rockies could see a storm slab problem develop if the low pressure system and arctic front collide, possibly producing heavy snowfall.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Natural avalanche activity will probably taper off. The March 9-11 weak layer should remain sensitive to human triggers depending on how well it was flushed out during the previous storm cycle. I would be most worried about any slope that did not already release and possibly on lower angle terrain. Triggering the mid February persistent weak layer is unlikely, but a smaller avalanche could step down to this layer. If triggered it would be a very large and potentially deadly avalanche.

Snowpack Day 6 – 10 (Monday to Friday):

For the south: There are a couple of potential scenarios. First, it could be a relatively dry and cool period. The cool temps may help stabilize any previous weaknesses in the upper snowpack. On the other hand we could see light to maybe moderate snow and periods of moderate westerly winds. This could lead to new wind slabs developing in exposed terrain. Periods of sun may also form new sun crusts on solar aspects.

For the north: Not really much change is expected. We could see some surface faceting or surface hoar growth from cool and generally dry weather.

Avalanche Activity Day 6 – 10 (Monday to Friday):

For the south: Natural activity will likely be limited to isolated thin wind slabs, loose dry sluffing, or solar induced cornice falls or loose wet avalanches. Rider triggering will probably become less likely but we could still see the odd large persistent slab avalanche. This is more likely to be at or above treeline.

For the north: Isolated human triggered wind slabs remain possible. Large glide slab releases, cornice falls and ice falls are possible in isolated areas.

Conditions Outlook March 6, 2013
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday, March 8 to Sunday, March 10.
Day 6 – 10 is Monday, March 11 to Friday, March 15.

Snowpack Day 3 – 5 (Friday to Sunday):

Clear skies and cool temperatures should result in new surface hoar growth, surface faceting, and a sun crust. It’s also very likely that large cornices will fail with daytime warming and sunny skies on Friday and Saturday. The late February persistent weaknesses, now down 60-130 cm, are becoming less likely to trigger, but if triggered the resulting avalanche could have very serious consequences.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Natural avalanche activity will most be in response to sunshine and daytime warming on Friday and Saturday. Loose wet avalanches are likely, while cornice failures and persistent slab avalanches are possible. The greatest concern is with riders triggering persistent slabs on slopes that did not previously release. This is most likely on steep rocky slopes or areas where the previous storm snow distribution is variable. Exposure to overhead hazard should also be minimized during the day.

Snowpack Day 6 – 10 (Monday to Friday):

For the south: If the forecast scenario of a moist southwesterly with a series of embedded systems holds true, then we will likely see new storm slabs and wind slabs forming. This new snow will bury a potential new weakness of surface hoar, facets, or a sun crust. It’s possible that lower elevations (below 1600-1800 m) see another healthy dose of rain.

For the north: Not really much change is expected. Thin wind slabs may form with each weak pulse that slides through from the northwest.

Avalanche Activity Day 6 – 10 (Monday to Friday):

For the south: Storm slabs, wind slabs and cornices will increase in size. Ongoing natural and human triggering involving the storm snow is likely. The potential for isolated very large persistent slab avalanches still exists where the Feb 12 interface exists and did not release in last week’s storm cycle.

For the north: Isolated human triggered wind slabs are possible. Large glide slab releases, cornice falls and ice falls remain possible in isolated areas. In the northern part of the region cornice or ice falls could trigger the basal weakness and result in full depth avalanches. 

Conditions Outlook February 20, 2013
Prepared by: Penny Goddard

Period
Day 3 – 5 is Friday, February 22 to Sunday, February 24.
Day 6 – 10 is Monday, February 25 to Friday, March 1.

Snowpack Day 3 – 5 (Friday to Sunday):

Moderate to locally heavy snowfall and wind is expected build new storm slabs on a widespread basis. These are likely to overload the Feb 12 (or Feb 16 in some areas) surface hoar/sun crust interface where it hasn’t already reached tipping point. This snowfall will be starting warm and getting cooler, and will be accompanied by moderate to strong winds. All regions are likely to be affected by the end of Friday and northern and central regions again on Sunday.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

A natural cycle is expected on Friday in most regions (particularly northern regions), as precipitation and wind associated with an intense cold front rapidly loads the snowpack. The timing of avalanche activity will be linked to the timing of the front, which is somewhat uncertain. In the far south and east, the first front may not arrive until Friday evening and precipitation amounts are likely to be less than in the north, so a sharp spike in avalanche activity may not be observed, or it may occur after dark. During Saturday’s brief respite in the weather, human-triggering of storm slabs/wind slabs and persistent slabs on the Feb 12 interface will be likely. These may be surprisingly large. Expect further natural activity on Sunday. There will be a slim chance of avalanches stepping down to a weakness deeper than the Feb 12 interface in isolated areas.

Snowpack Day 6 – 10 (Monday to Friday):

Further snow, wind and temperature changes will continue to build progressively deeper storm and wind slabs above the Feb 12 (or Feb 16) interface. 

Avalanche Activity Day 6 – 10 (Monday to Friday):

Storm slabs, wind slabs and cornices will increase in size. Ongoing natural and human triggering is likely. Where the Feb 12 interface exists and has not already failed, the potential for very large persistent slab avalanches will grow. Again, a slim chance of triggering a persistent weakness deeper than the Feb 12 interface will remain.

Conditions Outlook February 13, 2013
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday, February 15 to Sunday, February 17.
Day 6 – 10 is Monday, February 18 to Friday February 22.

Snowpack Day 3 – 5 (Friday to Sunday):

A frontal system is forecast to drop 20-25 cm in the north, 10-15 cm on the south coast, and 5-10 cm in the southern interior. This snow along with moderate northwest winds should form new reactive wind slabs in exposed lee terrain. In the south this new snow is also adding load to a freshly buried weak layer (Feb 12 surface hoar/ crust/ facets) down 5-15 cm and the early February weak layer down 25-50 cm. It remains unlikely to trigger the January weak layers but they could act as step down layers in isolated areas.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

The likelihood of triggering a slab avalanche on one of the recently buried weak layers will increase into the weekend. Sunshine could be a factor on late Saturday and Sunday and result in loose wet activity and cornice failures.

In the north activity will likely be direct action avalanching on Friday and/ or Saturday as the frontal system moves through. Human triggering will remain possible on Sunday and solar induced avalanches are likely if the sun comes out.

Snowpack Day 6 – 10 (Monday to Friday):

It is unlikely we will see any drastic changes. Most regions should see incremental loading with periods of sunshine. New wind slabs are likely in response to moderate northwest winds. By the end of the period the Feb 3 and Feb 12 weak layers could be in prime human triggering range. The snowpack is showing signs of becoming much more complex if/ when we see a return to a more active weather pattern.

Avalanche Activity Day 6 – 10 (Monday to Friday):

Human triggered persistent slab avalanche activity will likely continue through the period. The size and likelihood of avalanches could increase depending on how much new snow accumulates and whether or not a slab develops. Wind slabs and cornice releases remain a concern. 

Conditions Outlook February 6, 2013
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday, February 8 to Sunday, February 10.
Day 6 – 10 is Monday, February 11 to Friday February 15.

Snowpack Day 3 – 5 (Friday to Sunday):

Dry conditions, mild temperatures, and generally light winds all suggest that the snowpack will continue to settle and gain strength. I expect that southerly aspects will go through a spring-like melt-freeze cycle. There are several buried weaknesses (surface hoar, facets, sun crust) in the upper snowpack that could be triggered by light loads in specific areas. New wind slabs could also form in response to northerly winds, particularly along the Rockies and North Columbia.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Daytime warming and solar radiation will destabilize southerly aspects and could result in an increase in avalanche activity. Cornice failures are also possible during this period. Recently buried weak layers could become increasingly reactive as temperatures rise and a slab forms. Sunday looks to be the warmest day. I would watch for a spike in avalanche activity on this day.

A significant weather system is forecast to hit the Yukon and White Pass on Sunday. There could be enough new snow and strong winds to result in an avalanche cycle.

Snowpack Day 6 – 10 (Monday to Friday):

Not much change. New surface hoar growth, surface faceting, and wind slab development should continue. The melt-freeze cycle will continue on southerly aspects. The only area seeing any new snow is along the coast of northern BC and the Yukon. Here, new wind slabs and storm snow weaknesses are possible.

Avalanche Activity Day 6 – 10 (Monday to Friday):

The likelihood of avalanches will continue to decrease throughout the period; however, weak layers lurking in the top metre of the snowpack mean that the size and consequences of triggering an avalanche will be quite high. Cornices will likely continue to pop off as temperatures stay quite mild. 

Conditions Outlook January 23, 2013
Prepared by: James Floyer

Period
Day 3 – 5 is Friday, February 1 to Sunday, February 5.
Day 6 – 10 is Monday, February 4 to Friday February 8.

Snowpack Day 3 – 5 (Friday to Sunday):

Warm temperatures, particularly on Friday and Saturday, will likely make the snow surface moist in many areas. In the southern regions, this warming looks set to go into the alpine. Expect high rates of snowpack settlement, which may have a negative short term impact on stability (see below) but in the long run will help bond and consolidate the snowpack.

The incoming storm on Sunday will add some new snow to the surface, which may set up into wind slabs in more exposed areas.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

One of the bigger questions for this period is—how much warming will there be and how much solar radiation will we see? If alpine temperatures go above zero and/or there is significant solar radiation, we are likely to see some reactivity in response. Activity is expected to be largely confined to the upper snow layers, with the Jan 23^rd surface hoar layer acting as the predominant sliding surface. The problem is likely to be most dangerous in the Lizard range, where this layer is more deeply buried and solar/warming effects look more pronounced.

On Sunday, storm and wind slab activity is possible associated with an incoming storm, particularly for northern regions. At the time of writing (30-Jan), a big cycle associated with this storm is not expected. However, if it comes through with more intensity, and/or it tracks further to the south, interior regions could see further avalanche activity on the Jan 23^rd surface hoar layer.

Snowpack Day 6 – 10 (Monday to Friday):

New load will be added to the snowpack at the start of next week, as stormy weather looks likely during that period. Winds are most likely from the south and west quadrants, meaning wind slabs will develop on north and east aspects.

Towards the end of next week, snowpack consolidation from more warm weather is likely.

Avalanche Activity Day 6 – 10 (Monday to Friday):

Storm and wind slab activity is likely early in the week in response to an active weather cycle. Due to the consolidation of the snowpack expected with the earlier warm temperatures, the most likely scenario is that activity will be confined to the new storm snow. However, there is the chance that avalanches could step down to the Jan-23^rd layer, particularly in areas that remained a little cooler, increasing the size and destructive potential of avalanche activity through this period.

Conditions Outlook January 23, 2013
Prepared by: Cam Campbell

Period
Day 3 – 5 is Friday, January 25 to Sunday, January 27.
Day 6 – 10 is Monday, January 28 to Friday February 1.

Snowpack Day 3 – 5 (Friday to Sunday):

Light to moderate snowfall for the coastal areas, and light in the interior ranges, throughout the period is expected to add incremental load the January 23^rd snow surface. The coastal ranges and westerly upslope side of major mountain ranges likely already have a cohesive storm slab sitting on this weakness. On the drier east side of the major mountain ranges, slab formation will likely remain limited to wind-loaded areas.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Both wind and storm slab avalanche activity associated with the Jan. 23^rd surface is possible in all regions, and likely in the coastal ranges and on westerly upslope side of major mountain ranges where precipitation amounts are expected to be higher.

Snowpack Day 6 – 10 (Monday to Friday):

Weak frontal systems are expected to continue to incrementally load the Jan. 23^rd surface with an average of 5-10mm/day expected for the north coast, 5mm/day for the south coast, and less than 5mm/day for the Columbias and Rockies.

Avalanche Activity Day 6 – 10 (Monday to Friday):

Natural and human-triggered wind and storm slab avalanche activity is expected to increase throughout the period for all regions.

Conditions Outlook January 16, 2013
Prepared by: Cam Campbell

Period
Day 3 – 5 is Friday, January 18 to Sunday, January 20.
Day 6 – 10 is Monday, January 21 to Friday January 25.

Snowpack Day 3 – 5 (Friday to Sunday):

Little change is expected throughout the period. Surface hoar growth is expected to continue primarily below treeline, surface faceting is expected to continue on northerly aspects, and melt-freeze metamorphism is expected to continue primarily on sun-exposed slopes. Warm temperatures will likely keep persistent weaknesses buried at the beginning of January sensitive to triggering.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Natural wet loose avalanche activity is expected to continue on sun-exposed slopes in the afternoon. Isolated large slab avalanche activity associated with the early January persistent weakness is also expected to continue. Isolated thin wind slabs may also remain sensitive to human triggers.

Snowpack Day 6 – 10 (Monday to Friday):

I don’t want to sound like an alarmist, but the longer the snow surface is exposed, and the more diverse the conditions it’s exposed to, the more likely it is to become a persistent weakness once it’s buried by a sufficiently deep and cohesive slab. In most regions, expect the current snow surface to be exposed at least into day 8 of this outlook, which means around two weeks of total exposure. During that period, it has seen and will continue to see substantial surface hoar growth and surface faceting, extreme winds and melt-freeze metamorphism, freezing rain crust and sun crust formation. The bottom line is, unless we get a monsoon with heavy rain into the alpine, this current surface will be one to watch.

Avalanche Activity Day 6 – 10 (Monday to Friday):

Natural wet loose avalanche activity is expected to continue on sun-exposed slopes in the afternoon, while activity associated with the early January persistent weakness and wind slabs is expected to taper off, at least until day 8. After that any avalanche activity is expected to be associated with storm snow.

Conditions Outlook, January 9, 2013
Prepared by: ilya storm

Period
Day 3 – 5 is Friday, January 11 to Sunday, January 13.
Day 6 – 10 is Monday, January 14 to Friday January 18.

Snowpack Day 3 – 5 (Friday to Sunday):

Little change is expected throughout the period with two exceptions. First, previous storm snow (which ended January 09) will slowly settle and strengthen. The storm snow is above a variety of surfaces including near-surface facets (widespread at treeline and alpine elevations), suncrusts (isolated to steep southerly aspects), and localized surface hoar (shady treeline). Cold temperatures may mean this process will slowly progress. I don’t expect these weak layers will persist for an unusual length of time (for example surface hoar issues lingering for days or weeks is possible, but not months). Second, the snow surface will gradually weaken over time. Look for a new cycle of surface facet, suncrust and surface hoar growth, especially in interior regions where strong inversions / valley cloud is likely to be the dominant weather feature.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

In the interior, post storm natural activity will be declining and should end by the weekend; human triggering will remain possible or likely. Storm slabs could be quite large with 100cm of HST on surface hoar or fat wind slabs on facets. Solar triggering on steep solar aspects at alpine elevations could be the exception if an inversion develops earlier or stronger than I imagine.

There remains a lingering possibility of triggering a persistent basal weak layer in isolated thin snowpack areas, but this has become very unlikely except in a few areas (i.e. east side of the Purcells).

Snowpack Day 6 – 10:

By the end of the weekend (January 13), we should be able to better identify any lingering persistent slab issues, if there are any. Some regions (I’m thinking Kootenay Boundary and southern part of the South Columbia in particular) could develop localized PWL problems but even here the problems are likely to be localized to specific drainages or terrain rather than widespread.

Surface layers are likely to deteriorate with faceting, crusting, and surface hoar growth. Warm alpine temperatures could trigger slides. Most likely is small point releases but they could be more significant. January warming is easy to underestimate in terms of how it affects slab properties even when slab temperatures near the weak layer remain well below freezing.

Avalanche Activity Day 6 – 10:

Mid pack and basal layers are likely to gradually strengthen; at worst I would think any recently buried surface hoar would be a patchy lingering layer through the period as it slowly strengthens. Alpine warming could trigger short lived cycles on steep solar aspects. Surface faceting may develop to where sluff management is required on steep slopes. Avalanche activity reports will be worth scrutinizing for anomalous activity on surface hoar or with solar radiation / warming at alpine elevations.

Conditions Outlook, January 2, 2013
Prepared by: Penny Goddard

Period
Day 3 – 5 is Friday, January 4 to Sunday, January 6.
Day 6 – 10 is Monday, January 7 to Friday January 11.

Snowpack Day 3 – 5 (Friday to Sunday):

Little change is likely initially, except on the North Coast, where I’d expect some storm slabs to develop on Saturday/Sunday. These are likely to add to existing storm/wind slab problems, which may be touchy on the Dec 27 surface hoar.

In the Interior and on the South Coast, it looks like snow will incrementally load current surfaces (surface hoar, surface facets and sun/temperature crusts). It may be a slightly tricky situation to forecast, as the loading won’t be dramatic and the distribution of potential weak layers at the current surface is complex. Areas with the combination of most surface hoar now and increased precipitation in the system arriving on Sunday may develop a touchy storm slab problem.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

The North Coast is likely to have a direct-action avalanche cycle in response to incoming weather at the weekend. In other regions under the influence of a ridge of high pressure, I don’t expect major solar-related activity as most areas have already been through one or more cycles of solar warming. Relatively small soft slabs may be naturally- or human-triggered by Sunday in the Interior and on the South Coast.

There remains a lingering possibility of triggering a persistent weak layer in isolated thin snowpack areas, but this has become very unlikely and I don’t foresee any major change during days 3-5.

Snowpack Day 6 – 10:

By day 6 or 7, most interior regions may have enough storm snow above current surfaces for a storm slab problem to have developed. Ongoing winds will be likely to create wind slabs on lee slopes.

Snowfall totals don’t seem cataclysmic, and the current snowpack is very well settled, so I don’t anticipate old (pre-December) persistent weak layers to be awoken. The only exceptions are potentially in the NW Inland region, where the snowpack is generally shallow and rotten, and in parts of the Kootenay Boundary, where the late November surface hoar is particularly well preserved and buried within the top metre of the snowpack. In the wake of the cold change (days 8-10), storm snow settlement may be slow and reverse wind-loading may occur as winds switch to the NW.

On the coast, ongoing upslope precipitation will probably keep storm slab problems alive. On day 7/8, the forecast cold front has the potential to bring severe weather to the South Coast, leading to deep storm slabs and leaving wind slabs behind in its wake. The associated sharp drop in temperature has the potential to cause a short-term increase in slab propagation, which could surprise people. However, confidence in the intensity of the cold front is not high.

Avalanche Activity Day 6 – 10:

There’s likely to be natural and human-triggered avalanche activity in most regions by about day 7. I expect this to be generally confined to the upper snowpack, stepping down as deep as the late November surface hoar in places. The possibility of the November or December crust/facet layers being triggered in isolated thin snowpack areas will remain in the back of our minds.

There is an outside possibility of cooling-related avalanche activity around day 7/8 if we get the magic combination of a touchy weak layer below the storm snow, significant storm snow loading, and a sudden temperature drop.

Conditions Outlook, December 27, 2012
Prepared by: Joe Lammers

Period
Day 3 – 5 is Saturday, December 29 to Monday, December 31.
Day 6 – 10 is Tuesday, January 1 to Saturday, January 5.

Snowpack Day 3 – 5 (Friday to Sunday):
I expect ongoing settlement of old storm slabs and a general strengthening of the snowpack across most of the province. Persistent weaknesses have become less of a problem in most areas, but basal instabilities are still lingering concerns in shallow snowpack areas such as: the Rossland Range, the southeast Purcells, the South Rockies/Lizard Range and the Northwest Inland.

Along the coast forecast light accumulations and increased wind values may contribute to small wind/storm slab development. In interior areas influenced by the drying ridge I expect widespread surface hoar development, especially at elevations influenced by heavy valley cloud. Solar input is unlikely to be strong at this time of year; however, steep sun-exposed slopes may see a diurnal surficial melt-freeze cycle.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

The North Coast may see a short-term, direct-action avalanche cycle in response to possible snow and wind. Otherwise, no significant avalanche patterns are forecast to develop. It is worth mentioning the low-probability/high consequence scenario associated with deep persistent weaknesses. Weaknesses that exist on facets or a crust/facet combo near the ground have been lingering in the aforementioned shallow snowpack areas and may produce large avalanches in isolated terrain.

 Snowpack Day 6 – 10:
The generally dry weather pattern suggests ongoing settlement of the existing snowpack. There will most likely be further development of weak layers at the surface that will, no doubt, affect snow stability when significant snowfall occurs. These weak layers include surface hoar, surface facets and possibly melt-freeze crusts on sun-exposed slopes.

In the Northwest Coastal region, the ongoing possibility of light snowfall and increased winds may contribute to further short-term surface instabilities.

Avalanche Activity Day 6 – 10:
Possible snowfall and increased winds on the North Coast may contribute to ongoing storm snow  avalanche activity. On days 8 through 10, there is a slight possibility that this moisture may move inland, but confidence is low.

Although there may be a general strengthening of the snowpack, avalanche activity may be more a result of human behaviour rather than snowpack trends. As people head further into the backcountry, the likelihood of somebody finding and triggering that anomalous deep persistent weakness increases. As well, riders will likely gain confidence in steeper terrain and access lines from ridge tops where large cornices loom. Triggering cornices will remain a possibility throughout the forecast period.

The Conditions Outlook will commence this season on Thursday 13 December. It will come out on a weekly basis on either Wednesday or Thursday through the winter season until approximately mid-April.

Conditions Outlook, February 18, 2012
Prepared by: ilya storm

Period
Day 3 – 5 is Friday April 20 to Sunday April 22.
Day 6 – 10 is Monday April 23 to Friday April 27.

Snowpack Day 3 – 5 (Friday to Sunday):
A rapidly moving storm is either departing or will have recently departed from most regions leaving snow at mid and higher elevations. The rain / snow line is likely to fall somewhere around treeline. Combined storm snow & recent snow amounts over the last few days could hit 50 cm in Coastal areas, 30 cm or so in the Columbias, and 15 to 20 cm in the Rockies

Avalanche Activity Day 3 – 5 (Friday to Sunday):
It looks like there are two drivers for direct action avalanche cycles this weekend:

• Typical “wintery” storm slab & wind slab problems, possibly exacerbated by crusts on solar aspects & mid-elevations.
• Rising freezing levels, combined with late-April solar radiation in the Columbia & Rocky Mtns. Freezing level Sunday could hit 2700m Sunday.\

It’s likely a bunch of the new & recent storm snow will shed this weekend; avalanche size will be a function of the depth of recent snow accumulations.

Mid- and low-elevations (Below Treeline) could see an increase in wet slab activity with the warmest temperatures so far this spring; this could include more shady aspects.

Warming could trigger cornice falls, which in turn could test slopes below.

Snowpack Day 6 – 10:
The weather regime suggests a gradual evolution toward a spring snowpack. With no major shocks or extremes in the weather forecast it’s likely that isothermal snowpack conditions will continue to creep higher in elevation and move around to shadier (northerly aspects). After the weekend warming, storm snow instabilities in the upper snowpack should be settling out.

At higher elevations as warmth creeps deeper into the snowpack and progresses around to more west, northwest and north east aspects we could see some older layers (i.e. mid-February surface hoar) wake up. Most likely in combination with heavy triggers like cornice drops.

However, the most likely scenario is a gradual, continued transition to spring with more melting than catastrophic failures (aka avalanches).

Avalanche Activity Day 6 – 10:
Most likely scenario is a predictable spring diurnal pattern following the timing and intensity of melt-freeze cycles. When that daily pattern fails, the chance of wet slabs increases.

It is possible that mid-pack (February layers) or basal layers activate as the spring heat penetrates the pack; but that’s hard to forecast and doesn’t look like it’s in the cards quite yet. Cornice failures will be worth watching for and their impacts analyzed. Any anomalous or large avalanches are worth thinking about and trying to figure out what happened. 

Conditions Outlook: April 11, 2012

Prepared by: James Floyer

Day 3 to 5 is: Friday April 13 to Sunday April 15.
Day 6 to 10 is: Monday April 16 to Friday April 20.

Snowpack Day 3 to 5 (Friday to Sunday):

Moist snow surfaces exist almost everywhere in the southern interior. Along the Coast, dry snow remains only on higher elevation north aspect slopes.

With the approaching storm, moderate to locally heavy amounts of snow is expected to fall in interior areas above 1800 m by Friday. The bond between the new snow and old may be weakened at higher elevations if either a crust forms before the new snow falls (forming a good sliding layer) or if facets develop as a result of cold, dry snow falling on a moist snow surface. Wind slabs could develop in unusual areas in response to easterly winds. Subsequent warming over the weekend will likely turn snow on southern aspects moist once more.

With only light amounts expected, coastal and northern areas will likely experience little change in snowpack conditions.

Avalanche Activity Day 3 to 5 (Friday to Sunday):

There’s a short-lived transition in the works from mostly warming and solar-related avalanche concerns back to direct-action storm instabilities, especially for eastern upslope areas of the southern interior for Friday. Areas that see light or moderate precipitation will probably see isolated wind slabs and maybe the occasional wet slab avalanche at lower elevation with anticipated rain up to around 1800 m. Localised areas could see higher precipitation amounts (these will be difficult to pin-point); these areas could see more widespread avalanche activity, with the possibility to re-activate slabs on the late March crust. The Rockies from Jasper to Fernie and the Purcells are the most likely places where this kind of avalanche activity is possible.

Subsequent warming over the weekend could destabilize any new snow that has fallen, promoting loose and slab avalanches, particularly on solar aspects.

Ongoing concern for cornice-triggered releases as well as glide activity continues for all areas.

Snowpack Day 6 to 10:

A settled start to this period with seasonal temperatures and little in the way of precipitation will generally consolidate the snowpack in most areas. Precipitaiton amounts later in the week shouldn't amount to much in the way of accumulation.

Avalanche Activity Day 6 to 10:

Localized wind slabs may develop in response to weak systems towards the second half of the period. Concern remains for isolated cornice-triggered releases as well as glide activity for all areas.

Conditions Outlook: April 4, 2012
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday April 6 to Sunday April 8.
Day 6 – 10 is Monday April 9 to Friday April 13.

Snowpack Day 3 – 5 (Friday to Sunday):
The primary feature for the weekend will be sunshine. For the most part temperatures should remain cool with good overnight recovery. Solar aspects will go through a melt-freeze cycle while northern aspects (up higher) should remain dry and may see some surface faceting and surface hoar growth.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Avalanche danger will rise and fall with diurnal temperature swings. I would expect loose wet avalanches up to Size 2 most days, with the potential for larger slab avalanches failing on the March 27 sun crust. This layer is generally 60-100cm deep in the Interior and up to 150cm deep in parts of the South Coast. It has been quite reactive with numerous accidentally triggered and remotely triggered avalanches up to Size 4.

The potential for cornice failures and deep slab avalanches will increase through the period as temperatures gradually rise. I would be particularly wary of the mid-Feb surface hoar and basal facets in the southeastern Interior (Kootenays, Purcells, South Rockies) where there has been more recent snow and deeper weaknesses have been more problematic. Large cornices will probably be popping off in all regions.

Snowpack Day 6 – 10:
The spring regime continues with a melt-freeze cycle on solar aspects and all aspects below treeline. Surface faceting and surface hoar growth could continue on shady slopes but shouldn’t be a factor this week with very little or no precipitation on the horizon.

Avalanche Activity Day 6 – 10:
I would expect the same type of activity as the previous weekend, but the potential for very large full-depth avalanches will increase. I would expect to see isolated Size 4+ avalanches in many regions. It will be hard to figure out where these events will happen, but you can be pretty certain that they will occur during the daytime as temperatures rise.

Conditions Outlook: March 28, 2012
Prepared by: Peter Marshall

Period
Day 3 – 5 is Friday March 30 to Sunday April 1.
Day 6 – 10 is Monday April 2 to Friday April 6.

Snowpack Day 3 – 5:

Continued active weather with moderate precipitation will result in storm slab and wind slab development. Snowfall looks heaviest on Friday and primarily in the southern half of the province. The March 26 sun crust or surface hoar layer could be buried as deeply as 60-80 cm by the weekend. We may see brief periods of solar radiation in the Interior resulting in spikes in temperature and a melt-freeze cycle on southerly aspects.

The mid-Feb surface hoar layer is buried very deeply in most areas where it is still being reported. On average it is around 140-250cm deep and generally produced no results or resistant shears in snowpack tests. Cornices are very large in all areas and will most likely continue to grow during this stormy period.

Avalanche Activity Day 3 – 5:

A direct action storm cycle is possible on the South Coast as storm slabs and wind slabs build throughout the period. Avalanches could release on the Mar. 26 surface hoar/sun crust layer and could be up to 1m deep in some places. Avalanche sizes could be as large as Size 3 depending on the amount of precipitation and the extent of the Mar. 26 weakness.

The Southern Interior may also see wind slabs and storm slabs develop. The Mar. 26 sun crust layer (and spotty surface hoar layer) will most likely be buried around 40-60cm deep. Avalanches could be human or naturally triggered up to Size 2.5. Very isolated deeper events are possible. If anywhere, I would expect to see these in the eastern Purcells and Kootenays.

Northern areas should see less precipitation and may only experience wind slab development in exposed leeward terrain. There is greater potential for strong solar radiation and solar related avalanche activity.

Confidence Day 3 – 5:

Fair. Southern regions, particularly the South Coast, could see more intense weather if the storm track pushes a little further north. This would result in a more widespread and larger avalanche cycle.

Snowpack Day 6 – 10:

We should see a continuation of the previous week with wind slab development and cornice growth in the south. Brief sunny breaks may result in a melt-freeze cycle on solar aspects. This should be more pronounced in the Northwest, North Columbias, and Northern Rockies. Northern regions may also see new surface hoar growth or surface faceting on shady slopes.

Avalanche Activity Day 6 – 10:

The avalanche problems will most likely be wind slabs and the potential for loose wet activity on solar aspects if the sun pokes out. Avalanche sizes will generally be Size 1-2.5. Cornices continue to be a significant hazard and may pop off as they continue to build or during periods of sunshine.

Triggering the mid-Feb surface hoar layer is unlikely but it should still be a factor in decision making. Be wary of large triggers or thin/variable snowpack areas, especially in the eastern Purcells and Kootenays where this layer has been most problematic.

Confidence Day 6 – 10:

Fair. Much the same as day 3-5: If the track pushes a little further north we could see more intense weather for the southern half of the province and a more extensive avalanche cycle.

Conditions Outlook, March 21, 2012
Prepared by: ilya storm

Period:
Day 3 – 5 is Friday March 23 to Sunday March 25
Day 6 – 10 is Monday March 26 to Friday March 30

Snowpack Day 3 – 5 (Friday to Sunday)
Precipitation through Thursday should remain confined to the South Coast, Kootenay-Boundary, and South Rockies. In these areas fresh wind & storm slabs will likely become active, at least briefly with forecast solar radiation & warmth, before settling in. In general, upper layers should be strengthening, with the notable exception of weakening with day-time warming and strong solar radiation. Good overnight recovery with below freezing temperatures should help limit the warming problem to south and southwest aspects.

The warming theme is likely to play out in a couple of other ways:

Cornices – well, they won’t be strengthening with warmth. Overnight recovery should mitigate their loss of strength but I suspect they’ll continue to play a role as “large triggers”.

Deep Persistant Weak Layers – in deep snowpack areas the slab above is likely to play a “bridging” role. Therefore we should see an improving snowpack that’s evolving from moderate likelihood:: high consequence to low likelihood::high consequence.

1. In areas with thin snowpack depth or convoluted terrain with variable snowcover – in other words places ripe with trigger points – the moderate likelihood probability will continue.

2. Southerly and Southwest aspects – the snowpack on alpine solar aspects reveals complex late winter layering (lots of layers, including thin crusts that cause pros in the know to be suspicious about thin facets above or below), not a spring-like melt-freeze crust. (Despite the calendars telling us today is the first day of spring!) I think warming will continue to be a destabilizing factor in this kind of terrain for several cycles of diurnal warming. Add to this my PWL trigger point comments (2.1 above) and a concerning picture starts to emerge.

Avalanche Activity Day 3 – 5 (Friday to Sunday)
Friday is likely a day for storm snow instabilities involving the upper snowpack – we anticipate a natural avalanche cycle with warming and solar radiation; probably in the size 2 range. There’s an increased potential for step down with “heavy triggers” – cornices and storm snow size 2 (previous sentence) – in the size 3 or 4 range. We continue to have a couple of big slides reported daily and that number could bump up.

Saturday & Sunday should see a gradual decrease of storm snow avalanche activity and a focus away from lee slopes and toward solar aspects. Less predictable deeper layers will likely continue to be reported, primarily due to “heavy triggers”. They won’t be large in number but their large size makes them significant.

My biggest concern for human triggered large avalanches is alpine solar aspects (south or southwest) with variable snowpack / convoluted terrain. This could involve known “persistent weak layers” like the mid-February surface hoar, localized complex layering (including pesky thin crust-facet layers often found at this time of year), warming and solar radiation. Good traction and the general appeal that comes with a warm sunny spring day are contributing human-factors.

Confidence Day 3 – 5 (Friday to Sunday)
Good.

Snowpack Day 6 – 10
Until the weather pattern changes on Wednesday Day 8 (possibly Day 7 or Day 9) my above comments should apply. Generally that means a strengthening snowpack, with a daytime warming and solar radiation caveat. Once the first storm arrives around Day 8 three changes are expected:

South Coast: a new round of storm & wind slabs develop. Southern Interior: increased cloud cover should end the warm temperature/solar radiation concerns. No significant accumulations suggest only minor isolated wind slab issues developing. Northern Coastal & Interior Regions: little change because the storm track should only affect the southern regions.

Avalanche Activity Day 6 – 10
Storm snow avalanche activity will start up on the South Coast when the first storm arrives, possibly quite quickly if there are smooth hard crusts serving as bed surfaces. Interior areas aren’t expected to get much precipitation so anything more than pockets of wind slab lee of ridges isn’t likely. Northern regions should continue to see generally improving conditions with the day time warming / solar radiation and a low frequency:: high consequence problems slowly improving.

Confidence Day 6 – 10
Good. The uncertainty is primarily connected to timing the arrival of a SW flow delivering the first storm onto the coast: Tuesday, Wednesday, or Thursday???

Conditions Outlook, March 14, 2012
Prepared by: Karl Klassen

Period
Day 3 – 5 is Friday, 17 to Sunday, March 18.
Day 6 – 10 is Monday, March 19 to Friday, March 23.

Snowpack Day 3 – 5, Friday - Sunday:
In the coastal areas, I expect typical storm and windslab evolution, that is: old storm snow from last week will settle and bond relatively quickly and any new layering/instabilities will be non-persistent problems that follow the usual maritime pattern of short-term instability followed by relatively quick stabilization.

In the interior, 100-150cm+ of storm snow from the last weather cycle hasn’t yet fully settled so storm snow instabilities from the previous period will almost certainly remain active over the weekend. This unsettled snow is susceptible to wind transport so I expect ongoing windslab development at upper elevations. The February PWLs are probably going to become increasingly unreactive, partly due to the depth of burial which limits/eliminates stress from reaching the layer and partially due to ongoing metamorphism of the weak grains. Also, at lower elevations, rain and very wet snow from last weekend followed by cooling on Tuesday have likely formed a bridging crust that further insulates the deeper layers from stress. How high a strong enough crust may have formed is going to vary but my best guess is below 1300-1400m in most areas where the surface hoar has been most problematic. Probably a bit lower in the north and a bit higher in the south and southeast. I have to say that the low elevation bridging crust is educated guesswork, no one is really talking about it so it’s possible I’m wrong about this—or perhaps no one is bothering to go down that low because riding/travel conditions are not very pleasant.

All that said, the February PWLs have been more persistent than normal, especially in many southern and eastern areas so I would not write these layers off just yet, especially in places where they are less than 100cm down or in shallow/variable depth snowpacks.

Inland coastal areas and the far north will likely be a bit of a mix between coastal and interior scenarios.

As the weekend progresses, the weather is looking like it will become less intense and clear breaks are likely in many areas. There’s potential for crusts to form on solar aspects and new surface hoar is possible, especially on shaded and sheltered slopes. I expect the crusts and surface hoar, if they form, will not be widespread or well developed by the end of the weekend but this is something to watch.

I don’t think there will be enough new snow to create a significant storm snow instability on low elevation crusts.

My main concern is that localized high solar heating potential exists for the weekend. This could be the first decent spring-like warm-up of the snowpack and, especially in the alpine where significant amounts of not-yet-settled new snow and fresh windslabs will exist, this is likely to be a significant de-stabilizing influence. It’s hard to predict when or where this might be a critical problem but it’s a likely scenario by Saturday afternoon in most areas.

Avalanche Activity Day 3 – 5:
Friday I expect a moderate storm snow and windslab cycle now underway in most interior regions will continue. On the coasts, nothing significant.

On the weekend, I’m thinking we’ll see a pretty decent cycle if/when the sun comes out and warms things up. Cornice fall and cornice triggered storm/windslabs, storm snow avalanches, wind slab avalanches are probable in most regions. In the interior regions another round of action on the deep PWLs is possible, triggered by avalanches/cornices from above, as step-downs, and perhaps also as human triggered slides where the PWLs are not as deep or in variable snowpacks.

I think the action will not occur in all parts of each region but I’d be looking for it when and where the sun pops out. I’m pretty sure that activity will be most prevalent on southerly aspects at alpine and treeline elevations.

Confidence Day 3 – 5
Pretty good for the general pattern but fair at best for exactly when and where problems will crop up and how serious it will be due to the variable nature of the weather pattern: convective cells interspersed with clear spells are incredibly difficult to predict in specific spatial or temporal terms.

Snowpack Day 6 – 10:
North of the South Coast, Kootenay-Boundary, and Lizard/South Rockies:
Lots of uncertainty but it’s looking like a cool dry spell in most regions will slowly stabilize the snowpack. High solar gain during the day might cause some diurnal instabilities but in general should settle things and produce crusts on solar aspects at all elevations, especially where slopes are sheltered from wind.

Surface hoar formation is likely with cool temperatures, calm-ish winds, and clear overnight skies. This will probably burn off on solar aspects but could grow incrementally on shaded, wind sheltered slopes throughout the period.

It’s unlikely we’ll see enough new snow to produce significant instability on or even cover up these new surface layers. In fact, I would not be surprised to see some regions with a whole new set of developing PWLs by the end of the period, just waiting to be buried by a spring storm.

On the optimistic side, spring crusts and surface hoar tend not to be as problematic those that form and are buried in the winter.

South Coast, Kootenay-Boundary, Lizard/South Rockies:
This area will likely see more intermittent crust/surface hoar formation sandwiched between minor accumulations of new snow. The first layer of the sandwich is likely to occur Monday as new snow arrives to cover up any surfaces that formed on the weekend, then minor crust/surface hoar formation during clearer, calmer spells covered by light new snowfalls every day or two.

Avalanche Activity Day 6 – 10:
Monday, outside the South Coast, I think residual solar related storm and windslab action is likely. Then as the week progresses, gradually declining diurnal storm and windslab activity related to afternoon heating for a couple of days. By the end of the period, I’m thinking it’ll be pretty quiet.

On the South Coast a minor storm snow cycle might occur Monday, then a relatively quick decrease in activity becoming almost nil within a few days.

Areas where the February PWLs have been problematic (Selkirks, north and east Monashees, Purcells, K-B, SE corner) will likely move into a low probability/high consequence scenario as the week progresses. Most likely hot spots: solar aspects, shallow/variable depth snowpack areas, convex/unsupported slopes just above to somewhat below treeline in the Selkirks, Purcells, and North Monashees.

Confidence Day 6 – 10:
Pretty good for areas north of the South Coast, K-B, and SE corner. Fair along the border where there’s a lot of uncertainty about timing/track/intensity of weather systems.

Conditions Outlook, February 29, 2012
Prepared by: ilya storm

Period
Day 3 – 5 is Friday March 02 to Sunday March 04
Day 6 – 10 is Monday March 05 to Friday March 09.

Snowpack Day 3 – 5 (Friday to Sunday):
Much of the province (Sea to Sky Corridor and Northwest Coastal Areas being the exception) continue to have snowpacks that are near the tipping point as evident by the number and size of remotely-triggered avalanches and close-calls.

The February 8 interface (surface hoar, facets, crusts and combinations of the three depending on aspect, elevation, and specific location) is down 100 to 150 cm in most regions. It remains the primary concern. In the Columbia Mtns. storm snow layers may be a close secondary concern; for example, around Revelstoke a prominent layer of stellars (a semi-persistent grain form that can act like surface hoar) is found around 50 or 60 cm deep. Don’t let this description fool you: the upper snowpack is a complicated mash-up of layers.

I’m hoping we’re in a period of short-term pain for long-term gain. The biggest fear of many pros right now is incremental loading; a scenario that’s hard to forecast. Confidence plummets due to the uncertainty about how the snowpack will react to another 10cm of snow. Will there be wicked avalanches or just good riding? The weather forecast is looking like many regions will receive a shock: warmer temperatures, significant loading, and moderate wind. This sets the stage for natural avalanche cycles this weekend. That would help clean out some of the nasty layers in the upper 150 cm of the snowpack.

The exception seems to be the southern and eastern sections of BC. Current storm tracks don’t suggest much precipitation, but it should warm significantly with freezing level rising to near treeline. I have less confidence that a shock and avalanche scenario will come to fruition. More likely is the incremental loading scenario.

Avalanche Activity Day 3 – 5:
Although forecast storms don’t look like whoppers, the pack is primed and should tip over to natural activity on or before Sunday wherever there is more than 20 or 30 mm of water equivalent precipitation. In these areas (most areas other than the south and eastern regions) I suspect avalanches to step down or release deep – they could be larger and wider than many folks might think for the amount of new snow. The current pattern of remote avalanches to size 3 or 3.5 show the type of instability that’s out there.

Areas that see rain are primed for a rain-on-snow avalanche event. It’s been cold enough that the snow could get twitchy really fast and size 2 avalanches start running in below treeline glades.

Snowpack Day 6 – 10:
Sunday’s warm storm should be short-lived. By Monday we should be back into cooler temperatures with few new negative inputs into the snowpack (snow, rain, wind transported snow, etc.) I think the snowpack will start to regain strength, and fairly quickly. But that strengthening will likely start at the top and take time to creep down. I expect a few days of lingering issues. I doubt the early February will get toasted by the weekend storms, they just don’t look strong enough. The most likely scenario to me is they become dormant in most areas but shouldn’t be forgotten.

Southern and eastern parts of the province (Kootenay Boundary, South Rockies, Purcells) are where I’ll be watching most closely. An incremental loading scenario seems more likely to continue to play out and plague those areas.

Avalanche Activity Day 6 – 10:
Remote and accidental triggering will slowly diminish over time as the snowpack returns to a happier balance. Again, I don’t think we’ll have seen the last of the early February interfaces.

The exception is Kootenay Boundary, South Rockies, and maybe the Purcells. I fear the weekend storms will pass by to the north and the current problems of incremental loading and remote triggering could continue.

Conditions Outlook, February 22, 2012
Prepared by: Karl Klassen

Period
Day 3 – 5 is Friday, February 24 to Sunday, February 26.
Day 6 – 10 is Monday, February 27 to Friday, March 2.

Snowpack Day 3 – 5, Friday - Sunday:
Additional loading by new snow and wind on Friday will reload paths that slid in the cycle that started Wednesday and add load to storm snow and persistent weak layers in any paths that have not yet avalanched. This will set the stage for the weekend when settlement, residual wind, and cooling temperatures coupled with the previously existing snowpack will almost certainly maintain/exacerbate a variety of old, recent, and developing instabilities.

If the sun comes out (most likely later in the weekend for some areas) it will further promote settlement and the evolution and development of slab properties on solar aspects. Cool temperatures and wind will mitigate potential solar gain so suncrusts, if any, are most likely to occur only on steep, sheltered, south and southwest aspects. High relative humidity is possible Saturday and if overnight clearing is experienced in some areas, even for a short time, yet another crop of surface hoar might start but I doubt it will get very large before the weather pattern changes again on Monday.

It’s a complicated picture and trying to predict specifics is difficult. However, I’m pretty confident that the end result will be an increasingly complex upper snowpack with a mix of old, new, and developing storm, wind, and persistent weak layers. Instabilities will likely exist simultaneously in more than one layer and the most active interface will probably vary from one place to another and shift over time from one layer to the next (I’m thinking from higher to lower in the upper snowpack) as incremental loading combines with settlement and wind to produce stress at different levels as slab properties change.

Deep basal weaknesses in shallow and variable depth snowpacks (the central-east Selkirks, Purcells, Kootenay-Boundary, and possibly the South Rockies) will bear watching as loading and overlying slab property evolve, and as the potential for large trigger mechanisms (cornice/step-down) develop.

Avalanche Activity Day 3 – 5:
I suspect a complex avalanche scenario will play out starting Friday and continuing over the weekend. Whether re-loaded paths will run again is not yet clear but it’s a possibility where new snow accumulations and windloading are higher than currently anticipated, so early signs of this scenario are worth looking for. In most regions, paths that did not slide in the mid-week cycle will have the complex existing upper snowpack with another load of new snow/wind load on it combined with increasing slab properties. Trying to guess at the specifics of what’s going to happen, not to mention when and where is a fool’s game.

In general, however, I suspect the avalanche activity that started Wednesday will have slackened by early Friday but a new round of action is likely later on Friday and into early Saturday. This second wave of activity will likely be less widespread and more complex in terms of its pattern and predictability. Activity will then likely further decline over the weekend with decreased likelihood of triggering and fewer naturals leading to a dominance of human triggered slides by the end of the weekend. New storm and wind related problems will almost certainly transition to persistent slab problems and I would not be at all surprised to see increasingly larger avalanche size on average as the number of avalanches goes down.

In shallow or variable depth snowpacks with deep, basal instabilities it’s possible that isolated full depth avalanches might start showing up again. Areas of concern include the central-east Selkirks, Purcells, Kootenay-Boundary, and possibly the South Rockies

Snowpack Day 6 – 10:
Under the influence of a zonal westerly flow containing a series of weak systems, snowpack evolution will likely mirror the last couple of weeks: that is, variable incremental loading with coastal and southern areas getting most of the new snow and west-facing up-slopes being favoured. There’s potential for surface hoar layers to form during short clear spells between storms and for some localized suncrusts to build during breaks in cloud cover. The big difference this time around is we’ll likely see more wind than what occurred during the incremental loading cycle of the previous 10-14 days.

In short, an increasingly complex snowpack is likely to develop. But this time, we’ll start with more load and slab property than we had in the last round.

Deep persistent weak layers that have recently been dormant/inactive may re-activate (if they have not already done so over the weekend) in the central-east Selkirks, Purcells, Kootenay-Boundary, and possibly the South Rockies under the influence of increasing load, changing weather, and evolving slab properties.

Avalanche Activity Day 6 – 10:
My bet? A mix of wind slab and storm slab problems, decreasing likelihood of triggering but still fairly widespread and bigger persistent slabs in layers at and above January 29 level. Notably Feb 8^th surface hoar/crusts and the underlying facets on shaded slopes, possibly with Jan 29^th (where it is a well-developed, smooth, firm layer) serving as a bed surface for deeper/bigger ones.

A low-very low probability/high consequence scenario might well develop in the central-east Selkirks, Purcells, Kootenay-Boundary, and possibly the South Rockies on basal deep persistent weak layers of facets/depth hoar.

Conditions Outlook, February 15, 2012
Prepared by: ilya storm

Period
Day 3 – 5 is Friday February 17 to Sunday February 19.
Day 6 – 10 is Monday February 20 to Friday February 24.

Snowpack Day 3 – 5 (Friday to Sunday):
Past weather patterns were pretty uniform and widespread across the province; therefore upper snowpack layers are pretty similar across our forecast regions. Of course variations on the theme exist depending on region, mountain range, elevation, aspect, etc. Having said that, “the theme” that’s both most common and relevant is that recent storm snow is sitting on near-surface facets (shady aspects), surface hoar (size depending on elevation and aspect), sun crusts (solar aspects), and a mixed bag of other stuff. In other words, weak layers in the upper snowpack are widespread, they are thinly covered, and have varying likelihoods of becoming persistent problems. There’s likely a more complex story below the recent snow than just a big bad layer of surface hoar. Mid-winter snowpack’s are often complex with multiple layers of concern at different depths, different problems depending on aspect and elevation, and a range in the sensitivity of these layers. I think we’re entering a time of increased snowpack complexity.

The South Coast is the only place with a significant storm possible, but by coastal standards they aren’t strong with nothing out of the ordinary. Direct action wind slabs seem to be the problem. Direct action avalanches may fracture wider and run farther than normally expected due to the facets, surface hoar, or facets on sun-crust they rest on.

For the rest of the province the story is similar, but with weaker storms. Therefore I expect incremental loading one day, solar warming the next. Incremental loading, and the challenges it creates, is the big idea to carry forward into Day 6 to 10 Outlook (discussed below). I doubt the snowpack will cross any major thresholds during Day 3 to 5 period.

Avalanche Activity Day 3 – 5 (Friday to Sunday):
Forecast weak & short-lived disturbances will provide the initial load on recently buried weak layers. Any avalanches during this period are, by definition, direct action avalanches. Likely a typical wind slab problem with the exception that slabs might fracture a bit wider and run farther than normally expected given their thickness. There’s a residual risk of deep releases in thin snowpack areas: namely Purcells, S Rockies, & possibly some parts of the Cariboos. Large triggers, really bad terrain choices, or bad luck are likely required.

Snowpack Day 6 – 10:
Snowpack evolution is most likely to occur under the scenario of continued incremental loading and the associated problems that come with this. I see two major concerns in the snowpack:

1. The cooler shady slope problem is primarily the Feb 8 Surface Hoar issue, especially in the interior. Crystal size is largest at lower elevations, often corresponding to where valley cloud fed its development during inversions. It was reported high into the alpine in the interior.

In many places this SH sits on a 10 to 20 cm layer of softer near-surface facets, formed during the dryish & coolish first week in February Below the facets is a firm layer, in some places it’s more like a hard and smooth crust. This is the layer from our January warm spell. Is there a thin layer of facets above (and below) this crust? These slopes are likely to receive incremental lee-loading through the outlook period.

2. The warmer sunny slope problem is possibly more complex because it adds a February 08 sun crust to the mix. The weather around the time it was buried suggests wet crust faceting both above and below is possible. And, it may be a surface hoar – crust combination. We know less about this layer because people avoided these slopes when on the surface (who wants to ride a crust) and until now it’s a dust on crust situation with no real issues.

I can see more of these thin sun-crusts (with facets growing above and below) developing between snowfalls and showing up every 5 to 25 cm in future snow profiles.

These slopes are likely to receive cross-loading through the outlook period.

Avalanche Activity Day 6 – 10:
If the snowpack structure is more complex than it appears on first impressions, I think avalanche activity will be too. My hunch is that in most places, most storms won’t have enough punch for an obvious or widespread cycle. That’s the problem of incremental loading: it’s good until suddenly, surprise, it isn’t. The challenge is going to be identifying patterns in avalanche activity on these early February problems. I think this applies at two scales:

I suspect that coastal mountains will help predict the interior. I suspect that, given likely storm tracks, northerly parts of the Columbias will help predict more southerly parts (more loading in the north). I’d watch for patterns retrogressing from shallow & weaker areas toward stronger areas. For example will typical surface hoar farms in the Kootenays react before areas where the surface hoar was less developed, despite have more additional load?

This also applies to areas with basal concerns – will they first react where weakest, even with less load. How does step-down fit in.

I think we’re entering a period where an empirical approach is the way to go. Class 1 data (and the patterns hidden within the data set) will be crucial to developing a better understanding of both relevant snowpack structure and predicting future avalanche activity patterns. It’s possible that we’re entering a period where it’s too complex to be too attached to favourite pet theories or stuck in narrow thinking. Incremental loading is tough!

Conditions Outlook, February 08, 2012
Prepared by: Penny Goddard

Period
Day 3 – 5 is Friday February 10 to Sunday February 12.
Day 6 – 10 is Monday February 13 to Friday February 17.

Snowpack Day 3 – 5 (Friday to Sunday):
While last week’s warming initially resulted in a widespread slab avalanche cycle, waking up deep persistent layers including basal facets, the mid-January crust/facet/surface hoar and the Jan 20 facets, the longer term effect has been an overall improvement in stability. Following successive melt-freeze cycles, the properties of the slab above these layers has improved so greatly that further triggering of persistent weaknesses is very unlikely. If triggered at all, it’ll be most likely from thin spots on north-facing terrain at upper elevations or with a very large trigger.

Static weather with cloud cover, little wind and no extremes of temperature will effect little change. Surface faceting will probably continue and surface hoar may slow down in its growth with cloudy skies, but existing crystals will probably persist, or continue to slowly grow. Surface hoar will get gently buried on Friday in coastal regions and the North Columbias, which could help to preserve it there.

Avalanche Activity Day 3 – 5 (Friday to Sunday):

Generally little avalanche activity is expected. The chance of a brief rise in the freezing level on the South Coast on Friday may weaken cornices, but the anticipated effect of cornice failure on slopes below is minimal. A few cm of snow expected in coastal regions and the north Rockies/Columbia could lead to human-triggering of localised wind slabs mainly in the size 1-1.5 range. Continued surface faceting on north-facing slopes in the alpine may lead to human-triggered sluffs in steep terrain. The chance of triggering a persistent weak layer is low, but remains possible in isolated areas (thin spots on north-facing start zones and relatively shallow snowpack areas, especially in the south-eastern section of the province).

Snowpack Day 6 – 10:
No major change is anticipated. Extra surface hoar growth may develop at the upper rim of valley inversion cloud.

Avalanche Activity Day 6 – 10:
Little avalanche activity is expected due to the absence of any mechanism for triggering (beyond cornice fall and increasingly bold human activity). Solar-related surface activity is possible in sunny coastal areas, however I wouldn’t expect as much of this type of activity as last week, as it’s already gone through a good round of melt-freeze.

Conditions Outlook, February 01, 2012
Prepared by: ilya storm

Period
Day 3 – 5 is Friday February 03 to Sunday February 05.
Day 6 – 10 is Monday February 06 to Friday February 10.

Snowpack Day 3 – 5 (Friday to Sunday):
Coastal areas essentially have structurally sound snowpacks. Columbia Mountain snowpacks have some mid-pack or deep layers that could be future weakness: Jan 20 facets, Jan 13 surface hoar/facets/crusts (remember Friday the 13^th?). Some parts of Kootenay Boundary (western sections?), the Purcells (east side), and South Rockies have older weakness from mid-December or earlier.

Sunshine and warm temperatures (without overnight recovery at higher elevations, with little to no cooling breeze) is expected to have a short-term deteriorating effect on the snowpack everywhere. Mostly the upper (storm snow layers). Deeper layers may take a little longer to come into play in the absence of large triggers (cornices). Thin snowpack areas (regional scale & localized in convoluted, variable terrain) are worth watching as per the layers described above.

Avalanche Activity Day 3 – 5 (Friday to Sunday):
Solar & temperature triggered surface layers are an obvious short-term concern Thursday & Friday. Cornice failures are expected – some triggering large slabs that run to valley bottom. These problems should diminish once the “shock” wears off and settling & strengthening start to dominate over the time.

We’re going into a period when it’s important to monitor anomalous, large avalanches. Unusual events, i.e. deep releases, may foretell what’s coming next. In the Columbia Mtns (Cariboos, Selkirks, Monashees) and Lizard Range the Jan 20 & Jan 13 layers could come into play, especially with cornice triggers. They’re buried around 150 cm. Jan 13 could be particularly relevant because it was a surface hoar / crust or sun crust issue – the aspects of concern which correspond to the forecast solar/temperature weather concerns. In shallow Kootenay Boundary the mid-December layer is less than 100 cm deep in 150 cm snowpack areas. This likely represents many places in the Purcells & South Rockies.

Snowpack Day 6 – 10:
Development of crusts, especially on solar aspects and all aspects at low-alpine and lower elevations. Surface hoar development likely at mid-elevations with the inversion/valley-cloud/bathtub-ring effect. Also surface hoar will develop in valley bottoms close to creeks. None of these will come into play until it next snows, but they’re worth monitoring & mapping while on the surface.

Avalanche Activity Day 6 – 10:
With the same weather pattern continuing, I expect surface avalanche activity to diminish. Attention should likely shift to deeper layers. How mid-pack and deep-pack weak layers react is worth paying close attention to. Specifically, it will be worth monitoring overnight recovery at high elevations, and patterns of anomalous larger avalanches. It’s really hard to pin-down weather specifics (despite high confidence in the general pattern), let alone how deeper layers will be affected by those specifics. It may turn into low-probability/high consequence scenario.

Conditions Outlook, January 25, 2012
Prepared by: Karl Klassen

Period
Day 3 – 5 is Friday, January27 to Sunday, January 29.
Day 6 – 10 is Monday, January 30 to Friday, February 3.

Snowpack Day 3 – 5, Friday - Sunday:
There is some potential for a weak surface layers to develop Wednesday/Thursday in areas in where clearer, calmer weather prevails—these could be crusts on steep solar aspects or surface hoar on shaded. sheltered aspects. Warm temperatures, winds, and precipitation will likely produce instabilities both within the new snow itself (more likely in the North and coastal mountains) and on the old surface almost everywhere. These problems will arrive earlier and be most pronounced in the Northwest, followed by the North Rockies and South Coast then the Columbias and SE corner. Load will be increased on any PWLs that are still in the mix: mid-December and basal facets in the Purcells and mid-December layer in the Kootenay-Boundary.

Avalanche Activity Day 3 – 5:
I expect storm snow and windslab avalanche problems to dominate the period. There’s some potential for stepdown or perhaps even initial failures in some of the January layers, the most likely culprit being the mid-January interface but I think that’s a long shot. I’d watch for deeper releases in the Purcells and Kootenay-Boundary that might indicate reactivation of the mid-December layer and perhaps the basal facets in the east where the snowpack is shallow.

Snowpack Day 6 – 10:
Day 6/7 look a lot like day 3-5. After that I expect we’ll see development of surface layers that could become persistent weaknesses. Warm temperatures and sunny days with little wind say crust to me, especially on steep, solar aspects. Cool, clear, calm nights will likely promote surface hoar formation. If I were a betting man I’d say a mixed bag of crusts on steep solar aspects at all elevations and surface hoar on shaded mid-high elevations where daytime temperatures don’t get high enough to break down any new surface hoar growth.

Avalanche Activity Day 6 – 10:
Day 6/7 look a lot like day 3-5. Wednesday will likely be transitional as storm and wind slabs settle out. After that, I’m guessing it will be pretty quiet, my one lingering concern is a low-probability/high-consequence scenario in the Purcells and Kootenay-Boundary.

Conditions Outlook, January 18, 2012

Prepared by: ilya storm

Period:

Day 3 – 5 is Friday January 20 to Sunday January 22

Day 6 – 10 is Monday January 23 to Friday January 27

Snowpack: Upper layers are likely be priming up for a cycle. Three scenarios for change in these upper layers are easy to identify, none of them promote short term stability:

1. natural settlement of the storm snow into a soft but cohesive slab

2. upside down slab developing with warming temperatures

3. wind slab formation once the wind hits. Lots of loose snow available for transport

Most regions fall under our watch list for these scenarios, the NW might be the exception.

The forecast incoming pacific storm, expected late Friday, overnight, and into Saturday morning (South Coast overnight, interior Saturday AM) will have warming, warm front winds, and a rapidly moving trailing cold-front with gusty strong wind.

Both recent (previous) storm snow from Jan 13 to 15 and forecast new snow could come into play for avalanche activity.

Avalanche Activity I think most areas are looking at predictable, direct action avalanche cycle. However, avalanches could be larger than might be expected because the “Friday the 13^th” interface may become the active interface.

The Purcells and South Rockies continue to report mid-December PWL concerns (moderate or hard sudden-planar test results). It’s possible we these layers get tested, either this weekend (Jan 21 storm) or mid-week (around Jan 25) with a warmer SW storm flow.

Conditions Outlook, January 11, 2012
Prepared by: Karl Klassen

Period
Day 3 – 5 is Friday, January 13 to Sunday, January 15.
Day 6 – 10 is Monday, January 16 to Friday, January 20.

Snowpack Day 3 – 5, Friday - Sunday:
Cool-cold temperatures will likely have tightened up the snowpack significantly in all areas by Friday. Surface hoar or surface facets are likely to form up to and including Friday. Sheltered, steep, south aspects may form suncrusts, especially at lower elevations but it’s unlikely these will be widespread or particularly strong.

Saturday and Sunday will see these new surface layers covered up, deeper in the northwest and north than in the south. Moderate gusty winds will add windloaded layers to the mix but probably mostly in the alpine at ridgetops.

Avalanche Activity Day 3 – 5:
Could be looking at a bit of a storm snow and windslab cycle again in the Northwest coastal areas where greater loads are most likely. Inland and to the south, it’s unlikely there will be much action if the weather forecast is right about snowfall amounts being relatively light; some windslabs in the alpine are the most likely scenario here.

Cornice avalanches may be an issue, early in the period due to solar radiation then later as due to the temperature drop.

Low-probability/high consequence avalanches might be a concern, especially in southern regions.

Snowpack Day 6 – 10:
Most likely we’re in for a good cold temperature lockup with the arrival of an arctic airmass. Surface faceting and surface hoar will likely dominate snowpack development. Even though it’s likely to be sunny, cold temperatures should inhibit suncrust formation except perhaps in the most sheltered, steepest, south aspects in the most southerly regions—maybe.

In the border areas of the south coast, Kootenay-Boundary, and South Rockies the surface facets and surface hoar that form earlier in the period might get covered by minor accumulations of low density snow on Thursday or Friday.

Avalanche Activity Day 6 – 10:
I expect little in the way of significant avalanche activity anywhere in the province for the entire extended period. Even low-probability/high-consequence avalanches are pretty unlikely except in extreme terrain with variable snowpacks and convex, unsupported slopes—perhaps a bit more so on steep southerly aspects where solar radiation might come into play. If this scenario occurs, it’s more likely in the southern areas than in the north or west.

A short-term cornice avalanche problem may linger on Monday and Tuesday as cornices adjust to the temperature drop.