Weather Outlook |
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This weather outlook is based on a combination of deterministic weather models, model ensembles that are highly probabilistic, and a briefing from a professional meteorologist. It's intended for internal discussion among professional avalanche forecasters and is unlikley to accurately predict conditions at any specific place or time. Rather, it suggests the most likely scenario for the periods indicated. Forecasters combine the weather outlooks with the Weekly Summary so they can extrapolate into the future in the Conditions Outlook.
We make this summary public to help our users learn about avalanche hazard and risk, understand how avalanche forecasting works, and see some of the background work that goes into the products and services produced by the CAC's Public Avalanche Warning Service.
This product is not a decision-making aid and should not be used for planning or risk management purposes. For the most up to date and current information, users should read the CAC's avalanche forecasts, which are updated daily and which contain a regional weather forecast overview in the Forecsat Details page. To learn more about forecasting weather, visit the Weather page on our website which is found under the Pre-Trip Planning tab.
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Karl Klassen - Manager
Public Avalanche Warning Service
kklassen@avalanche.ca
Weather Outlook April 9, 2013
Prepared by: Penny Goddard
Period
Day 3 – 5 is Thursday, April 11 to Saturday, April 13.
Day 6 – 10 is Sunday, April 14 to Thursday, April 18.
Overview Day 3 – 5:
This period brings a pronounced change from seasonal temperatures to colder conditions. A cold front on Day 4 is the main feature.
Day 3 – Thursday
A transient ridge builds on the coast. A weak upper cold front brings generally light, convective precipitation to the Columbia and Rocky Mountains. Light NW winds are forecast, except for some gusts associated with the front.
Day 4 – Friday
A well-developed system hits the coast, with highest precipitation intensity in the north. There is only light spillover into the western Columbia. Winds are moderate to strong. A cold NW flow lowers the freezing level, with snow possible to valley floor.
Day 5 – Saturday
The jet stream points south of the border, leaving BC in cold air. Convective conditions affect the province in the wake of the cold front (which is still crossing the SE corner). Flurries to valley bottom are likely in most places. A NE upslope flow may bring enhanced precipitation to the North Rockies.
Confidence: Fair. Areas of enhanced precipitation are hard to pin down.
Overview Day 6 – 10
Cold temperatures continue, but with a more westerly flow. Days 6 and 7 bring ridging on the coast, while clouds or convection linger in the interior. Days 8 and 9 bring active systems embedded in a westerly flow to the coast, with snow to fairly low levels. These push into the Columbia Mountains on Days 9 and 10. On Day 10, modified arctic air finds its way to the North Rockies.
Confidence: Fair to poor, as models disagree on the timing of systems which are in a fast-moving W to NW flow.
Weather 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.
Overview Day 3 – 5:
No major systems are expected through this period. Generally clear skies are forecast with rising freezing levels.
Day 3 – Friday
A ridge will continue to bring dry conditions to the province. Winds will be generally calm which will augment the effect of solar radiation.
Day 4 – Saturday
The ridge will persist with continued clear skies and a strong solar influence, except for the North Coast where clouds may develop. No precipitation is expected with the cloud.
Day 5 – Sunday
Generally clear skies and high freezing levels are expected throughout most of the province, although a more northerly flow may bring cooling and some snowfall to slopes east of the Continental Divide.
Confidence: Good.
Overview Day 6 – 10
No major systems are forecast. Gradual cooling is expected by the 2nd half of next week as a continued blocking pattern is forecast to persist and bring generally dry conditions to the province. The exception may be in the Rockies where there is a continued chance of snowfall on eastern slopes.
Confidence: Fair to good. The greatest uncertainty lies in the timing of the cooling and how far west forecast snowfall may extend.
Weather 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.
Overview Day 3 – 5:
Lingering convective activity gradually gives way to a ridge of high pressure that slowly moves in from the west. Temperatures cooler than seasonal norms.
Day 3 – Friday
Unstable air following a Pacific frontal system will generate scattered convective showers in the interior ranges of BC/AB. However, the relatively dry nature of this air mass combined with generally light (but occasionally gusty) winds should keep snowfall amounts generally light. On the coast, clear skies will start to develop, with significant daytime solar radiation.
Day 4 – Saturday
The ridge of high pressure moves inland and starts to dominate the mountain regions with stable weather. Lingering moisture will likely retain some cloud and the occasional convective shower for interior regions, while the coast should experience a clear, sunny day. Out of the sun, temperatures should still feel cool. Mostly light northwesterly winds, occasionally gusty.
Day 5 – Sunday
Very similar weather to Saturday, although the ridge becomes more fully centred over BC, increasing solar radiation and reducing the chance of showers in almost all regions. The only regions that could see scattered flurries are the South Rockies and the Yukon.
Confidence: Good for the pattern and timing. The convective nature of the lingering precipitation makes it locally possible that a region forecast with no snow may see 10 cm.
Overview Day 6 – 10
The ridge that slowly builds on Saturday and Sunday will very likely continue into the first half of next week, continuing dry, stable conditions. Sunny days with strong solar inputs can be expected, especially on Monday and Tuesday (25/26 March). Around Wednesday, the most likely scenario sees a blocking pattern setting up, with a closed static low pressure system off the coast diverting moisture either north to the Yukon or south to Oregon. If this comes true, the result will be further benign, stable weather for the majority of the mountain regions south of the Yukon. One exception is the south coast, which could potentially see a weak system in the middle of the week. If the block fails, we can expect slightly more cloud and precipitation, but the chance of big storm over the period is very low.
Confidence: Fair to good.
Weather 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.
Overview Day 3 – 5:
The period is marked by an upper level flow change from southwesterly to westerly for Friday and Saturday, and then northwesterly by Sunday. Overall this leads to gradual cooling and slightly drier conditions. However, cloud cover is still expected to be high due to a trough and low pressure system moving across BC.
Day 3 – Friday
The persistent southwest flow of the previous several days backs off to a more zonal (westerly flow). A brief ridge of high pressure could give sunny breaks to interior regions but the coast should stay cloudy with at least light precipitation.
Day 4 – Saturday
A weakening low moves through BC bringing light to locally moderate precipitation to most regions. Temperatures continue to drop a couple degrees to more seasonal values and winds are generally light from the west.
Day 5 – Sunday
The flow becomes more northwesterly resulting in further cooling to slightly below seasonal temperatures. Drier and colder conditions are expected in the north as the arctic front pushes back in. The weak low is now near southeast BC and may give moderate snowfall to the Kootenays and South Rockies.
Confidence: Fair. There is reasonable certainty in the overall pattern. The tricky one is determining snowfall amounts from the weak low sliding across BC on Saturday and Sunday. The low may mix with the arctic air pushing in from the northeast, which could lead to locally heavy snowfall amounts over eastern regions (i.e. Fernie factor).
Overview Day 6 – 10
It’s always tough to draw out any details from the long range weather outlook, but it’s particularly difficult this week. There is essentially no computer model agreement beyond Wednesday (day 8). Up until that point it looks as though conditions will remain cool (seasonal at least) and generally inactive. I don’t expect a strong ridge to become established so it’s likely that most regions will see high cloud cover. Precipitation amounts look light for all areas. Any stronger weather is most likely to be directed to the South Coast and possibly into the Kootenay Boundary. Some weather models currently show decent accumulation in Washington and Oregon. If the storm track slides a little further north we could end up seeing this.
Confidence: Poor. There is essentially no agreement between computer models for day 8-10. Some models suggest a ridge over the province leading to fair weather, while others show a very active southwest flow. It’s really anyone’s guess at this point.
Weather 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.
Overview Day 3 – 5:
The period starts off with dry conditions and calm winds under a ridge of high pressure, but quickly and significantly changes by Sunday as the ridge flattens and returns to a more southwesterly flow.
Day 3 – Friday
A ridge of high pressure sits over most of BC resulting in mainly sunny skies, strong diurnal temperature variations, and light winds. We may see lingering cloud in the southeast corner of BC.
Day 4 – Saturday
The ridge of high pressure maintains sunny and relatively mild conditions for most regions. Freezing levels in the south could rise to 1800-2000 m. Expect increasing cloud along the North Coast as an offshore system approaches.
Day 5 – Sunday
The ridge should flatten resulting in a split flow over BC. The north is under a cool northwesterly flow and the south changes to a moist and mild southwesterly flow. Both the north and south should see cloud and light precipitation but conditions will be much milder in the south.
Confidence: Good for the general pattern – the uncertainly lies with the timing of the pattern switch and when the more intense precipitation and warming will occur. At this point it looks like overnight Sunday and into Monday will be the start of heavier precipitation.
Overview Day 6 – 10
The pattern split pattern setting up on Sunday should persist at least through Wednesday. We should see a series of waves or disturbances affecting the southern part of BC and Alberta bringing moderate to heavy accumulations and relatively high freezing levels. The North Coast should see generally benign weather and cooler temperatures. Further to the north, in the White Pass and Yukon, expect a return to cold temperatures under the influence of the arctic front. There is poor model agreement on what will take place on Thursday and Friday, but at this point it looks like we could see a change in the southwesterly flow and potentially drier conditions.
Confidence: Fair. There is relatively good agreement on the overall pattern for Monday to Wednesday but not much certainty on the details (precip intensity, freezing levels, etc). If the flow slides a little further south we may not see much precip at all. Beyond Wednesday the confidence is much lower.
Weather 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.
Overview Day 3 – 5:
A fast-moving, dynamic westerly flow will drive the weather, with precipitation, winds and temperature changes affecting all regions.
Day 3 – Friday
A low pressure centre over the Alaska Panhandle will extend a trough over the north coast. A cold front embedded in a pushy onshore flow will sweep across all regions during the day, bringing warm to cold temperature changes, precipitation (mainly snow, with a slight possibility of freezing rain below treeline in some areas ahead of the front), and moderate to strong winds.
Day 4 – Saturday
The trough will exit to the south-east. A ridge builds, but it’s not well-defined, allowing light convective cloud or precipitation to continue. In the evening, a warm front approaches the coast, bringing light to moderate precipitation. This front fizzles before reaching the interior.
Day 5 – Sunday
A cold front will affect the north coast, then slide inland and south, bringing light to moderate precipitation and moderate winds to most regions. The ridge of high pressure should persist in the south, leaving the south-east corner of BC in a mild SW flow.
Confidence: Good for the general pattern, but poor for timing.
Overview Day 6 – 10
A continued active, zonal flow should focus 2 to 3 fast-paced systems on the central and south coasts, with some spillover to the north coast and inland. All areas should receive some snowfall. Around Day 9 (Thursday 28 Feb), a change to a milder/moister SW flow is expected, with high precipitation amounts in coastal areas and moderate amounts in the Columbia and Rocky Mountains. Winds will increase, and temperatures should be mild but still seasonal.
Confidence: Good for the general pattern and poor for timing.
Weather 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.
Overview Day 3 – 5:
The weather pattern is slightly more active than it has been for the past few weeks. A large ridge of high pressure over the eastern Pacific is directing a northwesterly flow over Western Canada. In general, this should result in cool temperatures and periods of light snowfall with northwest winds. The flow pattern will probably get interrupted by one or two brief short wave ridges that move across the province.
Day 3 – Friday
A surface ridge over BC will give dry conditions, sunny skies, and mild temperatures to most of southern BC. The freezing levels in the south should be around 1200 m and possibly higher on the south coast. A frontal system approaches the north spreading moderate to locally heavy precipitation to the northwest coastal region and the White Pass area. Freezing levels are around 1000 m.
Day 4 – Saturday
The frontal system slides south affecting the south coast and interior with generally light precipitation and gusty northwest winds. Temperatures will drop in the wake of the cold front and conditions remain unsettled. In the north conditions are cool and unsettled with light snowfall.
Day 5 – Sunday
A short wave ridge redevelops resulting in drier conditions and periods of sun in all regions. The only exception is the east side of the Rockies where the northeast flow could result in light upslope snowfall.
Confidence: Good overall. The pattern is well handled and weather models are in agreement. However, snowfall amounts are a little uncertain. Westerly upslope areas should see greater accumulations as the system moves through on Saturday, but unsettled convective weather in the wake of the system could result in variable snowfall amounts.
Overview Day 6 – 10
The northwest flow pattern continues into next week. Cool conditions with light snowfall and sunny breaks are expected. Winds are generally light to moderate from the northwest. The northwest region should see the most active weather, but no significant storms are forecast at this point. Unsettled conditions with light snowfall seem to be the story at least until late next week. The south coast will likely see a lot of cloud with periods of light precipitation. The interior should see more sun during the week.
Confidence: Good. Weather models are in good agreement with the overall pattern.
Weather 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.
Overview Day 3 – 5:
A ridge of high pressure establishes off the coast of BC bringing dry conditions and sunny skies (valley cloud is likely) to much of the province. Temperatures are expected to be slightly above normal with high solar affect. Northern regions could see more cloud and possible light snowfall as weak systems slide over the ridge. Winds are generally from the north-northwest which could help moderate the alpine temperatures a little.
Day 3 – Friday
A strong ridge of high pressure builds in off the coast of BC bringing dry conditions (except for the extreme north of BC and the Yukon). Southern regions will be bright and sunny (with possible valley cloud), while the northern regions will see more cloud with possible light snowfall. Alpine temperatures should remain a few degrees below zero.
Day 4 – Saturday
The ridge of high pressure strengthens. Dry conditions and sunshine are likely in most regions, but we could see valley cloud develop. Temperatures should rise with strong solar input. Winds are light from the north-northwest along the coast and moderate to strong in the Columbia’s and Rockies.
Day 5 – Sunday
The ridge continues to dominate most of the province but flattens enough to allow a system into northwest BC and the Yukon. The Yukon could see very strong winds and moderate snowfall. All other areas continue to enjoy sunshine, valley fog, and above 0 alpine temperatures.
Confidence: Good overall. The blocking high is well handled. There is some uncertainty about how warm it will be and whether or not we will see valley cloud and temperature inversions.
Overview Day 6 – 10
The blocking high (Omega block) is expected to remain in place resulting in continued dry weather and lots of alpine sunshine. Temperatures will likely be quite mild with generally light north-northwesterly winds. Valley cloud is pretty likely but could burn off during the day. The ridge could flatten enough on Tuesday and Wednesday to allow a weak system to slide into the northwest and the Yukon.
By Thursday and into Friday, there is surprisingly good agreement that the ridge will rebound and strengthen resulting in sunshine and warm temperatures for all regions.
Confidence: Good. Considering this is a long range forecast, models are in surprisingly good agreement. Probabilities of accumulated precipitation of over 10 mm for the entire period are very low, except for the North Coast.
Weather Outlook January 30, 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.
Overview Day 3 – 5:
A ridge of high pressure should bring dry, bright, and warm weather on Friday and Saturday to most parts of BC and western AB. A Pacific frontal system moves through on Sunday bringing moderate precipitation to the north and central coast, but only light amounts inland.
Day 3 – Friday
A strong ridge of high pressure centred over coastal BC will bring dry conditions (except for the extreme north of BC and the Yukon). Southern regions will be bright and sunny, while the North Columbias will be cloudy. Over the South Coast, alpine temperatures may creep above zero during the middle of the day.
Day 4 – Saturday
The ridge of high pressure still dominates BC. Dry conditions, light winds, plenty of sunshine. Temperature inversions, with valley cloud are likely in the Columbias. Alpine temperatures are likely to go above zero, particularly in the south.
Day 5 – Sunday
A Pacific frontal system moves in bringing moderate precipitation to the north and central coast, but only light amounts to the south coast and inland areas. Temperatures will cool to more seasonal values. Increased southwesterly winds will blow, particularly in areas to the north.
Confidence: The general pattern is well handled by the models. However, there is uncertainty in the timing of the frontal system – some models indicate it moves in a little earlier.
Overview Day 6 – 10
Initially an active weather pattern at the start of next week with southwest flow making enhanced precipitation amounts likely, especially for coastal areas. Currently, Monday and Tuesday look like the most likely days for stormy conditions.
By Thursday and into Friday, there is surprisingly good agreement from the models for a return of the high pressure ridge. Assuming this comes true (remember we’re at days 9 and 10 at this point), we’ll see dry, mild conditions with little wind for much of BC.
Confidence: Good. Considering this is a long range forecast, models are in surprisingly good agreement. Don’t hang your hat on anything here, though, especially the timing of events.
Weather 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.
Overview Day 3 – 5:
Gulf of Alaska low is driving an upper trough into the north coast. A weak default ridge ahead of the trough is positioned over the Columbias and Rockies. Northwesterly flow will cause temperatures to gradually drop throughout the period.
Day 3 – Friday
Patchy moisture embedded in the air mass will bring fairly cloudy conditions to all mountain regions. 10-15mm is expected over the north and central coast with trace amounts for the south coast, while a default ridge keeps the Columbias and Rockies relatively dry. Moderate westerly winds with seasonal temperatures.
Day 4 – Saturday
The upper trough is expected to move further south splitting the flow over BC. There are no organized systems, but continued patchy moisture and unsettled onshore flow with only coastal upslope precipitation expected. Light winds and continued seasonal temperatures, but generally cooling.
Day 5 – Sunday
A large wave ridge starts to build in the eastern pacific, which slowly veers the BC coastal flow towards west and northwest with an embedded poorly defined upper trough. Very light precipitation is expected primarily in westerly upslope coastal areas. Continued patchy disorganized moisture is expected with the split flow over the Columbias and Rockies. The south arm of the split flow is generally over Oregon and Washington but may clip the Lizard Range with enhanced precipitation.
Confidence: Good for general pattern as models tend to agree, but fair for timing of frontal systems as they are not well defined.
Overview Day 6 – 10
The long range pattern is dominated by the flat offshore stagnant ridge of high pressure. Active northwesterly flow with embedded disorganized systems is expected to continue through Wednesday. On Thursday and Friday the ridge shifts closer to the south coast bringing a milder and less active scenario. The east slopes of the Rockies should see very strong winds with no precipitation throughout the period.
Confidence: Good for the general pattern as the models are in good agreement. But uncertain precipitation amounts and timing; however, any precipitation is expected to be light.
Weather 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.
Overview Day 3 – 5:
Large scale ridge over the pacific persists with little to no precipitation and above normal temperatures. Above freezing layers and inverted temperature gradients, with associated valley cloud, remain possible but difficult to determine when and where; likely to be drainage dependant.
Day 3 – Friday
Ridge of high pressure rebuilding over the BC coast with sunny skies, continued mild temperatures and light winds. The Rockies and Columbias will be under a slightly cooler northwesterly flow with embedded patchy moisture that will bring near normal temperatures and cloud cover with very light precipitation possible the north.
Day 4 – Saturday
The ridge is flattening slightly allowing a system into the far north coast. At the same time arctic air will push south into the Peace region. This arctic front will bring light flurries to the eastern north Rockies. But the South Coast will continue to be mild and dry.
Day 5 – Sunday
Very similar to Day 4 - Saturday, but the ridge is building into BC bringing milder alpine temperatures again. A frontal system moving into the Alaska Panhandle will likely only result in cloud for the north coast. The arctic air mass remains centered in Saskatchewan resulting in very cold temperatures in Alberta, with light precipitation possible in the eastern slopes of the Rockies and perhaps even the Lizard Range.
Confidence: Good – the general pattern is clearly defined and simple to interpret.
Overview Day 6 – 10
The long wave ridge continues to dominate until Day 7 - Tuesday with mild/dry conditions.
There is poor agreement between models after that, but most models flatten the ridge to an active zonal pattern allowing some light systems into the north/central coast and north Rockies Wednesday or Thursday. And there’s very poor agreement on Friday.
Confidence: Generally good through Day 7 when the pattern starts to change. Deterministic models generally try to end blocking patterns early so it’s possible the forecast change back to a zonal flow could be delayed.
Weather 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.
Overview Day 3 – 5:
Large scale ridge over the eastern pacific has the looks of an Omega Block. Cold dry northerly flow where embedded disturbances are minor and confined to the coast and modified arctic air dominates inland regions.
Day 3 – Friday
Cold dry northerly flow. North Coast influenced by a mild system embedded in the pattern suggests it’s the only area likely to see significant cloud; all other regions should be sunny. Modified arctic air pushing into the Rockies toward the interior. North Shore mountains should see freezing level near surface.
Day 4 – Saturday
General pattern remains in place. Coastal areas could see a few cm of snow otherwise dry, little wind, sunny, and temps between -7 C coastal and -15 C North Rockies.
Day 5 – Sunday
Ridge builds further inland. Similar temperatures, no precipitation, little wind (except outflow Northwest Coastal), and lots of sun (exception is the NorthWest and valley cloud in the interior). Yes – think alpine inversions!
Confidence: Good – the general pattern is clearly defined and simple to interpret.
Overview Day 6 – 10
The general pattern described above is likely to continue through Thursday January 17. The most interesting parameter through this time seems to be strong temperature inversions with strong solar radiation in the alpine and valley cloud (and cold temperatures) below. The pattern might change starting January 17th with models suggesting a shift to westerly flow over the North Coast and North Rockies. Same models continue this pattern change on January 18th with almost a zonal flow setting up once again.
Confidence: Generally good through January 17th when the pattern starts to change. Deterministic models generally try to end blocking patterns early so it’s possible the forecast change back to a zonal flow could be delayed….
Weather Outlook, January 2, 2013
Prepared by: Penelope Goddard
Period
Day 3 – 5 is Friday, January 4 to Sunday, January 6.
Day 6 – 10 is Monday, January 7 to Friday January 11.
Overview Day 3 – 5:
A synoptic ridge over the BC coast is replaced on Saturday by an active series of frontal systems approaching from the East Pacific. The entire province should get some precipitation, with highest amounts on the coast and least in the SE corner, where the ridge may persist longer. Temperatures are mainly seasonal. Wind speed and direction will vary with the passage of the frontal systems, but winds are generally from the westerly quarter.
Day 3 – Friday
A ridge of high pressure over the BC coast brings sunny skies and valley cloud. A weak cold front is exiting the South Coast and Columbias, where light precipitation should taper off to be replaced by sunshine. Winds are light to moderate from the NW.
Day 4 – Saturday
The ridge moves east while a frontal system approaches the North Coast. The interior mountains should remain in the sun with valley cloud and no precipitation, while the North Coast will become increasingly cloudy and windy ahead of the approaching system. Light to moderate precipitation begins late in the day there.
Day 5 – Sunday
A weak upper trough moves inland, bringing light precipitation to all regions. Westerly upslope precipitation will also occur. The South Rockies and Lizard Range may be protected from the system by the remnants of the ridge.
Confidence: Good for the general active pattern but poor for the timing of frontal systems and precipitation amounts.
Overview Day 6 – 10
Days 6 and 7 remain very unsettled, with a westerly flow, windy and wet weather. Late on Day 7 (Tues 8 Jan), an abrupt change is expected when a cold front brings strong winds, a sharp temperature drop and snow, especially to the south coast. In the wake of the cold front will be NW winds, cooler temperatures, and drier air in the interior. Modified arctic air is expected in the North Rockies. On the coast, an onshore flow will continue to bring light orographic precipitation.
Confidence: Generally good, but the intensity of the cold front is uncertain. There is a possibility of an arctic outbreak towards the end of the period, but confidence is not high.
Weather 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.
Overview Day 3 – 5:
Mainly dry conditions will prevail across most forecast regions as an upper ridge sets up over much of the province. Interior areas will be influenced by the ridge and clear skies, valley cloud and temperature inversions should develop throughout the period. Strong diurnal temperature swings will also be noted. Intermittent light snowfall is possible in coastal areas, particularly in the north.
Day 3 – Saturday
A cold front exiting the province into Washington may bring mild moisture and moderate winds primarily to the south and coastal areas. By the end of the day, most of the province should be well under the influence of the drying ridge.
Day 4 – Sunday
The upper ridge should become well-anchored over most of British Columbia with light winds, valley cloud, possible temperature inversions, and strong diurnal temperature swings for most regions. The exception may be the North Coast which may see increased southwest winds and light snowfall.
Day 5 – Monday
The dry upper ridge will compete with a more moisture laden trough which may bring light snow and increased southwest winds to coastal areas. The north coast should see the brunt of the precipitation. Most of the interior should remain protected by the ridge staying dry.
Confidence: Good for the overall pattern. Fair for specific snowfall amounts along the coast.
Overview Day 6 – 10
On day 6 and 7 the ridge appears to remain well established over the province; however, on day 8 the pattern erodes somewhat as a more moist zonal flow seems to develop. On days 9 and 10 all bets are off on the overall pattern in that there seems to be greater model disagreement. What I can tell you is that snowfall and wind should be minimal in most areas with generally seasonal temperatures. Light snow accumulations and increased winds are most likely in the Northwest.
Confidence: Relatively good for day 6 and 7. Diminishing on days 8-10.
Weather Outlook: December 5, 2012
Prepared by: Peter Marshall
Period
Day 1 – 3 is Thursday December 6 to Saturday December 8.
Day 4 – 6 is Sunday December 9 to Tuesday December 11.
Day 7 – 10 is Wednesday December 12 to Saturday December 15.
Overview Day 1 – 3:
In general, an unstable westerly (zonal) flow establishes. Weak disturbances are embedded in this fast paced flow regime, bringing light precipitation to most westerly upslope areas with subsidence breaks in east slope areas. Ridge top winds should be generally moderate from the west and temperatures should be near normal or slightly below normal for this time of year.
Day 1 – Thursday
Light precipitation for the South Coast and Interior regions, with little or no precipitation for the Rockies. The Northwest could see moderate precipitation. Winds are generally moderate from the SW-NW. East slope areas should see sunny breaks.
Day 2 – Friday
No organized system but the unstable westerly flow continues. Light precipitation expected for westerly upslope areas of the coast and interior. Ridge top winds remain moderate from the W-NW. Temperatures are cool with freezing levels at the surface (except S. Coast ~ 800m).
Day 3 – Saturday
The flow veers to a more northwesterly direction. The Interior and Rocky Mountains should remain relatively dry and cool with sunny breaks. A frontal system may hit the coast on Saturday afternoon and into Sunday bringing strong W-NW winds, moderate to locally heavy precipitation, and rapidly rising freezing levels.
Confidence Day 1 – 3:
Fair. It is a very fast moving flow pattern which makes it difficult to predict the timing of the disturbances and weak ridges. Precipitation amounts may also be higher than forecast.
Overview Day 4 – 6:
There is a brief interruption the flow pattern on Sunday as a more organized frontal system pushes through. The flow should revert back to northwesterly in the wake of the system. We should see a series of weak disturbances imbedded in the northwesterly flow bringing light precipitation and slightly cooler than normal temperatures.
Day 4 – Sunday
A frontal system should push through the province on Sunday. Winds should be strong to very strong from the NW and freezing levels along the coast could jump to 2000 m in the south and 1600 m in the north (staying cooler inland). Precipitation amounts should be greatest along the coast and northern interior.
Day 5 – Monday
The flow returns to northwesterly. Temperatures should begin to drop. Continued light precipitation and moderate NW winds.
Day 6 – Tuesday
A slightly stronger system could slide down the coast bringing moderate precipitation and briefly rising freezing levels to coastal regions, and light to locally moderate precipitation to interior regions.
Confidence Day 4 – 6:
Fair. There is pretty good agreement in the overall flow pattern, but there is some uncertainty about the timing and intensity of the systems embedded in the fast moving flow pattern.
Overview Day 7 – 10:
The flow pattern should remain northwesterly resulting in cool temperatures with a series of weak systems or disturbances and brief ridges pushing through. Snowfall amounts should be generally light. The pattern may change near the end of the period (day 9-10) as models suggest a more northerly flow or Arctic outbreak scenario (cold and dry). It’s a bit far out to bank on this, but this will be something to keep an eye on.
Confidence Day 7 – 10:
Fair. There is good model agreement that we should see below normal temperatures and near normal precipitation amounts for this period.
Weather Outlook, April 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.
Overview Day 3 – 5:
An active pattern is expected, but with only weak systems. The most intense disturbance (for the entire 10 day period) arriving Thursday (Day 2) and moving through interior BC on Friday (Day 3). A Gulf of Alaska Low is the primary feature driving the weather pattern through Day 5.
Day 3 – Friday
Jet is over southern BC propelling systems along. Specifically, yesterday’s disturbance should get pushed out of the Columbia Mtns. and SE British Columbia. A trailing cold front suggests convective showers. North Coast could also see some western upslope convective precipitation.
Day 4 – Saturday
Gulf of Alaska Low sets up a SW flow but a surface ridge should keep most regions dry with only minimal afternoon convective precipitation possible. Generally light wind with moderate winds possible in the Rockies. A system approaching the South Coast is not likely to arrive until overnight or Sunday.
Day 5 – Sunday
A weak system for the South Coast under a warming SW flow. Clouds should limit warming (and freezing level) on the coast. The SOLAR input in the interior could bump freezing levels to 2700m.
Confidence: Good
Overview Day 6 – 10
Ensemble forecast 546hPa Spaghetti Plots show no agreement regarding system positioning. At first brush they suggest such high disagreement as to be worthless. However, further analysis allows four important conclusions for this extended period:
Confidence: Good
Despite a nearly chaotic pattern for position of systems, good agreement for only weak systems overrides this limitation resulting in good overall confidence.
Weather 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.
Overview Whole Period:
Enhanced precipitation for eastern upslope areas of the southern interior is expected for Friday. High pressure and generally good weather is anticipated for the weekend for all areas. Next week is likely to start out dry and then transition into a series of low intensity storms from Wednesday to Friday.
Medium Range: Day 3 to 5
Overview
An unusual storm tracking northwards with easterly winds will bring considerable amounts of precipitation to eastern upslope regions of the interior on Friday. The highest intensity will be seen in a zone from Jasper to the US border. A ridge builds on Saturday, bringing more settled weather and some sunshine for the weekend.
Day 3 - Friday
A broad upper low centered initially over the northeastern US tracks north into central Alberta and influences the weather over the whole central interior for Friday. Moist air combined with easterly winds will bring generally enhanced precipitation to eastern upslope areas, particularly the Rockies from Jasper to the US border, but also affecting the Selkirks, North Monashees and possibly the Cariboos and North Rockies. Local hot-spots with more dramatic precipitation (20-30 mm) are possible but difficult to forecast. Most likely candidates: areas around Castle, Fernie, Golden, Banff. Freezing levels generally 1500-1800 m. (close to seasonal norms).
South/North coast most likely receive trace to light amounts.
Day 4 – Saturday
A transitional day, with lingering moisture that is gradually being driven out by a broad ridge building over the whole of western Canada. Calm winds. The clearest skies and highest temperatures (freezing level up to 2000 m) likely to be over the South Coast.
Day 5 – Sunday
A broad ridge lies over western Canada bringing generally dry conditions with some cloud but likely good periods of sunshine pretty much across the board. One exception is the Yukon, which may see some low-intensity precipitation around the Pine Pass area.
Confidence: Day 3 to 5
Good confidence with the large-scale weather features and the general pattern and timing. Poor confidence for the localized hot-spots of enhanced precipitation in the southern interior for Friday.
Long RangeDay 6 to 10:
Overview
The ridge that develops over the weekend will likely persist into the first half of next week, keeping the weather initially mostly dry. Winds may pick up a little as the slack zone left behind as the previous low pressure system dissipated to the north is replaced with a more conventional westerly flow pattern.
By mid-week, a transition to a series of low-intensity storms is the most likely scenario. This could happen for coastal areas by Tuesday and for interior areas by Wednesday. Best indications are precipitation will be light, possibly moderate at times. It is unlikely any area will see a significant storm or significant accumulations through the period. Temperatures are likely to be close to seasonal norms for all areas.
Confidence
Fair. Models diverge for Tuesday and Wednesday, but it is most likely a timing issue, rather than a change to the overall expected pattern.
Weather 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.
Overview Day 3 – 5:
It looks like a stagnant and inactive period that is dominated by a ridge of high pressure off the BC coast and an upper level low off the coast of Oregon. Most areas should see a lot of sunshine, light winds, and gradually rising freezing levels. We should continue to see good overnight recovery throughout the period.
Day 3 – Friday
Northerly flow keeps temperatures relatively cool. Sunshine for most areas with the exception of light convective precipitation in the South Coast and the central/southern Rockies.
Day 4 – Saturday
The flow remains northerly but weakens. All regions should see sunshine with the potential for instability and light precipitation in the eastern Rockies.
Day 5 – Sunday
The flow switches to southerly bringing in milder air and rising freezing levels (~2000m). The South Coast could still be influenced by the offshore low but any precip would be light.
Confidence Day 3 – 5:
Good overall. The greatest area of uncertainty revolves around the South Coast and how much cloud cover there will be. Any precipitation should be very light.
Overview Day 6 – 10:
The pattern should remain very similar with a blocking type of scenario. Most areas should see a significant amount of sunshine, particularly in the northern regions. Winds should remain light. The flow is increasingly southerly, meaning freezing levels should gradually climb. There is potential for substantial warming for the second half of the week with warm and dry air invading from the south. The South Coast may continue to see some cloud and light precipitation, but strong systems remain unlikely.
Confidence Day 6 – 10:
There is good confidence that we should see little or no precipitation, light winds, lots of sunshine, and relatively mild temperatures. It might feel like spring!
Weather Outlook: March 28, 2012
Prepared by: Peter Marshall
Period
Day 3 – 5 is Friday March 30 to April 1.
Day 6 – 10 is Monday April 2 to Friday April 6.
Overview Day 3 – 5:
An upper level low over the Gulf of Alaska pushes a moist westerly/southwesterly flow onto the BC Coast. Most of the energy is focused just south of the border but southern regions should see light to moderate precipitation with brief breaks between pulses. Temperatures remain slightly below seasonal with a slight cooling trend into the weekend. Northern regions should see convective precipitation with a greater potential for prolonged solar radiation.
Day 3 – Friday
An approaching system should affect the South Coast and S Interior with light to moderate precipitation and moderate winds. The NW and N Interior should see patchy convective precipitation.
Day 4 – Saturday
An offshore trough and southwesterly flow may bring a system into southeastern BC. The South Coast could see some spill over from this system. North should be dry.
Day 5 – Sunday
A weak system may affect the South Coast with ridging over the Interior resulting in the potential for some clearing. Another stronger system is forecast to hit the South Coast later in the day. A low over central Alberta may result in an upslope snow event in the Central and Northern Rockies.
Confidence Day 3 – 5:
Fair to poor. There is reasonable agreement that most of the energy will be directed at the southern regions, leaving northern areas relatively dry with more potential for sunshine. If the track of the systems pushes a little further north (particularly on Friday) we could see heavier precipitation and stronger winds for most regions.
Overview Day 6 – 10:
There is a great deal of uncertainty in the long range forecast this week. Perhaps it’s best to try and draw out what we most likely won’t see. It doesn’t look like we will see a strong ridge forming and giving us widespread sunshine. There is also no indication that we will see a very pronounced and strong storm track affecting the province. This would suggest a continuation of the previous week with patchy convective precipitation, weak systems affecting the southern regions, and relatively dry conditions in central and northern BC. We could see a more southerly flow resulting in slightly warmer temperatures for the week.
Confidence Day 6 – 10:
As mentioned, there is low confidence in the details but reasonable certainty that we won’t see any weather extremes.
Weather 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
Overview Day 3 – 5:
Main feature for the period is an upper Low off Washington/Oregon coast creating a slight blocking pattern, almost a split flow in the Jet, and a default ridge over BC. This supports a cool pattern, rising afternoon freezing levels with solar radiation, and overnight freezing. No significant wind. Dry conditions with the S Rockies the only exception with lingering cloud and light snow more likely.
Day 3 – Friday
Northern areas set to be the sunniest as the ridge is aligned almost East-West on a line from Terrace to Prince George.
Day 4 – Saturday
East-West ridge slumps south allowing a light westerly wind over NW and N Rockies regions; no flow over the southern ½ of BC. Lingering cloud in the S Rockies.
Day 5 – Sunday
S Rockies joins the rest of southern BC with sunshine. In the NW region, the light westerly wind carries in a weak wave with some cloud and a little bit of precipitation.
Confidence Day 3 – 5:
Good for the general pattern. Uncertainty is focussed on solar radiation and freezing level; a small change in cloud cover could bump temperatures, especially on south facing slopes.
Overview Day 6 – 10:
The period starts with the same pattern as the weekend described above. It finishes with a more active, progressive pattern. The big question is when the transition happens: models suggest Tuesday but human interpretation of the models is to delay the shift to Wednesday, maybe even Thursday. The new regime that comes in looks like a SW flow carrying systems with moderate precipitation and moderate to strong southerly wind, aimed at the South Coast (North Shore/Sea 2 Sky in the bull’s eye). The coast should wring out most of the moisture so current thinking is that the interior will only see light precipitation which should be confined to South Columbia, Kootenay-Boundary, and Lizard-South Rockies. My guess is that freezing level will be near or slightly below treeline in the southern interior.
The North West, North Columbia, North Rockies should escape the systems so I’m thinking the most likely scenario is a mix of sun and cloud, light to mod SW wind, trace of precipitation, warmer temperatures but still a daily pattern of afternoon warming and overnight freeze.
Confidence Day 6 – 10:
Good for the general pattern to a more active SW flow; the uncertainty is whether this tranition is delayed to Wednesday or even Thursday.
Weather Outlook, March 14, 2012
Prepared by: Karl Klassen
Period
Day 3 – 5 is Friday, March 16 to Sunday, March 18.
Day 6 – 10 is Monday, March 19 to Friday, March 2.
Overview Day 3 – 5:
Main feature is Gulf of Alaska low. Spring-like conditions with strong diurnal temperature fluctuations especially in the interior, where clearer conditions allow overnight cooling and daytime solar heating. Any weather that does occur will be focussed on the South Coast and border regions. Potential for upslope event on the Alberta side of the southern Rockies on the weekend. Fairly major disagreement on track of Friday’s system.
Day 3 - Friday:
Broad upper trough over Gulf of Alaska with jet stream south of the province. Seasonal/slightly cool, unstable airmass under a light southwesterly flow over BC. Disorganized but persistent upslope precipitation over coastal regions. Weak ridge over interior with more or less benign convection. In the far north, local convective flurries producing light accumulations in White Pass but dry, cool, with sunny breaks farther inland.
Day 4- Saturday:
Upper trough digging along coast, driving weakening upper low over south coast and into SE late in the day. Outside of South Coast, more stable and less convective. Up north, White Pass cloudy but dry, with ridging inland and continuing mix of sun/cloud with light winds.
Day 5 Sunday:
Cooler upper trough moving over BC coast. Remnants of an upper low moving onto North Coast and over north Rockies. Weak ridge elsewhere. White Pass sees nil significant precipitation with convective cloud due to daytime heating and little wind while inland weather remains benign.
Confidence Day 3 – 5:
Fair due to disagreement in models on track and intensity of the low on Friday. GFS puts it on the South Coast then driving along the border. NAM has it at WA/OR border, then brushing the SE corner of BC.
Overview Day 6 – 10:
Gulf of Alaska low maintains a trough throughout the period. Active scenario for the south. The trough moves gradually south bringing predominantly SW winds and temperatures near/slightly below seasonal. Spring-like diurnal temperature fluctuations.
Monday:
Good agreement on late day system coming into South Coast. Ridging and sunny for all eastern areas.
Tuesday:
Upper trough moving south pushes a system along the coast. Position highly uncertain, could hit south BC coast or might end up south of the border. Convective showers in most areas. Possible moderate late day accumulations in SE corner as Monday’s low moves east.
Wednesday:
Slightly milder air enhancing diurnal temperature swings. No major system expected. Possibly a bit of snow in SE corner as cold front exits the province.
Thursday/Friday:
Models disagree on systems but regardless of what happens, expect a southerly flow to bring warmer temperatures into the southern regions.
Day 6 – 10: 24 Hour Precipitation Probabilities
Chance of precipitation accumulation exceeding 10mm in any 24 hour period:
Chance of precipitation accumulation exceeding 25mm in any 24 hour period:
Day 6 – 10: Total Precipitation Probabilities
Chance of total precipitation accumulation for Day 6 – 10 exceeding 10mm:
Chance of total precipitation accumulation for Day 6 – 10 exceeding 25mm:
Chance of total precipitation accumulation for Day 6 – 10 exceeding 50mm:
Confidence Day 6 – 10:
Good for Day 6. Good for general pattern Day 7 – 8 but fair at best for timing/track of systems. Poor for Day 9 and 10.
Details Day 3:
I can't put graphics into this blog. I've put this outlook with graphics here.
We are unable to prepare a weather outlook this week due to high workloads and staffign issues. one of our forecasters is stuck in the field due to high avalanche hazard--ironic isn't it?
Weather 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.
Overview Day 3 – 5:
The large, stationary high pressure system anchored over the eastern pacific for the past month is moving on. Its effect was to effectively weaken incoming storms, turning them into minor systems, primarily affecting coastal areas. An ative storm pattern, including a semi-pineapple fire hose is forecast to point toward BC this weekend.
Day 3 – Friday: Eastern Pacific ridge progresses east over BC. Jet stream should be positioned over north & central coast in a west, southwest orientation. A weak upper warm front moving over the south/central coast and interior overnight. Less than 10cm snow, warmer but below zero temperatures, moderate SW winds for all regions from this system.
Day 4 – Saturday: The big upper ridge builds stronger pulling in warmer temperatures into all southern and central areas with a SW flow. The slow moving warm front continues to move east with light precipitation (moderate upslope west side of the Columbia Mtns.) The jet stream/polar front aimed at central coast where moderate to heavy precipitation is forecast, including southern parts of the north coast and northern parts of the south coast. Wind should be cranking up from the SW in the mtns (W or NW flow aloft). Chinook pattern starting in the east Rockies.
Day 5 – Sunday: Pattern is almost a semi-Pineapple / Chinook scenario. Moisture feed isn’t quite sub-tropical though. Focus is central/south coast across to the Cariboos & N Rockies (Alta Elbow). An active day with moderate to heavy precipitation on the coast and North Columbia. Little precip in the Southern Interior and South Rockies. Moderate SW winds. Freezing level approaching treeline is possible. Watch for an easterly upslope developing in the northern rockies (e.g. Kakwa).
Confidence: Good
Overview Day 6 – 10 Mild SW flow pattern changing back to cooler seasonal temperatures and not that active. Beyond Day 7 ensemble & deterministic models widely divergent: GEM suggests ridging, GFS indicates zonal flow, Ensembles show a trough.
Day 6, 7: Day 6 suggests a weak flow, cooler, and limited convective precipitation under a cool trough. Day 7 shows the flow becoming more NW flow and a ridge pattern. Seasonal temperatures, little wind, more solar radiation, and 5 – 10 cm of convective snow showers possible.
Day 8 – 10: Can’t say much other than no major warming (pineapple) and no major cooling (arctic outbreak); no major wind (light to moderate, likely from the W or NW). Other than that, little is knownable at this time.
Confidence: Low Weather models provide little long-term guidance.
Weather 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.
Overview Day 3 – 5:
Stormy Friday, then cooling off a bit and drying out over the weekend.
Day 3 - Friday:
Strong upper trough/low moving over entire BC coast and Columbias from the west/northwest. Moderate accumulations over south and central coastal areas and light over the north coast. Light to moderate accumulations for west Columbias and north Rockies. In coastal regions, strong surface winds and moderate/strong outflows. Alpine winds moderate/strong over the central areas of the province and light/moderate over the south.
Day 4- Saturday:
Upper low weakening and becoming a broad upper trough as it moves over southern BC. Patchy moist airmass in trailing NWly flow. Scattered upslope precipitation for coastal areas and west Columbias. Light convective precipitation mostly in Columbias.
Day 5 Sunday:
Transient ridge delivering a NWly flow of dry, cool air (borderline arctic for the north and Rockies). Unsettled airmass remains in the far south with light NW winds.
Confidence Day 3 – 5:
Good, although successive model runs have moved Friday’s trough a bit farther north each time so watch location of the low carefully.
Overview Day 6 – 10:
Steady persistent zonal flow. Seasonal temperatures with moderate upper winds from the west. No strong systems.
Monday:
Zonal flow establishes, weak system of light to moderate intensity likely.
Tuesday:
Zonal, unsettled, seasonal/slightly above seasonal temps.
Wednesday:
Jet over border region or south of border. Some uncertainty but looks like a weak system for south coast and south Columbias.
Thursday/Friday:
Models disagree on trough/ridge timing and intensity but general agreement that no significant storms will occur.
Day 6 – 10 24 Hour Precipitation Probabilities
Chance of precipitation accumulation exceeding 10mm in any 24 hour period:
Chance of precipitation accumulation exceeding 25mm in any 24 hour period:
Day 6 – 10 Total Precipitation Probabilities
Chance of total precipitation accumulation for Day 6 – 10 exceeding 10mm:
Chance of total precipitation accumulation for Day 6 – 10 exceeding 25mm:
Chance of total precipitation accumulation for Day 6 – 10 exceeding 50mm:
Confidence Day 6 – 10:
Good for overall zonal pattern. Fair to poor for timing of weak systems. Poor for timing and track of systems after Day 7.
Details Day 3 – 5:
I can’t include graphics in this blog post. Check here for the full text with graphics.
Weather 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.
Overview Day 3 – 5:
Large stationary H pressure system over the SE Pacific is the bully dominating the weather through Day 5, and even through the foreseeable future. Disturbances arriving onshore are best understood in the context of riding over this ridge and along the downside – all the while weakening and breaking apart. They look impressive but won’t amount to much.
Day 3 – Friday.
The big high extends to Aleutians and Yukon, but between these arms an upper level cold-trough is approaching. When it hits, it only looks like light to moderate wind and 10-15 mm to the S Coast bulls-eye. Less intensity further north along the coast. Probably won’t arrive on the coast till late Friday or more likely Saturday. So generally a ridge dominates all regions in the morning, in the interior the H continues all day.
Day 4 – Saturday
Yesterday’s cold-trough should continue on its track SE and affect the interior. It’s weakening so probably a story of mid-level cloud, light to moderate wind, and light precipitation for westerly upslope areas. The big ridge rebuilds quickly so clouds should break up.
Day 5 – Sunday
Ridge looks to rebuild with NW upper flow and W mid-level flow. The only place significant wind is expected is NW & N Rockies. Expecting a slight cooler (seasonal) & drier airmass so clearing trend across the province (the exception might be N coast). The clearing means solar warming during the day.
Confidence: Good
Overview Day 6 – 10
The general pattern continues and only slowly evolves. Precipitation amounts remain modest and confined to the coast. The coast may see 50 mm over the five days, in the interior 25 mm is unlikely during the period.
Day 6, 7: the “jet” should reappear over BC (but isn’t really very jettish). That big stationary H offshore from California creates a big long arching ridge in the nearly zonal flow. The ridge is long and flat so systems can override it, but as they’re carried along they’re set to weaken and dissipate. Storm track appears to go from N coast through the Columbias and along the Rockies into Alberta. Wind and mild Chinook warming on the down-slope of the Rockies in Alberta is likely in this pattern.
Day 8 & 9: A transition period with increased weather forecast uncertainty. Still looks like weak systems on the coast, weaker inland it’s just hard to tell where they track. Most likely is N Coast>>N Col>> Rockies; but could be further S or further N.
Day 10: ensemble forecasts converge again and show that the Ridge has retrogressed slightly west and gained amplitude. Looks like a NW flow for most of BC, possibly with a warm::cold boundary somewhere near the coast. Looks like a coolish, dryish pattern for most areas (inland). Yukon (White Pass) is where the storm track points.
Confidence: Good Days 6 & 7, Fair Day 8 & 9, improving (F to G) Day 10
It seems most of the uncertainty surrounds the location of the storm track, not the intensity of the systems.
Weather 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.
Overview Day 3 – 5:
A well-established ridge, which has dominated the weather for the last week, maintains its position over Alberta and BC. An upper split flow leaves most of BC in slack air, with minimal wind and fairly static weather. Systems approaching the coast will have very limited impact as they are weak and fighting a losing battle against the ridge. They should only bring cloud cover and small amounts of precipitation, mainly isolated to the coast. Temperatures will be near seasonal with relatively minor diurnal variation. Freezing levels will be slightly above the surface.
Day 3 – Friday
A ridge sits over Alberta and northern BC. A southerly flow over the BC coast changes to a split flow by evening due to the influence of an embedded cutoff low in the Pacific. The low brings a little moisture to the south coast but soon fizzles. A weak warm front leaves a few cm of snow in the north Rockies. Solar radiation will be low, especially near the coast. Winds will be light south-westerly.
Day 4 – Saturday
A well-developed split flow (reminiscent of classic El Nino patterns) causes benign winds. Skies will be mostly cloudy, especially in the south where an unthreatening moisture blob associated with the weakening low exists. Some sunshine and more pronounced diurnal temperature change is possible in the north. Temperatures will be near seasonal.
Day 5 – Sunday
An upper trough approaches from the eastern Pacific and impacts the coast with only light snowfall. It hits the north coast by afternoon and the south coast by evening. Very light westerly upslope precipitation is expected in the Columbias. Winds near the coast will increase and become southerly.
Confidence: Good, except freezing levels are hard to pinpoint.
Overview Day 6 – 10
The pattern will change from a split flow to a ridge, which effectively means a continuation of inactive weather. The tilt of the ridge brings a northwesterly flow which will cool temperatures to slightly below seasonal in the interior. Coastal temperatures will be slightly above seasonal due to sunshine. Winds are expected to be light. Valley inversion cloud may form in the interior.
No dramatic weather is anticipated for the entire week.
Confidence: Good
Deterministic & Ensemble models agree from Day 7-10. On Day 6 there is disagreement about the timing of the change from a split flow to the dominance of the ridge. However, the timing of this change will have little impact on the weather.
Weather 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.
Overview Day 3 – 5:
Last of the weak upper disturbances moves through BC; start of what’s likely to be the driest pattern of this winter, drier than any period last winter. Temperatures warmer than seasonal. How warm is difficult to put numbers on but something like South Coast 2000m, North Rockies 1200m, Southern Interior 1500m, and North Coast 1000m. Friday should help calibrate temperatures for the next few days.
Day 3 – Friday
Stable pattern, somewhat similar to a Rex Block, with a huge long-wave ridge extending from the Pacific to the Atlantic oceans. A couple of minor short-wave upper troughs approaching the coast. Warm southerly flow, strong solar radiation, temperature inversions likely, especially overnight. Valley cloud and strong diurnal temperature swings at low elevations.
Day 4 – Saturday
The weak upper trough moved over the N Rockies, but expected to weaken as it runs over the ridge so not much oomph left, mostly it means cloudy. The rest of the province should be under sunshine (solar component) or valley cloud. Light southerly winds, so light that inversions are supported. Temperatures warm. North Coast, White Pass on the edge of this general pattern.
Day 5 – Sunday
Ridge retrogrades to the west and amplitude builds, all the way to the north slope of Yukon & Alaska. Still a light southerly wind with sub-tropical feed, still moisture kept off-shore, still strong solar radiation, still valley fog. It even looks like the North Coast is in the same pattern.
Confidence: Good
Overview Day 6 – 10
The entire area, for the entire period, looks warmer than seasonal. It also looks dry, very very dry.
North Coast may be slightly moister than the South Coast, and the White Pass may be slightly moister again. There is essentially zero evidence to suggest any significant precipitation anywhere. Iff the flow veers to the SW, and there’s a system embedded in it, the White Pass could get hit on Day 10.
The general pattern continues: strong solar radiation, very little Southerly wind, inversions with valley cloud, strong diurnal temperature swings at low elevations, warm temperatures.
Confidence: Good
Deterministic & Ensemble models agree: no significant change until Day 10 when models start trying to move the ridge out. Typically models try to change blocky patterns too fast.
Weather Outlook, January 25, 2012
Prepared by: Karl Klassen
Period
Day 3 – 5 is Friday, January273 to Sunday, January 29.
Day 6 – 10 is Monday, January 30 to Friday, February 3.
Overview Day 3 – 5:
Warm. Becoming very wet on the North Coast. Lesser amounts inland in the North and in southern regions.
Day 3 - Friday:
Upper low over Beaufort Sea and broad upper ridge off California driving a strong W/NW flow into northern regions with a system exiting the N Coast and moving into N Rockies. This flow is moderate in central regions. Southern third of BC/AB protected by ridge. Seasonal to slightly above seasonal temperatures.
Day 4- Saturday:
Ridge builds northward bringing milder coastal temperatures. Significant warm/wet system hits North Coast. South Coast and interior milder, less windy, and protected from precipitation by ridge. Potential for moderate Chinook in N Rockies. Models show very high freezing levels the N Coast; these seem unrealistic and have been reduced in the tables. Something to watch though….
Day 5 Sunday:
Ridge retreats southward. Trailing cold front from system that hit the NW yesterday slides SE across South Coast and Columbias/Rockies. Southern regions see increased wind and precipitation. Most areas now in mild SW flow.
Confidence Day 3 – 5:
Good for general pattern and timing. Fair for freezing levels and southern extent of precipitation on Saturday.
Overview Day 6 – 10:
Warm for the entire period.
Monday/Tuesday:
Zonal (westerly) flow but uncertainty about timing and intensity of systems. Above seasonal temps.
Wednesday:
Flow gradually shifts to SW as ridge builds into western regions. North Coast could see some weather but warm and dry in the south and interior.
Thursday/Friday
Mild SW flow as ridge builds and then becomes centred on BC. Warmer. A system might just brush the NW region but the rest of the province gets lots of sun, warm temperatures and little wind.
Chance of precipitation accumulation exceeding 10mm in any 24 hour period is 80%+ in all coastal mountains, 40-50% in the Columbias and 20% in the SE. Chance of over 25mm in any 24 hour period is zero in all interior and inland coastal regions, 20-40% in the southern coastal ranges, and 50% central/80-100% north coast.
Chance of total precipitation accumulation for Day 6 – 10 exceeding 10mm is near 100% in all areas except 50% in SE. Total precipitation amounts of more than 25mm is near 100% in all coastal mountains and 30-60% inland coastal and Columbias, less than 30% in N Rockies and SE. More than 50mm is zero chance in all inland coastal and interior areas, 50% in the South Coast, 60-70% in the central coast, and near 100% in the north coast.
In all cases, the precipitation noted above will almost certainly arrive early (Monday/Tuesday).
Confidence Day 6 – 10:
Fair for Day 6/7: zonal flow looks pretty certain but poor agreement on position/timing of ridge/trough features. Good for Day 8 – 10; good agreement in ensemble and deterministic models.
Details Day 3 - 5:
Graphics are hard to post in this blog. You can view the entire original document with graphics here.
Weather 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
Overview Day 3 – 5:
The cold, clear, dry pattern that’s dominated BC is coming to an end. Friday & Saturday are stormy transition days. The new pattern beginning Sunday is a west or southwest flow across BC & Alberta with embedded alternating bands of ridges and systems.
Day 3 – Friday:
Cold NW flow is moving out to the north and east. An upper Low in the Gulf of Alaska sets up a SW flow across BC & AB. That means warm air hitting the coast and overriding any remaining cold air in the valleys. South & Central coastal areas should see moderate to heavy precipitation, especially overnight Friday into Saturday. Freezing rain possible.
Day 4 – Saturday:
Disturbance moves inland as a warm front across the Columbia Mtns and through the Rockies during the day. A trailing cold front should be over the coast in the morning and the interior by afternoon. Precipitation in the interior expected to be widespread from the US border to the North Columbia & North Rockies. The cold front will have strong winds and convective precipitation.
Day 5 – Sunday:
Upper Low sits over the Gulf of Alaska setting up a light to moderate westerly flow across BC. This flow is expected to carry alternating bands of ridges (dry) and disturbances (precipitation) across the south and central parts of BC every day or two. Jet stream to our south so staying seasonably cool. No Chinook in Alberta. Sunday looks like a ridge over the interior with light localized upslope precipitation.
Confidence Day 3 – 5:
Good for pattern change & timing. Fair for snowfall amounts, especially coastal regions.
Overview Day 6 – 10:
The pattern for the entire period is quite zonal – that is a more or less westerly flow with embedded systems every day or two. Jet stream stays south so generally seasonal temperatures expected; the exception is the Wed/Thursday system which looks warmer (say 16 - 1700 m freezing levels). Most systems passing to the south of BC so precipitation confined to southern parts of the province: south coast, west side of columbias, west side of rockies. If storm track shifts further south, watch for upslope on east side of Rockies.
In any single day, storms could bring more than 10 mm to the Columbia Mtns, and more than 25 mm to the South Coast.
During the entire 5 day period much of the province should get more than 10 mm, the Columbia Mtns should get more than 25 mm, and the South Coast should exceed more than 50 mm.
Confidence Day 6 – 10:
Good for general pattern although can’t get specific on timing or intensity of systems.
Weather 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.
Overview Day 3 – 5:
One more system passes through BC on the weekend before a transition to an extended cold, clear, dry spell.
Day 3 - Friday:
Cutoff upper cold low moves into the Gulf of Alaska. Default flat-ish ridge with SW/W flow over BC. Generally, a sunny day with seasonal temps. Looks like the polar front arrives on North Coast late in the evening with the onset of precipitation.
Day 4- Saturday:
Low opens into a trough and moves inland into BC/AB with a leading wave producing moderate coastal precipitation in the northwest and light/locally moderate precipitation elsewhere more so on the coast, light to moderate and gusty winds, and lowering freezing levels. Arctic air on the doorstep.
Day 5 Sunday:
Arctic temperatures arrive for the first time this year. Modified arctic air dips across the US border. The true arctic front looks like it lies from the BC/AB elbow to Smithers and westward. Temps plummet in the north and drop significantly in the south. Winds die out everywhere. Flurries or light snow may be occur with passage of the cold front and arrival of cold air.
Confidence Day 3 – 5:
Good for general pattern and timing. Fair for precipitation amounts.
Overview Day 6 – 10:
Arctic air dominates for the period. True arctic air looks to remain in the northern half of the province the whole period with modified arctic air in the south. Monday to Wednesday the whole province looks dry, cold, calm, and clear. Right now it looks like the 546hPa isobar aligns with the US border on Thursday. This brings the potential for some precipitation to the South Coast mountains and the inland border regions but this is far enough out that I wouldn’t bet on it.
Chance of precipitation accumulation exceeding 10mm in any 24 hour period is zero over most of the province, 50-70% in pockets of the south coast and inland border regions.
Chance of total precipitation accumulation for Day 6 – 10 exceeding 25mm is zero over most of the province, 40-60% in tiny areas of the extreme southern coast and teeny pockets of the inland border regions.
Confidence Day 6 – 10:
Good for Day 6 to 8. Good agreement in ensemble and deterministic models.
Good for general pattern, timing and intensity Day 9 – 10 but uncertainty position of the 546 and track of any potential systems; if it goes even a bit south of the current prognosis any weather late in the period will miss BC entirely.
Details Day 3-5:
It's difficult to include graphics in this blog. Check the original document with details for day 3 to 5.
