Mountain Weather Forecast

Valley Cloud Today Snow Tuesday

An arctic ridge of high-pressure continues to be the main attraction this morning with interior valley cloud, cold temperatures and light upslope snow for the Alberta Rockies.

However, as an upper trough swings over AB this morning, a north-south gradient over BC will ensue, where moisture will get squeezed out and snow over the Cariboos down to the Monashees will begin starting tonight. Tuesday looks most interesting over the interior along the north-south line which stretches from Muncho all the way down to Castlegar. Snowfall accumulations, while on the lower side at first glance, looks to be enhanced due to the cold inversions AND high snow to liquid ratios. This means fluffier snowflakes are likely, which can lead to higher accumulations than expected.

A pre-frontal trough will track over the Panhandle on Tuesday spreading snow to inland regions and higher terrain. However, it won't be until Wednesday once the strong cold front sweeps along the Northwest Coastal Ranges increasing snowfall intensity. The front will slide down to the South Coast Wednesday evening/night and spread snowfall to the South Coast and Sea to Sky.

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The 500 MB chart depicted above shows upper ridging over western Yukon, Northwestern Coastal Ranges, and down to the South Coast. However, any upper-level ridging over the North Rockies down to the border will weaken as deep cyclonic rotation over much of Central Canada and including the Prairies prevails.

Today the upper trough will rotate southward through the Northwest Territories and into northern Alberta, followed by Saskatchewan. This means a quasi-meridional (slow-moving north-south air mass) flow pushes colder air westwards into BC and strengthens the upper-level northwesterly flow.

Stepping forward into Tuesday a tight gradient between the upper ridge and the upper trough will become fully established from Muncho Lake down to the Monashees. Therefore cool air near the surface followed by slight moisture aloft will result in accumulating snowfall along the gradient.

On Wednesday we can see a shift in the pattern as by the time we get to Wednesday afternoon the upper-level flow over BC has switched to a warmer and more moist westerly flow. A deep frontal system will slide over the Northwest Coastal Ranges and progress southwards to the South Coast by Wednesday night.

Forecasts and graphics produced by the Meteorological Service of Canada (MSC)