Avalanche Forecast
Issued: Jan 19th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
jpercival,
Avalanche Canada
A period of high danger begins. Expect heavy snowfall and strong winds that will continue both Friday and Saturday.
Make very conservative travel plans and seek low-angle and low-consequence terrain as both the new snow and a buried weak layer combined have the potential to produce very large avalanches.
Summary
Confidence
Avalanche Summary
On Wednesday numerous reports from professional operations outline a myriad of notable both storm and persistant slab avalanche occurrences. These avalanches were reported as natural, explosive controlled, and some accidentally triggered by skiers. One noted avalanche was a natural very large ( size 3 ) that scrubbed down to the ground. Primarily these avalanches occurred between 1700 and 1800 m on north-aspect terrain with most being large ( size 2 or greater).
On Tuesday, several natural storm slabs were observed (size 1-2) from the alpine and treeline. Numerous wet loose avalanches were observed at lower elevations where the precipitation fell as rain.
As the incoming storm will continue to add both mass and new snow supply to already touchy conditions. Riders should exercise restraint and patience as the new and past storm instability requires time to settle and bond. Choose low-angle well supported terrain and avoid steep and wind-loaded areas at upper elevations. Keep in mind the potential for deeper instabilities to produce large and surprising avalanches that will run far and fast.
Snowpack Summary
Expected snowfall totals of 40 to 50 cm over the next 48 hours will add to 20-40 cm of recent reactive storm snow. At upper elevations, southerly winds are scouring windward areas and redistributing this storm snow into wind slabs in lee areas. Below 1000 m moist snow or a crust can be found at or near the surface.
A weak layer of surface hoar buried in early January is now down 30-60 cm. This layer is spotty in its distribution and is of greatest concern in sheltered and shaded openings at treeline.
Weak layers that were reactive over the Christmas and New Year's period have shown signs of bonding and gaining strength. These include a surface hoar layer buried on Dec 28 found 50 to 100 cm deep and a facet layer buried on Dec 23 found 70 to 120 cm deep.
Weather Summary
Thursday night
Cloudy with heavy snowfall, 25 to 40 cm of accumulation. Alpine temperatures slowly rise to -5 °C. Ridge wind southwest 50 km/h gusting to 75 km/h. Freezing level rising to 500 m.
Friday
Cloudy with snowfall, 15 to 25 cm of accumulation. Alpine temperatures slowly rise to -2 °C. Ridge wind southwest 75 km/h gusting to 100 km/h. Freezing level rising to 1500 m.
Saturday
Cloudy with snowfall tapering in the afternoon, 5-10 cm of accumulation. Alpine temperatures cool to -6 °C. Ridge wind southwest 50 km/h gusting to 70 km/h. The freezing level descends to 500 m.
Sunday
Cloudy with some clearing and very light snowfall, with trace amounts of accumulation. Alpine temperatures continue to cool with a low of -9 °C. Ridge wind northwest 25 km/h. The freezing level descends to the valley bottom.
SundayMore details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Dial back your terrain choices if you are seeing more than 30 cm of new snow.
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Problems
Storm Slabs
Storm slabs will grow in size and sensitivity as the snowfall and wind increase. Expect the deepest and most reactive slabs to exist in wind-loaded terrain at upper elevations.
Keep in mind that storm slab avalanches have the potential to step-down to deeply buried weak layers, resulting in large and consequential avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A series of storms are adding a significant load to buried weak layers in the upper meter of the snowpack. The primary layer of concern is a layer of surface hoar now buried 30-50 cm deep. This layer is spotty in distribution and is not present on the very western boundary of the region. Primarily the PWL is found inland and most likely to be a concern in sheltered and shaded openings around treeline.
The second layer is comprised of facets and in isolated areas surface hoar that was buried in late December. This layer is now down 70-120 cm. It has shown evidence of strengthening but remains on our radar as active loading continues.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 20th, 2023 4:00PM
