Avalanche Forecast
Regions: North Columbia.
The next storm system moves in on Tuesday. Watch for changing conditions and dial back terrain choices as new snow accumulates.
Confidence
Moderate - Uncertainty is due to the timing of the incoming weather system. Forecast snowfall amounts are uncertain.
Weather Forecast
Monday night: Mostly cloudy, isolated flurries with trace accumulations, light southwest wind, alpine temperature -9 C.
Tuesday: Cloudy, 15-25 cm of snow, light to moderate southwest wind, temperatures warming throughout the day with a high of -3 C in the late afternoon.
Wednesday: Cloudy, 20-30 cm of snow overnight and into the morning, moderate west wind, alpine high temperature -6 C.
Thursday: Mostly cloudy, isolated flurries with trace accumulations, light west wind, alpine high temperature -10 C.
Avalanche Summary
New snow and wind are expected to form a new storm slab problem as snow accumulates. Smaller, more reactive avalanches in the new snow have the potential to step down to a layer of buried surface hoar formed in late December producing large and destructive avalanches. Throughout the past week, avalanche activity on this weak layer has been widespread and large (size 2+) and from both natural and human triggers. Several of these avalanches have been remote-triggered.
Snowpack Summary
The incoming storm is forecast to bring up to 25 cm of snow to the region throughout the day on Tuesday with moderate southwest wind, forming a new storm slab problem that will need to be managed. Expect areas where the snow is being drifted by wind to more rapidly develop this storm slab problem.
Over the past week, a total of 60-100 cm of snow has buried a weak layer of feathery surface hoar and a hard melt-freeze crust on sun-exposed aspects. This layer continues to produce large avalanches across aspects and elevations. Small avalanches in the new snow have the potential to step-down to this persistent weak layer.
Terrain and Travel
- Watch for changing conditions today, storm slabs may become increasingly reactive.
- Dial back your terrain choices if you are seeing more than 25cm of new snow.
- Choose simple, low-angle, well supported terrain without convexities.
- Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Avalanche Problems
Persistent Slabs
A layer of surface hoar from late December is now buried 60-100 cm deep. This layer has produced many large avalanches across aspects and elevations with incremental loading from new snow and wind. Another round of snow and wind on Tuesday has the potential to bring this weak layer to it's tipping point and to create conditions for step-down avalanches.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 2 - 3.5