One more day of warm sunny weather before cool cloudy weather arrives. Avoid sun-exposed slopes on Wednesday.
Summary
Confidence
Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
TUESDAY NIGHT: Clear skies, light northwest wind, freezing level drops to valley bottom with treeline temperatures dropping to -3 C.
WEDNESDAY: Sunny with some clouds in the afternoon, light northwest wind with some moderate gusts in the afternoon, freezing level climbs to 2400 m with treeline temperatures reaching +2 C.
THURSDAY: Scattered flurries bring 5-15 cm of snow above 1500 m and light rain in the valleys, light southeast wind, freezing level around 1500 m with treeline temperatures around -3 C.
FRIDAY: Mix of sun and cloud with some isolated flurries, light wind, freezing level climbs to 1900 m with treeline temperatures reaching -1 C.
Avalanche Summary
Multiple days of above freezing temperatures resulted in widespread wet loose and wet slab avalanches on sun-exposed slopes over the past week. The most recent observations are from the Dogtooth Range on Monday, where several large wet slab and wet loose avalanches released. There was also a large wet slab avalanche reported near the Bugaboos on Saturday in this MIN report. There were also natural cornice failures triggered by warming over the past week, some as big as size 3.Â
You can still expect wet loose avalanches and cornice falls on Wednesday, but they will be less widespread and destructive than they were over the weekend due to the relatively cooler temperatures and thicker surface crusts.
Snowpack Summary
A surface crust will form overnight and then gradually break down with daytime warming. Dry snow may still be found in high north-facing terrain (above roughly 2300 m). While there have been no recent avalanches on buried weak layers, there are a few layers that could potentially be triggered during periods of intense warming or by a large cornice fall. This includes 30-60 cm deep crust layers from mid-March and the early November crust near the bottom of the snowpack.
Terrain and Travel
- Avoid being on or under sun exposed slopes.
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
- Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Problems
Loose Wet
Expect wet loose avalanches to run naturally when steep slopes are exposed to the sun. Activity will start on east-facing slopes in the morning, south-facing slopes throughout the day, and continue on west-facing slopes into the evening.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Cornices are large and fragile when exposed to the sun. Cornice falls are dangerous on their own and can possibly trigger avalanches on slopes below.
Aspects: North, North East, East, South East, South.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 21st, 2021 4:00PM
