Cool cloudy weather will make avalanche conditions safer. Be careful around cornices and the isolated areas where the snowpack isn't capped by a thick crust.
Summary
Confidence
Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
A shift to cooler cloudy weather as a cold front crosses the region on Thursday.
WEDNESDAY NIGHT: Increasing clouds, 40 km/h northwest wind, freezing level drops to 1400 m with treeline temperatures dropping to -3 C.
THURSDAY: Cloudy with some sunny breaks and isolated flurries bringing a trace of new snow, light north wind, freezing level climbs to 1800 m with treeline temperatures around -1 C.
FRIDAY: Mostly cloudy skies with some isolated flurries, flurries easing in intensity throughout the day, light southwest wind, freezing level climbs to 2000 m with treeline temperatures near 0 C.
SATURDAY: Cloudy with scattered flurries bringing 10-20 cm of snow, light southeast wind, freezing level climbs to 1800 m with treeline temperatures around -1 C.
Avalanche Summary
Warm temperatures over the past week resulted in widespread wet avalanche activity. The most notable activity was on Saturday where there was both widespread size 1-2 wet loose avalanches and a few larger and destructive (size 2.5-3.5) wet slab avalanches. The large wet slabs were mostly on south and west facing slopes. Avalanche activity has been on the decline since then with relatively cooler temperatures. A cornice fall triggered a large (size 3) slab avalanche on a north-facing alpine ridge in Glacier National Park on Tuesday.
The cooling trend will make wet avalanches problems less likely in the coming days, but brief periods of sun could still promote wet loose avalanches in isolated areas. The primary concern will be cornice falls.
Snowpack Summary
A dusting of new snow will sit above a thick surface crust. The upper snowpack has been undergoing a daily melt-freeze cycle, so with the cooling temperatures a hard crust will form everywhere except in high north-facing terrain where there still may be dry snow above roughly 2400 m. Brief periods of sun could break down the surface crust in some areas on Thursday.
There are no layers of concern in the snowpack, which has been melting and settling over the past week. Large cornices loom along many ridgelines.
Terrain and Travel
- When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
- Minimize exposure to sun-exposed slopes when the solar radiation is strong.
Problems
Cornices
Minimize your exposure below cornices. Cornice falls are dangerous on their own and can possibly trigger avalanches on slopes below.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Wet loose avalanches may occur on sun-exposed slopes. The weather forecast has uncertainty about whether there will be sunny breaks on Thursday.
Aspects: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Apr 22nd, 2021 4:00PM
