Wet loose avalanches become increasingly likely during the heat of the day. Back off slopes as the surface becomes moist or wet with daytime warming and avoid slopes with large cornices overhead.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
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MONDAY NIGHT: Clear / Light, southwest ridgetop wind / alpine low temperature -3 / Freezing level 1000 m.
TUESDAY: Mix of sun and cloud / Moderate, west ridgetop wind / alpine high temperature 1 / Freezing level 1300 m.
WEDNESDAY: Sunny / Strong, north ridgetop wind / alpine high temperature -4 / Freezing level 800 m.
THURSDAY: Sunny / Moderate, north ridgetop wind / alpine high temperature 0 / Freezing level 1300 m.
Avalanche Summary
Avalanche observations were very limited over the weekend. However, numerous naturally triggered wet loose avalanches and cornice failures likely occurred given the very warm weather. Natural avalanche activity will likely decrease as the temperatures cool.
Several naturally triggered wet slab avalanches up to size 2.5 and numerous wet loose avalanches up to size 2 were reported on Thursday. See MIN.
Keep in mind that periods of rapid warming can weaken deeply buried weak layers and increase the likelihood of large natural avalanches.
Snowpack Summary
Successive days of temperatures well above 0 at mountain tops have created moist surfaces at all elevations/aspects. Clear skies and cooling temperatures will form firm crusts overnight which will lock up the snowpack until the surface crust melts. Avalanche danger can increase rapidly after the sun melts the frozen snow surface and begins to penetrate deeper into the snowpack. Strong solar radiation and warming often trigger wet loose avalanches and large cornice failures. Cornice falls could trigger large avalanches on deeply buried weak layers.Â
While there have not been many weak layers of concern this season, Keep in mind that periods of rapid warming can weaken deeply buried weak layers and increase the likelihood of large natural avalanches.This will more likely be an issue in shallow snowpack areas like the Wheaton compared to the thicker and stronger snowpack around White Pass.
Terrain and Travel
- Avoid travelling on slopes below cornices.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Loose Wet
Wet loose avalanches become increasingly likely during the heat of the day. Back off slopes as the surface becomes moist or wet with daytime warming.
Warming could initiate slab activity in shallow snowpack areas like the Wheaton Valley.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Cornices are large and will weaken with daytime warming. Stay well back from them on ridges and avoid travelling beneath them. A cornice fall has the potential of triggering large slab avalanches on the slopes below.
Aspects: North, North East, East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Apr 21st, 2021 4:00PM
