Rapidly rising temperatures will increase the likelihood for large cornice failures and wet loose avalanches. Start early and plan to be out of avalanche terrain before the heat of the day. Check out the Forecaster's Blog for more information on managing current conditions.
Summary
Confidence
Weather Forecast
SATURDAY NIGHT: Clear / Moderate, southeast ridgetop wind / alpine low temperature -3 / Freezing level 1700 m.
SUNDAY: Sunny / Moderate, southeast ridgetop wind / alpine high temperature 11 / Freezing level rapidly rising to 2900 m.
MONDAY: Sunny / Light, southeast ridgetop wind / alpine high temperature 11 / Freezing level 2700 m.
TUESDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature 2 / Freezing level 1500 m.
Avalanche Summary
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
Lingering wind slabs may still be reactive in isolated areas on northerly aspects at upper elevations. All other terrain is undergoing a melt-freeze cycle with successive days of high freezing levels.
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.
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
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- 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 are very likely on Sunday. 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 19th, 2021 4:00PM
