Avalanche Forecast
Issued: Apr 17th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Loose Wet, Cornices and Deep Persistent Slabs.
astclair,
Avalanche Canada
Start (and finish) your day early and avoid exposure to sun-exposed avalanche terrain. Steer clear of cornices overhead, and plan your egress route carefully.
Summary
Confidence
Weather Forecast
Saturday night: Mostly clear, winds becoming east and increasing to moderate, alpine temperatures dropping to -2 C, freezing level dropping to 1300 m.
Sunday: Mainly sunny, strong east ridgetop wind, alpine high temperatures near 0 C, freezing level rising to 1600 m.
Monday: Sunny, light southeast ridgetop wind, alpine high temperature +2 C, freezing level 2100 m.
Tuesday: Sunny, light northwest wind, alpine high temperature +2 C, freezing level 2100 m.
Avalanche Summary
As the spring diurnal cycle continues, there have been reports of numerous large (size 2) wet loose avalanches on south-facing slopes at all elevations and a few large (size 2-2.5) cornice failures on all aspects.
One wet slab was suspected to have released on the November crust layer on a shallow west aspect in the alpine, triggered by a loose wet avalanche from above. Triggers, such as cornice fall, loose wet avalanches, or a rider hitting a thin spot in the snowpack, are particularly concerning on steep, rocky slopes with a shallow or thin to thick snowpack as they are the most likely ways to trigger deeply buried weak layers.
Snowpack Summary
Lingering wind slabs may still be reactive in isolated locations on steep northerly aspects in the alpine that still have dry snow. All other terrain has been undergoing a melt-freeze cycle with successive days of warm sunny weather. Check out the Forecaster's Blog for information on spring conditions.
Strong solar radiation and warming will trigger more wet loose avalanches on Saturday as the snow loses cohesion. Cornices are large and fragile. Cornice falls could trigger large avalanches on the slopes below.
The snowpack is overall strong and settled in most areas, however, sustained warming can increase the likelihood of large avalanches failing on deeply buried weak layers.This is most likely to occur on steep, rocky alpine slopes with a shallow or thin to thick snowpack.
Terrain and Travel
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- Extra caution is needed around cornices under the current conditions.
- As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
- The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
Problems
Loose Wet
Strong sun and rising temperatures will weaken surface snow and may initiate loose wet avalanches on steep, sun-exposed slopes. The more the snowpack warms-up and weakens, the more conservative you'll want to be with your terrain selection. Wet loose avalanches can entrain a lot of snow and cross elevation bands.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Cornices
Strong solar radiation and warming will likely trigger the large cornices that hang over ridge lines. Cornice falls are a hazard on their own, but could also trigger large avalanches on the slopes below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
Prolonged warming could increase the sensitivity of deeply buried layers in the snowpack. While these layers have not been reactive lately, you should practice increasing caution during this period of warm weather. Steep rocky terrain with a shallow or thin to thick snowpack are most suspect.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 18th, 2021 4:00PM
