Avalanche Forecast
Issued: Feb 26th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Persistent Slabs and Deep Persistent Slabs.
AL,
Avalanche Canada
The winds have begun to decrease, but the extent of the windslab development at upper elevations is widespread. Reports over the weekend have shown that this problem is reactive to human triggering.
Summary
Confidence
Avalanche Summary
The field team Monday observed active loading at upper elevations, with sloughing and audible avalanches out of extreme terrain. Local ski hills reported reverse loading with small reactive windslabs at ridge crest.
Saturday, several human-triggered avalanches to size 2.5 were reported in the forecast region.
Snowpack Summary
10-15cm of new snow overlays a faceting upper snowpack. Moderate to Strong W winds continue to form windslabs at alpine and treeline elevations. These windslabs overlie the various Jan PWL interfaces of sun crusts, facets and surface hoar down 70-110 cm. The weaker Nov 16 basal facet layer is down 100-180 cm and still produces mod-hard sudden collapse test results. Deeper snowpack areas west of the divide have a stronger and more supportive lower snowpack than areas to the east.
Weather Summary
Partly cloudy conditions with light precip are expected Monday. Winds will gradually decrease through the day with peak values of moderate from the West in the morning. Daytime high temperatures will be near 0 degrees near valley bottom. By late Monday into Tuesday, increased flurries are expected with a few centimeters of accumulation.
Terrain and Travel Advice
- Make conservative terrain choices and avoid overhead hazard.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Cornice failure may trigger large avalanches.
Problems
Wind Slabs
20 to 80 cm of storm snow fell in the past week with strong winds from muliple directions. This created extensive wind effect, fresh cornice growth, and new wind slabs at treeline and above. These wind slabs are slowly becoming more difficult to trigger, but if triggered they could step down to the deeper weak layers and create larger avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Three persistent weak layers formed in January are down 70-100 cm. The biggest concern is triggering these buried suncrusts on steep solar slopes, but weaker facets and isolated surface hoar can be found on the same interface on shaded aspects. Key an eye out for these layers in steeper terrain.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Weak facets and depth hoar are present at the bottom of the snowpack in most places. Last week's storm overloaded this interface resulting in numerous large avalanches running long distances. The snowpack is slowly adjusting to the new load, but natural triggering is still a concern with ongoing wind loading and cornice failures, and human triggering is still possible especially in shallower snowpack or rocky areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 27th, 2023 4:00PM
