Avalanche Forecast
Issued: Feb 1st, 2020 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs, Cornices and Deep Persistent Slabs.
ahanna,
Avalanche Canada
Start with conservative terrain and make observations to inform your decisions. Natural avalanches are still possible, and human triggered storm slabs are likely.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
Saturday night: Clear periods. Moderate southwest wind. Freezing level valley bottom.
Sunday: Mostly cloudy with flurries bringing 10-15 cm new snow. Moderate southwest wind. Alpine high -8 C. Freezing level 300 m.
Monday: Sunny. Light north wind. Alpine high -6 C. Freezing level valley bottom.
Tuesday: Mostly cloudy. Moderate southwest wind. Alpine high -6 C. Freezing level valley bottom.
Avalanche Summary
On Saturday, reports came in from Friday's widespread storm cycle, of up to size 3 storm slabs in the alpine and size 2 loose wet below 2100 m prior to the cooling trend. Extensive explosive work conducted Saturday morning produced mostly size 2 avalanches with storm slabs up to size 3 and cornices up to size 2.5.
The deep persistent problem most recently reared its head on Monday with large explosive loads producing a size 2.5. in shallow, rocky terrain.
Snowpack Summary
Above 1900 m, storm totals are in the range of 50-70 cm. Extreme southwest wind during the storm has scoured windward aspects, formed loaded pockets up to 150 cm deep in alpine lees and contributed to rapid cornice growth. Below 1800 m, snow overlies a crust and tapers with elevation.
Weak faceted grains and crusts near the base of the snowpack continue to be a concern in inland parts of the region such as the Spearhead Range. With the recent new loads, we are watching these layers closely.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Be alert to conditions that change with elevation.
- Extra caution is needed around cornices under the current conditions.
- Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
Problems
Storm Slabs
Storm slab avalanches up to size 2.5 have been observed since the storm. Storm slabs will remain especially sensitive where the wind continues to deposit recent snow into deeply loaded pockets in lee features.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Mild temperatures, strong winds and new snow have been a recipe for significant cornice growth. Recent explosive work has produced numerous cornice results up to size 2.5.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
As recently as Tuesday, explosives testing continues to periodically trigger a weak layer of snow at the bottom of the snowpack, producing very large and destructive avalanches. Significant loading from recent snow, rain and ongoing wind weigh heavily on deep weaknesses near the bottom of the snowpack.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 2nd, 2020 5:00PM
