As freezing levels rise, the likelihood for large cornice failures and wet loose avalanches will increase. Start early and plan to be off large slopes before the heat of the day.
Check out the latest Forecaster's Blog for more information on managing current conditions.
Summary
Confidence
Weather Forecast
FRIDAY NIGHT: Sunny / light, northeast wind / alpine low 0 / freezing level up to 2700 m possible.
SATURDAY: Sunny / light northwest wind / alpine high temperature +11 / freezing level 2900 m.
SUNDAY: Cloudy with rain/flurries; 5-10 mm / moderate northeast wind / alpine high temperature +1 / freezing level dropping during the day to 1400 m.
MONDAY: Mostly cloudy / light northerly winds / alpine high +2 / freezing level 1700 m.
Avalanche Summary
The field team didn't notice any new avalanches in the Crowsnest area on Friday. Recent wet loose avalanches have so far been limited to surface snow running on crusts from April and March.
Prolonged warming may increase the sensitivity of deeply buried layers, although there is a fair bit of uncertainty about how likely this is in the South Rockies region.
There have been some notable slab avalanches reported to the north of the region recently including a skier triggered avalanche in Kananaskis Country on Saturday (see reports here and here) as well as cornice triggered deep persistent slab avalanche in Kootenay National Park on Tuesday (see photo here). These avalanches provide a good reminder of why it's good to be extra cautious during the heat of the day this time of year.
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 is undergoing a melt-freeze cycle with successive days of warm sunny weather. Things will be "more melt, less freeze" on Saturday as we do not expect a good overnight recovery.
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 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.
The snow line is slowly creeping up the mountains, making some access areas snow-free.
Terrain and Travel
- 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.
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
Problems
Cornices
Strong solar radiation and continued warming may trigger the large cornices that hang over ridge lines. Cornice falls are a hazard on their own, but could also trigger avalanches on the slopes below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
With a chance of no overnight refreeze, there is potential for natural and human triggered wet loose avalanches on a variety of aspects and elevations. Danger will be greatest 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: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Apr 17th, 2021 4:00PM
