Avalanche Forecast
Issued: Jan 21st, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Cornices and Deep Persistent Slabs.
swerner,
Avalanche Canada
Strong wind and recent snow have formed reactive wind slabs.
Warm temperatures combined with a lingering deep persistent slab problem may equal large and destructive avalanches. Its a good time to approach the mountains cautiously and even expect surprises.
Summary
Confidence
Weather Forecast
A ridge of high pressure brings warming and sunny skies through the weekend. Valley bottoms may see some valley cloud trapping cooler air down low.
Saturday: Freezing levels rise through the day to 2000-2500 m with generally clear skies. Possible inversion especially in tighter valleys may hold valley cloud and cooler temperatures down low. Ridgetop winds moderate from the northwest. Expect some cooling overnight.
Sunday: Sunshine and freezing levels hovering around 2000-2500 m. Strong northwest wind.
Monday: Freezing levels forecast to drop to 1000 m.
Avalanche Summary
On Friday morning the field team reported four new wind slabs size 2.5 to size 3 that looked to fail on the (re-loaded) early December interface in the Crowsnest North. One of these appeared to be triggered by a cornice fall.
Sunshine, warm weather, and a complex snowpack are concerning this weekend. Smaller surfaces avalanches and cornice fall could trigger deep persistent slabs. This layer has been dormant but to no surprise could wake up.
Snowpack Summary
Strong winds have redistributed the recent storm snow from earlier this week onto leeward slopes forming stiff and reactive wind slabs. The wind slabs prove to be more reactive where they sit above older hard snow surfaces or a crust.
The upper snowpack is variable throughout the region with a melt-freeze crust found 10-20 cm down (aspect and elevation dependant) in some locations to barely existing in other locations, especially above 2000 m. One common theme throughout the region is that the mid-pack is well settled above the deeper December crust/facet interface which is currently the primary concern in the snowpack.
The early December crust is now generally down 80-150 cm. This layer is found widespread through the region but with varying test results. Recent snowpack tests have shown more reactivity in shallower snowpack areas as well as reactivity to step down avalanches. This indicates that there is potential to trigger this weak layer from a thin spot which may propagate to a thicker slab within the snowpack. In turn, triggering a very large avalanche.
Most concerning is the warm weather this weekend and its effect on the complex snowpack. Warming, solar radiation, and cornice fall could all play a role in triggering deep persistent slabs. This layer has been dormant but to no surprise could wake up.
Terrain and Travel
- Cornices become weak with daytime heating.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Back off slopes as the surface becomes moist or wet with rising temperatures.
Problems
Wind Slabs
The recent snow from Tuesday's storm accompanied by strong winds and slight warming has formed new and reactive wind slabs. They could have a poor bond to the crusty snow surfaces below.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Cornices
Natural cornice fall is possible with upper elevation warming and solar radiation. Cornice fall could be a hazard on its own and it could trigger a deeper slab avalanche from the slope below.
Loose wet avalanches are possible, especauilly on southerly aspects and steeper slopes.
Aspects: North, North East, East, South East.
Elevations: Alpine.
Likelihood
Expected Size
Deep Persistent Slabs
The early December crust can be found 80-150 cm deep. A deep persistent slab problem could wake up with forecast warming, solar radiation, cornice fall, and step-downs from smaller avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 22nd, 2022 4:00PM
