Choose simple terrain, and avoid large features. Warm temperatures and sun are forecasted to hit a complicated snowpack. It's a good time to make conservative decisions, and our recent forecasters' blog explains why.
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.
On top of all the other avalanche problems, sunny weather continues, and temperatures are forecasted to stay above 0 C at both low and high elevations through Sunday morning at least.
Avoid avalanche terrain and overhead hazard when it feels like the sun is packing a punch. Remember that even a small wet avalanche can be dense and may push you around more than expected.
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.
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 Night: Partly cloudy. No new snow expected. Freezing levels fall to around 750 m.An above freezing layer (AFL) could keep temperatures above 0 C between 2500 m and 3000 m. This AFL is less likely any further north than Sparwood.
Sunday: Partly cloudy. No new snow expected. Strong northwest wind. Freezing levels drop to 500 m overnight, rise back to 1250 m by the afternoon. AFL breaking down.
Monday: Partly cloudy. Possible trace of snow expected. Moderate ridge wind from the northwest through northeast. Freezing levels drop to valley bottom overnight, rise back to 900 m by the afternoon.
Tuesday: Partly cloudy. no new snow expected. Strong ridge wind from the northwest. Freezing levels drop to valley bottom overnight, rise back to 1000 m by the afternoon.
Sunshine, warm weather, and a complex snowpack are concerning this weekend. Smaller surfaces avalanches and cornice fall could trigger deep persistent slabs.
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.
Incoming warm air may ride on top of colder air in the valleys, so the snowpack may experience above zero temperatures at higher elevations, where you may not expect them. Combine this with the potential for strong solar input, and the alpine snowpack could experience some rapid change for the worse.
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.
