Avalanche Forecast
Issued: Dec 27th, 2019 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
ahanna,
Avalanche Canada
Large avalanches may still be sensitive to human triggering. Hazard may be improving but keep in mind that potential size and consequences of avalanches remain high. Deep instabilities like this are difficult to assess from the surface, so let terrain selection be your solution.
Summary
Confidence
Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
Friday night: Cloudy, alpine low -15 C, alpine wind moderate northwest.
Saturday: Scattered cloud with isolated flurries, alpine high -9 C, alpine wind moderate northwest, trace of snow possible in the evening.
Sunday: Scattered cloud, alpine high -7 C, alpine wind light northeast.
Monday: Scattered cloud, alpine high -7 C, alpine wind light northwest.
A bigger storm is on the horizon as we enter the New Year.
Avalanche Summary
The spectacularly large and destructive natural avalanche activity observed during the previous storm cycle has largely tapered. But as recently as Thursday, natural size 2.5 persistent slab avalanches were still being reported in large alpine terrain features on both north and south aspects, in neighboring Glacier National Park.
Snowpack Summary
Moderate winds over the last couple of days are likely to have blown around some of the 60 to 100 cm from last weekend's big storm, forming soft windslab in alpine lees. Anywhere from 100 to 160 cm of snow is now resting on a widespread layer of large, feathery, surface hoar which we're calling the "December 11th Surface Hoar." This layer was the culprit for the very large and destructive natural avalanche cycle during and after last weekend's big storm. Activity on this interface has largely tapered off, there remains some uncertainty as to how quickly the snowpack is gaining strength.
A combination of surface hoar, crust & facets formed in late November is now over 170 cm deep. This layer is likely trending toward dormancy.
Terrain and Travel
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Avoid convexities, steep unsupported terrain and rocky outcroppings.
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Problems
Persistent Slabs
All of the old storm snow is slowly settling into a slab which rests on weak surface hoar 100 to 160 cm below the surface. Natural avalanche activity has waned, but human triggering may still be possible, especially in more challenging/complex terrain. This isn't the kind of avalanche problem you can feel under your skis, track or feet, it's far too deep for that. The answer lies in terrain selection.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
A bit of new snow and wind out of both the southwest and northwest on Thursday and Friday is likely to form fresh wind slabs in lee terrain features in the alpine.
Aspects: North, North East, East, South East, South.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Dec 28th, 2019 5:00PM
