Avalanche Forecast
Issued: Dec 20th, 2019 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs.
MBender,
Avalanche Canada
There is uncertainty with the distribution and reactivity of a recently buried weak layer of surface hoar. Until there is a better understanding of how reactive it is and where it can be found, it is best to make conservative terrain choices.
Summary
Confidence
Low - Uncertainty is due to the limited number of field observations. Uncertainty is due to how quickly the snowpack will recover and gain strength.
Weather Forecast
Friday Night: Flurries, accumulation 5-10 cm. Alpine temperature -4 C. Southwest wind 20-30 km/hr. Freezing level 500 m.
Saturday: Scattered flurries. Alpine temperature -3 C. Southwest wind 20-40 km/hr. Freezing level 600 m.
Sunday: Cloudy with sunny breaks. Alpine temperature -4 C. Southwest wind 10-20 km/hr. Freezing level 500 m.
Monday: Flurries. Alpine temperature -5 C. South wind 15-30 km/hr. Freezing level 500 m.
Avalanche Summary
There were reports of a few natural size 1 storm slab avalanches in the Shames area on Thursday.
Natural storm slab avalanches to size 1.5 were observed around treeline on Wednesday and loose, dry snow was running from steep alpine features. Avalanche control work Wednesday and Thursday triggered numerous large (size 2) avalanches with explosives, crown depths ranged from 30-80 cm.
Snowpack Summary
40-70 cm of snow has accumulated over a weak layer of surface hoar, old faceted surfaces, and/or a crust on south/southwest aspects in the alpine. Reports from the Shames area suggest the surface hoar layer is prevalent on all aspects at treeline elevations down to 800 m, and more likely on leeward and sheltered alpine areas. Check out this MIN report from sheltered terrain near Shames.
The lower snowpack is generally considered strong, as there has been very little to report in terms of recent avalanche activity or snowpack test results on deeper layers. Snowpack depths at treeline range from 100-200 cm and taper quickly at lower elevations.
Terrain and Travel
- Continue to make conservative terrain choices while the storm snow settles and stabilizes.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Be careful as you transition into wind affected terrain.
- In times of uncertainty conservative terrain choices are our best defense.
Problems
Storm Slabs
40-70 cm snow has accumulated over a weak layer of surface hoar. There is uncertainty with the distribution and reactivity of this layer. Until there is a better understanding of how reactive it is and where it can be found, it is best to make conservative terrain choices.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 21st, 2019 5:00PM
