Avalanche Forecast
Issued: Dec 4th, 2019 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Persistent Slabs.
dsaly,
Avalanche Canada
Storm snow totals have varied across the region, with field observations reporting deeper layers in the snowpack being becoming more reactive. Conservative terrain choice is recommended until the distribution of weak layers is better understood.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations.
Weather Forecast
Wednesday night: Cloudy with periods. Alpine temperature -10 C, west wind 10-25 km/hr.
Thursday: Cloudy with sunny periods and isolated flurries. Alpine temperature -9 C, southwest wind 10-20 km/hr.
Friday: Snow, 10-25 cm. Alpine temperature -10 C, southwest wind 20-35 km/hr.
Saturday: Snow and flurries, 5-10 cm. Alpine temperature -6, west wind 20-40 km/hr.
Avalanche Summary
On Wednesday, storm snow continued to be reactive to skier traffic, including triggering slab avalanches to size 2 and cracking on small, supported slopes. A couple of field observations reported slab avalanches failing on a layer of surface hoar (down 50-80 cm) at treeline elevations.
On Tuesday, a natural avalanche cycle was observed in Glacier National Park. Numerous size 2 storm slab avalanches were observed on all aspects at 2200 m and above. Additionally, 2 size 3 storm slab avalanches were observed on a north aspect at 2165 m and a northwest aspect at 2400 m. Near Revelstoke, storm slab avalanches to size 2 were reacting easily to explosives, many occurring on north and northeast aspects from 1800-2300 m.
Snowpack Summary
Storm snow totals reached 20-40 cm along with moderate westerly winds. Slabs have formed in areas exposed to wind.
The new snow covered a faceted upper snowpack and previously wind-affected surfaces, and surface hoar in sheltered areas around treeline and below.
Below the 15-40 cm layer of old, wind affected snow, a layer of surface hoar (feathery crystals) may be found in sheltered areas around treeline. In these areas old, stubborn wind slabs may still be reactive where they overly the weak surface hoar on a crust.
A variety of crusts from late October are buried deeper in the snowpack.
Problems
Storm Slabs
Upwards of 30-40 cm new snow accumulated in the last storm. Reactive storm slabs have developed, especially in areas affected by wind.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Persistent Slabs
A layer of surface hoar, down 50-80 cm has become reactive with the loading of new storm snow. Use caution around open slopes and unsupported terrain around treeline and below.
Aspects: All aspects.
Elevations: Treeline, Below Treeline.
Likelihood
Expected Size
Valid until: Dec 5th, 2019 5:00PM
