Avalanche Forecast
Issued: Jan 26th, 2020 5:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Storm Slabs and Deep Persistent Slabs.
dsaly,
Avalanche Canada
Snowfall and wind will drive avalanche hazard, the most reactive deposits will be around ridgelines and steep rolls.
Summary
Confidence
Weather Forecast
SUNDAY NIGHT: Snow, 10-15 cm. Alpine low temperature -5 C. South wind 35-55 km/hr. Freezing level 1000 m.
MONDAY: Snow and flurries, 5-15 cm. Alpine high temperature -4 C. South wind 20-40 km/hr. Freezing level 1000 m.
TUESDAY: Flurries, 5-10 cm. Alpine high temperature -3 C. Southeast wind 20 gusting to 50 km/hr. Freezing level 1400 m.
WEDNESDAY: Snow, 20-30 cm. Alpine high temperature -2 C. South wind 35-50 km/hr. Freezing level 1100 m.
Avalanche Summary
A few large to very large (size 2-3) natural storm slab avalanches were observed in the Whistler backcountry on Saturday morning, and explosives triggered storm slabs and cornice-triggered avalanches up to size 2.
On Thursday and Friday, explosives easily triggered large (size 2) storm slab avalanches, producing 40-60 cm thick slabs with wide propagation. Large storm slab avalanches (size 2) failed naturally or were triggered by falling cornices.
Explosive control on Wednesday resulted in a very large (size 3.5) deep persistent slab on a west aspect the alpine, suggesting the deep persistent slab remained reactive and sensitive to new loads. With more loading on the way natural storm and deep persistent slab avalanches remain concerns.
Snowpack Summary
Strong to extreme winds have left a variety of wind-affected surfaces in alpine and open treeline areas. Windward slopes are scoured down to the January 20 crust and wind slabs have developed in more leeward terrain. Moist surface snow has been pressed into slabs and notable cornice growth has been observed. A surface crust has developed on all aspects below 1700 m, and direct solar (south-facing) slopes at treeline and above. Forecasted flurries and southerly winds will accumulate over these surfaces and load previously developed slabs.
Weak faceted grains and crusts near the base of the snowpack continue to be a concern in inland parts of the region such as the Spearhead Range.
Terrain and Travel
- Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
- Extra caution is needed around cornices under the current conditions.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
Problems
Storm Slabs
Continued flurries and gusty winds will contribute to an ongoing storm slab problem. Strong to extreme winds have scoured and loaded some areas and pressed moist snow into slabs in other areas. Expect to find the most reactive deposits in open areas and around ridge features at treeline and above.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Deep Persistent Slabs
Explosives testing continues to periodically trigger a weak layer of snow at the bottom of the snowpack (the latest being 2 avalanches on January 22, one a size 3.5). If triggered, this deep persistent layer will produce very large and destructive avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 27th, 2020 5:00PM
