Archived

Avalanche Forecast

Dec 15th, 2017–Dec 16th, 2017

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

4: High

The avalanche danger rating at treeline will be high

Below Treeline

4: High

The avalanche danger rating below treeline will be high

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Saturday is storm day! Avoid avalanche terrain during periods of heavy loading from rain, new snow and wind.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

Saturday: Snow amounts 20-30 cm. Alpine temperatures -2 and freezing levels 800 m. Ridgetop winds strong from the southwest.Sunday: Cloudy with sunny periods and new snow amounts 3-10 cm. Alpine temperatures -3 and freezing levels 600 m. Ridgetop winds light with strong gusts from the southwest.Monday: Cloudy with isolated flurries. Alpine temperatures -3 and freezing levels 600 m. Ridgetop winds light from the southwest.Check out the Mountain Weather Forecast for more detail.

Avalanche Summary

On Friday, wet slab avalanches size 1-2 were reported from steep terrain where the ground cover consists of smooth rock slab features. These avalanches went to ground. Widespread natural avalanche activity expected through the forecast period with new rain, snow and wind.

Snowpack Summary

Up to 30 mm of precipitation fell as a rain and saturated the snowpack up to 800 m on Thursday. On Friday, the freezing levels dropped and the new snow is currently building storm slabs on all aspects and elevations. Below the surface sits a well-settled snowpack overlying several layers of interest. Down 70-100 cm you'll likely find a 5-10 cm thick crust which was buried on November 23 and in some areas, a feathery surface hoar layer down 50-60 cm producing moderate snowpack test results. The widespread crust/facet interface that was buried at the end of October can now be found 100-200 cm deep and exists region wide.

Avalanche Problems

Storm Slabs

New storm slabs will likely build through the forecast period on all aspects and elevations. Wet loose avalanches may occur from steeper terrain features below treeline.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely - Certain

Expected Size: 1 - 3

Deep Persistent Slabs

Weak layers buried near the base of the snowpack can't be dismissed while new snow or rain load the surface.

Avoid areas with overhead hazard.Take extra caution around areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3