Avalanche Forecast

Issued: Jan 27th, 2013 9:42AM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is considerable. Known problems include Storm Slabs and Deep Persistent Slabs.

swerner, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Forecast snowfall amounts are uncertain

Weather Forecast

Monday: A low pressure system over Gulf of Alaska will move onto the North Coast. Precipitation moderate-heavy (15-35 mm) accompanied by strong-extreme ridgetop winds from the NW. Alpine temperatures rising to -2.0 and freezing levels near 700m. Tuesday: An intense warm front will continue to bring moderate precipitation (5-15 mm). Ridgetop winds will switch and blow strong-extreme from the West. Alpine temperatures near -1 and freezing levels up to 1000 m. Â Wednesday: An upper ridge continues to build generally bringing dryer conditions during the day. Alpine temperatures near -4.0. Â Ridgetop winds blowing form the SW in the light ranges.

Avalanche Summary

On Saturday, loose dry sluffing was reported from steep terrain.

Snowpack Summary

New storm snow is building over a variety of old surfaces. These include old wind slabs, scoured thin slopes, blue ice, thin melt-freeze crusts and surface hoar. The new storm snow may have a poor bond with the old surfaces buried below. The average snowpack depth at treeline is near 100 cm but remains quite inconsistent across the region. A strong mid-pack currently overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall and larger amounts of new storm snow.

Problems

Storm Slabs

New snow may build touchy storm slabs on all elevations and aspects. Strong NW winds will transport new snow and form wind slabs that can be found behind features like ridges and ribs. Natural avalanche activity is likely through the forecast period.

Avoid avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Deep Persistent Slabs

Near the base of the snowpack exists a deeply buried weak layer. This layer has been unreactive lately, but with such variability in the snowpack I suspect this layer could be triggered by large loads such as a cornice fall or from a thin-spot.

Be aware of thin and variable snowpack areas that may propagate to deeper instabilities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Jan 28th, 2013 2:00PM