Avalanche Forecast

Issued: Apr 9th, 2014 9:53AM

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

swerner, Avalanche Canada

Northwest Coastal.

The ongoing storm continues and is driving the Danger Ratings. Deeply buried persistent weak layers have become overloaded.

Summary

Confidence

Good

Weather Forecast

Another frontal system over the North Coast will continue to bring moderate precipitation and rising freezing levels 800-1400 m on Thursday/ Friday. The weekend looks to get very warm and sunny.Thursday: Higher elevations could receive up to 30 cm. Rain at lower elevations. Ridgetop winds light gusting strong from the SW. Freezing levels 1300 m.Friday: Snow amounts 5-10 cm on the coast. Mix of sun and cloud inland and in northerly areas. Ridgetop winds moderate from the NE. Freezing levels rising to 900 m. Saturday: Â A mix of sun and cloud. Alpine temperatures near 4.0 degrees. Ridgetop winds light from the NE. Freezing levels near 1300 m.

Avalanche Summary

A widespread natural avalanche cycle up to size 4 occurred on Monday and Tuesday and will likely continue through the forecast period. Deep persistent weak layers became overloaded, initiating very-large avalanches. In shallower snowpack areas, storm slab avalanches have stepped down to the December facet/ depth hoar layer. With more precipitation and strong forecast winds, natural avalanche activity will likely persist.

Snowpack Summary

The recent storm has brought 70 cm or more too coastal regions (60-110 mm) forming thick storm slabs and wind slabs on leeward features. Cornices have grown large. At lower elevations the snowpack has become saturated and weak adding to the already spring-like isothermal conditions.Two persistent weak interfaces exist deeper in the snowpack. The early March layer can be found down 75 -140 cm. The early February layer is down 150 - 240 cm. These layers have become overloaded and are failing in some places initiating very-large avalanches.

Problems

Storm Slabs

New snow driven by strong ridge top winds have built thick storm and wind slab problems at higher elevations. The new snow likely has a poor bond and is expected to be unstable initiating large-very large avalanches.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 6

Deep Persistent Slabs

Persistent weak layers exist in the snowpack. These weak layers could be activated by cornice fall, a surface avalanche in motion, or intense loading from snow, rain and wind. Avalanches failing on these weak layers will be large and destructive.

There is potential for large, deep avalanches due to the presence of buried facets and surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 7

Wet Slabs

At lower elevations the snowpack will likely become saturated and weak with heavy rainfall. Wet slab avalanches typically move slower, however they can be destructive and can mow down anything in their path. Smaller loose wet avalanches are likely.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid run-out areas, road cut banks and steep slopes at treeline and below. Indicators of the snowpack becoming moist or wet is snowballing, larger pinwheels and of course natural avalanche activity. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Apr 10th, 2014 2:00PM