Avalanche Forecast

Issued: Apr 8th, 2014 9:41AM

The alpine rating is high, the treeline rating is high, and the below treeline rating is high. 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. The snowpack does not typically handle rapid change well and deeply buried persistent weak layers have become overloaded.

Summary

Confidence

Good

Weather Forecast

Another frontal system is targeted for the North Coast Wednesday/ Thursday bringing moderate-heavy precipitation and freezing levels hovering around 800-1200 m.Tuesday night: Snow amounts 5-10 cm. Ridgetop winds strong from the SW. Freezing levels falling to 600 m. Wednesday: Snow amounts 15-25 cm. Ridgetop winds strong from the SW. Freezing levels rising to 800 m. Thursday: Snow accumulations up to 20-25 cm. Ridgetop winds light from the SW gusting strong. Freezing levels near 1000 m.Friday: Unsettled conditions follow the frontal system bringing light-moderate precipitation, light SW winds. An approaching upper ridge will gradually start to dry things out later in the day.

Avalanche Summary

An ongoing, widespread natural avalanche cycle up to size 4 occurred on Monday and will likely continue through the forecast period. Deep persistent weak layers are overloaded in some places, initiating very-large avalanches. Travel in avalanche terrain is not recommended.

Snowpack Summary

The recent storm has brought 50 cm or more too coastal regions (60-100 mm) forming thick storm slabs. Consistent strong southerly winds have transported the new snow building thick wind slabs on leeward features and cornices have grown large. At lower elevations the snowpack has become saturated with rain 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 in some places initiating some very-large avalanches.

Problems

Storm Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 6

Deep Persistent Slabs

Two buried 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 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. >Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 5

Valid until: Apr 9th, 2014 2:00PM