Avalanche Forecast

Issued: Apr 10th, 2014 10:02AM

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 Loose Wet.

swerner, Avalanche Canada

Northwest Coastal.

Winter transitions into spring! Rapid warming and intense solar radiation can increase the avalanche danger quickly. Check out the new Forecaster Blog which is directly focused on the Northern Regions.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Moderate-heavy precipitation is expected to come to an end on Friday as a strong ridge dominates the region bringing clear skies and rising freezing levels. Friday: Cloudy in the am with sunny breaks in the afternoon. Ridgetop winds light from the NW. Freezing levels rising to 1000 m. Saturday: A mix of sun and cloud. Alpine temperatures high of 6.0 degrees. Ridgetop winds light from the NE. Freezing levels near 1700 m rising to 2000 m overnight.Sunday: Mainly sunny skies. Alpine temperatures high of 8.0 degrees and freezing levels rising to 2500 m. Ridgetop winds light from the SW.

Avalanche Summary

On Wednesday, numerous naturals were reported up to size 2 from steeper start zones. I suspect with the continued snow ad strong SW winds, direct action natural storm and wind slab avalanche activity will persist through Friday. A widespread natural avalanche cycle up to size 4 occurred on Monday and Tuesday and 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.

Snowpack Summary

The recent storm has brought 90+ cm or more too coastal regions (80-120 mm) forming thick storm slabs and wind slabs on leeward features. At lower elevations the snowpack has become moist, wet and saturated from rain. Large cornices have formed and loom over slopes below.Several 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 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

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

Loose Wet

At lower elevations the snowpack has become moist, wet and weak. As freezing levels drop overnight melt-freeze crusts form. When the crust breaks down during warming the snowpack will likely become weak and loose wet avalanches will occur.

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 - Very Likely

Expected Size

1 - 4

Valid until: Apr 11th, 2014 2:00PM