Avalanche Forecast

Issued: Apr 20th, 2012 10:26AM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is moderate. Known problems include Loose Wet, Wind Slabs, Storm Slabs and Cornices.

pgoddard, Avalanche Canada

South Coast.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Saturday: Warm, dry and mainly sunny in the morning. Freezing level around 2200 m. Light SE winds. A front is due to hit the area late in the day, bringing light to moderate precipitation and rising SW winds.Sunday: Moderate precipitation. Freezing level around 2400 m. Moderate to strong SW winds. Monday: Continued mild temperatures. Light precipitation. Freezing level near 2000 m. Light to moderate SW winds.

Avalanche Summary

Some wind slab and storm slab activity is expected to have occurred following Thursday night's storm, and more activity is anticipated as the next frontal system rolls through this weekend. Spring conditions exist in the region. Exposure to the sun, warm temperatures, and periods of rain are the most likely factors to influence the avalanche danger. If the temperatures go below freezing overnight, strong crusts should develop that are likely to hold the snowpack together. If the sun shines for a few hours, the crusts may break down quickly and moist surface snow avalanches may start running naturally. Continued warming from more sun, rain, or no overnight freeze may cause surface avalanches to step down and trigger deeper wet slab avalanches. Prolonged warming may cause very deep releases on weak layers that were deposited early in the season, or on depth hoar that developed during the winter. It is important to monitor the temperature and the freezing levels as they may change rapidly from day to day.

Snowpack Summary

Recent snow and wind is likely to have formed wind slabs. Solar radiation is expected to weaken recent snow quickly, especially where it sits over a slippery crust. As we transition into spring, the surface layers have a great deal of influence on the snowpack. When there is a solid re-frozen surface crust, travel is fast and easy, and the snowpack is held together by the surface cap. Any deeper persistent weak layers are unlikely to fail until the surface cap breaks down from daytime heating. When there is no crust, any deeper weak layers may fail depending on the amount of heat and the triggering force that is applied. If it cools off and snows, new snow and wind slabs may not bond well to the hard spring crusts.

Problems

Loose Wet

Wet loose avalanches are most likely on steep slopes when temperatures are warm, e.g. on slopes receiving sunshine, during rainfall, in the afternoon and at low elevations. Avoid exposure to slopes which are sporting glide cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Wind Slabs

Wind slabs have developed with recent snow and wind. Be alert for these behind ridges and terrain breaks.

Aspects: North, North East, East, South East.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 3

Storm Slabs

20-30 cm of recent snow may not be bonding well to a crust below.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Cornices

Large cornices are looming. A cornice fall can act as a heavy trigger for avalanches on the slope below.

Aspects: North, North East, East, South East.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Apr 21st, 2012 9:00AM