Avalanche Forecast

Issued: Apr 19th, 2012 10:22AM

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

jlammers, Avalanche Canada

South Columbia.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain

Weather Forecast

A frontal system is expected to arrive Thursday night bringing moderate to locally heavy amounts of precipitation, strong southwest winds at higher elevations and freezing levels to about 1600m. Light flurries should persist through Friday, but will give way to a ridge that will bring clear skies to the region over the weekend. Freezing levels on Saturday are expected to be at around 2000m, climbing up to about 2800m on Sunday.

Avalanche Summary

Over the past few days, loose snow avalanches to size 2 were reported from the region. Expect windslab activity at higher elevations and continued wet snow instabilities lower down with weather forecast for Thursday night.

Snowpack Summary

Since last week, light to locally moderate amounts of new snow have formed soft slabs that overlie a crust or wet grains at treeline and above while rain has continued to penetrate and weaken the isothermal snowpack at lower elevations. The mid-February buried surface hoar layer is down about 140-220 cm. The likelihood of avalanches failing on this layer has been very low due to cooler temperatures, however it may wake up with warming and the consequence continues to be very large destructive avalanches. Cornices in the region are very large and have may become weak with spring temperatures.

Problems

Wind Slabs

With forecast weather, wind slabs are expected at higher elevations by Friday morning. Wind slabs may not bond well to melt-freeze crusts where they exist. Watch for triggering in gullies, over steep rolls and behind ridge crests.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Loose Wet

Spring temperatures will promote ongoing loose wet avalanche activity, particularly in steep terrain. Loose wet avalanches can be heavy and entrain mass quickly.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Wet Slabs

Buried crusts provide an ideal sliding layer for wet slabs, especially on sun-exposed slopes or with warmer temperatures at lower elevations. Destructive glide cracks are also releasing regularly at this time.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Apr 20th, 2012 9:00AM