Avalanche Forecast

Issued: Apr 7th, 2012 11:07AM

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

ghelgeson, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Freezing levels are uncertain on Tuesday

Weather Forecast

A ridge of high pressure intensifies over the region through the forecast period culminating with a significant warm up on Tuesday. Sun interrupted by periods of convective snow flurries continue for Sunday & Monday. Sunday: Freezing level starts near the surface, climbs to around 1900 m and then returns to the surface overnight. Winds calm at all elevations for much of the day. A bit of light east wind develops at upper elevations in the afternoon. Monday: Upper level flow switches from northerly to a more mild southerly in the AM setting the stage for a very warm Tuesday. Freezing levels start near the surface, climb to around 1900m and then return again to the surface; the classic spring diurnal temperature swing. Winds should be light to moderate with an easterly component at lower elevations, switching to a light southerly at ridge top. Tuesday: Looks to offer the most significant warm up the region has seen yet this spring. Freezing levels start near the surface and then climb to 3000 m. Winds should again be light east at lower elevations, light southerly ridge top.

Avalanche Summary

In the Fernie area a skier triggered a size 1.5 avalanche with a 20 cm crown on an E facing slope at 2000 m Friday. Some loose snow activity on a SE facing slope was also reported, but, there is surprisingly little avalanche activity in the region currently.

Snowpack Summary

Mild temperatures in combination with the strong spring sun have helped to settle out the 20 cm from Wednesday's storm which came to rest on the April 4th melt/freeze crust. The new snow was introduced to the sun Friday as skies clear and the temperature at 1600 m climbed to +5. The snow behaved well, very little activity was observed despite the warming. Recent storm snow has added up to 60-120 cm depending on the drainage. Our field team was out in the region Saturday; they were able to find the March 27th interface down around 90cm below the snow surface but test profiles did not produce any results on this layer. Large cornices loom over many lee slopes.

Problems

Loose Wet

Intermittent strong sun is forecast for Sunday as convective clouds and the sun dance through the sky. Watch for loose snow avalanches, with the potential for deeper slab avalanches on slopes that bake all day under the strong spring sun.

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Cornices

Cornices have grown large & unruly. Cornices receiving direct sun will eventually grow weak & there is potential for cornice fall to initiate deep persistent slab avalanches on underlying slopes. Pay attention to what's happening above you.

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

3 - 7

Storm Slabs

The odd deep slab could still be out there, I'm still suspect of steeper unsupported slopes & places where the snowpack goes from thick to thin, especially near ridge crest and around rock outcroppings.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Apr 8th, 2012 9:00AM