Avalanche Forecast

Issued: Apr 6th, 2012 10:23AM

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

swerner, Avalanche Canada

Cariboos.

Summary

Confidence

Good

Weather Forecast

A very benign weather pattern will bring little precipitation, convective cloud, light winds and sunny periods over the next few days. Saturday: Scattered convective cloud cover. Light flurries, with no significant accumulations. Ridgetop winds light from the NW. Alpine temperatures near -1. Freezing levels 1700m falling to valley bottom at night. Sunday/Monday: A dominating ridge with diurnal temperature swings and freezing levels rising to 2000 m during the day. Continued sunny skies, and light ridgetop winds. The ridge will weaken on Monday allowing bands of cloud, and light precipitation.

Avalanche Summary

Observations from the past few days are limited. On Thursday a natural cornice release size 2.5 was reported. This did not pull out a slab on the slope below. On Wednesday reports include one natural cornice triggered Size 2.5, 100cm thick wind slab avalanche on a north aspect. A couple days ago, a size 3 glide slab avalanche was also observed on a south aspect at 1800m. I suspect natural activity will occur throughout the weekend with warming temperatures, and sunny skies. Make observations continually as you travel. Pinwheeling, snowballing, loose sluffing, and avalanches are all indicators of the snowpack deteriorating. I would avoid slopes where these actions are occurring.

Snowpack Summary

Over the past week up to 60 cm of recent storm snow has fallen. Sustained southeasterly through northeasterly winds are contributing to continued wind slab formation as well as cornice development at upper elevations. Although generally settling and bonding well, recent snowpack tests on a north facing treeline slope resulted in easy to moderate shears down 25cm within the storm snow, and down 65cm on an underlying crust that formed near the end of March. Not only will daytime warming and sun-exposure cause surface snow to lose cohesion and cornices to weaken, they will also increase settlement rates and decrease slab stability.

Problems

Cornices

Large and weak cornices could easily start popping off with sun-exposure. Not only are they a hazard in themselves, but can also act as a heavy trigger for very large avalanches on the slope below.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Steep rocky terrain in the afternoon. Wet loose avalanches can entrain significant mass and run long distances.

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

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Wind Slabs

Generally lurking below ridgecrests, behind terrain features, and in gullies. Thick fresh wind slabs are highly sensitive to rider triggers, cornice falls, and sun-exposure is expected to make things even more touchy.

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

2 - 5

Valid until: Apr 7th, 2012 9:00AM