Avalog Join
Archived

Avalanche Forecast

Mar 26th, 2012–Mar 27th, 2012
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable

Regions: Purcells.

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period

Weather Forecast

The rather largo weather pattern that has been in place for the last week is being swept out of the province Monday setting the stage for an active weather week influenced by SW flow for the southern interior. Monday Evening: freezing level tops out around 1700m Monday evening as precip begins to fall. 10mm of water are expected, most of which will fall as rain as high as 1500m. Alpine elevations should receive 15 or so cm of snow. Winds should be moderate out of the NE, switching SW overnight. Tuesday: Freezing levels remain near 1500m, trace of precip expected. Treeline winds light out of the S, SW, Alpine winds Moderate, SW. Wednesday: Freezing level 1500m, 3mm water expected during the day. Winds light SE at treeline, moderate S in the Alpine. Look for clearing skies Thursday AM with precipitation expected to start back up in the afternoon.

Avalanche Summary

The strong spring sun initiated an avalanche cycle Sunday that included everything from small sluffing to size 2.5 avalanches in the afternoon. A natural cornice fall size 2.5 was reported from the high alpine on a NW aspect on Saturday. On Friday, a very large avalanche was triggered by a cornice in Gorman Lake (Dogtooth Range). It was wide, deep and covered sled tracks. Photos here: https://bit.ly/GMOYCv . There were four other close calls in the Purcell Mountains this week, all involving very large slabs releasing either from a distance or with a light load. On Thursday, a snowmobiler remotely triggered a size 3.5 slab on an east aspect at 2400m at Oldman Creek, east of Quartz Creek (video here https://bit.ly/GLHIbg). It failed 1-2 m deep, was 200-300 m wide and ran full path, taking out mature timber. A second slope also failed, either remotely or sympathetically.

Snowpack Summary

Warm alpine temperatures combined with strong solar radiation on Sunday caused moist snow up to about 2400 metres. The major concerns are the mid-February persistent weak layer, buried 1-2 m deep, and facets at the base of the snowpack. The February layer demands respect right now. It is very touchy and can be triggered remotely or by a light load on a variety of aspects, creating frighteningly large avalanches.

Avalanche Problems

Deep Persistent Slabs

Very large avalanches have been failing on a weak layer up to 2 m deep with alarming ease. This problem demands respect. Choose very conservative terrain, as the consequences of triggering this layer could be huge.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 4 - 8

Cornices

Large cornices are looming above many slopes. These may weaken with fluctuating temperatures and could act as a trigger for a very large avalanche. Variable wind slabs can also be found behind ridges and terrain breaks.

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

Elevations: Alpine.

Likelihood: Likely

Expected Size: 1 - 4

Loose Wet

Previous solar warming may not get a chance to recover overnight. Forecast rain up to about 1500 metres may weaken the snowpack. Loose wet releases at treeline may step down to the deeply buried weak layer.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 5