Avalanche Forecast

Issued: Jan 16th, 2014 9:19AM

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

slemieux, Avalanche Canada

South Coast.

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain

Weather Forecast

Tonight and Thursday: The South Coast will remain under a ridge of high pressure bringing dry and warm conditions. Freezing levels are expected to reach 3200 m by tomorrow afternoon, moderate NW winds and mainly clear skies. Friday: The whole Coast is under the high pressure system, clear skies, moderate W winds and freezing levels reaching record levels of 3300 m. Saturday: A frontal system is expected to reach the coast, expect cloudier skies, mild temperatures and winds tapering down.

Avalanche Summary

Explosive control in the North Cascades produced a couple size 2.5 on N and NE aspects.In the same area, there was also some loose wet avalanches below treeline up to size 1. In the Northern part of the region, there was also report of remotely triggering a couple size 2 avalanches which would have run on basal facets in the alpine on NE aspects.

Snowpack Summary

The main concern is the unusual warming and solar radiation shock that the snowpack will take. This will weaken the snow and most likely increase natural avalanche activity on SE and S aspects, but also in shaded areas because of temperatures rising to plus 10 C in the alpine! As well as surface wet slabs and loose snow avalanches, there is the possibility of it stepping down to a deeper persistent weak layer (PWL) especially in the Northern part of the region. Recent obvious clues include recent natural avalanches, skier remote avalanches, whumphing and cracking and sudden planar tests results all associated with one or the other PWLs. The basal facet layer is found mostly in the alp. and at treeline in shallower snowpack areas. The late Nov. facet/crust layer is also found in these elevation bands and the newly buried surface hoar seems to be starting to heal with the recent mild temperatures. In the southern part of the region, where the early season snowpack was deeper, these persistent weak layers do not seem to be as prevalent. However, temperatures and solar radiation will be even stronger in this part of the region, making wet slabs and loose avalanches even more probable.

Problems

Deep Persistent Slabs

A moist/wet avalanche or cornice drop could step down to deeper instabilities. This problem is more specific to the Northern part of the region, especially in shallower snowpack areas.

Minimize exposure to overhead avalanche terrain, large avalanches may reach run out zones.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

3 - 6

Loose Wet

Expect increased avalanche activity as the day progresses at all elevations and on all aspects, but mostly on SE and S aspects. Loose avalanches could trigger larger slab avalanches.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid exposure to sun exposed slopes.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Very Likely - Certain

Expected Size

1 - 4

Valid until: Jan 17th, 2014 2:00PM