Avalanche Forecast

Issued: Jan 19th, 2013 9:44AM

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

jlammers, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

The stationary ridge of high pressure is expected to bring continued dry conditions to the region until Tuesday at which point the ridge moves east allowing light snowfall to affect westerly slopes. Alpine temperatures are forecast to be about 0.0` for Sunday and Monday, and then dropping on Tuesday. Winds should remain light to moderate from the southwest.

Avalanche Summary

On Thursday and Friday numerous avalanches ran to size 3.5 in the north of the region where recent snow accumulations were the highest. They occurred in response to heavy snowfall and strong to extreme winds. Most recent occurrences were observed on east to northwest aspects at treeline and above. One result pulled down to basal weaknesses where it interacted with summer firn.

Snowpack Summary

A melt freeze crust is likely to exist in most areas below treeline that were previously rain soaked. Light amounts of recent snow (heavy amounts in the north) exist as storm slabs and windslabs at treeline and above. A persistent weakness of surface hoar buried at the end of December sits below all of the more recent storm snow and is still on the radar of professionals in the area. The mid and lower snowpack is generally well settled and strong, although well developed basal facets remain a concern in shallow snowpack areas.

Problems

Wind Slabs

Strong to extreme westerly winds have continued to create windslabs in exposed lee and cross-loaded terrain at higher elevations. Heavy accumulations in the north have created a very destructive storm/ windslab instability.

The new snow may require several days to settle and fully stabilize.>Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Loose Wet

Forecast warm temperatures and the possibility of sun will increase the likelihood of loose wet avalanche activity. Watch for triggering in steep, sun exposed terrain.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

Aspects: North, North East, East.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

There has been no new activity reported on this layer. Having said that, the weakness still exists with the potential to produce large avalanches.

Make observations and assess conditions continually as you travel.>Conditions have improved, but be mindful that persistent instabilities are still present.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Jan 20th, 2013 2:00PM