Avalanche Forecast

Issued: Feb 23rd, 2012 10:23AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Due to variable snowpack conditions

Weather Forecast

An approaching low pressure system will bring moderate-heavy precipitation to the coastal regions beginning Thursday night into Saturday. Friday: Snow amounts 15-25 cm. Ridgetop winds 30km/hr from the SE. Treeline temperatures near -5. Freezing levels 500m. Saturday: Snow ending by midday with scattered flurries. Ridgetop winds light -moderate from the SW. Freezing levels at valley bottom. Sunday: Light flurries during the day. Ridgetop winds light from the NW. Freezing levels valley bottom.

Avalanche Summary

Coquilhalla Area: Several natural size 2-2.5 slab avalanches occurred on West aspects. Crown depths being 50-100cm, and running 100m in distance. Skier triggered size 1.5 failed on the above mentioned graupel layer, @1650m on an East aspect, running 100m in length.

Snowpack Summary

Over the past week 20-30 cm of new snow fell over the Duffy Lake area, this snow fell incrementally and low density. The Coquihalla has seen up to 50 cm. This new snow has buried a variety of old snow surfaces. The old surfaces include: melt-freeze crusts on all aspects below 1700m and on steep solar aspects higher up, surface hoar (feather like crystals), old wind slabs, and facets (sugary crystals), which exist on north aspects as well as around crusts. I suspect these buried weak layers will become naturally reactive with forecast snow and wind, and the slopes that don't slide naturally may be ripe, waiting for a rider trigger. Below this sits a well settled snowpack, with treeline snowpack depths near 250cm. Test results on the Duffy today shows RB4 down 35cm on 3mm Surface Hoar, sudden planar results. The warning signs are clear and a large avalanche cycle has started in the interior regions. Please visit our Forecaster's Blog for more detailed information. To view recent photos of this buried surface hoar in the Coquihalla area please check out this link:http://www.avalanche.ca/cac/library/avalanche-image-galleries/avalanches2012

Problems

Persistent Slabs

An icon showing Persistent Slabs
Additional snow will continue to form storm slabs. Amounts look to be higher in the Coquihalla area, forming storm slabs faster then in the Duffy. These sit on a variety of buried weak layers that will likely reach threshold.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 6

Wind Slabs

An icon showing Wind Slabs
Strong winds will blow around the new snow creating wind slabs on lee slopes. As these slabs build, they will increase the load on buried weak layers.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Valid until: Feb 24th, 2012 8:00AM