Avalanche Forecast

Issued: Dec 22nd, 2013 8:20AM

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

ghelgeson, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Synopsis: The latest models suggest that there is still quite a bit of moisture associated with this storm. West of Terrace should see a lot of rain that may even fall on the peaks late Sunday afternoon. East of Terrace, the freezing level should remain steady around 500m. Temperatures drop in the wake of the cold front which should result in snow for much of the region Sunday night.Sunday Night: Freezing Level: Dropping to around 750m overnight. Precip: 10/30mm - 15/50cm Monday: Freezing Level Average: 750m Precip: 2/4mm - 2/8cm Wind: Mod, W gusting Strong.Tuesday: Freezing Level: 500m Precip: 2/4mm - 2/8cm Wind: Mod, W gusting Extreme.Wednesday: Freezing Level: 1200m Precip: 3/5mm - 4/10cm Wind: Lht. South.

Avalanche Summary

Not much new activity on Saturday. Lots of evidence from last weeks cycle that went to size 3 on the basal facets is still present. It should be interesting to see the results of the cycle induced by Sunday's storm.

Snowpack Summary

Another storm has arrived on the NW Coast and it's picking up in intensity at this time. (Sunday afternoon.) This storm should force the numerous weak layers in our snowpack to show their cards. Total pre-storm snowpack depths in the region vary between 150 - 250cm. On December 20th Kasiks (Between Terrace & Rupert) picked up almost 50cm while Bear Pass saw around 20cm. This snow rests on a variety of old surface layers: old wind slabs, a crust that formed on Dec. 14 in some locations and even small grained surface hoar. This brings the total load of snow on the December 12 layer to 75 - 130 cm. December 12th is a surface hoar/facet combo formed during the early December cold snap which rests on old wind slabs and melt freeze crusts. The last two systems have been accompanied by strong winds out of the South and West which has resulted in a wind slab problem that lingers for a couple of days after the storm. The mid pack is composed of deteriorating layers of old facets and crusts. A significant basal facet/crust combo lingers near the base of the snowpack and is most prevalent on NW - E facing aspects at the upper TL and alpine elevations.

Problems

Storm Slabs

Strong west winds will likely keep the natural avalanche cycle going Monday. Steer clear of overhead hazard and be aware that the setup is currently ripe for human triggering, even in sheltered terrain. Keep it conservative for another day or two.

Use conservative route selection, stick to moderate angled terrain with low consequence.>Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Deep Persistent Slabs

Give the problem layers deep in our snowpack some time to adjust to the new load. Now is not a good time for bold terrain selection.

If you're going to trigger the nasty deep slab avalanche, now is the time when it's going to happen. Be aware of the potential for remote triggering.>Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Avoid thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Dec 23rd, 2013 2:00PM