Avalanche Forecast

Issued: Dec 22nd, 2011 9:22AM

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

Avalanche Canada swerner, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Friday

Weather Forecast

Continued snow and wind through the Holiday weekend. Higher accumulations the further to the North of the region. Friday: Snow amounts 15-20cm. Ridgetop winds 70-105Km/hr from the SW. Treeline temperatures near -5. Saturday: Snow amounts 10-20cms. Ridgetop winds 45-75km/hr. Freezing levels hover around 1200m. Sunday: Snow amounts 10-20cm. Freezing levels 1200m in the morning falling back to valley bottom Sunday night.

Avalanche Summary

Natural avalanche activity up to size 2.5 occurred on Wednesday on a west aspect at 1900m. Heli-bombing control programs also produced slab avalanches up to size 2.5 on all aspects from 1000m and higher. We may see another widespread avalanche cycle through the early part of the weekend. Once it stops snowing and blowing the new snow should start to settle out, and avalanche danger will decrease.

Snowpack Summary

Earlier this week the forecast region got slammed by snow, wind and fluctuating freezing levels. The southern part of the region has received up to 70cms which totals over a meter of new snow over the past week (Kasiks, Terrace areas). Locations to the north are seeing less (Stewart up to 40cms). This new snow has been blown around by extreme-strong southwest winds creating stiff wind slabs on lee slopes. The winds have switched from the SW to the NW. This switch was short lived through Wednesday, but may have formed new wind slabs on SE - S facing slopes. This makes the wind slab problem even trickier to predict. The storms over the past 10 days have created several significant avalanche cycles. My guess is that these repeated cycles have cleaned out most of the mid-December buried surface hoar/facet interface. This is good. The region now sees firm wind pressed surfaces, old bed surfaces (from previous slides), and a crust that extends up to alpine elevations in the south and around 1000m in the north. The next storm will fall on these surfaces, and it's likely that the region will see another large avalanche cycle. The mid and lower snowpack are settled out and strong. Snowpack depths in the Kasiks, Terrace areas are reaching the 300cm mark. Further north Smithers, Bear Pass depths are ranging from 180-250cms.

Problems

Wind Slabs

An icon showing Wind Slabs
Strong winds will form large wind slabs on cross-loaded and lee slopes. They will be touchy and destructive in many parts of the region.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Storm Slabs

An icon showing Storm Slabs
Heavy snowfall amounts will create storm slabs at all elevations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Valid until: Dec 23rd, 2011 8:00AM