Avalanche Forecast

Issued: Jan 1st, 2014 9:03AM

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

jfloyer, Avalanche Canada

South Columbia.

A punchy storm will build during the day with rising temperatures. Be extremely cautious if traveling in the backcountry at this time.

Summary

Confidence

Good

Weather Forecast

Thursday: An incoming storm will build through the day and likely peak some time in the afternoon. 10-15 cm new snow likely by the afternoon. Freezing levels rising briefly to around 1500 m. Winds gusting to 50 km/h from the SW at ridgetop.Friday: The storm looks like it will linger in this area, giving a further 10 cm or so of new snow. Freezing levels should fall back to surface, with treeline temperatures of around -5C. Winds 20-30 km/h from the NW.Saturday: A clearing trend with some sunny breaks. Temperatures falling to around -10C. Winds increasing from the NW in the afternoon at all elevations as arctic air starts to descend from the north.

Avalanche Summary

There was a natural avalanche cycle in this region on Tuesday. Mostly avalanches were running to size 2 in recent storm snow on a variety of aspects and elevations of 1600 m and higher. One exception was a size 3.5 natural avalanche that ran on a steep NW aspect in the alpine and pulled out all the way to ground. As a general trend, the size and severity of avalanches has been greater in the north of the region where there has been more snow.

Snowpack Summary

Snowpack depths in this region average around 140-190 cm. 20-40 cm of recent storm snow has been reported to be poorly bonding to the older snow below. A weak layer consisting of surface hoar crystals, stellar crystals and/or a crust lies around 30-50 cm below the surface. At around 60-90 cm, another weak layer exists. This one was buried early December and comprises surface hoar, facetted snow, and/or a crust. It has shown variable reactivity in recent snowpack tests, but many professional operators are considering it carefully.There are two deeper layers of note. The late-November persistent weak layer consists of a sun crust on steep south facing slopes and surface hoar in sheltered areas and is now buried 70-110cm below the surface. The October deep persistent weak layer consists of a layer of facets sitting on a crust at the base of the snowpack. This layer is predominantly found on northerly aspects at treeline and in the alpine. The depth of both these layers makes directly triggering an avalanche on them unlikely (maybe a heavy load on a thin spot in steep terrain). Their presence could, however, increase the size of a potential avalanche through step-down.

Problems

Storm Slabs

Heavy loading from new snow and wind will likely overload the upper snowpack on a variety of aspects but particularly those on lee aspects in exposed areas.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1 - 5

Persistent Slabs

The presence of buried weak layers increases the likelihood of larger avalanches that could release to a depth of a metre or even more. The distribution and reactivity of persistent weak layers is highly complex at the present time.

Avoid traveling through runout zones during stormy periods when large avalanches are likely.>Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 2nd, 2014 2:00PM