Avalanche Forecast

Issued: Jan 2nd, 2014 8:28AM

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.

ghelgeson, Avalanche Canada

South Columbia.

A cautious and conservative approach is essential as the snowpack adjusts to it's new load.

Summary

Confidence

Fair

Weather Forecast

Precipitation will continue through the night tapering off before dawn. Storm totals should be in the 20 30 cm range. The freezing level drops after the storm and a ridge of high pressure looks to dominate for the foreseeable future.Thursday Night: Freezing Level: 1000m; Precip 5/10mm - 5/15cmFriday: Freezing Level: Valley Bottom; Precip: 2/8mm 4/15cm; Wind: Mod NWSaturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Mod, NW Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var.(Forecasted wind speeds are at 2000m)

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 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. Avalanche activity on Wednesday was limited to small wind and storm slab avalanches, most of which occurred above 2000m.

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

New snow and wind will likely overload the upper snowpack on a variety of aspects but particularly those on lee aspects in exposed areas. Keep it conservative Friday as the snowpack adjusts to this new load.

Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>With several weaknesses in the upper meter of the snowpack, the snowpack will require a few days to settle.>Good day to make conservative terrain choices.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

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 all avalanche terrain during periods of heavy loading from new snow, wind, or rain.>Avoid convexities or areas with a thin or variable snowpack.>Avoid areas with overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 3rd, 2014 2:00PM