Avalanche Forecast

Issued: Jan 3rd, 2014 9:17AM

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

ghelgeson, Avalanche Canada

South Columbia.

While humans crave simplicity the current situation is anything but. The answer to the avalanche problem this weekend is staying conservative with terrain selection.

Summary

Confidence

Good

Weather Forecast

A strong northwesterly flow prevails as an upper ridge establishes itself offshore. Winds will be the most important feature to watch over the next 24 hours. No precip in the forecast for the next 72 hours.Saturday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Mod NW, Strong at ridgetop. Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light Variable, Mod NW at ridgetop.Monday: Freezing Level: Valley Bottom, potential for a slight temperature inversion at ridgetop; Precip: Nil; Wind: Light Variable, Strong W at ridgetop.

Avalanche Summary

Both natural and human triggered avalanches were running to size 2 on all aspects and elevations Thursday. I suspect natural activity and size ramped up Thursday night into early Friday morning. Check back tomorrow for more details. 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

Thursdays storm delivered 20 - 50 cm of new snow bringing the average regional depth to 160 - 240cm.This new snow lies on top of old wind slabs, a thin melt freeze crust below 2100m and numerous weak layers. Down 50 -100cm is the mid December layer comprised of surface hoar, stallars and/or a crust. Around 80 -140cm down is the early December surface hoar, faceted snow and/or crust.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 90-160cm 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

The storm snow in conjunction with strong NW winds will likely continue to overload weak layers in the upper meter of the snowpack. Many slopes are primed for human triggered avalanches, particularly on exposed lee aspects at and above treeline.

Avoid freshly wind loaded features.>The new snow will require several days to settle and stabilize.>Avoid complex terrain and be aware of what's above you at all times.>

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 meter or even more. The distribution and reactivity of persistent weak layers is highly complex at the present time.

Choose well supported terrain without convexities and avoid slopes with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried week layers.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Valid until: Jan 4th, 2014 2:00PM