Avalanche Forecast

Issued: Mar 14th, 2013 10:22AM

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

Avalanche Canada ghelgeson, Avalanche Canada

Summary

Confidence

Fair

Weather Forecast

Synopsis:  The true pineapple breaks down Friday and a more zonal flow builds in its place which opens the door to a series of weak systems. Friday:  Freezing Level 1400m. Precip: Trace. Wind: Light, SWSaturday:  Freezing Level 1200m.  Precip: Trace. Wind: Moderate SW gusting to StrongSunday: Freezing Level 1000m in the afternoon, dropping to 500m overnight.  Precip: Trace Wind: Light, NW

Avalanche Summary

A widespread natural avalanche cycle to size 2.5 was reported from the Duffey on Wednesday.  The Coquihalla reports several wet naturals from size 1 - 2.5 running to the top of the runouts.  There was a report of a size 2 skier triggered slab avalanche on a steep southwest aspect in the Steep Creek area (Duffey Lake) on March 8th.  Granted, it's a few days old but it highlights the lingering potential for triggering large slab avalanches.

Snowpack Summary

The storm has delivered around 40 cm as of Thursday morning and another 5-10mm/5-15cm is expected Thursday afternoon/evening. This new snow is bonding poorly to the previous snow surface, which includes faceted snow, surface hoar, and/or a crust, but is most concerning where surface hoar is sitting on a crust on previously sun-exposed sheltered treeline slopes.  Strong southerly winds in the alpine have created slabs on N - E facing slopes that may be up to a meter in depth.  Around a 100 - 150cm below the snow surface is a layer surface hoar buried on February 20th. Although this layer has a history of producing large avalanches, triggering this layer has now become difficult, and would most likely require a very large trigger on a steep, unsupported slope. Below this interface, the snowpack is strong and well settled.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs from 40 - 100 cm in depth are present in the alpine with steep North through East facing slopes harboring the deeper slabs.  The storm will diminish Friday, but these storm slabs will likely remain sensitive to human triggering.
Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Be cautious as you transition into wind affected terrain.>The new snow will require another day or two to stabilize.>Avoid large alpine features.>Large loose wet avalanches remain a concern. Limit your exposure to overhead hazard.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Mar 15th, 2013 2:00PM