Avalanche Forecast

Issued: Dec 30th, 2014 9:03AM

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

ghelgeson, Avalanche Canada

South Coast.

Confidence is poor due to wildly variable wind slabs and a forecasted Above Freezing Layer that suggests we may not get a refreeze between 1500m and 2800m until Friday.

Summary

Confidence

Poor

Weather Forecast

Synopsis: Arctic air is now dominant over all of the South Coast. Warmer air riding up and over the arctic air has created an above freezing layer that should stick around through Thursday evening.Wednesday: Freezing Level: Valley Bottom, Above Freezing Layer 1500 to 2800m; Precipitation: Nil; Wind: Treeline: Light, NE | Ridgetop: Moderate, N.Thursday: Freezing Level: Valley Bottom, Above Freezing Layer 1500 to 2800m; Precipitation: Nil; Wind: Treeline: Light, NW | Ridgetop: Light, N/NW.Friday: Freezing Level: 300m; Precipitation: Trace; Wind: Treeline: Moderate, SW | Ridgetop: Extreme, W.

Avalanche Summary

Numerous wind slab avalanches ran naturally and were triggered by skiers/vehicles on Monday to size 2.5 on SE through SW facing features between 2000 and 2200m.A member of a very experienced ski touring party was caught and carried by an avalanche on an alpine feature near Tenquille lake Monday. Aspect/bed surface unknown at this time.

Snowpack Summary

Strong outflow winds on Dec. 28 left due north slopes mostly wind pressed, some may even be scoured down to the mid Dec. crust. Slabs up to a meter thick can be found on south facing alpine features and some degree of cross loading exists on everything but the most wind sheltered terrain..Three primary layers of concern: Late Dec SH (Surface Hoar): Previously covered by 5 to 15cm and present on all aspects/elevations, distribution post wind event is certainly different, but for the time being I would presume that every slope has it until proven otherwise.Mid-Dec SH: Down 60 to 80 cm, it is becoming harder to trigger, but snowpack tests are still showing that it has potential for wide propagation. It appears to be most reactive in sheltered treeline locations.Early Dec Crust: Down 40 to 100cm and reported to be on all aspects/elevations. In some places its just a crust, other spots feature mixed forms, small grained facets and/or even the above mentioned surface hoar on top of the crust. My gut says that surface avalanches in motion could step down to this crust. The mid pack below this crust contains several old crust layers, but they seem to have gone dormant for the time being.

Problems

Wind Slabs

Outflow winds left the biggest wind slabs on south facing features, but slabs of varying thickness/hardness will be found on all wind exposed slopes. Some of these may be resting on the late Dec. SH which should keep them touchy.

Be aware of the potential for wide propagations due to the presence of hard windslabs.>Avoid open slopes and convex rolls where fresh wind slabs may rest on buried surface hoar.>Seek out wind sheltered terrain for the next few days until wind loaded slopes have had a chance to stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Persistent Slabs

Warm alpine temps may reactivate a layer of small facets, mixed forms and in some places surface hoar that overlies a rain crust down 10 - 120 cm. Surface avalanches in motion may step down to this interface.

Be aware of the potential for large, deep avalanches.>Avoid steep, open slopes.>Avoid being on or below steep sun exposed slopes which may not refreeze with the forecasted Above Freezing Layer.>Avoid open slopes and convex rolls where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 31st, 2014 2:00PM