Avalanche Forecast

Issued: Nov 30th, 2013 8:19AM

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

jlammers, Avalanche Canada

South Columbia.

Snowfall amounts are uncertain for Sunday. If the new snow amounts are upwards of 20cm in your area actual danger ratings may be HIGH

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Sunday: Moderate to locally heavy snowfall / Strong southwest winds / Freezing level at about 1000mMonday: Light snowfall / Light west winds / Freezing level at valley bottomTuesday: Clear skies / Light north winds / Alpine temperatures of about -17.0

Avalanche Summary

No reports of recent avalanche activity have been received. I would expect a new round of storm slab activity with weather forecast for the weekend.

Snowpack Summary

Total snowpack depths range from 110 to 160cm at treeline across the region. On the surface a developing storm slab covers a variety of old surfaces which include: old wind slabs at higher elevations, melt-freeze crusts on previously sun-exposed slopes and surface hoar in sheltered terrain.In the mid snowpack you may find a layer of surface hoar buried in mid-November ranging from 60cm-100cm in depth. An October crust/facet combo exists near the base of the snowpack. The most likely place you'd trigger this layer is on smooth, planar, high north facing slopes, especially if the snowpack is unusually shallow in that area.These persistent layers are slowly becoming more difficult to trigger. However, they have the potential to cause large and destructive avalanches, and may 'wake-up' with the increased load of new snow forecast for the next few days.

Problems

Storm Slabs

The new storm slab may be especially touchy in wind affected terrain, or in areas where it overlies recently buried weak layers.

The new snow may require several days to settle and stabilize due to the presence of buried weak layers.>Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 4

Persistent Slabs

A few persistent weak layers exist in the mid and lower snowpack. The weight of the new snow forecast for the weekend could act as the tipping point for these layers, producing large and destructive avalanches.

Caution around large unsupported slopes and areas with a thin or variable snowpack. Persistent slabs have the potential for wide propagation.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 1st, 2013 2:00PM