Avalanche Forecast

Issued: Feb 26th, 2012 8:58AM

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

Avalanche Canada triley, Avalanche Canada

Summary

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

The ridge of high pressure should have moved into the region by Monday morning causing mostly clear skies and cooler overnight temperatures. Strong solar radiation may bring warm temperatures at or above freezing on southerly aspects. Temperatures are expected to drop down to near -14.0 in the alpine Monday night during clear skies and light northerly winds. High pressure should continue for Tuesday, and warm temperatures are expected on sunny alpine slopes. Shaded aspects are expected to remain cool and dry. Some cloud should move into the region by Tuesday evening. Forecast snowfall amounts are unsure for Wednesday at this time.

Avalanche Summary

Natural avalanches have become less frequent, but human triggered avalanches continue to release from light additional loads. The forecast new snow and wind may cause new windslabs that may overload the PWL in some areas.

Snowpack Summary

Moisture in the west of the region collided with cold air in the east and resulted in an intense period of heavy snowfall that was very low density. This new snow should settle with daytime warming and add to the 50-60 cm of recent snow that sits on a highly reactive weak layer of crusts, surface hoar and facets. At 1950 metres elevation we have some snow pack test results from Friday that show that the 40 cm slab of snow above the February 8th weak layer is sliding with easy to moderate forces applied and it is propagating widely with either sudden planar or sudden collapse characteristics. The slab is reported to be less consolidated on northerly aspects than it is on southerly aspects. In areas further north, less snow has fallen on this interface--in the northern Elk Valley for instance, only around 15-20 cm lies above this interface. In lower snow areas, avalanche activity will likely lag behind higher snow areas, except for areas which have seen significant wind transport. In general, the mid-pack is quite strong in most locations. However, lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones.

Problems

Loose Dry

An icon showing Loose Dry
Light dry snow that fell over the past few days has been sloughing in steep terrain and running far and fast.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

An icon showing Wind Slabs
Previous windslabs are getting buried by dry light snow. New windslabs may develop from forecast Northeast winds.

Aspects: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 5

Persistent Slabs

An icon showing Persistent Slabs
The weak layer of buried surface hoar, facets, and crusts continues to be triggered by light additional loads. Avalanches are expected to get larger as the slab above settles and consolidates. This weak layer may propagate into low angle terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Feb 27th, 2012 8:00AM