Avalanche Forecast

Issued: Feb 23rd, 2012 9:27AM

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

Avalanche Canada triley, Avalanche Canada

Summary

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

A low pressure system is moving inland from the coast on Friday. This system is forecast to bring snow and moderate southwest wind to the Kootenay Boundary by afternoon and to the South Rockies region by the early evening. Snowfall amounts are forecast to be about 5 cm for the South Rockies on Friday. Another 10-15 cm for the South Rockies and 15-20 cm in the Lizard Range are expected overnight and during the day on Saturday. Sunday is forecast to be a mixed bag of convective flurries and some sunny periods. The freezing level is expected to rise to about 700 metres on Friday, drop back to valley bottom overnight and then rise to near 1200 metres on Saturday.

Avalanche Summary

We have reports of numerous avalanches up to size 2.5 with crowns about 40-50 cm on N-NE aspects in the Corbin area of the Flathead.

Snowpack Summary

Gusty wind has transported snow into windslabs at all elevations. In southern and western parts of the region, 40-50 cm of recent snow sits of a highly reactive weak layer of crusts, surface hoar and facets. At 1950 metres elevation we have some snow pack test results 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

Persistent Slabs

An icon showing Persistent Slabs
Avalanches have been easily triggered on this layer between 20 and 70 cm below the surface. The highly reactive nature gives the possibility for remote-triggered avalanches as well as propagation into low angled terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

3 - 6

Wind Slabs

An icon showing Wind Slabs
Strong gusty winds have developed stiff windslabs. Windslabs may take a couple of days to settle, and may persist in areas where buried surface hoar or a crust is present.

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 6

Valid until: Feb 24th, 2012 8:00AM

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