Avalanche Forecast

Issued: Jan 20th, 2012 9:08AM

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

jlammers, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

Saturday: 15-20cm of snow (8-12 on the east side) - Strong southwest winds - Freezing level at 900mSunday: Trace amounts of snow - Moderate to strong southwest winds - Freezing level trending from surface to 600m throughout the dayMonday: Light snowfall - Moderate to strong southwest winds - Freezing level at about 800m

Avalanche Summary

Skiers easily triggered size 1 slabs in both the Flathead and South of Crowsnest regions on Thursday. In the Flathead, these were running on a crust/facet/surface hoar combo below the storm snow (about 50-60cm deep). A skier remotely triggered a size 1 slab on a NE aspect at 2300m from 20m away. Expect significant storm and wind slab activity with Friday night/Saturday's forecast weather.

Snowpack Summary

Over the week 40-60cm of snow formed soft slabs over a crust/facet/surface hoar combo. Forecast snowfall, wind and warming on late Friday/Saturday will create a more destructive and reactive storm slab problem.Deeper in the snowpack, a surface hoar layer buried in early December remains a concern, as avalanches triggered on this layer would be destructive. However, information is limited about its current reactivity. From preliminary observations, the rapid storm snow load on Tuesday did not cause any releases on this layer.Facets sandwiched between two firm layers in the top metre of the snowpack are being monitored in the south-east.

Problems

Wind Slabs

With forecast weather, destructive wind slabs will be easy to trigger on lee and cross-laded slopes.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Storm Slabs

Forecast temperatures, wind and snow will add load and reactivity to a storm slab that has been developing throughout the week.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 6

Persistent Slabs

A buried surface hoar layer in the top metre of the snowpack continues to be a concern. Although it has become stubborn to trigger, the consequences are high. It's most likely to be triggered from shallow rocky areas on a slope, or by a large load.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Jan 21st, 2012 8:00AM