Avalanche Forecast

Issued: Nov 30th, 2012 8:22AM

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

mike.koppang, Alberta Parks

Kananaskis.

New snow, winds and temps are creating ideal conditions for slab development in open terrain. A few cornice collapses were observed throughout the day so be sure to avoid traveling underneath these features.

Summary

Confidence

Fair - Intensity of incoming weather is uncertain on Saturday

Weather Forecast

Another 10-15cm of new snow is forecast to fall over the next 24hrs. Temperatures are forecast to be in the -8C to -10C range with a freezing level around 1800m. Winds are expected to increase into the strong range out of the SW so keep and eye on local winds because with all the new snow recently and forecast, stability can deteriorate quickly.

Avalanche Summary

3 separate cornice collapses were observed on Mt Murray within minutes of the winds picking up. Several loose dry avalanches up to size one were observed in the storm snow. Expect the upper snowpack to become increasingly "slabby" overnight due to winds and temps and as a result we will see an increase in natural avalanche activity on N and E aspects on saturday, especially at treeline elevations and above.

Snowpack Summary

15cm HST over the past 24hrs. Warm temps promoting rapid settlement in the upper snowpack and even moist surface snow at lower elevations (below 1800m). New snow is quick to for storm slabs up to 30cm thick in open wind affected terrain. Midpack well settled and the 1106 rain crust is down 60-110cm throughout the forecast area. Moderate to hard sudden collapse sheers are being observed in a facet layer below the 1106 crust.

Problems

Storm Slabs

New storm slabs are currently building with the recent snow, warm temps and moderate to strong SW winds. These slabs are 10-30cm thick at this time but they can quickly become thicker and more reactive if the winds increase.

Avoid freshly wind loaded features.>Whumpfing is direct evidence of a buried instability.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Wind Slabs

Pockets of buried wind slab are present in lee and cross loaded features in the alpine and isolated areas at tree line. These weakness are harder to locate with the new snow.

Avoid lee and cross-loaded terrain near ridge crests.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 5

Persistent Slabs

The Nov rain crust persists about 30cm off the ground throughout the forecast area and is reactive to stability tests in the moderate to hard range. Avalanches in the upper snowpack may step down to this weakness.

Be aware of the potential for full depth avalanches due to deeply buried weak layers.>Be aware of thin areas that may propagate to deeper instabilites.>

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

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Dec 1st, 2012 2:00PM