Avalanche Forecast

Issued: Nov 24th, 2012 9:15AM

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

swerner, Avalanche Canada

South Rockies.

This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the Forecaster Blog for further details on interpreting early season bulletins.

Summary

Confidence

Poor - Due to limited field observations for the entire period

Weather Forecast

The weather is doing a shift from a fairly active pattern to a more benign pattern through the forecast period. A cooler, dryer NW flow will be entering the mountains with patches of lower level clouds and sunny periods in the alpine. Freezing levels will stay near valley bottom, rising to 1200 m in the afternoons. Ridgetop winds will moderate be light from the NW, switching to a Westerly flow on Tuesday.

Avalanche Summary

No current avalanche observations have been submitted. If you and your friends have been out exploring and riding in the backcountry, and have some observations to share please send us an email to forecaster@avalanche.ca.

Snowpack Summary

In the alpine I suspect 100 + cm of snow, and treeline seeing an average around 90 cm. Storms slabs and wind slabs likely exist in alpine and treeline elevations. An early season (Nov 8) rain crust has been reported to exist around 2000 m and above on NW-NE aspects. I have no further information in regards to this crust, how deep its buried or reactive it may be. I do know that it has been a reactive sliding layer in other regions to the North, which makes me suspect this could be a problem also in the South Rockies. In the alpine I suspect 100 + cm of snow, and treeline seeing an average around 90 cm. Below treeline snow levels may just be reaching threshold.

Problems

Wind Slabs

Wind slab instabilities exist and may be touchy to rider triggers. Wind slabs can be found on lee slopes and behind terrain features. Storm slab instabilities may still exist on all aspects, and require a couple of days to settle out.

Avoid cross loaded slopes at or above treeline.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be alert to conditions that change with elevation.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 4

Persistent Slabs

The early Nov. crust is buried down approximately 80 cm of snow near the base of the snowpack. It is a suspect sliding layer that may have caused large avalanches recently. The weight of a skier or sled may be able to trigger this slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Nov 25th, 2012 2:00PM