Avalanche Forecast

Issued: Nov 25th, 2012 8:54AM

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

Avalanche Canada swerner, Avalanche Canada

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

Summary

Confidence

Fair - Due to limited field observations for the entire period

Weather Forecast

Monday-Tuesday will see patchy valley cloud in the mornings with clear, sunny skies in the afternoon.  No precipitation is expected, ridgetop winds will be light from the NW. Alpine temperatures will remain near -4 with freezing levels generally sitting near 800-1100 m. Wednesday should start to see a change as the next system sets up. Timing and intensity of Wednesdays system is uncertain.  Freezing levels may climb to 1900 m, and winds will switch out of the South.

Avalanche Summary

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

Snowpack Summary

The previous storm has formed new storm slabs which may have buried existing wind slabs. Storm slabs may be touchy and easy to trigger and may take a couple days before they settle out. An early November crust is located near the bottom of the snowpack under the past weeks snow accumulations.  This crust has been seen from 1700 m to ridgetop on all aspects. Recent tests done have resulted in CTM-H ranges with SP characteristics. I have also received reports of a SH layer buried 100 cm down. The SH sits about 10 cm above the November crust and is 3-4 mm in size. Tests on this layer are in the mod-hard range with a SP characteristic. At this time the SH may just be localized and not widespread, not sure?  Dig down, do some detective work, and see how the snowpack is looks, feels and reacts in your neck of the woods. 

Problems

Storm Slabs

An icon showing Storm Slabs
Recent snow has continued to build storm slabs. They may be touchy to rider triggers and require a few days to settle and bond to the upper snowpack. Winds slabs have formed on lee slopes and ridges. Use caution with changing winds and patterns.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.>Use ridges or ribs to avoid pockets of wind loaded snow.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
An early Nov. crust and a surface hoar layer sit near the base of the snowpack. There is low probability that a rider could trigger this, but if you hit a sweet spot, or a thin area that propagates deeper, the severity of the avalanche would be huge.
Be aware of the potential for full depth avalanches due to deeply buried weak layers. Low probability but high consequence.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 5

Valid until: Nov 26th, 2012 2:00PM

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