Avalanche Forecast

Issued: Dec 27th, 2014 8:16AM

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

jlammers, Avalanche Canada

South Rockies.

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Summary

Confidence

Poor - Due to the number of field observations

Weather Forecast

A moist low pressure system will linger on Sunday bringing mostly patchy light snowfall, moderate northerly winds and freezing levels at valley bottom. By Monday a dry arctic ridge will set-up for the rest of the forecast period. With this ridge, we'll see mainly clear skies, light to moderate northeast winds and alpine temperatures around -20.

Avalanche Summary

Wind slabs to size 1.5 were observed in high elevation terrain on Friday. Strong winds on Saturday may still be blowing loose surface snow into fresh wind slabs, and reactivity may persist for a few days.

Snowpack Summary

On the surface, up to 30cm of low-density snow exists. In the alpine and at treeline, winds have been conducive to blowing this snow into wind slabs in exposed lee areas. 30 - 60 cm below the surface (more in wind affected areas) you may find a crust that may have surface hoar on top of it. The crust is reported to extend into the alpine to at least 2100 m, while the surface hoar was reported to be most reactive on shady aspects around treeline and just below, between around 1600 m and 1900 m. Where the crust exists, it may be bridging triggers from penetrating to deeper persistent weaknesses that formed earlier in the season. However, on high alpine slopes above where the rain crust formed, or in areas where rain didn't occur, facets, and/or buried surface hoar may still be susceptible to triggers.

Problems

Wind Slabs

Strong and variable winds have redistributed loose surface snow into wind slabs in lee terrain. Watch for triggering behind ridge crests and terrain breaks.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A crust which formed in December should remain on your radar. Not much is known about its distribution in the South Rockies. However, in neighboring regions it has produced large avalanches. Dig down and test weak layers before committing to a line.

Stick to well supported terrain and be aware of what is above you at all times.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Dec 28th, 2014 2:00PM