Avalanche Forecast

Issued: Feb 11th, 2015 8:13AM

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

ccampbell, Avalanche Canada

South Rockies.

Recent snowpack observations have been extremely limited, and the snowpack will likely need more time to adjust to the recent heavy precipitation.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

Warm and dry for the forecast period. Freezing levels could rise above 3000 m on Friday, before dropping back down on Saturday. Expect brief periods of solar radiation interspersed with cloudy conditions.

Avalanche Summary

Observations have been essentially non-existent in recent days. This likely speaks more to a lack of observers rather than actual conditions. I'm confident recent storm loading has produced large storm slab avalanches at higher elevations, while loose wet or wet slab avalanche activity occurred at lower elevations where rain fell.

Snowpack Summary

The rain line during recent heavy precipitation generally hovered around 1700m, although there were periods where rain fell into the alpine. Above that elevation, heavy accumulations of moist, dense snow have been pushed by strong southwest winds into much deeper deposits on the lee side of ridgecrests and terrain breaks. This recent storm snow overlies a hard crust, which may have overlying surface hoar that was buried late January. The mid-December crust/facet/surface hoar weakness may be persisting in the mid to lower snowpack at higher elevations.

Problems

Storm Slabs

Deep unstable storm slabs may linger at higher elevations. As you head into the alpine in search of drier snow, be wary of steeper slopes that haven't avalanched as very large avalanches are a concern.

Choose conservative lines and watch for clues of instability.>Be cautious as you transition into wind affected terrain.>Be alert to conditions that change with elevation.>The new snow will require several days to settle and stabilize.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Cornices

Warm temperatures could make large cornices overhanging the leeward side of ridgecrests unstable. Not only are they a hazard in themselves, but they could also act as a heavy trigger for large slab avalanches on the slope below.

Cornices become weak with daytime heating, so travel early on exposed slopes.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried week layer which formed in December should still be treated with suspicion. Although not much is known about the current reactivity of this potentially destructive layer, I'd use extra caution in steep, unsupported alpine terrain.

Avoid steep convexities or areas with a thin or variable snowpack.>Be aware of the potential for very large, deep avalanches due to the presence of buried surface hoar or a facet/crust layer.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 5

Valid until: Feb 12th, 2015 2:00PM