Avalanche Forecast

Issued: Mar 15th, 2013 11:14AM

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

jlammers, Avalanche Canada

South Columbia.

Observations were limited on Friday and uncertainty exists with forecast freezing levels. Be alert to conditions that change with elevation and make observations continuously as you travel.

Summary

Confidence

Fair - Freezing levels are uncertain on Saturday

Weather Forecast

Saturday: Light snowfall becoming moderate overnight / Moderate to strong west winds / Freezing level at 1200mSunday: Light snowfall / Light to moderate northwest winds / Freezing level at 800mMonday: Light snowfall / Light southwest winds / Freezing level at 1100m

Avalanche Summary

An impressive natural cycle of slab activity to size 3.5 took place on Thursday with many features running full path. Loose wet activity to size 2 was also observed in terrain that was more rain-affected.

Snowpack Summary

Strong southwest winds, heavy snowfall, and warm temperatures in recent days have formed deep and cohesive storm slabs at treeline and above. Widespread cornice development has also taken place. At lower elevations heavy rain has continued to penetrate the snowpack. The recent storm snow overlies a weak layer of surface hoar or a sun crust that were buried on March 10th. Some areas had strong winds before the surface hoar was buried, so its distribution may be specific to sheltered and shaded terrain features. Some professionals are still expressing concern for the buried layer of surface hoar from February 12th that is now down more than 1.5m in most places. Although unlikely, the new load of snow and wind may overload this deeply buried weak layer in isolated, unsupported terrain.

Problems

Storm Slabs

Touchy storm slab conditions will continue in the wake of heavy precipitation and strong wind, especially in wind-affected terrain or in areas where recently buried surface hoar exists.

Choose conservative lines and watch for clues of instability.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>Be wary of slopes that did not previously avalanche - even on low angle terrain.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 6

Persistent Slabs

A layer of surface hoar buried on February 12th would now require a large trigger such as a large cornice fall, or an avalanche in motion. Although unlikely, the resulting avalanche would be very large.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely

Expected Size

4 - 7

Valid until: Mar 16th, 2013 2:00PM