Avalanche Forecast

Issued: Dec 11th, 2013 8:11AM

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

swerner, Avalanche Canada

South Rockies.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The South Rockies will begin to see mostly light amounts of new snow, gradual warming and strong ridgetop winds as the weakening cold front passes through on Thursday. Thursday: Cloudy with some flurries. Alpine temperatures near -8. Ridgetop winds moderate from the SW.Friday: Precipitation will taper off as we see a break in the system. Cloudy skies, a trace of new snow. Alpine temperatures -7. Ridgetop winds moderate from the SW.Saturday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -4. Ridgetop winds moderate from the SW gusting to 100 km/hr.

Avalanche Summary

No new avalanche observations have been reported, however I suspect that wind slabs may be easily rider triggered. Use extra caution on cross-loaded slopes, and in the immediate lee of ridgelines. Small loose dry avalanches are likely from steeper slopes, and do not support a significant problem unless you were pushed into a terrain trap like a cliff, or a gully.

Snowpack Summary

Incremental snowfall amounts have begun to bury surface hoar and a faceted upper snowpack. Snowpack depths at treeline seem to vary from 50 - 110 cm and widespread wind effect is noticeable in the alpine and at treeline.Down 30-40 cm sits a surface hoar/ facet/ crust interface. Snowpack testing showed easy results and some whumphing (failure of a weak layer below your feet). If you're seeing or feeling this, consider it a direct indicator of a buried weakness below.Near the base of the snowpack, weak sugary facets and depth hoar exist. This layer may be stubborn to trigger, especially in deeper snowpack areas. In shallower locations the likelihood may increase especially on a steep, convex slope.In some areas it is below threshold below treeline, and early season hazards like open creeks, and stumps exist.

Problems

Wind Slabs

Winds from the SW have developed wind slabs at higher elevations on lee slopes and behind terrain features. Avoid cross-loaded slopes.

Be careful with wind loaded pockets. Be aware of wide variation in snowpack depth>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Sugary facets near the base of the snowpack represent the most worrisome layer at this time. A surface hoar layer 30-40 cm down may be easily rider triggered with forecast new snow and warmer temperatures.

Avoid shallow snowpack areas on steep, convex terrain where triggering is more likely.>Dig down to find and test weak layers before committing to a line.>Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Dec 12th, 2013 2:00PM