Avalanche Forecast

Issued: Dec 12th, 2013 8:24AM

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.

swerner, Avalanche Canada

South Rockies.

Continued strong ridgetop winds are driving the Danger Ratings in the alpine.

Summary

Confidence

Fair - Intensity of incoming weather systems is uncertain on Saturday

Weather Forecast

Light snow is forecast overnight as the weakening cold front moves east from the coast. By Saturday another pacific frontal system will spread light amounts of precipitation accompanied by strong southwesterly ridgetop winds and gradual warming temperatures.Friday: Cloudy with sunny breaks and flurries. Alpine temperatures near -8. Ridgetop winds light from the SW. Saturday: Cloudy with snow amounts 5-10 cm. Alpine temperatures -6. Ridgetop winds strong from the SW.Sunday: Cloudy with snow amounts near 10 cm. Alpine temperatures -4. Ridgetop winds moderate from the SW.

Avalanche Summary

Explosives control saw a couple size 1.5 slab avalanches from NE-E aspects around 2000 m. I suspect that wind slabs may be easily rider triggered with the recent strong to extreme winds. 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 buried surface hoar crystals 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. This layer seems to be less reactive to snowpack testing. However, with windy, warmer temperatures and new snow it may become more reactive as the slab above it develops.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

Strong winds have developed stiff, touchy wind slabs at treeline and above. Cross-loaded slopes, gully features and loaded pillows in the immediate lee of slopes are most suspect and may be touchy to rider triggers.

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

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

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

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.

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

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Dec 13th, 2013 2:00PM