Avalanche Forecast

Issued: Dec 29th, 2013 8:32AM

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.

ghelgeson, Avalanche Canada

South Rockies.

Summary

Confidence

Poor - Wind effect is extremely variable

Weather Forecast

Synopsis: NW flow continues to dominate the pattern. A few cms may make it into the region, but no significant accumulations are expected. The big player over the next few days will be the wind. 2000m wind forecasts are provided below, 3000m winds are roughly 1.5x greater.Monday: Freezing Level: Valley Bottom; Precip: Nil Wind: Mod NW/WTuesday: Freezing Level: Valley Bottom; Precip: 1/2mm 2/5cm Wind: Mod W switching to Strong NW near sundown.Wednesday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Initially Mod NW switching to Light SW by Wednesday evening.

Avalanche Summary

On Christmas Eve a backcountry skier triggered a size 2 slab avalanche on an alpine slope in the Harvey Pass area. The slab was reportedly 70cm deep and 150m wide and was thought to have slid on the late-November crust/facet interface. There were no reported injuries with the avalanche.No other avalanches have been reported.

Snowpack Summary

There appears to be a lot of snowpack variability across the region. Snowpack depths at treeline seem to vary from 60 - 130 cm with high variability in wind-exposed areas. Winds have been strong out of the SW on Sunday at all wind stations. With 10 - 15 cm available for transport I expect wind slabs to be touchy on Monday. In the mid pack is the late-November/early-December interface which is made up of surface hoar, a crust, and/or facets. This layer is typically down 30-70cm and has reached the tipping point for rider triggering in a few areas including the Harvey Pass area. Check out this video of a recent snowpack test on this layer. We're probably getting close to this layers tipping point in wind loaded terrain at treeline in much of the region.

Problems

Wind Slabs

Strong SW winds continue to form snow into fresh sensitive wind slabs. Strong winds may have an effect on open slopes at treeline. Take care to avoid snow that feels stiff under your machine or skis and watch for signs of wind loading.

Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

It's getting a little tricky out there. Wind slabs avalanches have the potential to step down and trigger an avalanche on the buried surface hoar. Plan an escape route when sizing up your lines and regroup in safe zones.

Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.>Dig down to find and test weak layers before committing to a line.>Make observations and assess conditions continually as you travel.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1 - 5

Valid until: Dec 30th, 2013 2:00PM