Avalanche Forecast

Issued: Jan 20th, 2013 9:49AM

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

Avalanche Canada ghelgeson, Avalanche Canada

Low danger doesn't mean no danger. Be cautious around steep sun exposed slopes Monday afternoon.

Summary

Confidence

Good - Forecast snowfall amounts are uncertain on Wednesday

Weather Forecast

Monday: Inversion. Freezing level at surface. Above freezing layer from 1500m – 2500m. Ridgetop winds strong NW. Treeline winds mod NW. No precip. Scattered cloud, clearing in the afternoon.Tuesday: Should be the last inverted day. Freezing level at surface. Above freezing layer from 1500m – 3000m. Ridgetop winds Mod NW. Treeline winds light W. No precip.  Broken cloud cover for most of the day.Wednesday: Freezing level at valley bottom.  Snowing all day Wednesday with total daytime accumulations in the 5 – 10 cm range. Snowfall tapering overnight. Ridgetop winds initially strong W, steadily increasing to extreme NW by late afternoon.

Avalanche Summary

Activity has been limited to size 1 loose snow avalanches on slopes receiving direct sun.  Interestingly, a glide avalanche was observed on Mt. Fernie Saturday. 

Snowpack Summary

Intense recent winds have redistributed snow and created large cornices. The snow surface is now a mix of sastrugi, hard slab and soft slab in open areas. While the effects of the wind were dramatic, the sensitivity of the wind slab to triggering is decreasing. With the warm temps, slopes receiving direct sun are moistening in the afternoon. Surface hoar is continuing to form in protected areas too with recent observations of 10cm crystals. Below this around 50cm of settled snow rests on a myriad of old surfaces (January 4th interface) that include sun crust on steep south and west facing terrain, surface hoar in sheltered locations at treeline and below and facets everywhere else. Tests on this interface are still yielding sudden planar results, but the overlying slab has settled significantly and there haven't been any reported avalanches on this layer in some time now.  There are some reports of glide cracks on Mt Fernie, these mysterious phenomena should be given a wide berth.

Problems

Loose Wet

An icon showing Loose Wet
  Loose snow avalanche activity will likely pick up Monday afternoon on slopes receiving direct sun.
Beware of afternoon loose snow avalanches on steep south facing slopes.>

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Watch for the odd tired old wind slab just below ridge crest or lee of a midslope feature like a rib or rock outcropping.  Sensitivity may increase slightly on slopes receiving direct sun Monday afternoon.
Be cautious as you transition into wind affected terrain.>Watch for glide cracks and give these unpredictable natural phenomena a wide berth.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 4

Valid until: Jan 21st, 2013 2:00PM