Avalanche Forecast

Issued: Jan 26th, 2013 10:04AM

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

swerner, Avalanche Canada

Northwest Inland.

Summary

Confidence

Poor - Due to limited field observations

Weather Forecast

Sunday: Northwest flows aloft will bring continued snowfall accumulations. Snow amounts 5-10 cm accompanied by strong ridgetop winds from the NW. Alpine temperatures near -8.0 and freezing levels near valley bottom. Monday: A low pressure system over Gulf of Alaska will move onto the north coast bringing moderate precipitation. Snow amounts 10-15 cm with strong NW ridgetop winds. Alpine temperatures near -2 and freezing levels hovering around 700 m. Tuesday: Moderate snowfall amounts expected. Alpine temperatures will fluctuate from -11.0 to an average -4.0 and possibly rising to above zero degrees in areas closest to the coast. Ridgetop winds will shift out of the SW in the light-moderate ranges.

Avalanche Summary

No new natural avalanches have been reported. Several size 1.0 skier triggered avalanches occurred specifically over convex rolls at treeline elevations.

Snowpack Summary

Variable accumulations of new snow continue to build over a variety of old surfaces. These include old hard and soft wind slabs, scoured slopes, blue ice, thin melt-freeze crusts and surface hoar. Many windward slopes are scoured and thin. Recent snowpack tests recently gave generally hard to no results near Smithers. An otherwise strong mid-pack overlies a weak base layer of facets/depth hoar. Triggering of this basal weakness may still be possible from thin spots and/or rocky outcrops. I suggest digging down, or probing the snowpack to get a handle of average snowpack depths, variability and test results. Be cautious on slopes that go thin from thick. The average snowpack depth is around 100 cm at treeline, but remains quite inconsistent across the region.

Problems

Wind Slabs

Wind slabs may be found behind terrain breaks such as ridges and ribs. Hollow sounds and cracking snow beneath you is a good indicator of unstable snow.

Avoid freshly wind loaded features.>Use ridges or ribs to avoid pockets of wind loaded snow.>Be aware of sluffing from steep terrain; especially if terrain traps lurk below.>

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 4

Deep Persistent Slabs

A deeply buried weak layer near the base of the snowpack could be triggered by large loads such as a cornice collapse or from a thin-spot trigger point.

Be aware of thin and variable snowpack areas that may propagate to deeper instabilities.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 6

Valid until: Jan 27th, 2013 2:00PM