Avalanche Forecast

Issued: Mar 16th, 2014 9:37AM

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

bcorrigan, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to the number and quality of field observations

Weather Forecast

Synopsis: A low pressure system in the Gulf of Alaska will feed moisture onto the coast and into the north west interior for the next 4 or 5 days.Tonight: Clearing as precipitation tapers off, freezing level around 1100 metres winds from the north west up to 50 km/hr.Monday: Sunny periods with a few clouds, no precipitation in the forecast, freezing level around 700 metres, winds from the west, 40 Km/hr.Tuesday: Cloudy with flurries, possible 5 to 10 cm of precipitation,, freezing level around 800 metres winds from the south west light occasionally gusting to moderate.Wednesday: Sunny with cloudy periods and isolated flurries, not much precipitation expected, freezing level around 800 metres, winds light from the west, gusting moderate to strong.

Avalanche Summary

Reports from commercial operators indicate the Feb.10th weak layer has been re-activated with recent new snow loading, and on Friday, a natural size 2 slab avalanche released on the early-March weak layer down 30-40cm on surprisingly low angle terrain (25-30 degrees).

Snowpack Summary

Conditions are highly variable throughout the forecast region. An additional 10 cm of storm snow in the Hudson Bay Mtn. area brings the slab to between 40 and 80cm overlying the early-March weak layer of surface hoar and/or a thick layer of faceted snow. This layer is most likely present on shady slopes at all elevations. There is a sun crust on steep solar aspects, and various wind affected surfaces in exposed terrain. Strong southwest winds have created dense wind slabs on exposed lee slopes and in cross-loaded features. In wind exposed areas, the snow surface is reported to be wind scoured or a very supportive wind-pressed slab. Moist/wet snow or melt-freeze crusts in the upper snowpack are likely at lower elevations, below roughly 1200m. The early February weak layer of facets, crusts, and/or surface hoar is buried down about 60-100 cm. Test results and isolated avalanche activity suggest this layer is still reactive to human-triggering. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.

Problems

Storm Slabs

Recent storm snow is sitting on a crust at lower elevations and wind-affected surfaces in the alpine. Strong SW winds have been redistributing the new snow into wind slabs on lee slopes at tree line and above. Route selection is critical right now.

Choose well supported terrain without convexities.>Use conservative route selection, stick to moderate angled terrain with low consequence.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

The early-March weak layer appears to have been re-awakened by new snow loads and might now be triggered by light loads like skiers and sledders The slab is now typically 40 to 80 cm thick and continues to produce large avalanches.

Be aware of thin areas that may propogate to deeper instabilites.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

3 - 6

Deep Persistent Slabs

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

4 - 7

Valid until: Mar 17th, 2014 2:00PM