Avalanche Forecast

Issued: Mar 11th, 2014 10:03AM

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

rbuhler, Avalanche Canada

Northwest Inland.

Summary

Confidence

Fair - Due to the number of field observations

Weather Forecast

The precipitation is expected to ease late Wednesday and a ridge will build on Thursday. Another frontal system is expected for Friday but should only result in light flurries. Tues. Night/Wednesday: Snow or rain 3-6mm, freezing level progressively falling from around 1500m to 900m, ridgetop wind 60-80 km/h SW-W easing during the dayThursday: A mix of sun and cloud, dry conditions, freezing level 500m overnight, 1000m afternoon, ridgetop wind light SWFriday: Snow or rain beginning Thursday night 6-10mm, freezing level 700m overnight, 1200-1500m afternoon, ridgetop wind 20-40 km/h SW

Avalanche Summary

Avalanche activity has tapered off since the weekend but isolated activity is still being reported. Reports from Monday of natural and human-triggered storm slab avalanches up to size 1.5. In thinner snowpack areas, isolated activity up to size 2 has been reported on the early-Feb layer down 60-80cm.

Snowpack Summary

Roughly 20-50 cm of dense storm snow now sits on a weak layer consisting of surface hoar and/or a thick layer of faceted snow on shady slopes at all elevations, 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. 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

Up to 50 cm of dense storm snow overlies the previous snow surface of weak sugary facets, old wind slabs, or a melt-freeze crust. Strong wind, typically from the SW, has created stiffer wind slabs in lee features.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

2 - 4

Persistent Slabs

A weak layer buried in mid-February is now down 60-120 cm deep. The layer remains reactive to human triggering. Smaller avalanches have the potential to step down to this layer resulting in large, destructive avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

3 - 6

Valid until: Mar 12th, 2014 2:00PM