Avalanche Forecast

Issued: Feb 14th, 2017 4:34PM

The alpine rating is high, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Loose Wet.

jlammers, Avalanche Canada

Northwest Coastal.

The effect of recent warming is uncertain, and buried weak layers exist in the snowpack. Conservative terrain selection remains critical.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Wednesday

Weather Forecast

Wednesday: 5-15cm of new snow / Strong southwest winds / Freezing level at about 1100mThursday: 4-8cm / Light and variable winds / Freezing level at about 1100mFriday: Light flurries / Light and variable winds / Freezing level at about 800m

Avalanche Summary

Over the past few days a natural avalanche cycle up to size 3 occurred in response to heavy snow and wind. The peak of the natural avalanche activity occurred a few days ago; however, human triggered slab avalanches to size 1.5 were observed failing on recently buried surface hoar as recently as Monday. Recent naturally triggered wind slabs were also observed.Ongoing storm slab activity is expected in response to new snow and wind on Tuesday and Wednesday. New snow will also add stress and destructive potential to deeper weak layers. Loose wet avalanches are expected to continue at lower elevations where precipitation falls as rain.

Snowpack Summary

Anywhere from 40-80 cm of recent snowfall has fallen. Precipitation has been falling as wet snow or rain at lower elevations. The new snow overlies a variety of old surfaces which include wind slabs, facets, sun crusts on steep solar aspects and well-developed surface hoar in sheltered locations. Deeper in the snowpack, the mid-January surface hoar/facet layer is now down roughly 80-120 cm. Recent observations suggest the layer has generally stabilized but isolated weaknesses may still exist, mainly where buried surface hoar is still intact. Below this layer, the snowpack is generally strong and well settled. The exceptions are areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern, especially in shallow snowpack areas.

Problems

Storm Slabs

Fresh storm slabs continued to build on Tuesday. Expect increased reactivity in higher elevation wind-exposed terrain. New snow will also add stress to recently buried surface hoar which appears most reactive around treeline.

If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be cautious as you transition into wind affected terrain.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

2 - 3

Loose Wet

Rain and moist snow accumulating at lower elevations will promote loose wet avalanches over the course of the storm, especially in steep terrain.

Use extra caution on slopes if the snow is moist or wet.Be cautious of sluffing in steep terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 15th, 2017 2:00PM