Archived

Avalanche Forecast

Feb 14th, 2017–Feb 15th, 2017

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

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

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.

Avalanche 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