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Avalanche Forecast

Archived

Mar 4th, 2014–Mar 5th, 2014

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

A fairly benign weather pattern with continued outflow winds until Friday. The pattern will then change and the coastal areas will see light-moderate amounts of precipitation, rising freezing levels and strong SW winds.Wednesday: Sunny. Alpine temperatures near -12.0. Ridgetop winds light from the North. Slight alpine temperature inversion.Thursday: Sunny with some cloudy periods. Alpine temperatures -10.0. Ridgetop winds light from the North. Freezing levels valley bottom with a stronger alpine temperature inversion.Friday: Snow amounts 5-10 cm. Alpine temperatures -5.0. Ridgetop winds light - moderate from the SW. Freezing levels 800 m.

Avalanche Summary

Natural avalanche activity has tapered off and only sluffing from steep terrain has been reported. Over the weekend a minor natural avalanche cycle occurred in the northern part of region. Slab avalanches up to size 2 were reported from alpine and treeline cross loaded features. North aspects in the alpine continue to be the most likely slopes for triggering the February weak layer where it may be well preserved and allow for long fracture propagations resulting in very large avalanche.

Snowpack Summary

Cold arctic air has developed melt-freeze crusts on all aspects at lower elevations, and all but North aspects in the alpine. No recent reports of whumpfing or remote triggering on this weak layer of crusts and facets. Forecast strong Northeast outflow winds continue to develop wind slabs in areas that still have snow available for transport. Basal facets and/or depth hoar remain a concern in shallow snowpack areas in the northern part of the region. Cornices are also large and may become weak if northerly winds start to undercut them.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.