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

Regions

Northwest Inland.

Check out the Forecaster Blog for more information on the persistent weak layer.

Confidence

Fair - Wind effect is extremely variable

Weather Forecast

A fairly benign weather pattern until Friday. The pattern will then change and the region will see light amounts of precipitation, rising freezing levels and strong SW winds.Wednesday: Mix of sun and cloud. Alpine temperatures near -15.0. Ridgetop winds moderate from the SE. Slight alpine temperature inversion.Thursday: Snow amounts 5 cm. Alpine temperatures -15.0. Ridgetop winds moderate from the SE. Freezing levels valley bottom with a strong alpine temperature inversion.Friday: Snow amounts 5-10 cm. Alpine temperatures -5.0. Ridgetop winds light-moderate from the SW. Freezing levels 500 m with an alpine temperature inversion.

Avalanche Summary

No new avalanche activity reported.

Snowpack Summary

Temperatures have remained cool even with solar radiation, and now the temperatures have dropped to very cold with the influence of arctic air sliding down from the Northeast. Surfaces are seeing significant new surface hoar growth and surface facetting, especially in treeline and below. The early February weak layer of facets, crusts, and surface hoar is buried down about 35-90 cm. The snow above the crust has been transported by Southwest winds and then reverse loaded by Easterly or Southeast winds. Cold temperatures have not settled the snow above the weak layer into a cohesive slab, and the cold has preserved the weak layer and associated crusts. I suspect that there will not be much change or improvement in the bonding of the late February snow to the crusts and facets. Snow pack tests may help to show when this layer demonstrates more resistance to added forces.

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.