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Avalanche Forecast

Archived

Apr 11th, 2014–Apr 12th, 2014

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

Winter transitions into spring! Rapid warming and intense solar radiation can increase the avalanche danger quickly. Check out the new Forecaster Blog which is directly focused on the Northern Regions.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

A strong ridge, with a northwest flow dominates the region bringing clear skies and rapidly rising freezing levels. Saturday: Mainly sunny. Alpine temperatures high of 2.0 degrees. Ridgetop winds light from the NW. Freezing levels rising to 1800 - 2100 m for the 24 hr period.Sunday: Mainly sunny skies with possible cloud. Alpine temperatures high of 5.0 degrees and freezing levels rising to 2100 m. Ridgetop winds light from the SW.Monday: Cloudy with sunny periods. Alpine temperatures high of 4.0 degrees and freezing levels 2000 m. Ridgetop winds light from the SW.

Avalanche Summary

A couple of size 1.5 wet slabs were reported around 1000 m and continued loose wet surface sloughing below treeline. Below is a link showing natural avalanche activity over the past couple of days, sometimes photos say more then words...Hankin-Evelyn Trail-crew update

Snowpack Summary

Up 30 cm of new snow fell at upper elevations and up to 40 mm of rain. A strong rain crust exists up to 2000 m on all aspects. At higher elevations the new snow fell onto a variety of old snow surfaces consisting of surface hoar, facets and melt freeze crusts. Strong SW winds have built thick wind slabs on leeward aspects and a poor bond may exist, especially on a buried crust.At lower elevations (1200 m and below), surface snow is moist and/ or wet, creating melt-freeze conditions.Two persistent weak interfaces exist deeper in the snowpack. The early March layer can be found down 75 - 100cm. The early February crust/facet/surface hoar combo is down 150 - 200cm. Recently, these layers have become overloaded with the new load from snow, rain and wind. They should remain on your radar, and could become reactive with solar radiation and high freezing levels.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.