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Avalanche Forecast

Archived

Feb 22nd, 2015–Feb 23rd, 2015

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

Regions

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Small loose wet avalanches and lingering wind slab will most likely be found above treeline Monday. 

Detailed Forecast

Generally light winds and warmer temperatures are expected Monday as freezing levels rise to 8000-9000 feet. 

As a result, small loose wet avalanches may be possible on steeper solar slopes near and above treeline in the late morning or early afternoon. 

Recent shallow wind slab formed on non-traditional westerly aspects above treeline may still be sensitive. 

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard. 

Snowpack Discussion

Since the mild and wet start to February, fair weather through mid-February has lead to generally thick surface crusts and further consolidation of the snowpack, as well as further deterioration of the snow cover below treeline especially further from the crest.

A few weather disturbances passed through in NW flow aloft the latter half of the week, bringing an inch or two of new snow near and above treeline and near the Cascade crest.

Winds veered to the east or northeast on Saturday, likely causing some very shallow new wind slab formation on non-traditional westerly aspects mainly above treeline.  

No new avalanches or instability was observed in the Washington Pass area Saturday by the NCMG.  

While the January 15th facet/crust layers can still be identified in parts of the NE Cascades, this persistent weak layer has been stabilizing and become unlikely to trigger. As a result the Persistent Slab problem has been removed from the northeast zone.

Problems

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.

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.