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Avalanche Forecast

Archived

Feb 2nd, 2015–Feb 3rd, 2015

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

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Storm and wind slabs remain possible Tuesday, especially on lee aspects near and above treeline. Watch for wind transported new snow received Sunday and Monday, especially higher terrain. 

Detailed Forecast

Little or no precipitation is expected early Tuesday, with light rain and snow increasing in the afternoon along the west slopes. 

Shallow storm slabs formed Sunday and Monday may be poorly bonded to old surface crusts, especially near and above treeline on lee aspects. 

Snowpack Discussion

The weekend of Jan 24-25th, a warm and wet weather system caused high snow levels and rain and allowed for extensive snowpack settlement. Last week, high pressure aloft caused abundant sunshine and mild temperatures. A frontal system crossed the PNW on Sunday, producing generally light amounts of new snow, except moderate amounts in the Mt. Baker area above 4-4500 feet. Another but weaker front moved across the region Monday. Moderate S - SW winds built new shallow wind slab near and above treeline in the Mt. Baker zone near Artist Point as reported by NWAC observer Jeff Hambleton on Monday, February 2. The winds had redistributed the storm snow, which ranged from 0 to about 10 inches depending upon terrain with wind affects noted and cross loading as well. Under the recent storm snow the strong crust was about 10 inches thick and stability tests indicated a fairly good bond existed. Some shallow failures were noted in the upper few inches of storm snow and just above the crust with little to no propagation observed.     

Prior to the recent frontal systems, the snowpack was dominated by strong surface crusts, limiting the avalanche potential. There had been surface hoar growth noted last week on shaded terrain mainly below about 5000 feet, along with some near surface faceting (NSF) on non-solar slopes. Surface hoar/NSF may have been buried by the light snowfall and initial cool temperatures Sunday. Warning and some rain may have subsequently destroyed this in the BTL band however, where little new snow accumulated as of Monday. 

See Jeff Ward's video from the Steven's Pass area below.

The snowpack west of the crest mainly consists of the generally shallow recent storm snow over stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.