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Avalanche Forecast

Archived

Jan 25th, 2015–Jan 26th, 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.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Stevens Pass.

Be aware of heightened avalanche danger in steeper terrain and near terrain traps relating to wet avalanches.    

Detailed Forecast

Monday should be quite warm (freezing levels 10-11 kft) and mostly sunny. Despite the high freezing levels, a few factors should help tamp down the avalanche danger Monday; a melt-freeze crust formed overnight in sheltered locations, significant snowpack settlement over the past few days, weak solar input (January sun), and stiff winds near crest level will all help limit the likelihood of human or natural wet avalanches.

Keep in the mind that although the likelihood of triggering an avalanche is unlikely outside poorly supported steeper slopes, the central and north Cascades have had more recent snow available for entrainment with the potential for larger slides near and above treeline. 

Generally avoid steep slopes especially near terrain traps where you might be able to push off enough saturated snow to start an avalanche large enough to take you for a ride. Wet slabs, human or natural triggered, are unlikely Monday but be aware of their destructive potential and low predictability. 

Remember, due to the unseasonably low snowpack especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.  

Snowpack Discussion

The most recent significant snow from one week ago was involved in generally small avalanches Friday and Friday night during periods of heavier rain. 48 hr storm totals through Sat AM for NWAC stations west of the crest were 1.5 to 3 inches of rain from Snoqualmie Pass and north and 0.25 - 1.5 inches south of Snoqualmie. Mt. Baker received the most precipitation and Crystal the least. High freezing levels along with plentiful sunshine were seen around the Northwest Sunday. Recent weather has caused significant settlement of the snowpack with the upper portion consisting of wet grains.  

Our NWAC pro-observers were at Stevens Pass for a class Tuesday and found a potential persistent weak layer of 2 mm facets on the Jan 15th crust. Pro-observer Jeremy Allyn was in the Skyline area on Stevens on Sunday and found this layer under a settled and wet 45 cm of snow on Sunday. While this layer failed at a density change below the crust during snowpack tests, it did not seem likely to propagate. Professional patrollers from Mt. Baker and Alpental saw little in the way of natural or explosive triggered avalanche activity over the weekend. 

West of the crest the middle and lower snowpack should consist mostly of stable rounded grains or melt forms and crusts from warm periods this winter.

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.