Avalanche Forecast
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.Â
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.Â
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. Â
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. Â
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.Â
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.
Avalanche Problems
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1
Wet Slabs
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 Slab avalanches can be very destructive.
Avoid terrain where and when you suspect Wet Slab avalanche activity. Give yourself a wide safety buffer to handle the uncertainty
A Wet Slab avalanche. In this avalanche, the meltwater pooled above a dusty layer of snow. Note all the smaller wet loose avalanches to either side.
Wet slabs occur when there is liquid water in the snowpack, and can release during the first few days of a warming period. Travel early in the day and avoiding avalanche paths when you see pinwheels, roller balls, loose wet avalanches, and during rain-on-snow events.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1