Avalanche Forecast
Regions: Stevens Pass.
Older settling wind slabs may linger in higher shaded terrain Monday. An overnight refreeze, followed by clouds and cooling winds should limit the danger on Monday. Monitor surface snow conditions, and watch for surface snow becoming wet more than the top inch or two.
Detailed Forecast
The melt freeze cycle has seen more melt than refreeze by this third day of a high amplitude ridge. The forecast is being updated Monday morning due to the potential for small to large loose wet avalanches in locations that saw minimal refreeze Sunday night. This includes Snoqualmie Pass and Mt. Baker. In other areas where easterly winds have kept the snow surface cool, loose wet avalanches are less likely and should remain small.
Increasing clouds and moderate south winds and warm temperatures are expected during the day Monday. This should allow for slowly weakening surface snow, however wind and clouds should limit the surface snow melt to just a few inches at most.
Older wind slabs formed late last week will continue to strengthen, but may linger above treeline, especially on steep shaded slopes below ridges. Identify and avoid locations where avalanches are more likely triggered, such as unsupported slopes, steep convex roles, below cornices, and other shallow locations within the snowpack.
Monitor changes in surface snow conditions throughout the day, especially in areas void of a surface crust. It only takes a few inches of wet surface snow to avalanche.
Snowpack Discussion
Monday morning update: Mostly clear skies with high clouds and warm temperatures were seen Sunday night. A mix of unsupportable crusts and lack of crusts were observed Monday morning. With temperatures above freezing in most areas only areas receiving moderate easterly flow in the south Cascades saw a decent refrozen surface. Elsewhere, a shallow refreeze was observed at Mt. Baker and no refreeze was observed on the lower mountain at alpental.
Mild weather over the weekend and abundant sunshine away from the passes allowed for lingering storm and wind slabs from last week’s storms to gain strength.Â
Cooler and cloudy weather in the passes limited surface snow melt and maintained firm settled storm snow.
The very mild air temperatures and sunshine over the weekend has allowed moist to wet surface snow conditions to develop during the day, especially on the volcanoes and higher terrain away from the passes.Â
Above the recent rain/snow line last Friday, a series of storms deposited 2 or more feet of cold snow. Winds redistributed snow throughout the storms, depositing snow onto a variety of aspects. A high degree of uncertainty remains in the conditions above treeline where a lack of observations have been made since the strong storm Thursday.
The storm snow from late last week sits on a thin crust (Jan. 9) Found in the near treeline elevation band in most areas. A more supportable and thicker crust (Jan. 5) from rain or freezing rain is easily identifiable in the upper snowpack.
Below the 1/5 crust, observations continue to indicate a strong snowpack with no notable layers of concern.
Observations
North
Mt Baker Ski Patrol reported rain at 4800 feet in the ski area Friday. Recent loose wet avalanche activity was observed below treeline in the surrounding terrain. Low visibility limited observations in the near and above treeline terrain outside the ski area.
Central
Snoqualmie Pass WSDOT and Alpental Pro Patrol Reported rain to 5000 feet Friday with ice pellets above. Several natural loose wet avalanches were observed from Thursday night, some running 1000 feet. No new avalanches were observed on Saturday.
An avalanche professional in the Alpental valley on Saturday observed wet surface snow down 4 inches and moist snow all the way to the 1/5 crust below treeline. He reported very difficult travel conditions due to the wet heavy snow.Â
South
NWAC professional observer Jeremy Allyn traveled in the Crystal Mountain backcountry Friday. He observed rain to 5400 feet. In near treeline areas observations showed storm snow weaknesses gaining strength.Â
Avalanche Problems
Wind Slabs
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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: All aspects.
Elevations: Alpine.
Likelihood: Possible
Expected Size: 1 - 1
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: East, South East, South, South West, West.
Elevations: All elevations.
Likelihood: Unlikely
Expected Size: 1 - 1