Avalanche Forecast
Regions: Stevens Pass.
Loose wet avalanches and possible wet slab avalanches should be the main avalanche problems west of the crest on Saturday.
Detailed Forecast
The ridge will slightly amplify and gradually shove the incoming warm front moisture north to BC on Saturday. So rain will initially decrease in the south Cascades Saturday morning and then in the north Cascades Saturday afternoon and night with high snow levels and very mild temperatures.
West of the crest loose wet avalanches should still be likely in all zones on Saturday. This greatest likelihood will be in the Northwest to Central West zones where rain will continue much of Saturday. Avoid steep slopes if you are in significant rain and start to see wet snow deeper than a few inches or increasing natural pinwheels or rollerballs.
West of the crest the possibility of wet slab avalanches on Saturday should also be in the Northwest to Central West zones where significant rain should continue through Saturday morning.
The avalanche danger should be lower by later Saturday but it is difficult to say how much due to the rapidly changing conditions.
Snowpack Discussion
Snow on the back end of the last storm Sunday and Monday was mostly in the 8-25 inch range west of the crest except at Stevens Pass where the extra snow from last Saturday night caused a storm total of about 33 inches.
Here is a video from Monday by NWAC pro-observer Dallas Glass at Stevens Pass via our YouTube Channel. It should give an idea of the snow available for avalanches Friday.
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 15 January crust. Here is a link to the Instagram video. While in this particular pit it gave a pretty remarkable score of PST 15/100 End it will not be listed as an avalanche problem due to a lack of activity on this layer, inconsistent distribution and that is should require a very large trigger.
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.
Warm front moisture from the sub tropics will move over an upper ridge and mainly over the Olympics and Washington Cascades through Friday night. This will bring rain and greatly rising snow levels Friday and Friday night. This will give the snowpack a good test in most areas and we should find out if there much of an avalanche cycle from reports on Saturday.
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: Likely
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: Possible
Expected Size: 1 - 1