Avalanche Forecast
Regions: Cascades - South East.
A variety of avalanche problems are expected east of the crest on Saturday so read the forecast carefully.
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.
Loose wet avalanches should still be likely in all zones east of the crest on Saturday. This greatest likelihood will be in the Northeast to Central East zones where some 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.
East of the crest the possibility of wet slab avalanches Saturday should be in the Northeast and Central East zones where significant rain may continue through the morning.
A persistent slab problem will also be forecast for the Northeast zone due to the report on Wednesday from Washington Pass. There is less certainty about this problem but it should get a good test via rain and warming on Friday and if this layer is human triggered it is still likely to have greater consequences due to size and propagation.
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 6-24 inch range east of the crest. Snow was most significant in the northeast with about 12-24 inches at Holden and Washington Pass through Monday morning.Â
We have no new information about the non-reactive PWL in the Jove Peak from last week, but following this storm cycle it is likely more than 1 meter down and even harder for a human to trigger.
An avalanche class near Mission Ridge on Saturday reported via the NWAC Recent Observations page that facets between crust layers in the mid pack gave a Q1 shear but did not show a tendency to propagate via an ECT.
A person reporting via the NWAC Recent Observations page Tuesday reported an extensive natural storm slab cycle in the Cutthroat area likely from early this week.
NWAC pro-observer Jeff Ward was at Washington Pass on Wednesday. He reported whumping and sudden collapse and sudden planar tests in up to 10 mm buried surface hoar on the January 15 crust at 60 cm below the surface. He also noted a previous natural shooting crack that had propagated about 1/2 mile. This report is similar to a report from 2 days earlier.
NWAC pro-observer Tom Curtis was at Mt Cashmere on Friday and at 5600 feet found 30 cm of recent wet snow on old facets that were turning to rounded grains on the January 15 crust. Compression tests gave sudden collapse and sudden planar results but PST and ECT tests did not show indicate propagation.
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.
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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: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1