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Avalanche Forecast

Archived

Jan 22nd, 2019–Jan 23rd, 2019

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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The Bottom Line: Another round of snow with warming temperatures and strong winds will create slab avalanches. The additional shot of snow will continue to stress multiple deeper weak layers in the snowpack in the East Cascades, which could create very large avalanches. Avoid avalanche terrain if you see recent avalanches, shooting cracks, or hear whumphs.

Snow and Avalanche Discussion

Widespread avalanches occurred over the weekend and into the week. On Saturday, Mission Ridge Ski Patrol triggered multiple avalanches up to 3 feet deep on northwest through northeast aspects between 6-6500ft. To the north, a skier was caught and carried in an avalanche in the Cutthroat drainage near Washington Pass. Observers noted remotely triggered avalanches near Mission Ridge and a natural avalanche at Blewett Pass. Observers continue to find instabilities and on a layer of buried surface hoar from January 17th, even at elevations as low as 4,600ft. Deeper persistent weak layers still exist within the snowpack, especially further east in the range. All over the East Cascades, these layers are being stressed to their breaking point. Will the added load overnight into Wednesday be the straw that breaks the camel's back?

Be sure to check out the observations page for a number of recent, excellent entries!

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.