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Avalanche Forecast

Archived

Jan 20th, 2020–Jan 21st, 2020

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
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 avalanche danger will increase throughout the day. By Tuesday afternoon, you may be able to trigger small avalanches in the new snow at upper elevations. Check how well the new snow is bonded to old surfaces, and use caution on slopes steeper than 35 degrees if you find six inches or more of recent snow that slides easily.

Discussion

On Monday, observer, Mark Allen toured in the Rattlesnake and Robinson drainages and found a shallow and weaker snowpack compared to areas closer to Washington Pass. Snow depths ranged from about 4 feet at lower elevation to about 5 feet at mid-elevations. A notable layer of well-developed facets lies about 2 feet below the surface and is more prominent than further west in the zone.

While new snow accumulation is forecasted to be light on Tuesday, there is some uncertainty. Snow will add up throughout the day, but should only accumulate around 3 inches by dark. You may find deeper snow totals and drifts at higher elevations. Expect moderate snowfall with up to another 8" of accumulation Tuesday night. Expect an increase in avalanche danger after dark on Tuesday. You can see recent observations from Washington Pass here.

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

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.