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Avalanche Forecast

Archived

Jan 8th, 2020–Jan 9th, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
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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You can trigger large and dangerous avalanches. Put a large buffer of terrain between where you travel and large slopes 35 degrees and steeper. Significant snowfall stressed older weak layers of snow earlier this week.

Discussion

On Wednesday, observers on Washington Pass confirmed a significant cycle of large to very large natural avalanches from January 6-7th. Avalanches were reported from the Hardscrabble drainage, First Bowl (in the Cuthroat drainage), and the Cuthroat and Liberty Bowl highway paths. Most avalanches were big enough to bury or kill a person with at least one size D2.5 avalanche reported.

 

Observers investigate the December 27th surface hoar, found about 4 feet below the surface on a southeast aspect at 5600ft in the Cuthroat drainage. 1/8/2020 Photo: Matt Primomo

Snowpack Discussion

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

Problems

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.

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.