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Avalanche Forecast

Archived

Dec 23rd, 2019–Dec 24th, 2019

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

Regions

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The snowpack is still adjusting to a large amount of new snow produced during the storm and needs time to stabilize. Avalanche danger and snow depth increases as you gain elevation. In the Crystal region, very large and destructive avalanches have been observed and require an added layer of caution.

Discussion

The snowpack and resulting avalanche hazard change by location and elevation around the West South region. You may experience locally lower avalanche danger in areas that did not receive the massive water numbers of Crystal and Paradise (7.45” and 6.57” respectively). At lower elevations there just isn’t enough soft snow to form an avalanche hazard. Instead, expect difficult travel conditions with refreezing snow, exposed objects, and open creeks. 

Several very large (D3) natural and explosive triggered avalanches were observed in the Crystal region over the last few days. These events occurred on Friday and Saturday during the meat of the storm. Recent avalanches clearly indicate unstable snow is present. 

A very large natural avalanche near the Crystal Mountain ski area which likely occurred during the storm. Lizard’s Back, N aspect, 6000ft. Photo: Robin Pendry. 

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.

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.