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Avalanche Forecast

Archived

Feb 13th, 2019–Feb 14th, 2019

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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The new snow buried variable and weak old snow surfaces. Widespread natural and human-triggered avalanches were reported recently. Continue to use extra caution around steep slopes at upper elevations, and put plenty of space between where you travel and large pieces of terrain where avalanches could start or run to from overhead slopes.

Discussion

Snow and Avalanche Discussion

The Washington Pass area received over 1ft of new snow (1.25in SWE) since Monday. On Wednesday, we received reports of a widespread natural storm slab avalanche cycle at all elevations and aspects. Avalanches with the widest propagation occurred on southerly slopes. On Tuesday, a remotely triggered avalanche occurred on the old/new snow interface where buried facets on a crust were found (observation). Shooting cracks and touchy slab conditions at ridge crest were also reported. The old snow surface is weak, and all observations point to dangerous avalanche conditions in the northeast Cascades right now.

Most avalanche accidents occur with Considerable Danger. Continue to be aware of your surroundings and check for instabilities. Ask yourself, "Am I in avalanche terrain? Could the snow slide?" Traveling one at a time is good practice, but it does not eliminate the hazard of choosing to enter avalanche terrain. Stick to lower angle, supported terrain, and places well away from large, steep, open slopes.

We have received a lot of snow over the past few days. These are the conditions when tree well and snow immersion suffocation accidents occur. Don't travel alone, and keep eyes on your partners. Check out https://www.deepsnowsafety.org/ for more information. 

Snowpack Discussion

Regional Synopsis coming soon.

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.