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Avalanche Forecast

Archived

Feb 9th, 2019–Feb 10th, 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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Saturday’s storm piled up some light dry snow in the West-South zone. Strong winds drifted the recent snow into firmer and thicker slabs. It’s these wind loaded areas where you are most likely to trigger an avalanche Sunday. When you see snow drifts or fresh cornices, avoid nearby slopes greater than 35 degrees.

Discussion

Snow and Avalanche Discussion

The West-South zone received some light dry snow on Saturday. Most areas piled up 10-14” of powder, with areas near Mt Rainier accumulating 18-24”. Even though these are some impressive snow totals, we didn’t receive reports of any avalanches on Saturday.

We’re a little worried about how this new snow could change on Sunday, and this isn’t an easy avalanche forecast. We know that in some locations this recent snow is sitting on a layer of weak sugary facets and/or surface hoar. These old weak snow surfaces may be the most intact at lower elevations and into the near treeline band. So far, we haven’t heard about avalanches on this old snow layer. That could be because the new snow hasn’t formed a slab. As the snow settles, that may change. Locations, where the sun affects the snow, could see faster settlement rates Sunday, allowing a slab to form quickly and avalanches to become more likely. If you see new natural slab avalanches, experience collapses, or see long shooting cracks, dial back you terrain use and avoid avalanche terrain.

Snowpack Discussion

New Regional Synopsis Coming Soon

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.

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.