Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
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The Bottom Line: The avalanche danger is slowly dropping, but the hefty new load of snow is still a concern. You may trigger avalanches in areas where the wind has formed firm slabs or in locations where weak old snow layers exist. You can stay safe by avoiding slopes greater than 35 degrees.
Snow and Avalanche Discussion
The recent upslope storm revived winter in the lowlands of the eastern slopes. It also added a hefty load to the upper elevation snowpack in some places. Snowfall totals appear to vary widely, from 5" to 14", likely more at higher elevations. The snow came in cold and warmed up as it fell, creating a density inversion that may still be noticeable. A common structure to be found out there will be storm snow (with or without a wind slab) over a crust. On the 10th, avalanche workers were able to trigger a number of wind slab avalanches in closed areas at Mission Ridge with explosives. These were from 6" to 16" deep and from 60' to 125' wide, running on the crust. One of these broke into older, weak snow near the ground. This one was on a Northwest aspect at 6300ft.
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.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
