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Avalanche Forecast

Archived

Jan 24th, 2019–Jan 25th, 2019

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

Regions

Stevens Pass.

The Bottom Line: The snowpack is adjusting to its heavy new load, but lack of a solid freeze is causing uncertainty with a deeper weak layer. Wear your best thinking cap, and travel with care through avalanche country. 

Snow and Avalanche Discussion

Stevens Pass racked up over 2” of snow water equivalent in about 13” of snow Tuesday night and Wednesday. Snow accumulated rapidly as heavy snow fell and the temperatures warmed up, this caused a widespread natural avalanche cycle throughout the Cascades. Many large paths in the area ran including Wellington, Highway Chutes, Lichtenberg Southeast side, Arrowhead Northeast Bowl, The Swath, and likely others. These slides entrained wet snow as the debris ran through the water saturated lower elevation snowpack. It rained up to around 5,000ft, but at that elevation the crust is reported to be fairly thin.

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.

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.