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Avalanche Forecast

Archived

Mar 18th, 2019–Mar 19th, 2019

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

Regions

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The snowpack is undergoing a major thaw. Large and dangerous natural wet avalanches are possible. This is a good time to step back, and allow the mountains to make the transition. 

Discussion

Snow and Avalanche Discussion:

After a prolonged period of below average temperatures with light snowfall, we are experiencing a heat wave with very warm temperatures. The snowpack is making a transition from cold and dry, to a spring-like pack. Meltwater is beginning to make its way through the upper snowpack. Along with this, there is a high degree of uncertainty regarding avalanche size over aspects and elevations. The only dry snow left is on direct north facing slopes, elsewhere, wet snow is commonplace. Cornices may begin to sag and break off. The most active period for wet avalanches will likely be late in the afternoon.

A number of wet loose slides hit the closed Hwy 20 recently, one was quite large (D2.5). Professional guides reported several recent wet loose slides on a variety of aspects, and even watched a small one (D1) run on Monday on a northeast aspect at 7,500ft. Over the weekend observers reported small to large loose wet avalanches on steep, sun-exposed slopes near Washington Pass and in the Twisp River drainage. Last week's storm brought variable snow totals throughout the East-North zone. In areas that received more snow, several natural slab avalanches (up to size D2.5) were reported and were believed to occur on Wednesday, primarily in steep upper elevation north facing terrain.

The heat wave is on. Temperature graph from early March through current.

Snowpack Discussion

Coming soon.

Problems

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.

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.