Avalanche Forecast

Archived

Jan 6th, 2015–Jan 7th, 2015

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

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Areas of wet snow are expected, especially on steeper southerly facing slopes exposed to direct sunshine.

Detailed Forecast

Drying, clearing and very warm air with freezing levels exceeding 10,000 feet are expected Tuesday. This should allow for the recent rain soaked upper snow layers to drain and gradually consolidate. Clearing overnight Monday may have allowed for radiational cooling to form a thin melt-freeze crust.

Snowpack Discussion

From 1 to over 3 inches of rain has fallen over the Cascade east slopes from Sunday night to Monday evening, following about 6-12 inches of snowfall that accumulated prior to the warming. It is difficult to assess just how impactful the warming and rain was along the east slopes, especially in the north part, where more precipitation fell as snow prior to the full warming Monday.

No observations were received Monday, however the rain and warming should have caused widespread avalanches involving any recent snow received before the substantial warming arrived Sunday night. The rain has reached to near the Cascade crest elevations and this may essentially reset the snowpack, with the possible exception of the highest terrain in the northeast part.. The rain should have eliminated most, if not all, layers of concern in the upper snowpack, leaving behind wet or saturated upper snow layers.

We'll await more detailed impacts of the rain later in the week, as conditions will become more amenable to making observations.

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.