Avalanche Forecast

Archived

Feb 22nd, 2015–Feb 23rd, 2015

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

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Small loose wet avalanches and lingering wind slab will most likely be found above treeline Monday.

Detailed Forecast

Generally light winds and warmer temperatures are expected Monday as freezing levels rise to 8000-9000 feet.

As a result, small loose wet avalanches involving the most recent storm snow should be possible on steeper solar slopes near and above treeline in the late morning or early afternoon.

Recent shallow wind slab formed on non-traditional westerly aspects above treeline may still be sensitive.

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow (new or existing) to pose an avalanche hazard.

Snowpack Discussion

Since the warm and wet start to February, fair weather through mid-February has lead to generally thick surface crusts and further consolidation of the snowpack, as well as further deterioration of the snow cover below treeline.

A few weather disturbances passed through the latter half of the week, bringing a welcome few inches of snow near and above treeline. Winds veered to the east or northeast on Saturday, causing some new wind slab formation on non-traditional westerly aspects mainly above treeline.

On Saturday, NWAC observer reports from the Crystal Mt backcountry described a few inches of new snow bonding well to the old surface through mid-day. However, at Winchester Mt in the Mt. Baker area, new wind slab 10-40 cm thick was observed above treeline on multiple aspects with new NE wind transport in progress. A small loose wet slide was triggered on a south slope late in the day even with the the cold temperatures and wind. On Sunday, Dallas Glass at Skyline found the 10-15 cm of most recent snow well bonded near treeline with minimal new wind transport.

The mid and lower snowpack west of the crest snow consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.

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.