Avalanche Forecast

Archived

Feb 8th, 2015–Feb 9th, 2015

Alpine

Natural avalanches possible, human triggered probable.

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

Snoqualmie Pass.

A heightened avalanche danger will mainly be limited to steep open terrain or lee slopes above treeline, especially on the volcanoes where greater precipitation is expected.

Detailed Forecast

Warming is expected Monday with periods of light to moderate rain and snow with generally light to moderate winds. Rain near and below treeline should maintain some wet surface snow conditions, making triggered small loose wet avalanches possible on steeper slopes.

At the highest elevations, generally above 6000 feet, some building storm or wind slab is expected, especially on the volcanoes where more snow is expected. These areas of storm or wind slab may build on isolated terrain features, such as lee aspects near ridges, mainly NW through NE facing.

Do note as a result of the unseasonably low snowpack, especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.

Snowpack Discussion

Another beat down of heavy rain over the past three days was somewhat redeemed Saturday, as snow levels lowered enough for snow to accumulate above about 4500 feet in the north and 5000 feet in the central and south.

In the Mt Baker area Sunday, observer Jeff H reported there was, on average, 7-10 inches of new snow near Artist Point about 5100 feet. Pit tests indicated at that area, the new snow was fairly well attached to the moist old snow surface. Of note were the numerous loose-wet avalanches releasing on most solar aspects, entraining most of the new snow.

Small loose wet slides, involving about 4 inches of new snow, were being intentionally ski triggered by the patrol at the top of Crystal Mountain Saturday midday.

Warm temperatures with some sunshine during the day Sunday, have allowed any recent snow to settle and possibly melt, especially on solar aspects, helping to stabilize any new storm or wind slabs that may have formed above treeline Saturday.

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

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.

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.

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.