Avalanche Forecast

Archived

Feb 6th, 2015–Feb 7th, 2015

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

.

Expect increasing avalanche danger with elevation on Saturday... with the likelihood of wet loose avalanches decreasing and new storm and wind slab avalanches increasing.

Detailed Forecast

The next system in our active weather pattern should bring on average another inch of water to the west slopes Saturday during the daylight hours as a weather system lifts northward.

Lowering snow levels and light to moderate precipitation Saturday should build new storm and wind slab above about 5000 feet or so. Storm related avalanche concerns will increase with elevation Saturday. Despite the cooling trend, expect the snow surface below any new snow near and even above treeline to be wet, and skier triggered loose wet avalanches will still be possible during this transition.

The below treeline snowpack should continue to drain and be capable of handling additional rain without a significant increase in avalanche danger. Small wet loose avalanches will still be possible on steeper slopes below treeline.

Remember, due to the unseasonably low snowpack especially at lower elevations, numerous terrain hazards such as open creeks, partially covered rocks and vegetation are widespread.

Snowpack Discussion

Mild weather the last week of January led to significant snowpack consolidation. The snow level oscillated around 4000 feet earlier this week... with a few inches of new snow accumulating generally near and above treeline, the most at Mt. Baker above 4500 feet. The atmospheric river faucet turned on Thursday and Friday, with most west slope locations picking up several inches of rain due to the mild snow levels. As of 5 pm Friday, Mt. Baker has picked up an amazingly wet 9 inches of mostly rain over the last 48 hours.

Observer Tom C. was in the Rainy Pass area near Stevens on Thursday. With a transition to rain in the late morning, Tom observed natural small wet loose and wet slabs releasing on steeper slopes below treeline involving the most recent snow over a rain crust. Wet loose involving the most recent snow were also ski cut by professional patrollers at Crystal and Alpental Thursday. By Friday, no significant wet loose slides were observed below treeline by professional patrols across the west slopes. Dallas Glass in the Skyline area of Stevens on Friday found above 5000 feet (approaching near treeline), there was enough recent storm snow for more significant natural or skier triggered wet snow avalanches and observed pinwheeling of the surface snow.

Small wet loose, Rainy Creek. 2-5-15 by T. Curtis

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

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.

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.