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Avalanche Forecast

Archived

Feb 25th, 2016–Feb 26th, 2016

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

Regions

Olympics.

Moderately high freezing levels and light amounts of rain or snow at slowly cooling temperatures should not cause a significant increase in danger Friday. Shallow areas of wet snow or isolated wind slabs should be the primary avalanche concern in the Olympics. 

Detailed Forecast

Increasing high clouds overnight Thursday should still allow for stabilizing surface crust formation early Friday.

A weak front should allow for light rain and snow at moderate freezing levels later Friday. Only light amount of precipitation is expected during the daylight hours and this should not cause a significant increase in the danger.  

Some shallow new wind slabs may form at higher elevations by late Friday on some lee slopes that receive greater precipitation.

Snowpack Discussion

Weather and Snowpack

Springlike weather under high pressure Wednesday and Thursday caused abundant sunshine with temperatures climbing into the upper 40's Thursday afternoon!

This weather has allowed for melt-freeze crust formation overnight and varying amounts of wet surface snow depending on slope aspect. 

The last snowfall occurred late last week when about a foot of snow fell by last Saturday. Some cornices and wind slabs formed during this period, however, recent warm weather and sunshine have likely settled and stabilized wind slabs.

A strong rain crust is below the recent storm snow and mid and lower layers consist of a well drained mix of moist and rounded grains, limiting any avalanche problems to surface snow layers.

Recent Observations

Professional NWAC observer, Matt Schonwald was at Hurricane Ridge on Friday. Recent storm snow deposits of about 4-6 inches had accumulated in wind sheltered locations. Very strong southerly winds were building shallow wind slabs on lee slopes near tree line below ridges and also building small cornices.

A small wind slab was triggered on a lee slope called Sunrise Slope on Saturday although details are not available.

Following two days of sunshine and very warm temperatures, Wednesday and Thursday of this week, with temperatures well into the mid and upper 40's at Hurricane, any previous wind slabs should have stabilized or become much more stubborn to trigger. Wet snow conditions and softening cornices remain the greatest avalanche problem.

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.

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.