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Avalanche Forecast

Archived

Feb 24th, 2016–Feb 25th, 2016

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

Olympics.

With high freezing levels and generally light winds Thursday, loose wet avalanches should be again be the primary avalanche concern on solar slopes in the Olympics. 

Detailed Forecast

With high freezing levels and generally light winds Thursday, loose wet avalanches again should be the primary avalanche problem on solar slopes in the Olympics.

Temperatures should be even warmer Thursday, so watch for pinwheeling and rollerballing as precursors to more significant loose wet activity and especially be wary of loose wet avalanches around terrain traps, such as slopes that would funnel wet snow like gulleys or depressions, also slopes above cliff bands or dense trees. 

Older wind slab may still be sensitive in isolated terrain features near and above treeline. 

Snowpack Discussion

Weather and Snowpack

Last week, heavy rain and mild temperatures dominated along the west slopes and the Olympics, forming the latest rain crust. There were about 1.5 inches of rain at Hurricane over the 2 days ending Tuesday morning, February 16th.

An active and at times cooler and stormy pattern began to bury the crust on February 17th and deposited about a foot of snow at Hurricane from Wednesday through Saturday morning. A few additional inches of snow fell from Sunday through Monday morning.

High pressure over the past few days has brought warm temperatures, with periods of sun and clouds along with light SE winds. 

The mid and lower snow pack in the Olympics should be a stable mix of crusts and layers of moist and rounded snow crystals.

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.

By Wednesday afternoon of this week, daytime temperatures climbed into the mid 40's at Hurricane, allowing for settling wind slabs and causing surface snow melt, especially on solar aspects.

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.