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Avalanche Forecast

Archived

Feb 25th, 2017–Feb 26th, 2017

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.

Initially watch for generally shallow new wind slab on lee easterly aspects but a wind shift on Sunday may transport new snow to westerly aspects beginning late Sunday morning. Fresh wind slab should mainly be found near and above treeline but may also form in the upper portion of the below treeline band. Fast moving loose dry avalanches are possible on steeper slopes in non-wind affected terrain.

Detailed Forecast

A low pressure system moving south along the Washington Coast on Sunday should produce light amounts of low density snow in the Olymipcs. 

Existing weak surface snow in addition to new low density snowfall will be transported to lee slopes mainly near and above treeline. Initially watch for generally shallow new wind slab on lee easterly aspects but a wind shift on Sunday may transport new snow to westerly aspects beginning late Sunday morning. Fresh wind slab should mainly be found near and above treeline but may also form in the upper portion of the below treeline band.  Be aware that lower density snowfall received as the winds ease during the day on Sunday may obscure recently wind loaded slopes.  

Watch for loose dry avalanches on steeper slopes in non-wind affected terrain. Be especially wary of fast running loose dry avalanches near terrain traps. 

Storm slabs will not be listed as a primary avalanche problem on Sunday but watch for shallow storm slabs if new storm layers form a cohesive slab above weaker snow in specific terrain on Sunday. 

Give cornices a wide berth when traveling along ridgelines and avoid lingering on slopes below cornices as they may fail at any time.

Snowpack Discussion

Weather and Snowpack

The most recent atmospheric river arrived on Valentines Day 2/14 forming the uppermost significant rain crust in our snowpack. A short period of fair weather on Friday 2/17 caused another surface crust, especially on solar aspects.

A mix of sun and light snow showers Tuesday to Friday has freshened the surface snow daily, with up to a few inches of snow daily at cool temperatures and generally light winds. Sun crusts likely formed on solar aspects.

After a mostly sunny start to Saturday, clouds increased in the afternoon with light snow showers developing. 

Recent Observations

No observations have been received from the Olympics in the past few days.

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 Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.