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Avalanche Forecast

Archived

Mar 1st, 2017–Mar 2nd, 2017

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

Regions

Olympics.

The avalanche danger will be increasing Wednedsay. Unstable wind and storm slabs should be widespread. Cautious routefinding and conservative decision-making is essential. Avoid steep terrain where wind deposited snow is evident.

Detailed Forecast

An approaching disturbance should bring renewed light to moderate snow showers at low snow levels with strong ridgetop winds overnight Tuesday and early Wednesday.

This should build new unstable wind slabs in exposed terrain, near and above treeline and some isolated features below treeline. Wind slabs should build on primarily on NE-SE facing slopes, but may build on a variety of terrain features.

Storm slabs may become increasingly sensitive to human trigger, especially in areas receiving the greatest snowfall amounts Wednesday.

Expect dangerous avalanche conditions near and above treeline Wednesday. Evaluate the snow and terrain carefully Wednesday. 

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

Heavy rain to high elevations arrived on Valentines Day 2/14 and subsequently formed the uppermost, very strong rain crust within the snowpack. 

Cool NW flow over the past two weeks brought several disturbances across the region. Mostly with very cool temperatures and light winds. The storm snow amounts in the Hurricane Ridge area, has been about 15-20 inches following the rain crust, producing event on Valentines.

 NPS Rangers reported that the most recent rain crust was very supportable in many areas and aspects around Hurricane Ridge.

Older wind slabs have stabilized while generally 10-15 inches of low cohesion snow over the crust, have made for some nice touring conditions of late. 

Recent Observations

No observations have been received from the Olympics in the past several 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.

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.