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Avalanche Forecast

Archived

Mar 1st, 2017–Mar 2nd, 2017

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Olympics.

Dangerous avalanche conditions are expected to develop in the Olympics Thursday afternoon. Careful snowpack evaluation and cautious route finding will be essential in this area.

Detailed Forecast

The next front will begin to move over the Northwest Thursday afternoon and night. This should mainly bring increasing moderate to heavy snow to the Olympics Thursday afternoon with increasing SW-W alpine winds.

Existing wind slab should linger and possibly further build on NW-SE aspects on Thursday.  New wind slab is also likely to build on NW-SE aspects Thursday afternoon due to the incoming front. Remember to watch for wind transported snow on other aspects as well in all areas.

Existing storm slab may also linger on Thursday.  New storm slab is also likely to build Thursday afternoon due to the incoming front. Storm slab is generally found on more sheltered slopes that experience rapid snow accumulations for several or more hours.

Remember to change your plans if the weather deteriorates sooner than expected in any area.

The cornice accident at Washington Pass on Tuesday is a reminder to avoid ridges or mountain tops where there may be a cornice and avoid slopes below cornices.

Loose wet avalanches also won't be listed as an avalanche problem but it is March so watch for roller balls and loose wet snow deeper than a few inches in you are on solar slopes in sun breaks.

Further increasing alpine winds and snow with a further increasing avalanche danger should be seen in all areas Thursday night and Friday.

Snowpack Discussion

Weather and Snowpack

The most recent wet warm storm arrived on Valentines Day 2/14 and formed the uppermost, very strong rain crust in the snowpack. 

A series of disturbances in cool, NW flow aloft from Saturday through Tuesday caused periods of moderate to strong S-SW-W alpine winds at Hurricane.  The 4 day storm snow amounts look like about 10 inches at Hurricane.

See the information near the top of the Avalanche Forecast tab regarding the cornice accident at Washington Pass on Tuesday.

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.