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Avalanche Forecast

Archived

Mar 6th, 2017–Mar 7th, 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.

Deep storm snow and recent, fresh wind slabs should maintain dangerous avalanche conditions, especially near and above treeline. Avoid steep slopes recently loaded with wind transported snow. Conservative decision-making remains essential.

Detailed Forecast

Light to moderate snow showers at cool temperatures are expected overnight and Monday. Winds should be moderate and strong enough to easily transport loose surface snow, building some fresh wind slabs on lee exposed slopes.

Generally light accumulations of new snow are expected and with cold temperatures and light to moderate winds this should maintain the current level of avalanche danger. Cold temperatures may help maintain older wind slab layers near and above treeline.

Dangerous avalanche conditions should persist near and above treeline Monday. Cautious terrain selection and conservative decision-making remain essential. 

Cornices won't be listed as an avalanche problem in this area, but avoid travel on ridges, where recent cornices may have formed and avoid steep slopes below cornices, that may fail at any time.

Snowpack Discussion

Weather and Snowpack

The Valentine's day crust is now buried 2-3 feet or more in the Hurricane Ridge area. A weak interface exists several inches above the crust.

Recent storm snow since Friday, ranges from about 12-18 inches in the Hurricane Ridge area. Warming and strong winds during the storm Friday, March 3rd created reactive wind and storm slabs.

Recent Observations

NWAC observer, Matt Schonwald was at Hurricane on Friday and found that ski tests were showing rapidly increasing propagation and increasing sensitivity of the deepening storm slab. Previous winds had loaded various slope aspects while south winds on Friday were loading N aspects.

Reports by NPS rangers early Sunday and a report listed on the NWAC observations page, indicate there were at least three and possibly four separate triggered avalanches in the Hurricane Ridge area Saturday, March 4th. Including the areas known as Maggies, Hurricane Hill and Sunrise Face. These touchy slab releases indicate the recent storm snow remains sensitive to human trigger and more conservative decision-making remains essential until the storm and wind slabs settle further. 

Problems

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.

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.