Avalanche Forecast

Archived

Jan 30th, 2018–Jan 31st, 2018

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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

Dangerous avalanche conditions exist near and above treeline where winds have transported significant new snowfall. You are likely to trigger a wind slab in wind loaded terrain on Wednesday. These wind slabs may be disguised by less wind-effected snow. Storm slabs are possible to trigger, so check test slopes and avoid steep or unsupported slopes.

Detailed Forecast

Light snow showers will be decreasing and westerly winds will be in the light to moderate range on Wednesday.

Small to large slabs formed Monday night through Tuesday with winds accompanying the recent storm snow. Wind slabs are likely to be particularly touchy near and above treeline. Expect the improving weather on Wednesday to begin to stabilize these slabs, but with the cold temperatures, significant time is needed. These slabs may be disguised by new snow.

Storm slabs are less likely to be encountered on Wednesday, but you should keep alert for them. Significant new snow has continuously loaded the terrain for more than 24 hours and several hours saw high snowfall intensities capable of storm slab formation. New snow continues to load the terrain Tuesday night into Wednesday.

Small loose dry avalanches are possible in steeper terrain. Avoid steep slopes where the consequence of an avalanche may be significant.

Snowpack Discussion

A warm and wet system brought 1.25" of water to Hurricane Ridge from 4 AM Monday to 5PM Tuesday, which is now beginning to refreeze into a crust. Following a strong cold frontal passage, the storm deposited 15"+ of storm snow which should be well bonded to the refreezing crust and generally right-side up.

Below the refreezing crust, the snowpack is generally well-consolidated and although there are no layers of concern.

Winds redistributed significant snow during a storm cycle beginning 1/16 forming variable snow depths in the snowpack.

Observations

No observations were received Sunday as the road remained closed due to the elevated threat of large avalanches.

NPS rangers reported several natural avalanches Saturday, several that deposited debris onto the Hurricane Ridge road.

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.