Avalanche Forecast

Archived

Feb 8th, 2017–Feb 9th, 2017

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural and human triggered avalanches likely.

Below Treeline

Natural and human triggered avalanches likely.

Regions

Olympics.

An approaching storm Wednesday will begin to load and stress the deep recent storm snow by Wednesday afternoon. Watch for changing conditions and be prepared to alter tour plans and leave plenty of safe margins.

Detailed Forecast

An approaching storm will bring increasing clouds and strengthening winds through the morning Wednesday. Snowfall will arrive midday Wednesday and increase through the afternoon with warming.

The warming and beginning of the new snow loading Wednesday afternoon, will begin to stress the significant recent storm snow. The avalanche danger will gradually increase through the afternoon Wednesday, however the significant loading and heavier precipitation rates are likely to hold off until Wednesday night and into Thursday.

If the approaching storm arrives sooner than forecast or with intially heavy precipitation, the avalanche danger could increase more rapidly than expected. Watch for changing conditions and be prepared to alter plans accordingly.

Snowpack Discussion

Weather and Snowpack

A strong storm cycle began Friday, continuing into Monday afternoon. As of Monday afternoon the three day storm totals have been about 2-3 inches of water equivalent with about 2.5 feet of snow accumulating in the Hurricane Ridge area. A cooling trend began Friday afternoon with a gradual decrease in overall snowfall intensities from Sunday morning. Winds through the storm cycle have been mostly light to moderate at times.

High clouds and cool temperatures and some sunshine Tuesday has allowed for recent storm snow to continue to settle and stabilize, as evidence by the 6 inches of snowpack settlement during the day Tuesday at the Hurricane Ridge study plot..

The older snowpack is well settled. Melt-freeze crusts formed a week ago during high freezing levels and light rain.

Recent Observations

NWAC pro-observer, Matt Schonwald was at Hurricane on Friday (before most of storm snow arrived) and found scoured slopes or shallow new snow on E slopes and shallow building wind slab on SW slopes. He found no significant signs of instability, ski tracks still visible from last week and lots of surface roughness to fill in on lee slopes.

No observations were received since Saturday.

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.