Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 15th, 2016–Jan 16th, 2016

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 are expected at Hurricane on Saturday. Careful snowpack evaluation, cautious route finding and conservative decision-making will be essential.

Detailed Forecast

Active weather and avalanches should be seen this weekend!

A front will approach the Northwest Saturday morning and should cross the Cascades Saturday midday. This will cause increasing winds and moderate to heavy rain or snow with warming on Saturday. A change to rain or snow showers should be seen following the front Saturday afternoon and night.

This weather will build generally upside down snow layers of increasing density near the surface and snow may also change to rain in some areas. About 6 inches to a foot of upside down snow should be seen at Hurricane by late Saturday.

New wind slab will also be very likely mainly on lee north to east slopes.

New storm slab due to the warming trend is also very likely on varied aspects where winds are lighter and snow rapidly accumulates to deeper than a few inches.

Avalanches releasing in near surface layers on Saturday may entrain previous snow producing large avalanches.

 

Snowpack Discussion

Deep storm snow that fell during mid-late December is well settled, homogeneous and has stabilized so the current avalanche danger focus will be on the upper snowpack.

Fair weather over the New Year caused extensive surface hoar and near surface faceted snow. This was buried by about 6 inches of snowfall at Hurricane about January 3-6th.

The last observation for Hurricane is from NWAC pro-observer Matt Schonwald at week ago and he generally found a right side up, stable snowpack. Older wind slab was limited to 6-12 inch (15-30 cm) pockets near ridges and tests indicated little propagation. Matt observed new surface hoar primarily on the sheltered north-east slopes. But this surface hoar was likely destroyed by mild temperatures and rain Monday or Tuesday. Strong winds and rain up to at least 5500-6000 feet Tuesday likely caused a loose wet avalanche cycle on steeper slopes near and below treeline.

The latest period of snowfall has been from about January 11-15th with about 5 inches of snowfall at Hurricane. A cooling trend was seen at the tail end Thursday.

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.