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

Mar 18th, 2015–Mar 19th, 2015

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Olympics.

Watch for new wind or storm slab layers above treeline Thursday afternoon in the Olympics.

Detailed Forecast

A southwest-northeast oriented front will move slowly to the International border area on Thursday with a series of waves beginning to move along the front. This should cause new snow above treeline and rain near and below treeline over the Olympics and north Cascades Thursday afternoon.

So the main change to watch for will be in the Olympics and northwest Cascades Thursday afternoon. In these areas above treeline watch for new wind and new storm slab to develop if there is more than several inches of new snow by the end of the daylight hours. Less new snow will mean less of an increase in new wind and storm slab avalanche danger Thursday afternoon.

Further snow above treeline and rain near and below treeline should be seen in the Olympics and northwest Cascades Thursday night.

In all areas in the Olympics and west of the crest Thursday watch for previous shallow wind slab on previous lee slopes. Loose wet avalanches should also remain possible especially on solar slopes.

Little snow in the Olympics below treeline should greatly limit the avalanche danger in that area.

Snowpack Discussion

Last weekend another warm and wet system brought a one-two punch to the Pacific Northwest. The initial system Saturday brought mostly rain with a few inches of snow at Hurricane. This was followed by 16-18 inches of new snow Sunday at the NWAC Hurricane Ridge station. 

A weak front may have caused minor rain or snow at Hurricane on Tuesday.

NWAC observer Tyler Reid toured above Hurricane Ridge on Tuesday and reported about 1-2 feet of wet snow with up to 3 feet in drifts near ridges. There were numerous recent small loose wet avalanches seen on all aspects with a few larger avalanches. Avalanches ran into ares with little or now snow cover.

Loose wet avalanche debris size 2 on Tuesday, March 17th, above the tunnels on road to Hurricane Ridge. Photo by Tyler Reid.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.