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 10th, 2017–Mar 11th, 2017

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Snoqualmie Pass.

The snowpack may remain reactive and dangerous on Saturday and is only beginning the spring stabilizing process. Backcountry travel in avalanche terrain is not recommended on Saturday.

Detailed Forecast

Another front will cross the Northwest on Saturday. This will bring another day of increasing strong alpine winds and increasing rain or snow to the Olympics and Cascades. Snow levels should rise up to about 5000 feet in the northwest Cascades and perhaps about 6000 feet in the southwest Cascades.

Potential deep wind slab should be suspected mainly above treeline on all aspects but is most likely on NW to SE aspects due to recent SW to W winds. Watch for firmer wind transported snow on varied aspects especially in areas of complex terrain.

New sensitive storm slab is most likely above treeline in areas that receive more than a few inches of rapidly accumulating snowfall.

Further loose wet avalanches are most likely in the near and below treeline due to moderate to heavy rain that should affect those areas.

Avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time. Cornices have been reported as large in many areas. They will have been loaded and weakened during the recent storms.

Although not listed as an avalanche problem wet slab avalanches are possible in areas that receive significant rain on Saturday.

The snowpack may remain reactive and dangerous on Saturday and is only beginning the spring stabilizing process. Higher precipitation intensities could trigger avalanches. Avalanches may step down or entrain deeper layers and be large and dangerous especially if they reach the Valentine's Day crust layer.

Backcountry travel in avalanche terrain is not recommended on Saturday.

 

 

Snowpack Discussion

Weather and Snowpack 

The first week or so of March was very cool and snowy. NWAC stations along the Cascade west slopes piled up about 3 to 8 ft of snow with the most at Mt Baker.

A strong frontal system brought increasing precipitation and winds along with a warming trend to the Cascades on Thursday. On Thursday night rain pushed up to about 5000 feet in the northwest Cascades and about 6500 feet in the southwest Cascades. By Friday morning NWAC stations along the Cascade west slopes had about 1-2 inches of WE  with only 0-7 inches of snow with most snow at Stevens and Mt Baker.

This caused an avalanche cycle along the Cascade west slopes. The snow and avalanche conditions are rapidly changing in the Olympics and Cascades!

Recent Observations

North

The Mt Baker patrol reported natural avalanches on Thursday night. An explosive control avalanche on Shuksan Arm produced a 8'x75-100 yd crown.

 

Shuksan Arm debris on 3/10. Photo by Sam Llobet.

Central

The Stevens Patrol and Stevens and Snoqualmie WSDOT crews reported many wet slab and loose wet avalanches from control and natural cycles the past couple days with some pass closures. Several large slab avalanches have recently run on the south side of Granite Mountain near Snoqualmie.

The Alpental patrol reports that a widespread natural cycle of slab avalanches occurred there Thursday night after full control on Thursday.

South

NWAC observer Dallas Glass was in the Crystal backcountry on Friday 3/10 and reported a wet slab cycle occurred there on Thursday night with several releases on the ridge running from 3 Way to Crown point on W-NW-N slopes in the 5800-6000 range. Natural loose wet avalanches also ran from steep rock terrain.

The Paradise rangers reported a large natural wet slab or loose wet avalanche covered the road this morning just up the road from the Nisqually Bridge.This was a northwest aspect at about 4500 ft.

Just above the Nisqually Bridge to Paradise on Friday morning. Photo Doug Jones.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

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.