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 22nd, 2015–Mar 23rd, 2015

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

Regions

.

There may be some shallow storm and wind slab above treeline Monday. Any new snow that does fall will be susceptible to sun breaks later Monday afternoon, so use extra caution on steeper solar slopes near and above treeline. 

Detailed Forecast

Light to moderate showers are expected as an upper trough passes Monday. Freezing levels should lower Monday, but be tapered by daytime warming.  Increasing SW ridge top winds may build shallow new wind slabs on some lee slopes, mainly below ridges on N-NE facing terrain near and above treeline. 

Any new snow that does fall will be susceptible to sun breaks later Monday afternoon, so use extra caution on steeper solar slopes above treeline. 

Less recent snow and ample terrain anchors should greatly limit the avalanche danger below treeline. 

Remember the NWAC forecast applies to elevations up to the Cascade crest (~7000 to 8000 ft). Significant new snowfall from late this week likely posses a higher avalanche danger at these elevations in the Mt. Baker area which received the greatest recent precipitation.   

Due to the low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation. Many areas below treeline do not have enough snow to cause an avalanche danger.

Snowpack Discussion

The storm snow from last weekend has mostly settled or melted over the past week as snow depths have decreased about 10 inches where the greater storm snow accumulated, mainly the Mt Baker area. 

The most recent new snowfall accumulated above 4000 feet in the Mt. Baker area Saturday with about 5 inches by early Sunday and 8-10 inches at about 5000 feet as reported by NWAC observer Jeff Hambelton, where there were some shallow loose wet slides seen on the north slopes of Table Mountain. No slab releases were seen with the new snow feeling moist, settled and mostly stable. 

Less new snow accumulated in the remainder of the west slopes, however, there was widely varied amounts of precipitation so expect to find varied recent new snow amounts near and above treeline.   

The latest new snow was accompanied by moderate winds that built some shallow wind slabs and sensitive cornices along ridges, as observed by NWAC observer Jeremy Allyn in Silver Basin at Crystal Mountain, Saturday, March 21. There was a small natural cornice failure that triggered a shallow soft slab of about 4-6 inches. Daytime warming leading to consolidation. 

The snowpack at low elevations remains meager to non-existent with the average snow-line around 4500 feet along the west slopes. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

Problems

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.

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.

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.