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 31st, 2014–Apr 1st, 2014

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

Regions

Snoqualmie Pass.

By Tuesday, the latest storm snow will be at least 2 days old and weaknesses in storm layers will have likely settled a great deal. Human triggering wind or storm slabs will be more difficult, but not impossible.  Watch for earlier wind slab deposits and also watch for solar effects on recent snow on steep exposed terrain.  

Detailed Forecast

A weak system should spread mainly increasing high clouds over the Cascades Tuesday with relatively light winds and moderate freezing levels.  This should cause mostly cloudy weather with a chance of a little light shower activity in the south to central part and mainly high clouds in the north part Tuesday.

A mix of winter and spring snow conditions should persist Tuesday.  As storm slab and wind slab layers continue to settle and stabilize Tuesday, the main concern should begin to shift to wet loose avalanches on steep sun exposed terrain. This should be likely on solar slopes in all 3 elevations bands and will be possible on non-solar slopes. Watch for wet surface snow deeper than a few inches, roller balls in surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches. Avoid terrain traps where a small but powerful wet loose avalanche could have unintended consequences.

Continue to watch for areas of recent wind slab on lee slopes. This is likely on shaded north to east slopes near and above treeline. Watch for signs of cracking or firmer wind transported snow and approach open lee slopes with caution.

Remember to watch for cornices if you venture onto ridges Tuesday and avoid slopes below cornices. Cornice failures are often seen during the transition to spring weather.

Snowpack Discussion

A wintery weather pattern was renewed over the Northwest starting last Tuesday. About 1-3.5 feet of snow fell at NWAC station near and west of the crest between last Tuesday and Sunday with less snow at lower elevations.

Avalanche conditions also became active through the weekend.  We are now seeing a mix of winter snow conditions mainly on shaded slopes at higher elevations and spring snow conditions on solar slopes and at lower elevations.  Here are some reports over the past few days.

NWAC observer Jeff Hambelton was near Church Mt along the Mt Baker highway on Wednesday. He saw several small but natural and human triggered storm slab avalanches on lee aspects near treeline likely failing within the new storm snow. He was at Table Mt near the Mt Baker ski area on Thursday and saw widespread natural wet loose avalanches on all aspects with solar effects and daytime warming.

Storm slab on Church Mtn 26 March by NWAC observer Jeff Hambelton.

A front crossed the Northwest on Friday. The Mt Baker ski patrol reported large skier triggered wet loose avalanches on Friday. The Alpental ski patrol and Snoqualmie DOT reported a natural cycle of loose snow avalanches on late Friday which were drier in the upper elevations and wetter at the lower elevations. NWAC observer Tom Curtis was at White Pass on Friday and reported 4-8 inch wind slab conditions at about 5800 feet.

Wind slab conditions near White Pass on 28 March by NWAC observer Tom Curtis.

Reports from over the weekend include the following. Ski cuts Saturday at the Mt Baker ski area gave mainly isolated wet loose avalanches below 4000 feet. NWAC observer Jeff Hambelton on the west side of Mt Baker Saturday reported building wind slab above about 6000 feet. The Alpental ski patrol reported a natural cycle of loose snow avalanches on Saturday night. Sunday the Mt Baker and Alpental ski patrols reported isolated 4-8 inch storm slab avalanches releasing in storm layers.

Multiple snowmobile triggered storm slabs on W-NW aspects near tree line were observed on Grouse Mountain near Mt Baker Sunday, 3/30 by NWAC observer Jeff Hambelton. The failures remained in the latest 24 hour storm snow and did not step to reactive weak layers experienced Saturday. Photo: J. Hambelton 

No new snow has accumulated since about Sunday afternoon, with sunshine Monday, sending the temperatures rising and the snow settling.  About 4-6 inches of snowpack settlement have occurred over the past 24 hours indicating that recent storm weak layers are also settling and stabilizing.  

While we are in a stabilizing pattern, do not let your guard down.  The likelihood of human triggering may have diminished, but it only takes being in the wrong place, such as higher elevation shaded slopes where stabilizing may take an additional day or two.  Continue to choose conservative terrain, watching for previous wind deposits.

Problems

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.

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.