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

Feb 5th, 2016–Feb 6th, 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

.

New wind and storm slab layers should be seen on Saturday. The skiing should be improved but don't forget to make careful snowpack evaluations.

Detailed Forecast

Strong southwest winds aloft will accompany a cold front will cross the Northwest on Friday evening. West winds will follow with orographic snow showers and a good cooling trend on Saturday morning.

The cooling trend may help bond new snow to old snow surfaces where the snow starts at above freezing temperatures. With a little luck many areas along the west slopes will have about 5-10 inches of new snow by the time snow showers taper off on Saturday.

The main avalanche problem should be new wind slab on lee slopes in the near and above treeline. Watch for signs of snowpack cracking and firmer wind transported snow on lee slopes.

A secondary avalanche problem should be new storm slab in areas with less wind if there is rapid loading. The cooling trend may help limit this avalanche problem.

 

 

Snowpack Discussion

Weather and Snowpack

The last heavy rain event January 27-28th further stabilized the mid and lower snowpack and formed a strong rain crust that is being loaded by recent storms.

A strong occluded front with strong winds crossed the Northwest January 29-30th. NWAC stations along the west slopes received about 1-2 feet of snowfall.

Cool, benign weather followed Sunday to Tuesday. A sun crust formed on many solar slopes and surface hoar was seen on many non-solar slopes.

A cold front and then a warm front crossed the Northwest on Wednesday and Thursday. NWAC stations along the west slopes for the 2 days ending Friday morning had about 9-14 inches of snowfall with 18 inches at Mt Baker and 21 inches at Paradise.

Recent Observations

The Alpental pro-patrol Thursday morning reported some natural and ski triggered 6-8" storm slab. By the afternoon some triggered small loose wet avalanches were seen below about 4000 feet.

Deeper, larger avalanches were reported from Paradise Thursday morning. The ranger reported shooting cracks and certain, sensitive, reactive human triggered 15 inch storm slabs on 40-50 degree south facing test slopes that ran onto 35 degree slopes.

NWAC pro-observer Lee Lazzara was near Mt Baker on Thursday mainly near and below treeline and found 65-90 cm of storm snow on the crust buried January 29th. He noted minor a minor storm layer at 20 cm, solar effects and rollerballs.

A skier on the NWAC observations page reported 2 skier triggered wind or storm slab avalanches on Mt Snoqualmie on Thursday.

The Alpental pro-patrol reported a quiet day today with no significant avalanches and east winds helping cool the snowpack.

 

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.