Avalanche Forecast

Another stronger front will cross the Northwest Tuesday night to Wednesday morning. This should cause stormy weather with strong west to southwest winds, heavy rain or snow and warming temperatures.

New wind slab will be likely in the higher elevations zone on lee slopes and storm slab will be likely on a wider variety of aspects. The warming temperatures will further build upside down heavier snow over initial lower density snow and weak surface snow from last week. Wind and storm slab may continue to release on layers from last weekend or on weak layers from last week. Buried surface hoar and crust layers from January may be available to act as a weak layer and bed surface.

Rain at lower elevations will also load and weaken surface snow layers and may cause wet loose avalanches in the lower below treeline zone.

Natural and triggered avalanches should be likely Tuesday night and Wednesday. Travel in avalanche terrain is not recommended Wednesday. The avalanche danger may decrease by later Wednesday. But another less defined front may maintain these conditions much of Wednesday so there is uncertainty in the forecast later Wednesday.

Limited snow at the lowest elevations will limit the avalanche danger there. The mid and base pack should still consist of mostly stable crust and melt form layers from periods of warm weather earlier this winter.

Last week very cold temperatures produced a variety of weak surface snow conditions including surface hoar, near surface faceting and preserved the generally light amounts of low density snow that fell last week. These layers should cause the avalanche danger to significantly increase this week as vigorous fronts move across the Northwest and snow and rain bury and load these layers.

NWAC observer Jeff Hambelton at Mt Baker on 6 February found low density snow and a crust from January that should be the types of layers that will be weak and act as a bed surface this week:https://www.youtube.com/watch?v=N_uMXEKsyvM  

A cold front moved across the Northwest on Monday afternoon causing west to southwest winds, moderate to heavy snow, and a warming trend. The front eroded the cold air mass east of the crest. Snowfall ending Tuesday morning was mostly in the 5-20 inch range west and east of the crest. This built upside down heavier snow over initial lower density snow and weak surface snow from last week. Back country reports are few but extensive 1 foot natural and triggered storm slab avalanches were reported by the Mt Baker and Alpental ski patrols late Monday to Tuesday morning. Slabs are releasing on layers from last weekend and likely on weak layers from last week.

NWAC observer Jeff Hambelton sent this photo of a storm slab triggered on a test slope at Mt Baker from 10 Feb.

Also just in late Tuesday afternoon - NWAC observer Jeff Ward in the Stevens Pass area reports further ski triggered collapsing of late January surface hoar layers. And the Stevens Patrol reports that a skier near the ski area triggered a slab avalanche of about 20 inches that released in late January crust and buried surface hoar layers. So the recent and new denser snow may be loading and re-activating late January layers where they are present. This should be mainly near Stevens Pass and possible Snoqualmie Pass for the region near and west of the crest.