Avalanche Forecast

A short relative break between fronts should be seen on Sunday morning. Then yet another very strong cold front should begin to move into the Northwest on Sunday afternoon. This will begin to cause stormy weather with strong winds and heavy snowfall. This system should have cooler temperatures and lower snow levels than the past few systems. Snow levels should stay below Snoqualmie Pass.

Rapid loading should cause new storm slab to begin to build on most sheltered aspects in all the elevations zones starting Sunday afternoon. Wind transport should cause new wind slab to begin to build on lee slopes mainly near and above treeline. This will begin to add further loads to underlying colder lower density and faceted snow from early February and to deeper potential hoar frost, faceted snow and crusts from late January. Natural or triggered large avalanches should start to become possible by the end of the day light hours Sunday.

The storm should peak on Sunday night as the very strong cold front crosses the Cascades. Rapid loading and wind transport will cause storm and wind slab to further build and become deep Sunday night. An avalanche cycle is likely Sunday evening or night. Natural or triggered large avalanches are likely Sunday evening or Sunday night.

Recent Regional Weather and Snowpack

An extended dry mild period was seen the latter half of January. The was followed by very cold weather and periods of low density snowfall in early February. Now for the past 5 days the Northwest is getting pummeled by daily frontal systems producing periods of strong winds, periods of warmer higher density snowfall and rain during periods of generally warmer temperatures.

Water equivalents/snow for the past 5 days mostly range as follows: Olympics and Cascades near and west of the crest 3-7 inches WE/2-4 feet of snow, east of the crest 1-4 inches WE/1-2 feet of snow, and at Mt Hood 10-12 inches WE/2-3 feet of snow! Note this is generally heavy wet snow for all areas especially at Mt Hood!

Regionally this weather is generally building heavy denser snow layers over colder lower density and faceted snow from early February over potential hoar frost, faceted snow and crusts from late January. So it is no surprise there has generally been a lot of regional avalanche activity especially in the Washington Cascades and at Mt Hood the past couple days. Several widespread natural avalanche cycles have run their course over the past several days with the largest cycle occurring late Tuesday to early Wednesday.

Similar weather and snowpack structures around the west have lead to numerous recent fatal avalanche accidents including in northeast Oregon on Tuesday.

Observations for Washington Cascades near and west of the crest

The Mt Baker ski area reported large explosively controlled avalanches on the north slopes adjacent to the ski area on Friday.

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

NWAC observer Jeff Ward has a great video from Tuesday demonstrating the touchy new storm slab failing on near surface facets and triggering a remote slide near Stevens Pass near treeline and of high quality shears for an increasingly deeply buried layer of surface hoar at lower elevations on a north aspect.  This layer caused a skier triggered avalanche on Big Chief Mountain just outside the Stevens Pass ski area boundary Tuesday around 5000 ft on a NW aspect and resulted in an injury.

The rain and wet snow created some wet snow avalanches in the Snoqualmie Pass areas as reported by NWAC observer Dallas Glass Friday.  For more evidence of the recent cycle and some excellent suggestions see this short video produced by Dallas on Friday.

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