Avalanche Forecast

Strong winds and snow showers will gradually decrease, initially in the north Cascades on Monday with cool temperatures.

New potentially deep storm slab will be likely on all sheltered aspects. New potentially deep wind slab will be likely on lee slopes. Natural or triggered avalanches should be likely near or above treeline on Monday. Avalanches initially in storm layers seem likely to step down to deeper layers. Travel in avalanche terrain at least near and above treeline is not recommended on Monday.

Recent Northwest Weather

An extended dry mild period was seen the latter half of January. The was followed by very cold weather which produced low density snowfall and near surface faceted snow in early February. Now for the past 6 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 in the Cascades near and west the past 6 days are in the 3-7 inch range with snowfall in the 2-4 foot range. Note this is generally heavy wet snow.

Observations for Washington Cascades near and west of the crest

In the Washington Cascades near and west of the crest this weather has generally been building deep new snow over colder lower density snow from early February in turn over surface hoar frost and a crust from late January. Rain crusts may also be present in the upper snow pack from last week.

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 provided a great video from Tuesday demonstrating storm slab failing in old near surface faceted snow and triggering a remote slide near Stevens Pass. 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.

NWAC observer Dallas Glass reports likely skier triggered wind slab layers below treeline at Stevens Pass on Sunday. The failure layer is lower density snow at 40-60 cm below the surface.

A skier also triggered a 12 inch D2 wind slab on an east facing slope at 6000 feet near the White Pass ski area on Sunday. Images below.

Skier triggered new wind slab from Saturday night and early Sunday, no one caught, released in new snow. photo, D'Amico

Another view of the trigger zone of White Pass area skier triggered slab, near tree line. D'Amico

The mid and base pack should still consist of mostly stable crusts and melt form layers from periods of warm weather earlier this winter.

The next very strong cold front will cross the Olympics and Cascades Sunday night. This will produce stormy weather with very strong winds, slight warming and then cooling, and heavy snowfall. An avalanche cycle is likely Sunday night.

Note that persistent slab has been added as a concern east of the Cascade crest. Be sure to read the forecast for that area if you venture even slightly east of the crest.