Avalanche Forecast

Yet another atmospheric river is slamming the Cascades Wednesday, bringing stormy wet weather with rising snow levels through Wednesday night.

East flow should locally maintain snowfall Wednesday night in the Stevens and Snoqualmie Pass areas.

The heavy precipitation at rising freezing levels should produce one or more natural avalanche cycles during the warmest periods, mainly Wednesday night. 

By Thursday morning, cooling and light to moderate showers with continued strong winds are expected. 

The cooling should help wet snow to begin consolidating and cause a lowering danger during the day with shallow new snow accumulations expected. 

However, near and above treeline, very strong winds should build new areas of wind slab on a variety of aspects, but mainly on NW-E facing slopes below ridges. 

Be especially aware that new shallow lower density snow may mask earlier storm slab formations, especially on slopes that did not avalanche overnight Wednesday. 

Weather and Snowpack

Last week was wet and relatively mild with a series of active fronts transiting the region resulting in fluctuating freezing levels and periods of very strong winds. The heaviest snowfall and precipitation occurred late Sunday 2/28 and Tuesday 3/1. The latter half of the week featured more rain than snow at NWAC sites along the west slopes.

Mid and lower elevations late last week and over the weekend saw natural and triggered loose-wet avalanches most days due to increasing solar effects or during rain events.

A front Sunday and a cooler upper trough Monday brought some snow with 2 day storm totals of about 2-12 inches along the west slopes ending Tuesday morning.

A very strong storm arrived midday Wednesday bringing heavy snowfall/rain at rising temperatures and very strong south ridgetop winds.

Strong east winds through the passes maintained precipitation as snow Wednesday at Stevens and Snoqualmie Passes. 

The mid and lower snow pack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

Locally heavy rain at the Mt. Baker area led to sensitive loose wet ski cuts by the Mt. Baker pro-patrol Saturday morning. A natural loose wet cycle was observed in the Bagley Lakes area and one glide avalanche in unsupported terrain released nearby. Also in the Baker area, a glide avalanche occurred Saturday night off Shuskan Arm entraining moist surface snow and becoming very large while running to the valley bottom.

The pro-patrol at Alpental on Wednesday indicated the 6 inches of new snow received by Wednesday morning was combining with new snow and strong east winds to quickly form wind slabs that were sensitive to ski release.