Avalanche Forecast

A frontal system will continue to bring significant snowfall to the east slopes of the Cascades Tuesday night, with moderate to occasionally strong crest-level winds and a slight warming trend. On Wednesday temperatures will be warmer than in recent days, with light to occasional moderate rain and snow showers along with lighter crest-level winds.

Persistent weak layers may be found in isolated areas in the northeast and central-east zones. If entering a new area, you need to determine if a persistent slab problem exists before entering consequential terrain.

Storm slabs developing in many areas Tuesday afternoon will build to 8-16" in many areas by Wednesday morning. Storm slabs will remain touchy Wednesday, with the potential to entrain the deeper lower density snow from the past week that exists in most areas, allowing these slabs to run farther and become larger than you expect. Stick to lower-angle terrain that is well-supported or heavily terrain anchored. 

Moderate are transporting the new snow, particularly near and above treeline. These will continue to build touchy wind slabs near and above treeline on a variety of aspects. New or recent wind slabs may also produce large avalanches, entraining significant amounts of deeper loose dry snow. Avoid wind-loaded terrain and consider any aspect to be fair game for wind slabs on Wednesday.

The avalanche danger will lower slightly during the day on Wednesday, but the potential for triggering a large avalanche remains. Recent storm and wind slabs require time to heal, so be patient and match your terrain selection appropriately.

An estimated 5-10" of storm snow fell at increasing density along with moderate SE winds along the east slopes of the Cascades. This snow now sits above 8-16 inches of settled snow now sitting on the 1/16 melt-freeze crust. Observations generally show the recent snow as well bonded to this the crust.

Winds observed during the stormy period formed wind slabs on a variety of aspects.

Observations above treeline have been limited leading to a higher level of uncertainty in this terrain.

Buried surface hoar was observed on the 1/16 crust in the Cascade East - Central zone on Wednesday, January 17th. The layer was also found on the crust in the Twisp River drainage on Monday, January 22nd, but faceted grains below the crust were even more concerning. The crust layer interfaces were the suspect culprit for a large avalanche on Sunday in the Cascade East-North zone. This layer will need to be watched during the upcoming stormy period as the extent and distribution of these weak layers remain highly uncertain and likely confined to isolated areas.

Snow depth still decreases substantially east of the Cascade crest. In many areas below treeline, there has not been enough snow to present an avalanche danger.

Note - The NWAC Washington Pass station is back online - nice work DOT! Precipitation and other sensor repairs to be planned...

Observations

North

On Monday, snowpit tests by NCMG on a SE aspect Near Treeline in the Twisp River Valley gave sudden collapses within faceted grains below the 1/16 crust. Test results on a NE aspect yielded consistent sudden planar results above the 1/16 crust with partially decomposed surface hoar on the interface.

NWAC received a second-hand report of a large skier-triggered avalanche on west-facing slope (likely near treeline) on Abernathy Peak in the upper Twisp River drainage. The avalanche propagated widely and was suspected to have failed on the 1/16 crust. 

Central

On Saturday an avalanche professional on Dirty Face Mountain near Lake Wenatchee observed a well bonded upper snowpack near and below treeline. No buried surface hoar was found and no avalanches were observed.

On Wednesday, 1/17, NWAC observers traveled in the Icicle Creek drainage up to 6800 ft. Buried surface hoar was found over a melt-freeze crust. The buried surface hoar was not limited to valley bottoms, but found to all elevations up to 6800 feet.

South

No recent observations