Avalanche Forecast

Northeast or east winds will begin to redistribute new snow to lee westerly aspects Wednesday. New wind slab may become particularly touchy in areas where it bonds poorly to an underlying sun crust or builds over recently buried surface hoar. Wind slab should primarily be found near and above treeline but look for firmer wind transported snow down into the upper portion of the below treeline band. All aspects are listed to cover older wind slab formed over the weekend.  

The wind slab hazard may actually be the greatest in the near-treeline zone Wednesday where the combination of building wind slab over recently buried surface hoar come together to create dangerous avalanche conditions. 

More information is needed about several deeper potential persistent slab threats, particularly in the northeast and central-east zones. Dig a snow pit to check for weak layers in areas with shallow snow and avoid steep slopes with shallow snow and especially slopes without terrain anchors.

Weather and Snowpack

An atmospheric river arrived over the Northwest 1/17 causing heavy snow in the northeast zone, a mix of snow, sleet and freezing rain in the central-east zone and also in some lower elevation areas east of the crest. Rain was likely seen up to about 5-6000 feet in the southeast zone during this stretch. The 1/17 crust is very thin in the northeast zone and more notable in areas further south.   

A large upper ridge and warm air mass built over the Northwest last Thursday to Saturday. By Saturday temperatures warmed into the 30s at higher elevations along the east slopes but stayed cold at lower elevations. Moderate west winds were seen at higher elevations.

A front crossed the Northwest Sunday afternoon causing continued west-southwest winds at higher elevations along with slight cooling and little to no measurable precipitation. Light snow fell Monday night through Tuesday morning with generally 2-6 inches recorded along the east slopes, with the most at the Berne Camp east of Stevens. An observation from Mt. Cashmere Tuesday reported locally up to 10 inches of low density snow between 4000-5700 feet.  

Recent Observations

North

Reports from the NCH Barron Yurt last week indicated no direct signs of instability, but avalanche professionals did find unstable results in snowpack tests around faceted grains just below the 1/17 interface in isolated areas on cold northerly aspects. Persistent slab will be re-listed in the northeast zone to deal with this uncertainty. 

The NCMG were in the Hairpin Valley on Sunday and noted strong W-SW winds along the ridge crests with colder temperatures at lower elevations. Compression tests gave no results on the 1/17 layer at 45-50 cm.

Central

Tom Curtis was at Dirty Face above Lake Wenatchee Thursday, 1/26 and found a persistent weak layer of buried surface hoar, consistently buried about 2 feet (60cm). Test results were inconsistent upon multiple column tests. No avalanches were seen on this layer.

Stevens DOT personnel were on Tumwater Mountain on Friday and found a continental-like profile with 77 cm total snow, 20 cm of basal facets, foot penetration to the ground. 

Jeff Ward was at Cannon Mountain off of Icicle Creek Monday. He found a variable and shallow snowpack that ranged from 1 to 2 m, depending on elevation and wind affect. Many windward slopes had been scoured to the 1/17 crust with thin wind slab present on lee slopes. The 1/17 crust was down 20-40 cm but no avalanche activity was observed on this layer. Large surface hoar was found at all elevations in non-wind affected terrain. 

South - No observations