Avalanche Forecast

On Wednesday night, high pressure should allow for further stabilizing of recent storm and wind slab layers. 

A weak to moderate front should move across the Cascades near midday Thursday, causing a period of moderate to briefly heavy snow and moderate ridge level winds. This weather should build new areas of storm and wind slabs, especially in wind affected terrain, such as higher elevations and near ridges.

Watch for storm slabs in areas that received more than a few hours of moderate or heavy snowfall intensities. 

Watch for firmer wind-transported snow on lee slopes near ridges, generally northwest through southeast aspects, but expect wind deposited snow on a variety of aspects in areas of more complex terrain.

Storm or wind slab avalanches may entrain recent snow down to the firmer old refreezing snow from last week.

Although not  listed as a current avalanche problem, loose dry avalanches are possible Thursday, particularly on steep slopes. 

Watch for the numerous travel hazards such as open creeks, barely buried rocks and trees, creating poor and challenging travel conditions, especially below treeline. 

The avalanche danger should generally increase for all elevation bands on Thursday.

Remember that closed ski areas without avalanche mitigation are equivalent to backcountry terrain!  

The great start to the 2017/18 PNW Winter through mid November, retreated last week. Warm, wet weather before Thanksgiving caused wet snow and glide avalanches and snowpack consolidation with total snow depths decreasing by 50% or more from their mid-November peak depths. The old wet snow continues to slowly refreeze and from recent observations, the crust layer remains thin at the interface with the recent snow and buried 1-2 feet on average along the west slope zones.

Recent weak to moderate fronts from Monday to Tuesday deposited 24 hour storm snow amounts ranging from 6-12" ending Wednesday morning and 48 hour storm snow of 6-18". 

Several weak layers within the storm snow have mostly settled during a break in snowfall and some solar warming through the day Wednesday. 

Observations

Wednesday in the Alpental backcountry, an NWAC observer found areas of unreactive wind slab on some east facing terrain features near ridges. Daytime solar warming had allowed surface snow to consolidate and form shallow storm slabs, but no avalanches were observed or triggered.  

On Tuesday, the Mt. Baker ski patrol reported strong winds and snow transport Monday night, but full ski testing on Tuesday morning did not trigger avalanches. There were some upside-down layering in the snow from the past day's storms.

Also Tuesday, a Park Ranger at Paradise reported 5-8" of new snow that was bonding well to refreezing saturated snow. Tests were non-reactive.

On Monday, Professional Observers Dallas Glass and Jeremy Allyn traveled into the Crystal backcountry. They also found 3-4" of new snow moderately well bonded to the old moist to wet snow interface. The old wet snow is beginning to refreeze. It was supportive to skis, but not boots. They ski triggered a small loose wet avalanche on a directly sun-exposed south-facing slope. They also noted minimal wind effects.