Avalanche Forecast

On Wednesday, a shortwave ridge moves across the Pacific Northwest with a temporary decrease in winds and precipitation. This weather should generally allow new or recent storm and wind slab layers to begin stabilizing.

Watch for storm slabs in areas that received more than a few hours of moderate or heavy snowfall intensities. This is more likely in the Stevens Pass to Mountain Loop areas if a convergence zone forms there Tuesday evening, adding uncertainty in this vicinity. 

Watch for firmer wind-transported snow on lee slopes near ridges, generally northwest through southeast aspects, but watch for it on other aspects in areas of more complex terrain.

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

Although they will not be listed as avalanche problems, loose dry avalanches are possible Wednesday, particularly on steep slopes. Watch for potential loose wet avalanches on steep, solar slopes mainly in the South Cascades if there are significant mid-day sun breaks.

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 decrease for all elevation bands on Wednesday.

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

The great start to the 2017/18 PNW Winter took a giant step backwards last week. Warm, wet weather caused wet snow and glide avalanches and snowpack consolidation with total snow depths decreasing by 50% or more from their mid-November peak depths.

A front and a splitting upper trough crossed the US west coast Sunday and Sunday night. Along the Cascade West slopes, the passage of a sharp cold front on Sunday brought SW-W winds of 40-50 mph with gusts into the 70's and 80's at some higher elevation NWAC stations which decreased into the 10-20 mph range. Temperatures generally dropped from the 30's and 40's into the 20's on Sunday afternoon. New snow amounts were fairly light ending Monday morning, ranging from 0-5". 

Lingering light snow showers were seen on Monday at continued cooler temperatures and lighter winds, with 0-5" of lower density snow with the most at Mt. Baker.

On Tuesday, a front brought a brief bump in snow levels into the 3500-4500' range, with generally SW winds in the 20 mph range with gusts in the 30's and 40's. By Wednesday morning 24 hour snow totals are expected to be in the 6-12" range and 48 hour totals in the 6-18" range at most high elevation sites.

Observations

Also 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 is 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.

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 was some upside-down layering in the the snow from the past two days.

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