Avalanche Forecast

Cool easterly flow should abate on Wednesday with warming temperatures forecast across the west slopes and Cascade Passes. However, a dissipating frontal band will push mid and high clouds over the area, potentially limiting sun effects on Wednesday. 

Recent E-SE winds have redistributed recent snowfall to non-traditional westerly aspects forming generally shallow but touchy windslab primarily in the near and above treeline elevation bands, but may still be possible below treeline depending on local loading patterns.  

Watch for wind transported snow on a variety of aspects Wednesday: Don't let the combination of Moderate avalanche danger with non-traditional lee aspects/cross-loaded slopes catch you by surprise!  

Loose wet avalanches may be the primary problem in your area depending on the amount of sunshine Wednesday. Freezing levels will rise on Wednesday and combined with sunshine should activate loose wet avalanches on steeper solar slopes. Watch for pinwheeling and rollerballs as precursors to more significant loose wet activity and especially be wary of loose wet avalanches around terrain traps. 

Weather and Snowpack

Last week, heavy rain and mild temperatures dominated along the west slopes forming the latest rain crust. NWAC sites in the near and below treeline recorded 2-6 inches of water mostly as rain over the 2 days ending Tuesday February 16th.

An active and cooler pattern began to bury the crust on February 17th, dropping about 1-3 feet of storm snow mainly near and above treeline along the west slopes from Wednesday through Saturday morning. A weak front on Sunday only brought a few inches of additional snowfall through Monday morning.

Storm layers in the snow received from Wednesday to Saturday have had many days to stabilize. Bonding of storm snow to the February 17th crust varied along the west slopes initially, but also should have improved over the last few days.

Moderate E-SE winds Monday night and Tuesday redistributed surface snow most effectively near the Cascade Passes and the central and southern Cascades including the Crystal and Paradise areas. 

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

Recent Observations

Widespread skier triggered avalanches near the Mt Baker ski area were reported Saturday by the Mt Baker pro-patrol and via the NWAC Observations page with some partial burials but no injuries. These were 12-18" deep x 100-200 yards wide storm slabs running fast on the February 17th crust on the northeast side of Shuksan Arm in the near treeline band of 4500-5000 feet.

NWAC pro-observers Dallas Glass and Ian Nicholson were on Mt Snoqualmie Saturday and reported 2 skier triggered wind slabs 20 cm (8 inches) deep x 30-50 feet wide with ridges limiting the widths of the slabs. This was at about 5500 feet on a cross loaded southwest slope. They reported a good bond of storm snow to the February 17th crust.

Dallas was in Crystal backcountry on Monday and reported wind affected snow on a variety of aspects due to the redistribution of recent storm snow. He also observed a skier triggered soft slab avalanche on a north aspect draining into Union Creek @ 6300 feet Monday afternoon. Luckily there were no injuries. 

Observations from backcountry ski tourers in the Snow Lake area of Snoqualmie Pass and NPS rangers near Paradise both reported shallow yet sensitive new wind slab formation Tuesday. New wind slabs were most likely formed from the Stevens Pass area and south along the west slopes.