Avalanche Forecast

The pattern is a tricky forecast timing-wise for the daylight hours on Sunday. The timing and track of the incoming low pressure system remains pretty consistent among the numerical weather models.

The deep low pressure system should move across the northwest tip of the Olympic Peninsula and across south Vancouver Island Sunday afternoon and evening. This should bring stormy weather and heavy snow to the the south Cascades by Sunday afternoon and the remainder of the central to north Cascades and east slopes by Sunday late afternoon or evening. A vigorous, strong front should rapidly cross the area and cause rapidly shifting winds Sunday evening.

The main avalanche problem in the northwest and central west zones on Sunday through most of the daylight hours should be winds transporting and redistributing new or recent snow onto lee slopes. This is most likely to be northwest to southeast slopes at higher elevations but may be more varied in the Cascade passes. New or recent shallow storm slab should also be possible in the northwest and central west zones.

The main avalanche problem in the southwest zone Sunday should be increasing strong winds and increasing moderate to heavy snow rapidly building new wind slab on lee slopes. This is very likely to be northwest to southeast slopes. New storm slab should also be likely where there is rapidly accumulating new snowfall.

Dangerous avalanche conditions are expected in the southwest zone by Sunday afternoon and back country travel there is not recommended in avalanche terrain near and above treeline.

Rapidly changing weather and snow conditions are possible in the northwest and central west zones Sunday afternoon or evening. Be ready to change your plans if the storm arrives and conditions deteriorate sooner than expected.

Weather and Snowpack

The nonstop active weather pattern continues to push a storm system through the PNW almost every day or two with fluctuating but generally moderate snow levels.

The last storm impacted the area Wednesday through Thursday with a warming trend that peaked Wednesday night and very strong west winds seen throughout the Cascade range. Generally 1 to 3 inches of water accumulated along the west slopes in the 36 hours ending 4 pm Thursday. Outside the Cascade Passes, rain reached up to 5000' feet in the north and 6500 feet in the south with snow levels only rising to about 4000 feet at Stevens and 4500 feet at Snoqualmie Pass Wednesday night. About 4-14 inches of snow accumulated at NWAC stations through Thursday morning. Additional accumulations were light except above 5000 feet in the Mt. Baker area Thursday where another foot of snow likely fell.

A front on Saturday is causing west-southwest winds and there should be up to a few inches of new snow at most sites by Sunday morning.  

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

Recent Observations

The Stevens Pass and Alpental pro-patrols reported an extensive natural cycle Wednesday night. Control results were sensitive and widespread Thursday morning involving new storm snow. As the sun poked out and temperatures rose Thursday, large loose wet avalanches, both natural and skier triggered, were reported at Stevens with smaller loose wet noted in the Alpental area. The Crystal pro-patrol generally had 1-2 foot slab releases during control work Thursday with large and sensitive cornices along ridgelines. 

In areas that experienced rain Wednesday night, mainly outside the Passes and in the below and near treeline bands, a breakable crust made for tough skiing Thursday.

The Alpental pro-patrol on Saturday reported little if any results from cornice control, with bad b-c ski conditions and possible loose wet conditions on the lower mountain.

A ranger on Saturday above Paradise reported 16 cm of recent F snow on a crust from Wednesday, with little effect from wind, no results in pit tests and ski cuts, and good snow conditions.