Avalanche Forecast

Another break between systems is expected Thursday as brief high pressure transits the region. There may be a few showers early Thursday to midday, but little accumulation is expected. Winds should be light Thursday.

Freshly formed wind slabs found in the near and above treeline bands and on a variety of aspects will be the main avalanche problem again Thursday. Watch for signs of firmer surface snow layers that may indicate wind slab potential. 

In addition, watch for any recent cornice formations along ridges and give these early season cornices a wide birth as they may be fragile.   

In much of the lower elevation, below treeline band, there is insufficient snow to produce avalanches, but watch for early season hazards such as rocks and creeks.  Avalanche problems should be limited to the upper part of this elevation band and higher elevations.

Be aware of the potential of a buried surface hoar layer in the Washington Pass zone (see discussion). Reports are few early this season and it's not known how reactive or widespread this layer might be along the east slopes. 

Weather Discussion for the Cascade East Slopes

A frontal system passed through the Cascades Sunday night and was followed by NW flow aloft on Monday. This pattern favored the west slopes for significant snow accumulations. Near the Cascade crest along the east slopes, snow amounts were in the 3-5 inch range with lesser amounts further east. Moderate WNW winds continued through the day Monday as recorded at the Mission Ridge and Dirty Face weather stations. Tuesday was a fair day with light winds along the east slopes. The most recent front arrived after midnight Wednesday. This front arrived with moderate westerly flow and precipitation also favored the west slope areas, with only a few inches of new snow reaching most east slope locales. This weather should allow for further settling of the snowpack.

While the recent storm has not deposited a great deal of snow, the low density surface snow is very susceptible to wind transport. 

Recent Reports for the Cascade East Slopes

Last Friday a skier triggered a deep wind slab on a 40 degree northwest slope at about 7500 feet on Slate Peak near Harts Pass. The crown varied from about 2 to 7 feet and ran about 2-300 vertical feet with car sized chunks of debris. Fortunately the skier was not caught. He noted that windward slopes across the valley were scoured indicating recent wind transport.

On Tuesday, NWAC professional observer Jeff Ward was in the Washington Pass area. He found generally good ski conditions and a stable snowpack. Previous wind loading was obvious, but varied by aspect throughout the terrain. However, wind slabs were stubborn and unlikely to trigger in the drainages he traveled through. 

One layer of interest was buried surface hoar at 65 cm down on a north aspect at 7000 feet. Older avalanche crowns did not seem to step down to this deeper layer. It's not known how widespread this buried weak layer might be but the upcoming weather over the weekend should give it a good load.