Avalanche Forecast

A frontal system will cross the Northwest on Friday. This will cause increasing southwest to west alpine winds, increasing rain or snow and a rise in snow levels.

Perhaps about 5 inches of snow seems likely along the east slopes mainly in the above treeline band on Friday with a warming trend.

This weather should build shallow new upside down wind slab on lee slopes which should be mainly southeast to northwest slopes above treeline. Watch for firm wind transported or hollow sounding snow.

New shallow storm slab is possible in areas that see rapid accumulations of new snow. The warming trend will also aid in the development of new upside down storm slab.

The danger level in this forecast has been nudged up a notch from the outlook issued the previous day. Small human triggered avalanches in many areas along the east slopes in the above treeline seems likely on Friday due to the alpine winds, new snow and the warming trend.

In the lower part of the below treeline band there is still insufficient snow for avalanches but watch for early season hazards such as terrain traps, rocks and creeks.

Weather Discussion for the Cascade East Slopes

A frontal system passed across the Cascades Sunday night and was followed bynorthwest flow aloft on Monday. Along the east slopes snow amounts were in the 3-5 inch range with lesser amounts further east. Moderate west northwest winds continued Monday as recorded at the NWAC Mission Ridge and Dirty Face weather stations.

Tuesday was a fair day with light winds along the east slopes.

Another front passed over the Northwest on Wednesday. NWAC stations along the crest had winds generally in the 20-30 mph range with gusts places to the 40-50 mph range. It looks like new snow on Thursday morning was light along the east slopes.

A bit of a break has been seen along the east slopes on Thursday.

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 pro 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. Wind slabs were stubborn and unlikely to trigger in the drainages he traveled through.

Jeff relayed another report to the NWAC from the Washington Pass area for Wednesday. On east slopes near the pass no signs of instability were seen with compression tests giving inconsistent hard or negative results at a layer at about 45 cm. This coverage or open creeks were still an issue at the pass elevation. Stubborn wind slab was the only noted problem.

A layer of interest in the Washington Pass area was buried surface hoar at 65 cm down on a north aspect at 7000 feet seen about a week ago. From Jeff's report the layers is apparently not widespread and there have not been significant or alarming tests recently for this layer. It might still be worthwhile to check for it in snowpit tests.