Avalanche Forecast

Issued: Jan 3rd, 2019 10:00AM

The alpine rating is below threshold, the treeline rating is below threshold, and the below treeline rating is below threshold.

Northwest Avalanche Center NWAC, Northwest Avalanche Center

You'll likely find a slowly refreezing upper snowpack with pockets of new thin wind slab near and above treeline Friday. If you suspect the dangerous snowpack structure currently found north of I-90 also exists in the East Slopes South zone, put an extra buffer between you and terrain where large avalanches can run, start and stop.

Summary

Discussion

Avalanche and Snowpack Discussion

Light rain and high alpine winds buffeted the East Slopes South zone Thursday. Strong southwest winds and a few inches of fresh snow late Thursday night through Friday morning will likely limit new avalanche hazards to shallow wind slabs forming on a refreezing upper snowpack on lee slopes near and above treeline.

We have no direct snowpack or avalanche observations from this area. However, a weaker and more dangerous snowpack has taken root along the east slopes of the Cascades further to the north. We haven't confirmed the same weak and dangerous snowpack structure exists south of Icicle Creek drainage, so you will need to take the time to evaluate conditions for yourself before entering avalanche terrain.

Forecast Schedule and No Rating

At this time, we do not have enough specific snowpack information to issue an avalanche hazard rating for the East Slopes South zone. However, even when No Rating is applied, applicable avalanche conditions and backcountry travel advice will be provided throughout the season. When weather systems produce very dangerous avalanche conditions in adjacent zones, NWAC will issue an avalanche warning for this zone as well.

Snowpack Discussion

December of 2018 was fun (from a forecasting perspective) with three pronounced avalanche cycles, a couple different persistent weak layers, some rain events, and a flurry of human triggered avalanches to ring in the New Year. Most importantly, it seems that we made it through the last days of 2018 without anyone getting seriously hurt by an avalanche.

The deep (Dec 9) layer responsible for many of the avalanches early in the month no longer seems to be a problem in the western zones. That said, it is still possible to trigger an avalanche on its counterpart (or basal facets) in the eastern areas.

A widespread layer of surface hoar formed around Christmas. Late December storms preserved this layer in areas above the rain line and we have numerous (more than a dozen) reports of people triggering avalanches on it in the last three days. At least 4 people were caught and carried during this period, but so far we have no reports of serious injury. Most of these avalanches were soft slabs, D1-D2+, but there were several harder wind slabs in the mix.

It appears that the layer is most reactive and/or prevalent in the Crystal Mountain backcountry and in the mountains around Leavenworth and west of Mazama.

Surface Hoar can be an especially tricky and persistent weak layer. Read more about it here.

Valid until: Jan 4th, 2019 10:00AM