Avalanche Forecast

Issued: Dec 16th, 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

Email

The avalanche hazard remains limited to lee slopes at higher elevations. Approach areas with freshly drifted snow cautiously and avoid steep unsupported slopes. Watch for low snow coverage and ground hazards everywhere else.

Summary

Discussion

The snowpack is slowly growing in the East South zone. Weather stations in the area show 1-2 feet on the ground above 4500 ft after last week's storm cycle. Expect drifted areas of snow adjacent to slopes with very little snow.

Steep lee slopes at higher elevations are the only locations where you'll likely encounter enough snow for an avalanche hazard. There you might find recently formed wind slabs. Steer around steep unsupported slopes with wind-drifted snow. Look for firm or hollow sounding snow as a sign that wind slabs may be present. You can stay safe by traveling on ridges, wind-scoured areas and slopes less than 35 degrees.

Be especially cognizant of the consequences of even a small avalanche with so many shallowly buried ground hazards, like rocks, stumps, and creeks.

If you travel in the backcountry of the East South zone, submit an observation!

Forecast Schedule and No Rating definition

At this time, we do not have enough specific snowpack information to issue an avalanche hazard rating for the East 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 12th, 2019 (The regional synopsis is updated every Thursday @ 6 pm)

After a dry November, this week marks the beginning of more winterlike weather across the region with snow at middle and pass level elevations. While there’s uncertainty in the weather forecast, it does appear that the snowpack will continue to build to some extent over the coming week. 

Throughout much of the region, the slow start to winter has left avalanche conditions distinctly defined by elevation. Slopes above 5,500-6,000ft hold a layered snowpack that provides enough coverage for winter travel and avalanches. Below this elevation, most slopes were bare until the past week. At these lower elevations, it will likely take another round of storms before larger avalanches are possible and travel becomes easier.

 

Image courtesy of the Natural Resources Conservation Services interactive map showing Snotel weather stations measuring well below normal snow water equivalent for this season so far.

Upper Elevations

The lack of significant snowfall has resulted in commonalities throughout the region. Slopes above about 5,500ft currently hold the ”deepest” snow cover and the most layered snowpack. Until the lower elevation terrain builds a more substantial snowpack, the upper elevations will hold the most potential for producing large avalanches. If you dig into the snow in these areas, you’ll find a range of height of snow and a variety of layers. Here are a few layers to note:

  • The interface of older snow and any new incoming snow would be the first interface to check.

  • Snowfall around December 7th and 11th may have buried surface hoar and near-surface facets in some locations. As of Dec 12th, these interfaces can be found 1-2’ below the surface.

  • A layer of facets can be found near the middle of the snowpack, buried just before Thanksgiving. Where found, the facets are often rounded or have even undergone some melt-freeze metamorphism from liquid water.

While these layers give you something to look at in snow profiles, they may not be your main snowpack concern for the day. Continue to check the daily zone forecasts for the most up to date avalanche conditions. We’ll monitor these layers as future weather brings changes to the snow and avalanche conditions

 

A layer of facets in the middle of the snowpack resulted in sudden test results on Dec 11th. Rock Mtn, N, 6270ft. Photo: Josh Hirshberg.

Middle and Lower Elevations

At most locations below 5,500ft, slopes are still building uniform snow cover. In many zones, the hazard of hitting rocks or shallowly buried objects may be more significant than the avalanche danger. Depending on future weather, the snowpack could continue to form or could, unfortunately, melt out to the ground. While there’s little layering of note at these elevations, avalanches aren’t completely out of the question with the right weather input. Further low elevation snowfall or warming could drive avalanche activity. The East North forecast zone, including Washington Pass, has more low elevation snow than other zones and therefore more potential for avalanches at these elevations. As with the upper elevations, we’ll wait and see what the next round of weather brings.

Valid until: Dec 17th, 2019 10:00AM