Avalanche Forecast for Wednesday, January 15, 2020
This information was published 01/15/2020 at 7:04 AM.
The Bottom Line
Good cramponing and horrible skiing conditions persist despite a bit of new snow yesterday. The new snow blew into pockets here and there but connecting the dots in the dust-on-crust conditions will expose you to a sliding fall hazard. New snow this morning will not improve ski conditions much but may produce some pockets of unstable wind slab where wind driven snow accumulates. Triggering a small pocket or losing your footing could have significant consequences on the icy, hard surface.
Expect summit fog this morning with snow showers bringing another inch of accumulation. Northwest wind will diminish slightly through the day from 50-70 mph to 40-55 mph with some clearing of summit fog. Low visibility or flat light will persist most of the day with temps in the teens on the summit. The next round of desperately needed snow will begin late tonight and continue through morning.
Primary Avalanche Problem – Wind Slab
Any new snow today will contribute to the small and potentially reactive pockets of new snow. Most of these areas of fresh wind slab would ordinarily be considered harmless if they existed on an otherwise soft and stable snowpack. Unfortunately our snowpack is only stable, but far from soft.
What is a Windslab Avalanche?
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Two days of rain and snow-eating fog wreaked havoc with our snowpack last weekend. This is the second snowpack “reset” of the season. Despite the fantasy world that many of us backcountry skiers were living in the past two seasons, the rain on snow events are a regular occurance most Januarys in New England. In the language of snow and avalanches, our snow climate here is characterized as a “polar maritime” snow climate or, more recently, and perhaps more accurately, as a “rainy-continental” snow climate. In either case, it’s hard to sit back and watch as soft snow turns to cast iron unless you have other activities that better match the conditions. It is particularly difficult, and sometimes deadly, when bad snow is refreshed with new snow but an avalanche problem develops. Looking around the country, you’ll see many areas getting hammered by new snow but it’s falling on weak layers formed by early snowfall followed by drought and cold temps. Skiers in those areas mitigate the risk by skiing on low angle slopes, among other things. The new snow that will refresh our icy slopes in the coming days will create similar temptations but with limited options for skiing, at least until local ski trails and glades get their share of obstacle-covering snow. Beware of the new snow and resulting wind slabs that develop over the next few days and remember what lurks beneath as you make your plans.
The Sherburne and Gulf of Slides ski trails are icy with many waterbars and rocks exposed. Microspikes and crampons are better tools for ascent than skins.
Details on daily snowfall totals, precipitation type, total depth of snow and other information can be found on our page devoted to snow study plot data. Click here to check it out.
Recent snowpack and avalanche observations can be found here and on Instagram. Your observations help improve our forecast product. Please take a moment and submit a photo or two and a brief description of snow and avalanche information that you gather in the field.
Safe travel in avalanche terrain requires training and experience. This forecast is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
Avalanche danger may change when actual weather differs from the higher summits forecast.
For more information contact the US Forest Service Snow Rangers, AMC visitor services staff at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or seasonally at the Harvard Cabin (generally December 1 through March 31). The Mount Washington Ski Patrol is also available on spring weekends.
Posted 01/15/2020 at 7:04 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest