This information was published 01/26/2020 at 7:09 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Drifted snow may release naturally today in the steepest terrain and may entrain enough snow to push you into the rocks and terrain traps that exist in our sparsely covered slopes. These wind slabs are likely to avalanche from human triggers. Steep slopes should be approached with caution. Limit time spent in avalanche paths such as the floor of Tuckerman Ravine. Evaluate the snow and terrain carefully today and be cautious in your route-finding. CONSIDERABLE avalanche danger exists today. Even small avalanches today have the potential to become large avalanches by stepping down and into wind slabs formed Jan 13 – 16. Watch for terrain traps and keep in mind a small manageable slab could become a larger problem.
The summit recorded 5” of snow overnight on 55-70 mph SW wind before temperatures warmed, turning snow to freezing rain early this morning. Hermit Lake snowplot reports 4.3” with a thin ice crust on the surface. At 4am the summit temperature reached 27F, and just under 32F down to around 1600’. Due to warm air aloft, any remaining precipitation will fall as a freezing drizzle before turning back to snow showers as the temperatures drop throughout the day, eventually bottoming out at mid teens F.
South wind has already begun to shift W at 15-30 increasing to 45-60 mph. A trace to 2” of snow is possible later today and another 2” tonight with snow totals much less elevation dependent with cold air firmly in place.
Primary Avalanche Problem – Wind Slab
Wind slabs formed from dense new snow which fell overnight will add strain to existing wind slabs. New wind slabs will form today and will likely be sensitive to human triggering. Due to the shift in wind direction these new wind slabs will grow fairly thick. West wind this afternoon will have more snow to work with due to the sizable fetch in the alpine plateaus above treeline around the summit cone.
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.
Secondary Avalanche Problem – Wet Loose
Wet heavy snow at mid and lower elevations may release today until temperatures drop. These slow moving, often point release avalanches can increase in size and contain enough mass to drag a skier or climber down over dangerous terrain features such as cliffs. Be mindful of the terrain below you, and keep an eye on temperatures throughout the day.
What is a Wet Loose Avalanche?
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
The mixed bag of new precipitation combined with lingering wind slabs that have been very slow to fully stabilize confounds our ability to predict exactly how avalanche potential will play out today. After much discussion, forecasters settled on two avalanche problems that fall on a continuum of the potential avalanche issues that may exist today. One of the comments referred to the old adage about the dangers of trying to outwit the avalanche problem. If you choose to climb or ski today, you will encounter a wide array of snow on the ground as well as changing weather conditions with new snow and a new wind direction adding another layer of complexity to the widely variable existing wind slab and new snow avalanche problem. Be cautious as you travel, move one at time through avalanche paths, choose terrain carefully and use it to your advantage.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch and have been in good shape though a few of the usual wind scoured areas have rocks showing. Rain last night likely did a bit of damage.
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. Clickhere to check it out.
Recent snowpack and avalanche observations can be foundhere and on Instagram. Your observations help improve our forecast product. Please take a moment andsubmit 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 01/26/2020 at 7:09 AM.
USDA Forest Service
White Mountain National Forest
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