Avalanche Forecast for Wednesday, February 12, 2020
This information was published 02/12/2020 at 7:07 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Stubborn, hard wind slabs exist in most east side avalanche paths, generally regardless of aspect. You’ll find far fewer and smaller wind slabs on west facing terrain as well as many other areas exposed to strong, west winds where scouring has stripped most snow down to an icy crust. The majority of the existing wind slabs are stubborn and hard to trigger though you can find softer and possibly more reactive slabs in the most sheltered areas. Evaluate snow and terrain carefully as you move around avalanche terrain. MODERATE avalanche danger exists where these wind slabs sit, especially in the steepest terrain or any convex feature, such as the sluff piles below gullies, or bulges of ice beneath the snow.
Yesterday, moderate west winds blew in the 40’s mph, while summits sat in the fog with around an inch of new snow. Temperatures were relatively warm, near 30F at Hermit Lake, lower 20’s on the summit.
Today, winds will relax through the day from where they stand now in the mid-70’s mph with gusts just over 100 mph. The current temperature on the summit is 7F and will warm only to the lower teens with wind from the west 45-60 mph.
Tomorrow, new snowarrives with 4-6” possible by the end of the day. Winds from the west at 20-35mph will shift NW and increase to 35-50 mph.
Primary Avalanche Problem – Wind Slab
Hard slabs are largely stubborn with a mix of firm snow (often P over 1F) and some softer areas where you’ll find thin and a bit more reactive wind slabs. New snow has been slow in coming over the past 4-5 days and these wind slabs appear to be largely unreactive in most areas due to the bridging power that hard slabs exhibit. Some softer slabs are also scattered around and may be capable of producing a smaller avalanche.
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.
There has been no avalanche activity observed or reported since Monday. New snow and warming lead to widespread wet avalanche activity in Tucks and Huntington late last week when temperatures warmed and rain fell and then another cycle of dry slabs late Monday when Hillman’s and Left Gully ran far. (Correction-Hillman’s likely slid in the cycle on Friday night. -FC) The debris on the floor in Tuckerman Ravine from both cycles remained visible yesterday, testimony to the scouring wind speeds.
If you go skiing or climbing today, take the time to dig, with a shovel or your hands, or use your pole handle to poke into the snow. The softer snow beneath the surface slab will be a good reminder that human triggered hard slab avalanches remain possible despite the enormous strength and bridging power of the wind slabs. Well placed explosives or bad luck could lead to an avalanche so stay vigilant if you brave the cold and wind for some turns or alpine climbing today.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch with some patches of ice down low.
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 02/12/2020 at 7:07 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest
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