This information was published 02/16/2020 at 7:14 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Wind slabs formed over the past several days have become unlikely, but not impossible for a human to trigger. This is especially true where you’ll find protected pockets of softer snow that escaped the impact of recent wind.
Isolated pockets of wind drifted snow from snow showers today may be found in the terrain and should be on your radar, though these are not expected to increase the danger rating.
Avalanche danger is LOW. Generally stable conditions exist, but, like any day in the winter this is not the day to ski solo or leave your avalanche beacon in the car.
Yesterday, wind shifted to the west with speeds 30-40 mph increasing slowly throughout the day reaching 70-80 mph overnight. Some blowing snow was observed at the ridgetops but to a much lesser degree than observed Friday. The day was clear with temperatures in the single digits °F rising to the lower teens.
Today, morning snow showers (Moderate Snow at 5am) are forecast to end with a chance of snow showers again this afternoon. A trace to less than an inch is possible. West wind at 60-80 mph will decrease to 40-55 mph accompanied by a summit high temperature of 10°F. Overnight tonight another trace to less than one inch of snow is possible.
Tomorrow brings a slight chance of snow showers in the morning before clearing with temperatures in the low single digits °F. West wind 40-55 mph will increase through the day.
Primary Avalanche Problem – Wind Slab
Wind slabs remain a concern on larger, steeper slopes. Triggering one of these slabs is unlikely but not impossible. Look for hollow sounding pillows of snow that may appear smooth, but may also show some texture from the wind. Be on the lookout for the possibility of new slabs forming from new snow today. Snow totals are expected to be less than inch, and with the wind forecast we expect any new pockets to be isolated or unreactive.
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.
Left Gully,Tuckerman Ravine 2/15. Snowpack has grown from the 15″ of new snow over the last week.
West and northwest wind up to 70 mph has worked to harden wind slabs formed Thursday and Friday of last week. In some locations, typically where these slabs are the thickest, these firm slabs are sitting on top of a weak layer above the Feb 6-7 rain crust. While this is a red flag, this configuration is generally more “red” when the hardness difference between the weak layer and slab is greater than it has been observed to be in the past few days.
A good non-standardized snow test today to help identify the difference in hardness today is the Ski Pole Penetrometer test. In your travels, stick your ski pole down into the snowpack feeling for changes in density on the way down, and back up. In our current firm snow, handle first is best, but in softer snow basket first is more sensitive to subtle changes. If you find firm snow over soft snow today you’ve found the slabs of concern.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch and offer great skiing and riding.
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 02/16/2020 at 7:14 AM.
USDA Forest Service
White Mountain National Forest
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