Avalanche Forecast for Wednesday, January 22, 2020
This information was published 01/22/2020 at 7:02 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Firm wind slabs in steep, wind loaded terrain with an eastern aspect remain a concern. You will find these hard slabs of accumulated, wind drifted snow primarily beneath steep terrain features and places well sheltered from recent, howling west and northwest winds. These areas continue to have MODERATE avalanche danger today. None of these wind slabs have been triggered since they developed but they are worth a normal amount of vigilance as you ski or climb. Lower elevations and the scoured icy surface mixed in with the wind slabs have LOW avalanche danger.
After several days of seasonably cold weather, the summits return to relatively warm conditions. The current temperature is 10F on the summit. Some summit fog should dissipate this morning, after that expect a high near 20F today with west wind in the 25-35 mph range under clear skies. Lower elevations and sunny aspects may see temperatures rise above freezing. Looks like another weekend low pressure system will affect the forecast area.
Primary Avalanche Problem – Wind Slab
Wind slabs, which accumulated in many sheltered areas recently, sit on an icy crust in east facing avalanche terrain. These slabs will be stubborn in most places due to their size and bridging strength. Cold temperatures over the past few days haven’t encouraged bonding and may even have led to some facet development near this crust. Firm wind slabs such as these on steep slopes would require a thin spot in the slab, an unsupported slope or convexity, or a thicker and softer weak layer to trigger. A small amount of warming may occur today on sunny aspects near rocks.
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.
Patrick from Wildcat submitted this photo yesterday.
The good news is that cold temperatures have preserved the quality of the 80-100 cm of snow on the ground near 4,000’. The bad news is, well, there is just a meter or less snow on the ground even at that elevation. Some softer pockets of snow exist in avalanche terrain and likely formed as winds abated during the last blow. These spots appear to have yielded some fine turns yesterday as folks make the best of the meager January snowpack. The cold temperatures have limited the number of folks out and about and so our snow and avalanche observations are limited. History has shown that wind slabs like we have now in the terrain exhibit good stability in general despite showing moderate results in snow stability tests. Due to the wide variability of thickness and distribution of these slabs, these tests generally confirm the reasonable assumption that these slabs aren’t entirely trustworthy, thus the moderate danger rating.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch with icy areas and some open water bars.
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 01/22/2020 at 7:02 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest
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