Avalanche Forecast for Wednesday, February 5, 2020
This information was published 02/05/2020 at 7:01 AM.
The Bottom Line
Light freezing rain fell at 5,000’ in Tuckerman Ravine yesterday, reducing avalanche concerns primarily to new wind slabs which may have developed overnight. These wind slabs will likely be found in isolated areas and limited to very well sheltered areas protected from the strong west winds that blew overnight. There is LOW avalanche danger today though normal precautions are advised, especially in the steepest, sheltered east facing terrain in mid to high elevations.
Yesterday: A humid day with a high temperature of 23F on the summit. Light snow showers fell on the highest summit with freezing rain occurring between there and 5,000’. Wind from the west rose through the day, gusting at 80mph near midnight.
Today: Clearing skies, strong winds and temperatures in the single digits on the summits. Wind will diminish to 35-50 mph today as cloud cover returns.
Tomorrow: Wind will shift to the southeast as active weather returns. 3-6” new snow tomorrow with the threat of a transition to mixed precipitation in the afternoon as temps rise to the upper 20’s F on the summit.
Primary Avalanche Problem – Wind Slab
Older wind slabs in the terrain which exist above the stout melt freeze crust generally lacked energy for propagating a crack even late last week. Mild weather has been the norm for the past week with settlement and bonding the trend. No avalanches have been reported in these thicker wind slabs though the snow structure was inverted in many areas where soft, rimed snow had drifted deeply and was capped with thin wind slabs. Several dense layers of melt/freeze crust with a slick freezing rain crust nearest the surface deadened any significant reactivity. Moderate stability tests recently and no avalanches isn’t a green light to abandon safe travel techniques but avalanches remain unlikely through most of the range. The older wind slabs will be loaded by new snowfall tomorrow.
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.
Low tide continues for our region for one more day. Tomorrow will turn that story around, at least to some degree, with new snow from another coastal storm arriving over the next couple of days. An inch and a half of snow water equivalent is possible by the end of the second system on Friday and while deep powder doesn’t seem to be in the cards, slopes will get refreshed by mostly frozen precipitation forms. Multiple periods of upslope showers recently have yielded normal levels of precipitation, but of the unfrozen variety at times, especially at lower elevations.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch and in pretty good shape down to around 3,000’.
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 02/05/2020 at 7:01 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest