Avalanche Forecast for Friday, March 27, 2020
This information was published 03/27/2020 at 7:05 AM.
The Bottom Line
While much of avalanche terrain consists of refrozen snow that will require crampons and an ice axe, areas of snow in sheltered locations may have remained dry after yesterday’s warm-up. In addition to this, small wind slabs will have formed from the half-inch of snow that fell last night on the higher summits. Isolated areas of dry snow are where a human could possibly trigger an avalanche today. If you find soft snow on the surface rather than firm refrozen snow or a breakable crust, you’ve found today’s avalanche problem. Avalanche danger today is MODERATE due to the possibility of a human-triggered avalanche. Identify features of concern and evaluate the snow in these areas before committing to the slope.
The AMC has closed all facilities at Pinkham Notch, including the restrooms. The winter pit toilets at Hermit Lake remain open though the breezeway at the caretakers cabin remains closed, along with all shelters and camping. Please respect CDC or your local health department recommendations and recreate locally while respecting guidelines for social distancing.
Yesterday, wind was light from the N, skies were mostly clear, and temperatures warmed to 31F on the summit of Washington right around dusk. Overnight snow flurries produced a half inch of snow on the summit.
Today starts with wind from the W blowing in the 60-80mph range. This should shift to the NW early. Gusts up to 100mph may occur this morning and then wind should drop to the 50-70mph range. Current temperatures in the 20sF will cool slightly through the day. A trace more snow may fall this morning before skies clear for the rest of the day.
Tomorrow, wind from the NW starts strong and then calms through the day with temperatures rising into the 20sF on the summits. Skies should be clear for the first half of the day and then cloud over. Precipitation is forecast on Sunday with temperatures on the summit reaching very close to the freezing mark.
Primary Avalanche Problem – Wind Slab
Mount Washington Observatory recorded a half inch of snow last night that fell on 60mph wind from the west. This will blow into small wind slabs on slopes with an easterly aspect. These new wind slabs will be small in size and rest on a variety of surfaces that range from old ice crust, chunky avalanche debris, and refrozen snow. In addition to these new wind slabs, some of the snow that fell Monday and turned into a soft wind slab managed to stay dry despite warm temperatures the past few days. This is primarily on N, NE, and E aspects. Field observations yesterday involved a long discussion about where we could actually find this snow, and we did find it in isolated pockets, though some slopes with this aspect were swept clean of the issue by the widespread avalanche cycle that occured Monday night into Tuesday. While this wind slab is now several days old and has seen a period of warmth that improved stability, the structure, strength, and energy still display signs of propagation. An avalanche in this wind slab could be big enough to bury a person.
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.
If you go into avalanche terrain today, much of the snow you will find will be refrozen snow that warmed mid-week. This snow offers good stability but will deter skiers, as it will offer poor skiing. Snow that may have stayed soft and formed into isolated areas of wind slab will be today’s avalanche problem. If you are drawn into these areas and find good skiing, you’ve found today’s avalanche problem.
We appreciate folks being conservative in decision-making recently and recreating on less consequential terrain. I’ve noticed a few people leaving the helmet at home because they decided it would not be needed on “easier” terrain. Please remember all your PPE when you ski in the backcountry; even if it’s just the Sherburne, accidents have happened to the best of us.
The Sherburne and Gulf of Slides ski trails are snow covered to Pinkham Notch.
The Lion Head Winter Route remains the easiest route to the summit from Pinkham Notch but requires an ice axe, crampons (not just micro-spikes) and possibly a rope. This is a mountaineering route and requires solid skills for a safe, timely ascent.
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 03/27/2020 at 7:05 AM.
USDA Forest Service
White Mountain National Forest