Snowpack and Avalanche Information for Thursday, May 14, 2020
This information was published 05/14/2020 at 8:20 AM.
NOT THE CURRENT FORECAST
This is an archived avalanche forecast.
The Bottom Line
Wind slabs created by close to 20” of snow and strong west and northwest winds will warm and weaken beginning today. This warming trend will continue with rain forecast for Saturday. Wet slab and wet loose avalanches will become possible as these slabs warm. Be wary of slopes with a sunny aspect and be prepared to change objectives if snow becomes sloppy and wet. Rain arriving this weekend will accelerate this weakening and lead to the emergence of our spring hazards. Beware of swollen stream crossings and natural wet avalanches that could follow these thunderstorms. The weather has been unseasonably cold this month so consider the hazards of the first strong warming pattern on our snowpack and terrain as you make your plans.
MWAC has moved to a Snowpack and Avalanche Information bulletin (known in prior years as a General Bulletin) until the end of the season. Snowpack and Avalanche Information is issued when unstable snow may exist within our forecast areas but after 5-scale avalanche forecasts have stopped. Please remember that avalanches can and do occur after 5-scale avalanche forecasts have ceased!
On March 30th, the USFS MWAC took a tactical pause in forecasting operations. Since that time, forecasting and closure monitoring have continued, though forecasts were sent directly to local mountain rescue organizations only. As the public continues to recreate and winter conditions persist in the mountains, it is apparent that current snowpack and avalanche information could be helpful in reducing risks. Please realize that volunteer rescue resources are currently limited due to concerns about community spread of the coronavirus.
Tuckerman Ravine, Huntington Ravine and the Gulf of Slides will remain closed to all use until May 31 and possibly later as winter conditions and deep snow remain.
Air temperatures will warm above freezing today, reaching the lower 30’s on the summit of Mount Washington. Temperatures are already above freezing at 4300’. Low wind speeds and bright sunshine today will allow temperatures to climb well above freezing on sunny aspects. Rain arrives tonight with thunderstorm activity on Friday and summit temperatures reaching into the 40’s F. This warming trend will continue into early next week.
At this time, Gray Knob is the only shelter with caretakers available to record snow and weather data. You can check that data by clicking the Gray Knob tab below.
Thanks to those who have helped to make the remote weather station at Hermit Lake a reality. It is now online and communicating with servers! We’ll be making that data available real-time once we get a few kinks worked out but for now it’s great to have a look at snow depth at Hermit Lake in 15 minute increments!
Two low temperature records were tied or broken this month on the summit with close to 20” of snow falling since the beginning of last weekend. Northwest and west winds (100+mph) redistributed the new snow into dry, hard wind slabs in lee terrain. Air temperatures have remained below freezing at mid and upper elevations for the most part this week so these wind slabs are just beginning to warm and weaken. In most places, these slabs rest on an icy bed surface from the last thaw. The recent wind slabs will pass through a period of instability before going through the necessary freeze/thaw cycles that create an isothermal snowpack generally free of avalanche concerns.
Warming cold, dry snow creates travel conditions in a single day that could vary from the need for floatation in rotten lower elevation snow to thick, hard, mid-elevation wind slabs which demand crampons and ice axes on hard névé or ice. Be prepared for rapidly changing conditions.
Overall, there’s still lots of snow at mid and upper elevations (196cm at Hermit Lake!) with typical spring crevasse, moat and icefall hazards likely to emerge as we move into next week. Keep the following spring mountain hazards in mind as you make terrain decisions:
Despite the date on the calendar, new snowfall and winter conditions are possible during any month of the year at higher elevations in the Presidential Range. Spring and early summer bring rapid changes to our upper snowpack, with conditions often changing by the hour. Plan accordingly for these changes by reading the weather forecast before you head out (MWObs Higher Summits and NWS Hourly forecast).
One tool to help reduce the chance for unwelcome surprises is the hourly weather information produced by MWObs summit staff. The NWS displays the hourly data going back 7 days here.
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 05/14/2020 at 8:20 AM.
Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest
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