Avalanche Advisory for Sunday, February 26, 2017

This advisory expires at midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Wind Slab will form today from snow showers last night as well as likely continued upslope snowfall today. The hazard will increase as snow accumulates, but with 1.5” last night and up to another inch expected today, the unstable areas will be pockets on isolated terrain features large enough to cause a long, sliding fall. The area of main concern today for wind slab would be just under the rollover in the Lip, Center Bowl and Chute.  Across much of our terrain, a non-avalanche hazard that is real and present today is this possibility of long, sliding falls. Overnight, our snowpack went from wet and heavy to a skating rink. Acuity with crampons and an ice axe will be crucial to making it down safely at the end of the day.

WEATHER: Above freezing temperatures for several days has come to an abrupt end. The thermometer dropped below freezing on the Summit last night around 9pm and is now at 5F. Precipitation began yesterday afternoon with several hours of drizzle and light rain before transitioning to graupel and then snow. The Summit recorded 2.3” of snow with a trace falling at Hermit Lake. This morning, upslope snow showers should bring up to an inch of snow. Winds will be strong (55-75mph) and from the west. Tonight will remain cold with winds increasing slightly and skies clearing.

SNOWPACK: Over the past five days, the Summit recorded only two hourly temperature readings below 32F, the rest being above freezing. This is evident by looking at the snow stake at Hermit Lake which has lost 46cm (18”) of snow in that period. This snow loss can also be seen by the looking at the rivers that cross the trail. Five days ago these offered good skiing while many are now open water including the Little Headwall which will require careful navigation of a waterfall to descend (it may be better to try the tree skiing to either side of the main streambed). With the drop in temperature last night, the wet snowpack is refreezing. This refreeze will eventually lock up the snowpack into concrete. On top of this firm snowpack will be new snow from last night and today. Strong winds will scour some locations and create the aforementioned wind slab in the steeper terrain. This morning, travel on trails and areas that have seen traffic is firm and requires traction. As lower elevations have only recently dropped below freezing, traveling off-trail in the woods will likely still result in postholing for much of the day.

 

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory 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.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted  8:15 a.m., Sunday, February 26, 2017. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-02-26