Avalanche Advisory for Wednesday, March 8, 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. The Little Headwall is no longer forecast this season as it is now an open river.

AVALANCHE PROBLEM: Rain and warm temperatures created a wet slab problem this morning. Wet slabs will be found today in areas that contained wind slab over the past few days, largely in the Lip and Center Bowl with scattered pockets elsewhere. This avalanche problem is hard to predict and can be caused by quickly adding weight to the slab or by meltwater lubricating a sliding surface within the snowpack. With rainfall diminishing and temperatures dropping, the likelihood of wet avalanches will diminish due to the snowpack refreezing. Later in the day, a fast moving system may bring periods of heavy snow and up to 3” total. Increasing wind from the west has the potential to turn this snow into wind slab. If we receive the upper end of the forecast snow total, the avalanche hazard rating may exceed the current Low rating and require careful snow and terrain evaluation for safe travel.

WEATHER: Temperatures in the 30s and 40sF yesterday and into the night allowed 0.25” of water to fall as rain. A sudden downturn in temperature at 7am has the summit at 25F and Hermit Lake at 35F. Rain and mixed precipitation should be light and continue for the morning with less than 0.1” of liquid before clouds dissipate. Later in the day, an upper level trough may bring a brief period of instability to the region along with the possibility for snow. With winds increasing to 50-70mph and a possible period of heavy snow with 1-3”, watch for blizzard conditions if traveling later in the day.

SNOWPACK: Prior to this past Friday, our snowpack consisted of refrozen snow that was shaping up to offer good spring ski conditions. Cold temperatures over the weekend and a total of 7” of snow since March 3 created firm wind slab in lee areas of NW winds. Rain last night soaked these wind slabs creating wet slabs. With the heaviest rain and warmest temperatures pre-dawn today, the period of highest instability has likely passed. Temperatures are plummeting and the snowpack as a whole should freeze as the day progresses. Up to 3” of snow on strong W winds later in the day will likely create pockets of wind slab in lee areas of the steepest terrain and sheltered areas of terrain features. Travel in terrain today will require keeping an eye on the weather and constant revaluation of what the current conditions are doing to the snowpack.

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 Harvard Cabin.
  • Posted  8:15 a.m., Wednesday, March 8, 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