Avalanche Advisory for Friday, March 10, 2017

This advisory expires at Midnight.

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Lip, Center Bowl and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. The Little Headwall is not forecast due to lack of snow.

 AVALANCHE PROBLEM: Wind slabs that developed yesterday will be the primary avalanche problem for the first half of the day with danger ratings at the lower end of those written above. Snow squall activity along with steadier upslope precipitation this afternoon will drive these ratings up and make human-triggered avalanches possible in all forecast areas. Avalanche paths, like Lip and Center Bowl as well as Central and Pinnacle Gully, that are in the lee of west winds, will reach maximum instability towards evening as winds reach prime loading velocities. The size of potential avalanches will depend on the amount of snow produced by the combined upslope snow showers along with a Norlun trough. Expect potential wind slabs this morning to be on the smaller side in moderate rated areas but grow to medium sized avalanches capable of burying a person by nightfall if we receive the upper end of the 3-5” forecast by the MWObs. Wind speed and direction are prime to create touchy wind slabs which could propagate easily. Evaluate snow, weather and terrain carefully today.

 WEATHER: The timing of increasing west wind and amount of total snowfall are challenging forecast model consensus due to dry air aloft as well as the fickle nature of the Norlun trough. Bands of dry air may reduce much of the potential snowfall to only an inch or two. Should the trough stream moister air to the Whites than some models indicate, we could receive 5” of new snow. Light winds this morning will continue until mid-day and then begin ramping up. Visibility will begin to diminish in the afternoon, unfortunately just as accumulating snow improves skiing.

SNOWPACK: A combination of extreme temperature swings and liquid precipitation over the past several weeks has created a solid, relatively uniform snowpack in our forecast areas. Over the top of this, the past several days have brought as much as 8 inches of new snow along with very high winds. 100 + mph gusts were recorded on the summit of Mt. Washington yesterday.  As a result, Tuckerman and Huntington Ravines display a mixed bag of recently formed wind slabs and scoured old snow surface.  Avoiding these wind slabs will reduce exposure to our avalanche problem, but increase risk of sliding falls on the hard old snow. This wind transported snow has likely bridged many of the large glide cracks that had opened in the past several weeks, be aware that these bridges could be thin and unsupportable.  Overall, though, surface conditions have vastly improved over the past week, particularly on the Sherburne and Tuckerman Ravine trails between Pinkham Notch and Hermit Lake.

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  8:10 a.m., Friday, March 10, 2017. A new advisory will be issued tomorrow.

Frank Carus/Ryan Matz, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-03-10