Avalanche Advisory for Saturday, March 11, 2017

This advisory expires at Midnight.

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible.

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

 AVALANCHE PROBLEM: Widespread, boot top thickness, soft wind slabs which existed yesterday in Lip, Center Bowl and Chute, as well as scattered through other forecast areas, will add to the potential size of avalanches today. New wind slabs which formed overnight, and which will continue to form through the day, will create dangerous avalanche conditions in the floor of Tuckerman Ravine as well as higher in avalanche paths. Other forecast areas with a Moderate danger rating will have heightened avalanche conditions and will require careful snow and terrain evaluation. Wind, blowing snow and cold temperatures will reduce visibility and make group communication challenging so conservative decision making is advised in all forecast areas.

 WEATHER: Over the past 24 hours, temperatures have plummeted, consistent westerly winds have increased to gusts in the 80 mph range, and we’ve received a shot of new snow. Winds have challenged data recording, but several inches of new snow fell yesterday at Hermit Lake with the summit recording 5.8”.  Weather should be remarkably consistent throughout the day today, with summit conditions near -20 F, 60 mph winds with gusts to 80.  In the morning hours, models are showing a 20% chance of snow with little accumulation expected.  It goes without saying that today’s weather demands respect; plan and make travel decisions accordingly.

SNOWPACK:   Our deeper snowpack was exposed to a prolonged period of warm weather and rain which has created a strong snowpack but with an icy surface mixed with new wind slabs. It’s as if someone flipped the hazard switch back to the traditional winter problems involving avalanches, cold challenges and long sliding falls from the recent spring problems of icefall, crevasses and undermined snow over running water. Remember that we still have a relatively thick snowpack on east and north facing terrain which creates larger and more connected slopes that can produce larger avalanches. Southern facing terrain in both Ravines has much less snow coverage. Right Gully is mostly rocks and bushes at the top and has boulders showing in the runout. Lobster Claw remains snow to the top but is very tight. Northern gullies in Huntington are a mix of ice, rock and snow. Field time yesterday revealed much softer snow in the Lip area than 100 mph wind gusts would lead you to expect. That layer could be the weak layer in an avalanche propagating today or it could add volume to an avalanche starting in newly formed wind slab. Either way, the floor of Tuckerman Ravine is in the crosshairs. Overall, surface conditions on local ski trails have vastly improved over the past few days, 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., Saturday, March 11, 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

2017-03-11