Avalanche Advisory for Monday, February 20, 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: Our snow pack has refrozen on southern aspect which had seen some softening over the weekend. After prolonged NW winds in the 50-80 mph range, some snow was still being transported into our start zones in a limited way yesterday afternoon. Around a half inch of new snow added to the total amount available last night. Small pockets of soft wind slab will be the primary avalanche problem. Reloaded lee areas in the Sluice through Chute area following our last avalanche cycle is the area of most concern for larger, lingering wind slab. Though unlikely to be triggered by a skier or climber due to the strength and bridging power of these slabs, this would be larger than the pockets of new soft wind slab on the surface.
WEATHER: Northwest winds will continue to diminish and shift north. Currently in the 45-60 mph range, the wind will diminish a bit to 35-50 mph by this afternoon. Temperature on the summit is currently 5F but will rise to the mid-teens through the day. Summit fog should clear later this morning with partly sunny skies and good visibility through the afternoon.
SNOWPACK: Field observations over the weekend revealed that snow had softened a bit on Saturday in a few sun exposed areas. Generally, though, the snow remained cold and dry in our forecast areas despite the warmth of the ambient air temperature. The exception is the gullies with a strong southern aspect where a very thin breakable crust less than a 1cm thick now likely exists on areas of softer snow. Right Gully, which was the target of many skiers on Saturday, had a quite variable snow surface yesterday and was not particularly attractive for skiing. The thin melt/freeze crust would likely go unnoticed on smoother slopes of firmer wind slabs. Significant settlement (7cm on Saturday morning, 7cmSunday and 3cm this morning) was recorded at Hermit Lake due to the warm temperatures. This settlement is driving down our avalanche danger along with falling temperatures. This refreezing effect will be most noticeable at lower elevations where packed snow on trails is now hard and refrozen. You’ll also encounter deeper snow and challenging travel in wooded areas along with large drifts of deep snow above treeline.

 

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., Monday, February 20, 2017. A new advisory will be issued tomorrow.

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

2017-02-20