Avalanche Advisory for Monday, February 29, 2016

All forecast areas of Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely but human-triggered avalanches are possible. Evaluate snow and terrain carefully.

AVALANCHE PROBLEM:  We are starting this morning with Low avalanche danger in both ravines.  The Moderate rating will develop as the forecasted weather moves in.  Strong west winds and 1-3″ of new snow, possibly mixed with rain or even all rain, will create the instability for the day.  New wind slab will form if this precipitation falls as snow due to forecast wind speeds and direction. If a mix of precipitation types fall, anticipate potential wet loose avalanches or even a wet slab. Travel in avalanche terrain today will require a vigilant eye on the weather to keep track of increasing danger and what type of danger that will be.

 WEATHER: Summit and valley temperatures hovered just below freezing overnight. Currently, a mid-elevation warm band sandwiched between the summits and settled cold air in the valleys, is yielding temperatures in the high 30’s in the Ravines, with 41F at Hermit Lake. The mercury will creep up even further this morning before the first of two cold fronts passing through the area today returns the temperature to more seasonable levels. The first front should arrive mid-day, bringing with it higher windspeeds (60-80mph) and a chance for 1-3” of new snow. Unfortunately, temperatures are such that Ravines may see rain rather than the desperately needed snow. A second front will arrive near or after dark. By midnight, winds will push even higher into the 90’s mph with gusts to 110mph overnight with temperatures falling to 0F by tomorrow morning. Our rating today is most influenced by the first fast moving system to arrive mid-day.

 SNOWPACK: Last night, it is likely that the warm air band encouraged slow settlement of the old, firm wind slabs that exist in a few strong lee areas like Sluice and the Lip. Given the lack of ice crust on the snow’s surface at Hermit Lake, it is possible that some softening of the icy melt/freeze crust has occurred in the Ravines but this softening will be short lived. Hard surface conditions will return as temperatures drop this afternoon and leave the potential for long sliding falls near the top of the list of hazards you’ll face. If the coming precipitation falls as rain expect our avalanche hazard to increase slightly due to increased load on the older wind slabs. If precipitation falls as snow, expect new wind slabs to develop and be the main stability concern. In either case, assessments will be challenging due to reduced visibility.

Icy conditions on trails are creating very slippery conditions. Microspikes for down low with crampons and an ice axe in the steeps areas are recommended. Ski conditions are generally poor on the Sherburne with long stretches of water ice, particularly lower on the mountain.

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 8:15am, February 29, 2016. A new advisory will be issued tomorrow.

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

2016-02-29