Avalanche Advisory for Friday, March 31, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Overnight, a solid freeze of wind loaded slopes, which had softened in the sun yesterday, has reduced our stability concerns to snow arriving this afternoon. A low pressure system passing to the south will bring up to an inch of water to the area with the majority of this falling tonight and tomorrow. Low wind speeds from the southeast and 2” of snow will keep avalanche danger low today with natural and human-triggered avalanches unlikely in all areas. Avalanche danger will continue to rise through the weekend so anticipate elevated danger through Sunday, when winds from the northwest load snow into our forecast area.

WEATHER: Daytime temperatures yesterday reached 19F on the summit but low wind speeds and plenty of sun warmed things up quite a bit in our forecast areas. A southwest flow overnight has allowed temperatures to climb a bit more. Expect summit temperatures to reach into the low 20’sF today with continued light winds which will slowly shift counterclockwise from the current westerly position to the southeast by nightfall. Wind velocity is forecast to remain very light, reaching only the low 20’s mph this afternoon with the pitot registering 5.2 mph at this writing. Snow will begin this afternoon with a half inch falling by nightfall according to adjusted NWS models, though Observatory forecasts seem to indicate a trace-2”. In either case, low snowfall amounts and light wind speeds are key factors in avalanche danger today.

SNOWPACK: The rain soaked or otherwise settled deeper snowpack creates no stability concerns in our terrain now. The 2” of snow that fell through Wednesday night created some nice skiing and riding for folks yesterday with generally stable snow loaded into lee areas of a west wind. Solar aspects heated the new snow and created mashed potatoes by early afternoon, despite the summit temperature which reached only 18F by nightfall with wind speeds in the 10-15mph range. This snow is now refrozen and should allow for good bonding with the new snow which will most likely contain a weak layer due to increasing winds, increasingly dense snow or both. The hard snow and old icy bed surface will make long sliding falls possible in the terrain today with crampons and ice axes key equipment in steep terrain.

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 8:14 a.m., Friday, March 31, 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