Avalanche Advisory for Thursday, February 13, 2014

This advisory expires at Midnight.

Tuckerman Ravine has CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential.

Huntington Ravine has CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential.

AVALANCHE PROBLEMS:  Avalanche hazard will rise to CONSIDERABLE later today from yesterday’s Moderate rating. Wind Slab is the primary avalanche problem this morning with Storm Slab and new Wind Slab becoming an issue in the afternoon.  Additionally, we have persistent slabs lingering in a variety of locations. These older slabs may feel quite strong underfoot, but if you find and impact a weakness, a large avalanche might result. The exact timing and intensity of the new snow varies from source to source but anticipate the potential for naturally released avalanches to increase as the afternoon progresses. Today is not the day for a slow ascent leading to an after dark descent of any route in our forecast area due to the increasing avalanche danger and reduced visibility.

WEATHER: A Winter Storm Warning is in effect.  8-12″ (20-30cm) is forecast with localized higher amounts possible giving some mountain areas 10-14″ (25-35cm).  Snowfall should start during the late morning and get heavy at times in the afternoon and early evening.  Winds will likely be from a generally SE direction for the vast majority of daylight precipitation.  As snow falls, wind should increase from about 30 mph to gusts of 50.  The rising temperatures should stabilize and hover between the teens and low 20’s from avalanche terrain to the high summits.  Late in the day, models have winds moving from the E between 4 and 7pm.  This counterclockwise trend will continue through the night, moving around from the N after midnight, increasing with gusts over 60 mph.  As we work through a dry slot, snow should pickup again during the very early hours on Friday. As this occurs winds will shift some more and increase from the NW which will stimulate another round of loading.

SNOWPACK:  Pre-existing wind slabs from wind and new snow earlier in the week have once again lingered due to cold clear conditions that slowed the stabilization process. Experienced guides have wisely backed off of Moderate rated gullies and had their terrain management skills tested due to the inverted snowpack that exists in many areas. If you are out early, be suspicious of wind loaded “pockets” and sluff piles below steep areas of ice and rock. Pockets of snow released by a human trigger could become large enough to bury you in select areas and could easily knock you off your feet due to the deep location of the weak layer. Also be wary of the firm wind slab in areas which may allow you to travel on top with very little boot or ski penetration….these areas can crack and fail if loaded in the right spot and will also be stressed by the incoming snow load. Today’s new snow will be falling on a fairly cold snowpack so don’t expect great bonding right away and as temperatures rise a bit and warm air infiltrates our cold air mass, be on the lookout for periods of relatively damper, denser snow to make worse the inverted nature of the snowpack. As winds shift to the Northwest this evening, instabilities due to wind slab will really become a problem as snow is picked from above treeline and dumped into our start zones. North and east facing gullies, like Chute, Left and Hillman’s in Tuckerman’s with Escape wrapping around to Central will load with the new snow first this afternoon. Other areas will struggle to reach the Considerable rating during daylight hours but their stability issues prior to the incoming storm still require careful assessment and risk mitigation.

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 8:00a.m. 2-13-2014. 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

2014-02-13 Print friendly