Avalanche Advisory for Sunday, February 22, 2015

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravine have 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. Lower Snowfields has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEM: Wind slab is the primary avalanche problem today. This wind slab is likely to be sensitive to human-triggering due to relatively low summit wind speeds, by Mount Washington standards, last night. Wind at the start of the storm was from the SW and shifted around to its current WNW which built these wind slabs in all aspects of our forecast terrain. Expect these wind slabs to be on the softer side and capable of fracturing large enough to produce an avalanche which could hurt or kill you.

WEATHER: Snow began falling on the mountain last night around 4pm. At that time, winds from the southwest were blowing around 50mph on the summit. By 11pm winds were from the west at roughly the same velocity with snow falling at an increasing rate for a couple of hours. By 2am, the snow fall stopped but wind loading continued from the west with a bit higher wind speeds recorded. Wind speeds are diminishing as forecast for today with good visibility for a spell at 7:30am, though an undercast exists which is moving in and out of both Ravines making visibility uncertain. Summit winds should relax to the 20-35 mph  range, if they haven’t already, with temperatures in the low teens (-10C range). There is the potential for a trace to 2” of snow this morning. Later tonight, an arctic airmass will blow in, sending the mercury freefalling to -20F (-28C) with winds increasing to the 60-80 mph (95-130 km/h) range with gusts to 90 mph (145 km/h). The temperature on Monday will continue to fall to around -35F(-38C) with even higher winds making a backcountry adventure particularly dangerous.

SNOWPACK: A smooth blanket of snow covers Pinkham Notch and the Tucks trail and might lead you to believe that deep loose and unconsolidated powder waits for you in the Ravines. Don’t be disappointed when you arrive at the mouths of the Ravines to find steep wind drifts. The drifts tell the tale of wind affected snow, around 6” of which was recorded at Hermit Lake (12.5-14cm with wind effect on the boards). Snow here at Hermit Lake is also slightly denser than lower elevations, most likely due to settled cold air allowing larger crystals to grow. Good visibility this morning revealed smooth snow, wide spread large pillows of snow particularly in upper Hillman’s, through Chute, Center Bowl, the Lip and Sluice. Some sastrugi indicates a  stronger wind effect above the ice in Center Bowl with a cornice and wind drifts across the top of Left Gully. The only new crown line we are seeing so far is above the choke in Chute where it looks as if sluffing triggered a thin slab. Visibility was non-existent this morning in Huntington Ravine. Bed surfaces are growing in the Lower Snowfields along with the sluff and debris pile out of Duchess so be careful with your terrain and snowpack assessments if venturing into this area.

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. February 22, 2015. A new advisory will be issued tomorrow.

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

2015-02-22 print friendly