Avalanche Advisory for December 22, 2016

This advisory expires at Midnight tonight.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South Gully and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. North, Damnation, and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, The Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw and Right Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lower Snowfields and Little Headwall are not rated due to a lack of snow.

Avalanche danger is Low early this morning but is rising, with natural and human-triggered avalanches becoming increasingly possible through the day.

AVALANCHE PROBLEM: Wind speed and direction today will effectively build wind slabs, particularly in our upper start zones. Look for cross-loaded slabs in other lee areas of terrain features due to the shift in the wind to the west in the early afternoon hours. Our danger rating today is straddling the line between moderate and considerable ratings due to a combination of factors. Count on having your terrain and snowpack assessment skills being thoroughly tested today.

WEATHER: As snows showers begin at this hour, WSW winds in the 40 mph range are starting to move snow into our forecast terrain. Weather models show a shift in wind direction through the west to the northwest through daylight hours with the wind ramping up a bit into the 35-50 mph range. These wind speeds will effectively move the forecasted 2-4” of snow from our fetch zone in the flat alpine terrain into avalanche terrain creating the potential for new wind slabs to form throughout the day. Anticipate reduced visibility and flat light to challenge route-finding and surface snow assessment.

SNOWPACK: We are starting the day with a porous icy melt/freeze crust on the surface. This crust is coarse enough to allow weak bonding initially in many areas of our terrain but is certainly not strong enough to support building slabs in place in all areas. Wind speeds are light enough currently that the snow falling early on should blanket the terrain. This new snow is likely to be the primary weak layer for wind slabs that will form on top through the day. Remember that the bed surface is hard and icy and will remain the primary travel surface until more snow falls. This fast sliding surface will make self-arresting extremely difficult whether caused by a slip and fall or a small avalanche sweeping you off your feet.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine trail is still not really passable for snow machines. Thanks for your continued patience!

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 8:00 a.m., Thursday, December 22, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-22