Avalanche Advisory for Friday, March 2, 2018

Huntington and Tuckerman Ravine will have CONSIDERABLE avalanche danger. Dangerous avalanche conditions may exist. Careful snow and weather evaluation, and cautious route-finding will be essential. The Little Headwall is an open stream and is not rated.

AVALANCHE PROBLEM: We are starting the morning with low avalanche danger in all forecast areas. The storm system passing by to the south will likely generate 4-8” of new snow in higher terrain. Easterly wind, shifting to the northeast, will ramp up through the day, building wind slabs that may avalanche naturally in many areas. While wind will eventually reach a velocity capable of scouring lots of the terrain, we will pass through a period of peak instability before we get there. If you choose to travel in avalanche terrain today, remember that the new wind slabs will be forming over an icy bed surface and will be touchy and may fail above you naturally. Due to the wind direction today, wind slab avalanches won’t be large, but they may be large enough to carry you over cliffs or into rocks. Dry loose avalanches may be plentiful as well and will contribute to the volume of wind slab at the base of steep areas. Forecast areas sheltered from NE winds may grow larger wind slabs than usual. Lobster Claw, Right Gully and Sluice in Tuckerman Ravine meet that criteria. The northern gullies in Huntington have limited bed surfaces but their sheltered location could allow wind slabs to grow quickly in steep, upper and mid elevation start zones.

WEATHER: The snowfall amounts forecast today remain uncertain due to our distance from the center of the low passing to our south. Snow has already begun on the mountain though valley locations are seeing rain and snow mixed. Snowfall totals today are dependent on bands of precipitation passing over and spawning periods of moderate or even heavy snow. Snow began earlier than expected making the increased MWObs snowfall forecast of 4-8” seem likely. Currently, a gusty northeast wind on the summit is blowing at 55 mph and will continue to increase through the day and really howl by the end of the day with gusts over 100 mph in the mid-afternoon. Descending from a morning summit attempt with that wind speed and direction may require crawling.

SNOWPACK: The result of multiple thaws in January and February is a stable snowpack to begin the month of March. Warm spells recently have reduced the overall snowpack, resulting in the snow study area at Hermit Lake losing close to 12” since mid-February. Glide cracks and small holes due to undermining appeared briefly, but never had the chance to fully develop. Snow that arrives today will likely cover these, though holes in the Little Headwall streambed will remain open and visible. Any exposed area of old surface today will be firm. Over the past week, we received several reports of people losing their footing and being unable to self-arrest due to the icy nature of the snowpack. Bear this in mind when moving around in steep terrain.

The John Sherburne Ski Trail holds a wide variety of conditions, including exposed rocks, areas of water ice, which is sometimes thinly veiled covered with the new snow that fell earlier this week. Plenty of skiable snow remains but cautious and careful turns are advised.

The Harvard Cabin will be open Friday and Saturday night this weekend.

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 8:00 a.m., Friday, March 2, 2018. A new advisory will be issued tomorrow.

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

2018-03-02