Avalanche Advisory for Thursday, March 16, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. The only exception to this rating is Little Headwall which has Low avalanche danger. A combination of small wind slabs, ice bulges and open water exist there.

AVALANCHE PROBLEM: There is Considerable danger from new wind slabs that developed overnight and that will grow in size today. These wind slabs will be found in lee areas of west and northwest winds. Sluice, beneath the ice in Lip and Center Bowl, in Chute, as well as high in Left Gully and Hillman’s will see the greatest likelihood of a natural avalanche and the greatest sensitivity to a human trigger. It would be challenging to travel through these areas without triggering a wind slab. Similar conditions are likely to be found in Huntington Gullies that have an easterly aspect. Northern gullies in Huntington and Lobster Claw and Right Gully in Tuckerman Ravine have larger but likely more stubborn wind slabs lingering from the strong north east winds associated with the most recent nor’easter. These areas including, North, Damnation, and Yale, will also have some cross-loading of new snow which will complicate assessment and travel.

WEATHER: Lingering moisture from the exiting nor’easter will create fog and generate light snow showers at higher elevations today. The trace-2”, combined with 22-26” of recent snow on the ground, will give west and then northwest winds something to work with. Wind is currently blowing from the west in the mid-40’s mph with gusts to the mid-50’s. The past 12-14 hours have seen roughly these same wind speeds from the west with a 3-4 hour period early this morning of NW wind in the 60’s gusting to the 70’s mph. Peak wind loading of our forecast areas likely occurred during that time period but wind, continued blowing snow, and fog will continue to make conditions a bit rowdy. Wind transported snow is the critical factor affecting snow stability today.

 SNOWPACK: Wind driven snow will stress weak layers in wind slabs deposited during the recent big storm. Due to strong easterly and northeasterly wind, those slabs were limited to south facing aspects that were downwind of a sizable fetch. This means these slabs were primarily in Lobster Claw, Right Gully, low in the Bowl and on the approaches to climbs on the right side of Huntington. Yesterday, old, gray ice crust and sastrugi was visible in most of Center Bowl, Left Gully and Hillmans though certainly larger pockets of wind slab were mixed in. The alpine zone was heavily scoured as well, though plenty of snow likely remains in large drifts. It is important to remember that travel and assessment will be challenging due to fog, blowing snow and cold conditions. Today might be a good day to climb and ski at lower elevations and let the wind slabs sort themselves out in the higher and steeper 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 the Harvard Cabin.

Posted 8:30 a.m., Thursday, March 16, 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