Avalanche Advisory for January 28, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully may rise to Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas may rise to Moderate avalanche danger today. Evaluate snow and terrain carefully. The exceptions to this rating are Lobster Claw, Right Gully and Lower Snowfields which have Low avalanche danger.  Watch for unstable snow on isolated terrain features there. Little Headwall has not refrozen completely and is far from filled in with snow. The Lip still contains a large void in the snowpack from the recent wet avalanche.

AVALANCHE PROBLEM: New wind slab may develop today if the mountain receives the upper end of forecast snowfall of a trace to two inches. The new snow could add stress to the scattered wind slabs that already exist in the terrain due to the inch or so that fell last night in higher terrain and blew into our forecast zones. Wind slabs scattered through these lee, sheltered areas may become sensitive to human triggering if the new snow forms more slabs on them. Yesterday, wind slabs showed no tendency to propagate a crack but additional snow load on top could make them more susceptible to human triggers. Evaluate snow carefully as you find your way through the terrain today.

WEATHER: Summit temperatures peaked at 28F late afternoon yesterday ahead of the passing cold front and have been steadily dropping. Current temperature on the summit is 21F and 30F at Hermit Lake. Expect temperatures to continue to decrease today with the summit reaching around 10F. West winds of 50 to 70 mph will moderate to 35 to 50 mph. Between lingering upslope snow showers and a secondary front passing this afternoon a trace to 2 inches of snow is possible.

SNOWPACK: The dominant feature of the snowpack in Tuckerman Ravine yesterday was the bullet hard, ice glazed surface. Crampons were necessary to climb beyond the floor of Tuckerman Ravine due to this slick and hard surface conditions with similar conditions reported in Huntington. Stability tests and travel in Left Gully to the choke showed that the older wind slab was well bonded to this icy surface. Nearer the surface, firmer (1F) wind slab over the thicker 4F slab created a clean shear at the interface between these two layers but neither layer showed any desire to propagate a crack much beyond your feet. These layers seemed to behave like the typical slabs that form here when legendary high winds and cold temperatures punish snow grains until they become complacent, lifeless rounds. Snow and ice climbing conditions have been stellar though today’s new snow may complicate route-finding.

Sharp edges, speed control and a willingness to sacrifice some P-tex to the snow gods is required to ski or ride the Sherburne Ski Trail today. Microspikes and crampons are key tools for travel today.

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 Harvard Cabin.
• Posted 7:50 a.m., Sunday, January 28, 2018. 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

2018-01-28