Avalanche Advisory for Thursday, February 1, 2018

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions may develop on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions may develop on specific terrain features. Evaluate snow and terrain carefully. Little Headwall is no longer filled in with snow and is not rated. The Lip still contains a large void in the snowpack from the wet avalanche on January 12 or 13 and creates a significant fall hazard beneath the rollover and out of view from above.

AVALANCHE PROBLEM: The likelihood of triggering wind slabs in steep terrain may increase today as incoming snow forms slabs in wind sheltered areas. Currently, old wind slabs on top of an old refrozen and strong icy snowpack are scattered through the terrain. Stability tests and some foot traffic have indicated that these slabs are stubborn and resistant to triggering. More snow today could build new wind slabs due to ideal wind loading velocity and direction. If we receive the upper end of forecast snowfall through the day, the new wind slabs will be the primary avalanche problem. Loose dry avalanches or sluffs could develop as well which may build larger slabs beneath steep terrain. Be sure to assess incoming weather and execute an alternative route if necessary.

WEATHER: We start the day with a morning temperature on the summit of 12F with wind out of the west at 39 mph.  Both temperature and wind will remain moderate through the forecast period with temperatures mid-teens and west wind 45 to 60 mph. Warm moist air will keep the higher elevations in the fog. Finally, we have a good chance at covering our frozen snowpack with some fresh snow.  A cold front approaching today may deliver 1-3” of snow during the day with heavier upslope generated snowfall tonight. This could bring 2-4” more snow tonight and tomorrow. Keep your fingers crossed and check the advisory tomorrow for details.

SNOWPACK: Two periods of rain and warm temperatures in January, one starting the 10th and one starting the 23rd, changed the snowpack drastically. Despite multiple passing storm systems, very little snow has fallen on the mountain leaving the knife hard, ice glazed surface the dominant feature. Crampons are necessary to climb beyond low angle terrain due to this slick, hard surface. Stability tests and travel in Left Gully to the choke, about ¾ of the way up, last weekend 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 and no avalanche activity has been reported in these wind slabs. The rain and warm weather followed by cold temps has certainly replenished the ice climbs in Huntington and has created great neve for snow climbing in Tucks. Just remember the fast surface conditions don’t lend themselves to arresting a fall so travel carefully.

Microspikes and crampons are key tools for travel again today. Crampons are needed on the steeper slopes and above treeline. Conditions on the Sherburne Ski Trail remain icy with embedded rocks here and there.

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., Thursday, February 1, 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

2018-2-1