Avalanche Advisory for Monday, March 5, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, and Yale have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Watch for unstable pockets of snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Lobster Claw and Right Gully have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Watch for unstable pockets of snow on isolated terrain features. The Little Headwall is not rated due to a lack of snow.

 AVALANCHE PROBLEM: Wind slab is scattered through the terrain. This initially formed Friday into Saturday and likely developed further thanks to snow that fell overnight. Areas of largest wind slab development are expected in Moderate rated areas due to being lee of prevailing NE winds, though wind slab may still be navigable by staying on old surface.  While wind speed will be light by Mount Washington standards, the density of new snow (6% on the Summit and 7.7% at Hermit Lake) should still allow for wind transport and wind slab development in our terrain.

 WEATHER: After a clear start to yesterday, clouds moved in as snow showers began in the afternoon. As of this morning, 1.5” of snow fell on the Summit with 2” at Hermit Lake. Wind during the hours of snowfall began N with speeds under 20mph and shifted overnight to NE with a current speed between 30 and 40mph. Light freezing rain is falling at Pinkham and Hermit Lake, though not on the Summit. Approaching high pressure will end precipitation and may allow for periods of clearing today, though lingering lower elevation fog may persist. Temperatures should rise into the teens F and wind will remain from the NE between 30-45mph.

SNOWPACK: A stout melt/freeze crust is acting as the bed surface in all terrain. This crust is hard to penetrate even with a shovel and has also proven a difficult surface for new snow to adhere to. Easily identifiable pockets of wind slab were the result of Friday’s Nor’easter. Fog and new snow may make visually differentiating the wind slab from old surface more difficult today. While wind slab will be the avalanche problem and triggering a pocket may knock you off your feet, the inability to stop a fall due to the icy bed surface likely outweighs the risk of being buried in debris today. Crampons and an ice axe will be necessary tools to travel in avalanche terrain.

The Harvard Cabin will be open Monday night and reopen Thursday night. this week.

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., Monday, March 5, 2018. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2018-03-05