Avalanche Advisory for Wednesday, January 18, 2017

This advisory expires at midnight.

 

All forecast areas of Huntington and Tuckerman Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

AVALANCHE PROBLEM: The primary avalanche problem will be Dry Loose avalanches. Soft Wind Slab may also develop behind terrain features and near the tops of gullies. We received just 3.5” of snow overnight. This has fallen on top of the old firm bed surface. Remember that the new snow is only a few inches deep and underneath is a crampon-worthy surface. Though snowfall totals are fairly meager, don’t underestimate the hazards of being avalanched on the hard bed surface lurking beneath the new snow.  Crampons and an ice axe will be useful, maybe even mandatory for ascending steep terrain today. With more snow on the way today and tonight and with winds forecast to increase tonight, beware of larger and more widespread wind slab to form after dark.

WEATHER: Clear skies, low winds, and sunshine were enjoyed by many yesterday. Clouds moved in last night with snow beginning around 10pm. During snowfall, winds shifted between the south and southeast, maxing at 30mph. Snow continues this morning at a rate of just under an inch per hour (S2). Snow will lessen in intensity through the morning, bringing another 1-3” by dark. Winds will shift between the south and southwest, staying under 30mph. Tonight, we may see up to another 3” with winds starting to increase.

SNOWPACK: Our bed surface for the current snowpack is the melt-freeze crust that formed last week. This is a well textured surface that is not uniform. In the steepest terrain, primarily in Tuckerman, scattered wind slabs formed on top of this old surface on Sunday. On top of these layers lies the new snow that started falling last night and will continue through the morning. The density at Hermit Lake this morning was 8% and had accumulated 3.7” (9cm) by 6:30am. This was similar to field observations with fist (F) hardness in all places. Even with light winds by Mount Washington standards, soft wind slabs are forming as well as deeper drifts behind terrain features. These are the pockets that have the potential to entrain more snow and create probelms. Beware of deeper pockets of snow forming in the convex slopes below the steepest terrain and beneath ice climbs.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. Please be on the lookout for machine traffic on the Sherburne.

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 8:30a.m., Wednesday, January 18, 2017. A new advisory will be issued tomorrow.

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

2017-01-18