Avalanche Advisory for Monday, January 12, 2015

All forecast areas of Tuckerman and Huntington Ravines have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack evaluation, cautious route finding and conservative decision-making are essential.

AVALANCHE PROBLEM: 2-4″ (5-10cm) of new snow today on west winds will create new Wind Slabs in our terrain. The total amount of snowfall will determine the likelihood for these slabs to avalanche naturally and how problematic  they will be for people traveling in avalanche terrain. Areas in the strongest lee of W winds will see the greatest slab development and most potential danger. We are starting out with a Low rating but with isolated terrain features in many areas harboring unstable Persistent Slabs. These old wind slabs were easy to see and avoid yesterday in good visibility but limited visibility and a fresh blanket of snow today will make visual assessment and route-finding more challenging.

WEATHER: Today will be very wintry today with light snow falling throughout the day. The Observatory is forecasting 2-4” (5-10cm) for the higher summits, meanwhile valley locations are expected to get anywhere from 1-3” (7.5-12.5cm). In the mountains this will be accompanied by westerly winds around 50-70 mph (80-112 kph) with stronger gusts. The wind and snow will hamper visibility significantly above treeline, as well as transport snow to the lee areas of the mountain such as Tuckerman and Huntington ravines.

SNOWPACK: The relatively shallow nature of our snowpack is evident to anyone traveling into the ravines. In between the many rocks and water ice flows you’ll find hard gray snow exposed by the scouring action of the wind. Yesterday, touchy one finger wind slabs 10-30cm thick existed in a dimension worthy of respect in many areas. Firmer, pencil hard slabs beneath rested on a decomposing crust over the harder, old snow that was “reset” by rain around the Christmas holiday. I found the thin melt/freeze crust from January 4 remaining in a lee area beneath Chute with a facet layer of varying thickness. It is a weak layer worth keeping on your radar but doesn’t seem to be widespread since much of that crust has either decomposed entirely or been ripped up by the 90+mph winds this past week. Still, it is the deepest weak layer that a human trigger could reach and worthy of considering when in wind sheltered areas. Some slopes like Right Gully, Escape Hatch, and Lower Snowfields have very little snow and would make a difficult bushwhack.

The summer Lion Head Trail remains open and will remain so until we receive more snow. The Sherburne ski trail has improved with all waterbars now frozen and more filled in though not smoothed over. It is still a bumpy ski or ride though the accumulated snow over the past week is keeping it fairly soft.

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 8:00 a.m. January 12, 2015. 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

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