Avalanche Advisory for Friday, December 30, 2016

Huntington Ravine and Tuckerman Ravine have HIGH avalanche danger. All forecast areas will have HIGH avalanche danger today. Natural avalanches are likely and human-triggered avalanches very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended.

AVALANCHE PROBLEM: Widespread and possibly large wind slab avalanches will almost certainly occur today in our forecast areas. Travel beneath steep open slopes and gullies will put you in the bullseye for being struck and buried by these avalanches. The existing icy bed surfaces and prior avalanche debris will allow these avalanches to slide well onto the floor of either ravine. It is likely that many slopes slid last night but there is plenty of snow remaining in the alpine fetch zone to continue building large and dangerous wind slabs through the day today. 2-4” more inches of snow this morning will only add to the avalanche problem.

WEATHER: Though a slightly more easterly storm track downgraded our snowpocalypse to a healthy snowstorm, we did receive 14” of new snow at Hermit Lake and Harvard Cabin snow study plots. Snow showers will continue today with 2-4” more snow this morning. Wind is currently from the west at around 80 mph with gusts to 110 mph and the air temperature is 9F. Wind will decrease slightly through the day to the 65-85 mph range before increasing again after dark. Expect the westerly wind direction to continue transporting snow into east facing terrain, and cross-loading other aspects, reducing visibility in the process.

SNOWPACK: If you are looking for clues to alert you to possible avalanche danger today, consider heavy snowfall in the past 18 hours, increasing wind speed and continued snow fall. Also consider the wind slabs on the Tuckerman Ravine trail. You’ll notice cracking underfoot as you posthole up any trail today as cracks propagate through the layers of wind slab. Lots of small, low consequence test slopes exist in the woods and along the trail to study. You will find medium hard to firm wind slabs built by strong winds over soft, weak layers of snow deposited on calm winds yesterday afternoon which are somewhat representative of conditions elsewhere in our avalanche terrain. Above treeline and in the Ravines, low visibility due to fog and blowing snow will challenge your navigational skills along with your ability to assess your position relative to avalanche runout zones. Though it is likely that we passed the peak period of natural avalanche activity last night, the high winds speeds that we are experiencing tend to continue loading our slopes and building more wind slabs. Later today and tonight, as winds again increase, anticipate scouring in some terrain, possibly down to the old icy crust in some areas, such as in the northern gullies of Huntington Ravine. Today is a good day to stick to below treeline ski terrain or go ice climbing at lower elevations outside of steep gullies.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic on the Tucks and Sherburne Trail today. You may have noticed a new messaging product that MWAC is using to communicate our avalanche safety message. While new for us, the NWS Avalanche Watch and Warning system has been in use at other centers for a while now. With this system, we hope to reach a wider audience of backcountry travelers and possibly forewarn those who aren’t aware of the risk of avalanches. The NWS products are meant to supplement not replace the avalanche advisory found here daily through the season.

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 7:45 a.m., Friday, December 30, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-30