Avalanche Advisory for Friday, January 22, 2016

All forecast areas of Tuckerman Ravine have MODERATE avalanche danger.  Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain carefully. Lobster Claw, Lower Snowfields, and the Little Headwall are not posted due to lack of snow cover. Exercise caution in these areas.

Huntington Ravine is under a General Avalanche Bulletin. General Bulletins are issued when instabilities are isolated within forecast areas and are issued every three days or earlier if conditions warrant. Forecast areas in Huntington have less well-developed snowfields to produce avalanches, but understand instabilities in these smaller locations may exist.  It is critical that you assess snow and avalanche conditions if venturing into Huntington.

AVALANCHE PROBLEM: Wind slabs remain the primary avalanche problem. High winds over the past several days have forged hard slabs in most of our forecast areas. These slabs are strong and mostly resistant to human triggering but it may be possible to find the thin spot which could propagate a crack.  Where these slabs exist, especially in steeper terrain you could find a thin spot and perforate this slab, causing a section to fail. The possibility of triggering something is on the lower end of the rating but the consequences of triggering one of these thick and dense slabs is severe. Be on the lookout for hollow sounding areas in well sheltered locations.

WEATHER: Though winds will abate through the day, lingering moisture to the west will flow up and over the mountain creating fog at ground level during the morning hours. This fog will diminish as downsloping wind dries out. Temperatures are starting out in the -10F (-23C) range but will rise into the single digits above zero later on. Winds from the NW at 50-70mph (80-112kph) will diminish to the 35-50mph (55-80 kph) range. All in all a remarkably average January winter day is on tap.

SNOWPACK: Since our prolonged period of high winds began on Tuesday, we have received no significant snowfall. During this period, the summit recorded peak gusts of 127mph on Tuesday, 97mph on Wednesday, 112mph yesterday. In short, our snow pack in the Ravines, as well as the Sherburne Ski Trail, is wind hammered. The rain crust and water saturated refrozen snow and ice from a couple of weeks ago is showing in many places on the Sherburne. We’ll continue to look for this layer which may exist at some depth in certain areas of Tuckerman. In sheltered areas the crust is likely deep below a travelers stress bulb. In shallower areas, it may serve as a weak layer, but this remains a hypothetical. Other weak layers, in the form of varying slab densities, from mid-storm wind velocity changes would also be worth looking out for. Huntington Ravine may harbor some wind slabs at the base of Central, Pinnacle and scattered through Odell and South gullies but good visuals this morning show that the northern gullies have limited snow coverage so expect to find long stretches of low angle ice.

Barring some unforeseen circumstances, we will change over use from the Lion Head summer trail to the winter route starting tomorrow morning due to the growing bed surface for avalanches on the summer trail.

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 8:30 a.m. January 22, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856