Avalanche Advisory for Tuesday, Jaunary 31, 2017

This advisory expires at midnight.

Huntington Ravine has 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.

Tuckerman Ravine has CONSIDERABLE, MODERATE, and LOW avalanche danger. Sluice and the Lip have Considerable danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, Right Gully, Center Bowl, Chute, Left Gully, Hillman’s Highway, and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Little Headwall has Low avalanche danger. Generally safe avalanche conditions exist with natural and human-triggered avalanches being unlikely.

AVALANCHE PROBLEM: Soft Wind Slab developed from four inches of light density snow and west winds just strong enough to transport this snow. With a shift in wind to the NW last night, be on the lookout for new slab that could be responsive to a human trigger. This can be seen in the Tuckerman with a fresh crown line under the ice to looker’s left of the Lip. Isolated pockets like this in the steep terrain such as Lip, Sluice, and Central as well as on rollovers and terrain features will be sensitive to human-triggers today and should be heeded wisely when making travel-decisions.

WEATHER: Sunday delivered around 3” of 5% density snow to the Cutler River Drainage. This fell on steady west winds of 30-45mph. Another inch fell yesterday with winds shifting to the WNW around dark and increasing slightly to the upper 40mph range during the early morning hours. Today, high pressure will allow for clear skies early and winds decreasing to 15-30mph and shifting to the SW. A fast-moving clipper system will bring clouds this afternoon and a possible 2-4” of snow overnight.

SNOWPACK: Steady winds near the century mark last Friday scoured our terrain to a melt-freeze crust. Just over an inch of snow on Saturday blew in and formed pencil to one-finger (P-1F) hard slabs in most areas. As this snow continued to blow in on lessening winds, four-finger to fist (4F-F) slab formed on top of this with a thin wind skim due to a short time-period of increased winds. The upper reaches of northern gullies in both ravines somewhat avoided this snow and have scoured areas that will provide safer travel options for today. Sunday brought 3” of 5% snow with another 0.9” arriving on Monday. Winds around 30mph transported this snow into much of our terrain and created soft slab of fist hardness (F). Between Sunday afternoon and Monday morning, South, Left, Hillman’s and Dodge’s naturally avalanched with soft slab. These appear to have released from the upper reaches of the gullies where the slope angle is the steepest. Winds shifted to the NW last night, hitting 50mph for a brief period before dropping to the current 20mph range. This slight shift and increase in wind may be enough to strengthen the surface slab to one that will sustain a fracture, as evidenced by the slab release in the Tuckerman Headwall. In steep terrain, the soft slab that has formed will be quite deep in places and could entrain a significant amount of snow as forecast zones are now connected. Careful terrain evaluation today will go a long way towards a safe day in the mountains.

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  8:10 a.m., Tuesday, January 31, 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

2017-01-31