Avalanche Advisory of Thursday, January 28, 2016

All forecast areas of Tuckerman Ravine have LOW avalanche danger.  Natural and human triggered avalanches are unlikely.  Watch for unstable snow in isolated areas.  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 than Tuckerman, but understand instabilities in these smaller locations may exist.  It is critical that you assess snow and avalanche conditions if venturing into Huntington.

AVALANCHE PROBLEMWind slabs are today’s avalanche problem. Yesterday morning’s light snow added new thin slabs in some isolated areas on top of the older wind slabs that were built by high winds 8 days ago. Be wary of these wind slabs, particularly in steeper terrain. Additionally, the old hard wind slabs are not immune to human triggering just because of their apparent hardness. A thin spot in the firm slab and/or a larger expanse of the existing weak layer can allow these slabs to fail. Remember that cold temperatures have continued at our higher elevations with little heat penetrating the snowpack to bring about bombproof stability.

 WEATHER: This morning, there are clear skies, low wind speeds and temperatures in the single digits on the summit. Clouds will thicken and lower in the afternoon, bringing summit fog and increasing SW wind. A weak low pressure system will pass by us and redevelop offshore, send snow showers our way tonight, tomorrow and over the weekend. Although at this point forecast models are calling for only a couple of inches of snow on Friday and again on Saturday at higher elevations, you should anticipate more wind slabs developing as the high wind associated with this activity will move the snow into our avalanche start zones.

SNOWPACK: Firm slabs (P hardness) dominate our terrain. An underlying weak layer in the form of lower density (1F) wind transported snow exists beneath many areas. These weak layers are often far beneath the surface and may not be impacted by the weight of a person in most areas. However, this deeper layer should be on your radar when choosing your route through our terrain. In fact, several weak layers exist in the snow pack currently that create smooth shear planes for slabs to pop out on during stability tests. However, the firm surface slab, as it often does in our little microcosm of regular hurricane force winds, has exceptional bridging power and spans weaknesses in our snowpack allowing for safer travel in many areas of thicker slab. It is a wise traveler who keeps the remote possibility of triggering a hard slab in the part of their brain that makes route finding choices.

Huntington Ravine, while under a General Bulletin, may harbor some wind slab issues such as at the base of Central, Pinnacle and scattered through Odell and South gullies.  Good visuals show that the northern gullies have limited snow coverage so expect to find long stretches of low angle ice.  The Lion Head Winter Route is now open and is recommended for those opting to avoid avalanche terrain in the early season. Microspikes and ski poles are good supplemental tools, but are not substitutes for crampons and an ice axe on this route.  The John Sherburne Ski Trail is passable but becomes harder each day as water ice expands and snow is raked off. Expect challenging conditions.

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 28, 2016. A new advisory will be issued tomorrow.

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

2016-01-28