Avalanche Advisory for February 1, 2016

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger.  Sluice, Lip, Center Bowl and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.  Right Gully, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions on specific terrain features exist. Evaluate snow and terrain carefully to identify features of concern.  Lobster Claw, Lower Snowfields, and the Little Headwall are not posted due to lack of snow cover.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Pinnacle, Odell and South have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible.  North, Damnation, Yale, and the Escape Hatch are not posted due to lack of snow cover. Exercise caution in these areas and expect the potential for isolated patches of instability particularly on pitches of water ice.

AVALANCHE PROBLEM: Runnels visible in the Chute, signs of roller balls in the Lip and widespread melt channels in the surface are clear signs of heat penetrating the snow. The past 12 hours of melting temperatures at Ravine elevations has created the potential for Wet Slab and Wet Loose avalanches. Of these two avalanche problems, Wet Slab avalanches are the most dangerous problem and could occur without a human trigger in Considerable rated areas. These slabs could be large enough to easily bury a person. It is possible that a larger wet loose or wet slab avalanche in the newer snow could step down into a larger slab in steep Considerable rated areas in Tuckerman and Central Gully in Huntington.

WEATHER: Today’s warming trend is the main concern for snow instability. Temperatures will continue to increase into the afternoon hours and produce meltwater that will continue to weaken the snowpack. On the summit, west winds in the 70 and 80 mph range will continue to rise this afternoon, gusting near 100 mph later this afternoon and evening. The summit is currently in the clouds but breaks in the cloud cover are providing direct sunshine in Tuckerman Ravine.  Temperatures will not begin to drop significantly enough to lock up our snowpack until around sundown. Conditions will be right for upslope snow showers later this afternoon as temperatures fall.

SNOWPACK: Areas of firm wind slab up to 30cm thick where failing yesterday in the moderate range (CT 14). Softer areas of wind slab were also a threat in a number of lee areas yesterday. These areas of softer slab will be the first to destabilize with the older, firmer wind slab (P hardness) weakening next. Currently, the upper 3-4cm of snow is wet in Tuckerman Ravine and this dampening should continue today given the weather forecast. Most recent wind slabs were fairly soft (4F) and as a result have weakened quickly. There are older wind slabs and deeper faceting associated with the basal ice crust and another melt freeze crust above that is scattered around our terrain. This melt freeze crust can serve as a failure plane as melt water lubricates the snow sitting on top. In most areas, the thicker old wind slab that is more deeply buried is bridging well between anchors. In some areas a thick layer of facets exists beneath this slab of snow but it is unlikely that today’s heat will penetrate that far into the snowpack to cause failure on that layer without a significant load such as an overrunning avalanche.

The Lion Head Winter Route is open and is recommended for those opting to avoid avalanche terrain in the early season. Microspikes and ski poles are helpful on lower elevation trails, but are not substitutes for crampons and an ice axe on this route. The John Sherburne Ski Trail is melting further today with many bare patches exposed.

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 8:35 a.m.February 1, 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