Avalanche Advisory for Sunday, January 31, 2016

Tuckerman Ravine has 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 MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger.  Natural avalanches are unlikely and human-triggered avalanches are possible. Pinnacle, Odell and South have Low avalanche danger. Natural and human-triggered avalanches are unlikely. 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 around pitches of water ice.

AVALANCHE PROBLEM: Wind slabs are the avalanche problem today. Yesterday, the wind shifted to the southwest and west increasing in velocity, and in the process, built new wind slabs in sheltered areas of both Ravines. The underlying softer snow is the weak layer in these surface slabs, however the slab on top is not likely to be particularly touchy or widespread across the terrain. Another factor which helps push our Moderate rating down to the lower end of the definition, is our bedsurfaces which are generally still small.  Even the terrain in our strongest prevailing lee locations such as Odell and Pinnacle in Huntington and the Lip and Center Bowl in Tuckerman are lacking the snowcover needed to harbor large continuous slabs. Still, use caution when moving around in the Ravines today. Steep terrain features with patches of somewhat unstable snow and rocky runouts should still command respect.

WEATHER: Temperatures gradually warmed to the upper teens and 20’sF (-6.5C) in our Ravines yesterday and have continued to rise slowly overnight. WSW winds in the 50 to 60 mph (80-96kph) range late last night loaded some of our forecast areas with more of the available snow from the alpine as well as the 1.3” (3cm) of new snow. This filled ski and boot tracks in Left and Right Gully that were made mid-day yesterday. Expect W winds in the 35-45mph (56-72kph) range with some higher gusts today increasing to 55-65mph (88-104kph) after dark. The temperature will continue to rise to near the freezing point on the summit today. Today’s warming trend is unlikely to adversely affect snow stability.

SNOWPACK: Yesterday’s wind slabs were fairly soft (4F) and non-reactive to the human-triggers that were out and about. The lighter density snow beneath was not significantly lower in density and did not create much of a stability issue. The new loading that happened late yesterday and last night may have made a firmer slab atop all this so evaluate these layers for signs of stability before committing yourself to a larger expanse of snow. There are older wind slabs and deeper faceting beneath associated with the basal ice crust and another melt freeze crust above that is scattered around our terrain. In most areas it is deeply buried or bridging well between anchors. The upcoming warming trend may weaken and destabilize the overlying hard slabs but it remains to be seen how much the upcoming precipitation will load our slopes and how deeply the warming will penetrate. Keep these issues in the back of your mind as we move into the next few days.

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 passable but has become harder with expanding water ice each day. This issue can be added to many waterbars and occasional rocks. Very thin new snow will likely hide some of these demons. Expect very 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 8:45 a.m. January 31, 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

2016-01-31