Avalanche Advisory for Wednesday January 29, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Huntington Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features.

AVALANCHE PROBLEMS: Wind Slab and Persistent Slab are the two avalanche problems you will face today. Wind slab has formed in response to 9” (23cm) of snow between Saturday and Monday with a generally W wind direction. A number of locations have existing stability issues due to facet induced persistent slabs that has been developing over the last couple of weeks. Persistent slabs under new wind slab have a more complicated and spatially variable distribution of avalanche hazard. Evaluate your snow and terrain carefully.

WEATHER:  Yesterday dawned very cold with drifting and blowing snow with high winds.  As Tuesday afternoon came about, winds subsided to moderate speeds and a high pressure clearing trend began.  Temperatures began this morning at -10F for the higher summits and will slowly warm over the next 36 hours to about +10F late on Thursday.  Winds will build today gusting over 70mph towards darkness.  A slight weather disturbance will produce a brief period of clouds late today with a chance of some light snow before clearing again overnight and Thursday.

SNOWPACK: As Jeff discussed yesterday, crown lines from avalanches on Sunday and Monday are visible in Tuckerman Ravine highlighting signs of instability.  Yes, the level of instability has declined from the peak new snow loading periods that produced these natural avalanches.  However, we continue to be concerned about both weaknesses within the new windslab, and the more ominous and elusive weak facets, producing our persistent slab problems.   Our colleagues at western avalanche centers are challenged to keep backcountry users attention after days or weeks of persistent slab problems.  The persistent problem we have right now is atypical of an eastern snowpack so expect to find different conditions than what you are used to seeing. Therefore, we ask you to keep this facet problem on the forefront of your mind if venturing into avalanche terrain.  Anticipate finding the spectrum within the Moderate rating.  Some locations like the northern gullies (North, Damnation, and Yale) in Huntington, and the Sluice in Tuckerman, are close to Low. While some places with a more E facing aspect are in the middle to upper end of Moderate, due to a combination of wind slabs and persistent slabs.

As time progresses this persistent issue is becoming more widely dynamic.  If you were able to map these facets accurately you would see them become more ‘spatially variable’.  Some areas of facets have been wiped out by avalanches and some scoured out by wind. Others locales have intact 2-3mm weak faceted crystals under thin pencil hard slabs while other places they are barely approaching 1mm in size.  These preserved locations with 1-3mm facets are our main concern. Yet they are nearly impossible to identify and avoid from a distance as sweet spots for triggering because of their random and widespread existence.  Field time yesterday had stability tests that were dramatically different producing results as unstable as ECTPV (fracture propagates upon isolation with no load/taps).  It will very important to remember that tests are telling you what’s going on under your feet, but may not only meters away.  I would also be very concerned being under other users that are traveling above you.  Over the next 2-3 days we are expecting fairly cold and clear nights contributing to continued facet development.

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 830am 1-29-2014 A new advisory will be issued tomorrow.

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

2014-01-29 Print