Avalanche Advisory for Saturday, February 6, 2016

Tuckerman and Huntington Ravine will 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 in Tuckerman Ravine and North, Damnation, Yale and the Escape Hatch in Huntington Ravine are not posted due to lack of snow cover. Exercise caution in these areas and expect the potential for isolated patches of instability in larger snowfields.

AVALANCHE PROBLEM: Wind Slabs will continue as the main avalanche problem today.  2” (5cm) of snow yesterday and high winds overnight, coupled with additional light snow this afternoon, continue some concern for new wind slab.  In strongly sheltered locations protected from the wind you will find slab problems being harbored while on exposed slopes you are likely to find many areas scoured clean.  Expect high spatial variability of the slab problem from none on some exposed slopes, to touchy pockets in the sheltered deposition of W and NW winds.

WEATHER: After tying the record high temperature for February 4th (36F) on the summit Thursday, the temperature plummeted to currently just above 0 degrees F.  Winds are from the west around 60mph (96kph) and are expected to remain there for the duration of daylight hours, increasing to 80mph (128kph) overnight.  Low pressure will approach today with the greatest chance of snowfall occurring in the afternoon and evening.  Snow totals likely will amount to little; however, the +/-2″ that fell on the summit yesterday and the trace to 2″ expected today combined with strong winds will create whiteout conditions and wind chills approaching -30F.

SNOWPACK: As discussed yesterday the rain event/thaw from 2 days ago, followed by the steep drop in temperatures to below 0F (-18C), has created a slick icy bed surface for new snow.  The new 2” (5cm) of snow late yesterday with high WNW winds, coupled with a trace to 2” today and more light snow overnight, has us focused on newly developed soft slab conditions.  Sustained winds last night between 70-80mph (112-128kph), gusting to an occasional 90+mph (144+kph), has transported light density snow into the Ravines. Crystals from the alpine zone were likely blown apart into smaller particles, packing into slab of varying density, over the initial softer storm snow in the Ravines.  This dense slab over lighter snow is a recipe for instability. Expect a number of slopes exposed to winds to be down to the old icy surface while slight depressions, slopes protected by terrain features, and benches below ice pitches and rock bands having areas of newly developed wind slab.  I would be suspect of any new slab based on a likely weak bond to the old icy surface.  The steeper the terrain the more likely it will be to trigger.  Expect conditions to be variable from hard old surfaces to soft pockets so don’t be lulled into assuming too much about your entire route based on what’s at your feet.  Also, be wary of others climbing above you that may trigger one of these unstable pockets.  Based on the thin boney nature of the mountain right now even a very small pocket that knocks you off your feet could be very bad with the pinball machine below.   Overall the Moderate forecast is issued due to the instability of the new thin slabs you will find in sheltered locations rather than a widespread deeper issue.  The main challenge will be to negotiate your risk exposure due to low visibility and other human triggers running about.

ADDITIONAL ISSUES:  

  • The Mount Washington Valley Ice Festival is this weekend.  Routes will likely have multiple parties; beware the hazards of climbing underneath others.
  • Climbers should expect the potential for some ice dams under hydraulic pressure due to the recent thaw and refreeze.
  • Old surfaces will be rock hard and will make for long sliding falls if you slip.  Despite being well into February, run outs are still quite rocky. Immediate self arrest is critical with your ice ax and experience.
  • The Lion Head Winter Route is recommended for those opting to avoid avalanche terrain. Expect thin, mixed conditions necessitating the use of crampons and an ice axe.
  • The John Sherburne Ski Trail is passable, but a challenge.  Bring your rock and ice skis.

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 7:50a.m. February 6, 2016. A new advisory will be issued tomorrow.

Helon Hoffer/Christopher Joosen, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2016-02-06