Avalanche Advisory for Saturday, December 20, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully to identify heightened avalanche conditions and features of concern. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale, Central and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully to identify heightened avalanche conditions and features of concern. Odell, South and the Escape Hatch have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slab is our primary avalanche concern today. Thursday’s snow and loading winds that created new slabs continue to be our #1 issue.  A number of these slabs naturally avalanched on Thursday and partially reloaded that evening. The reloaded areas and slabs that did not avalanche are now about 30-36 hours old and we have not received new appreciable loading since winds died off late Thursday night. These slabs vary tremendously in depth, weakness, and size. Expect a constant changing condition and stability of the snowpack.

WEATHER: Yesterday’s low winds and moderately cool temperatures will continue this weekend becoming even more comfortable over the next 48hours.  Clear skies today may see a bit of clouds according to forecasts, but the low wind speeds falling to 10mph (16kph) and temperatures between 25-27F (-4 to -3C) degrees will make it quite pleasant to be sporting in the mountains. On Sunday it won’t be quite as nice with a slight chance of snow showers, a bit cooler, and winds up to 35mph, but clearly still a reasonable winter day.  This weekend’s weather should not add new avalanche concerns to our present conditions.
SNOWPACK: Frank and I got into Tuckerman yesterday and battled with a shifting cloud deck that pulled the veil back and forth over the terrain.  This gave us some visibility and then took back away.  We were able to see natural avalanche activity results out of the Lip, several locales in the Center Bowl, the Chute and Left Gully.  Some of these areas have reloaded by sluffing from steep terrain above and wind transported snow.  Other areas that were exposed to high NW winds, gusting regularly to 85mph (136kph) and peaking at 98mph (157kph) on Thursday, have been eroded sending crystals down into the trees. You will find an intense amount of variability as you move across the terrain. Expect to find a vast variety of snow stability so it will be important to choose assessment techniques that you can do quickly so you can perform them often.  Do not be happy with just one stability test, the variability in slabs dictates doing assessments frequently. In Tuckerman, we decided there was certainly enough concern to rate some areas at Moderate. With that said, an experienced user with avalanche knowledge should be able to pick out a route that links stable areas and islands of water ice and rock due to clear visual clues and clear sky conditions.  This is true if you are flexible with your route choices as some areas in the Ravine have less concerns to mitigate than others.  Pockets of slab near the Lip, under the Headwall ice, and above the fracture in the Chute are a few example of places to avoid.  In Huntington, this can be more difficult because your route choices become more limited in narrow gullies.  Again, the visibility today should allow you to spend some time picking out clues that will help your route decisions.  Certainly be prepared with rock and ice gear and lace up areas if you find yourself in unstable snow that you didn’t avoid through your pre-planning.  If you look closely you will see avalanche debris in many places and we believe most of the Huntington gullies sluffed or slab avalanched during this last cycle. As mentioned yesterday, be cautious of the bluebird day mentality. Beautiful days often find us enjoying our experience so much we avoid looking for hazards.  This leads us to fall into heuristic traps and drawing us in deeper into risk than we would if we were focused.

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 8:19 a.m. December 20, 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

2014-12-20