Dec 212014
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate 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. Odell, South Gully, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: The wind slab leftover from Thursday’s loading event is the primary threat today. This includes deeper sluff piles that have the tendency to act as areas of deeper slab and can harbor instabilities while more shallow locations move slowly toward stabilization.

WEATHER: In addition to being National Look on the Bright Side Day, today is the winter solstice, the first day of winter, and the shortest day of the year. With light winds and seasonable winter temperatures, there will be little weather-related movement in our avalanche danger either toward stability or instability. Yesterday was warm and sunny so there was likely some stabilization taking place in the upper layers of the snowpack. However, the sluff piles and slabs that we have concerns about tend to be deeper than the extent to which solar gain and warm temperature would have had a strong stabilizing effect.

SNOWPACK: Despite this year’s winter getting off to a good start, we are still looking at a very early season snowpack. In the ravines this is marked by intense spatial variability, broken and discontinuous snowfields, and large expanses of exposed rocks that should make you think about your travel route and its potential consequences in the event of a slide or fall. In Thursday’s avalanche cycle, multiple avalanches occurred in a wide variety of locations. Some were well outside of the “normal” avalanche paths, e.g. in Huntington to the east of North Gully and a small snow slope high above Diagonal. This should raise your hackles about any small pocket that didn’t release.

Solar gain and warmth yesterday likely had stabilizing effect, especially on slopes with a southerly aspect. However, we are reluctant to lower the ratings in many locations due to the depth of instabilities, particularly in sluff piles, may have prevented the solar energy from truly eliminating the weaknesses. There is a good chance you could be traveling on snow that has good stability, only to very quickly move into deeper slab with worse stability. This is where your ability to read the terrain and evaluate the snow becomes critical.

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 8:00 a.m. December 21, 2014. A new advisory will be issued tomorrow.

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

2014-12-21

 Posted by at 8:02 am
Dec 202014
 

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

 Posted by at 8:26 am