Avalanche Advisory for Tuckerman and Huntington Ravines


 Posted: 8:47 a.m., Thursday, December 6, 2007


 Tuckerman Ravine has CONSIDERABLE, MODERATE and LOW avalanche danger
 today. The Lip has Considerable avalanche danger. Natural avalanches
 are possible and human triggered avalanches are probable. Be
 increasingly cautious in steeper terrain. The Bowl, Headwall, and Left
 Gully have Moderate avalanche danger. Natural avalanches are unlikely
 and human triggered avalanches are possible. Use caution in steeper
 terrain. Right Gully and Hillman's Highway has Low avalanche danger.


 Natural avalanches are very unlikely and human triggered avalanches
 are unlikely except in isolated pockets. Normal caution is advised.


 The Lower Snowfields and the Little Headwall have little to no snow in
 them so they will remain "Not Posted". Forecasts for these locations
 will begin when needed.


 Huntington Ravine has MODERATE and LOW avalanche danger today. All
 gullies except the Escape Hatch have Moderate avalanche danger.


 Natural avalanches are unlikely and human triggered avalanches are
 possible. Use caution in steeper terrain. The Escape Hatch has Low
 avalanche danger. Natural avalanches are very unlikely and human
 triggered avalanches are unlikely except in isolated pockets. Normal
 caution is advised.


 Winds have finally picked up to start moving snow sitting above
 treeline from our recent storm down into the Ravines. Winds ramped up
 rapidly this morning gusting 60-70mph (100-112kph) from the NW. We
 expect winds from the NW to continue from 45-65mph (72-105kph) this
 morning before shifting to the W and diminishing a bit later in the
 day. The new loading has created a rising snow instability in most
 areas. Although the Lip in Tuckerman is the only location that we have
 bumped up a rating most all other locations are at the upper end of
 their rating. Pay particular attention to SE and E facing slopes that
 are in the direct lee of the current NW winds and the forecasted
 westerlies later. Some of these locations such as the strong lee
 across the Headwall and high in the Bowl will be pushing their rating
 and coming close to "Considerable" in some isolated areas. A major
 factor to keep on the forefront of decision making today is the
 formation of new denser slabs on top of the "touchy" low density snow
 we discussed yesterday. Right Gully, Hillman's Highway, and the Escape
 Hatch have only isolated pockets that can be easily avoided if for
 some reason you feel like an awful bushwhack in thick vegetated
 gullies with limited enjoyment potential. For this reason they remain
 posted a Low.


 As we often say in the early season "...if these conditions existed
 mid-season we would be up a rating..". The reason we're not continues
 to be the patchy nature of snowfields interrupted by anchors and major
 topographical features. This makes the areas of instability much
 smaller and more isolated from their neighbors. This allows the
 strength of interlayer bonds parallel to a potential bed surface and
 the tensile strength within the existing snowpack to hold smaller
 areas in place against the pull of gravity. If you compare these same
 snow bond strengths in a patch ten or twenty times bigger later in the
 season when the terrain is filled in with more snow you'll see major
 differences. Obviously similar bonds would struggle to keep this
 larger snowfield in place leading to failure and fracture. Saying this
 however instabilities exist so it's very important to keep the idea of
 spatial variability (a change in conditions) in your mind while
 traveling because you are apt to find very different snow stability
 moving from pocket to pocket. Remember that it isn't the size of the
 avalanche that counts, it's the consequences.


 By now you should have refreshed your avalanche skills and your beacon
 should have fresh high quality alkaline batteries powering it. Your
 annual early season review of safe travel rules, techniques for
 assessing snow stability, and signing up for an avalanche course
 should all be behind you. We now have all the avalanche courses
 offered in the valley this winter on our website, www.avalanche-center.org.


 Remember, maintaining avalanche skill takes practice and effort. Your
 life depends on it!


 Please Remember:
 o It is impossible to accurately predict natural events, such as
 avalanches, in every instance. This Advisory is one tool to help you
 make your own decisions in avalanche terrain. It should be used along
 with safe travel techniques, snow stability assessments, an
 understanding of weather's effect on the snowpack, and proficiency in
 avalanche rescue.


 o You should obtain the latest weather forecast before heading into
 the mountains. Anticipate a changing avalanche danger when actual
 weather differs from the National Weather Service forecast.


 o For more information, contact the U.S. Forest Service Snow
 Rangers or the AMC at Pinkham Notch Visitor Center or Hermit Lake
 Shelters or the HMC caretaker at the Harvard Cabin. This advisory will
 expire at midnight.


 Christopher Joosen, Snow Ranger
 USDA Forest Service
 White Mountain National Forest