Avalanche Advisory for Tuckerman and Huntington Ravines


 Posted: 8:30 a.m., Friday, February 8, 2008
 Tuckerman Ravine has LOW, CONSIDERABLE, AND HIGH avalanche danger
 today. The Little Headwall has Low avalanche danger. Natural
 avalanches are very unlikely and human triggered avalanches are
 unlikely except in isolated pockets. Normal caution in advised. The
 Lower Snowfields and Right Gully have Considerable avalanche danger.


 Natural avalanches are possible and human triggered avalanches are
 probable. Be increasingly cautious in avalanche terrain. All other
 forecast areas in Tuckerman have High avalanche danger. Natural and
 human triggered avalanches are likely. Travel in avalanche terrain is
 not recommended.


 Huntington Ravine has CONSIDERABLE and HIGH avalanche danger today.


 Yale, Damnation and North Gullies have Considerable avalanche danger.


 Natural avalanches are possible and human triggered avalanches are
 probable. Be increasingly cautious in avalanche terrain. All other
 forecast areas in Huntington have High avalanche danger. Natural and
 human triggered avalanches are likely. Travel in avalanche terrain is
 not recommended.


 After only a single week of February the Summit has recorded just
 about half of the month's average monthly snowfall. Although a bit
 early to place a wager, things are looking good in terms of finishing
 above average for the month with a solid winter weather pattern in
 place and a good-sized storm on the near horizon. In addition we'll
 get an extra day out of the month due to the leap year so let's hope
 it snows! Back to more pressing matters, the 2+ft (60+cm) of snow that
 has piled up in the last week is just starting to be bullied about by
 the wind. The average speed for the past 2 days was down somewhere
 around 18mph (29kph)! For the majority of the time a blanket of snow
 has sat undisturbed on the mountain but as the sun set yesterday
 afternoon things began to change. Since then the winds have increased
 to speeds high enough to have most of the Observatory's hourly
 observations include blowing snow. The forecast for the day calls for
 speeds up to 35mph (56kph) as winds wrap clockwise from their current
 origin in the south to their destination out of the west. This
 directional shift is opposite of what happened after dark last night
 and provides a valuable clue into the areas of most concern. N & NE
 aspects will be the greatest concern for natural activity through the
 first part of the day but E-facing slopes such as the Headwall in
 Tucks and Central Gully in Huntington will catch up later in the day.


 Areas with predominately S aspects are being given the Considerable
 rating today but cross-loading has the potential to lay down some soft
 and touchy windslabs in these areas as well.


 In terms of snowpack, we have a lot going on and anyone who's in an
 avalanche course this weekend will have some great stuff to look at.


 Many different layers currently exist in the snowpack including a
 number of weak layers and interfaces. Dense layers of graupel and
 rimed crystals are in there as are loose unconsolidated layers of
 fluff and of course a couple of crusts as well. Recent natural
 avalanche activity has been impressive, providing some big runners and
 associated clues about stability. Widespread sluffing was observed in
 both ravines during a period of visibility yesterday. Most of these
 loose snow slides were relatively small but a couple were still able
 to generate enough force to trigger slab avalanches. This makes me
 think that the windloading and 1-2" (2.5-5cm) of new snow expected for
 today should be enough to start another cycle of avalanche activity.


 Check out our weekend update tonight at www.avalanche-center.org for more
 information on how this cycle will roll into the next as the weekend
 storm arrives.


 Crampons, an ice axe and solid self arrest skills are recommended for
 travel in steep terrain. This includes the Lion Head Winter Route. The
 Sherburne Ski Trail is open with fantastic conditions.


 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, 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.


 Justin Preisendorfer, Snow Ranger
 USDA Forest Service
 White Mountain National Forest