Avalanche Advisory for Thursday 2-2-2012

 

Expires 12:00 midnight

Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted.

As anticipated Wednesday turned out to be pretty sloppy, but in true New England style things have changed once again.  After a full morning of rain in avalanche terrain temperatures nosed back down and fell overnight changing precipitation back over to snow.  A few glimmers through the fog this morning gave us some signs of avalanche activity due to yesterday’s rain.  Dodges ran full path to Hillman’s Highway, which also avalanched to the dog leg. Clouds have kept us from seeing much more this morning, but this evidence indicates it’s quite likely other activity has occurred.  Before losing a view yesterday we saw widespread wet point release sluffing in both ravines. Free water from melt and rain has been going through the refreezing process currently making instabilities below Wednesday’s surface moot.  The summit temperature this morning of 11F and Hermit Lake’s 19F is quickly changing sub-surface liquid to a solid state.  There is some evidence these wet rounds are already faceting under the multilayered crust. This change is on going, but the new snow issues from last night and early this morning are what we need to focus on today as the bulls-eye issue.

The summit never fell below freezing but got awful close at 30F (-1C), and subsequently did not get rain. However their 3” of new “snow”, with a water content of 0.63”, appears to have seen a period of mixed precipitation.  This new snow up high was delivered to the Ravines on an increasing W wind peaking at 86mph (138kph) during the overnight.   A thin blanket of snow and small drifts can be found on the trail from Pinkham to Hermit Lake, where about an inch was recorded.  Some new cross-loaded small cornices can be seen high near the climber’s left ridge of the Sluice and the Lobster Claw due to high W winds overnight.  This gives us some good clues about strong lee areas and the probability of new snow deposition.  A quick view of the Sluice before fog returned also showed evidence of new snow through out, in the early morning light.  Expect newly formed cold slabs to be found predominately in E facing slopes and some cross loading of others.  Some of these eastern aspects may be near the upper end of the “Moderate” rating definition.

Upslope snow showers are expected to give us about 1” (2.5cm) today associated with a wind shifting from the W to the NW and decreasing from 35-50 mph (56-80kph) to 20-35 (32-56kph).  I would expect a skilled traveler to find options to avoid new slabs and staying to old surfaces.  I will say that there is a good chance that post-holing through crust will be a real issue in numerous locations making travel rather heinous.  Cold air tonight with some clear periods will likely increase the faceting pace, increasing this problem.  Be particularly cautious while moving downhill as this issue has been the culprit of more than one broken leg on Washington.  Climbers should also be prepared for ice dams, or water under pressure, beneath the ice from yesterday’s rain and overnight freeze up.  An ice tool or crampon placement can release this with explosive results.  Bulges and rollovers are more likely to harbor these hazards than depressions.

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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 8:00a.m. 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