Avalanche Advisory for Wednesday 2-08-2012

Expires at midnight Wednesday, 2-08-2012

Tuckerman Ravine has both LOW and MODERATE avalanche danger. The Lobster Claw, Left Gully, and Hillman’s Highway have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features. All other forecast areas in Tuckerman have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

Huntington Ravine has MODERATE and LOW avalanche danger.  Central gully has Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.   All other forecast areas have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.  Expect these pockets to exist and avoid them by staying to more stable older surfaces. 

Last weekend I mentioned hitting a new benchmark soon as rock cliffs, islands of ice bulges, and brush anchors become buried leading to more frequent avalanche activity.  As these features disappear the bed surfaces become bigger which in turn struggle more to hold on to larger snowfields.  I’m impressed how far we’ve come, particularly in Tuckerman, since February began.  The summit has picked up snow everyday this month adding up to 9.2” (23cm) reinforcing the old discussion that Washington often gives snow to us slowly, but with dramatic results.  Of these 9.2” the summit recorded about 2 unexpected inches (5cm) yesterday showing the mountains are not 100% predictable all the time.  This loaded in through Tuesday and into early this morning on perfect NW and W loading winds from 40-65mph (65-105kph).  This gave much of Tuckerman a nice new blanket of snow most notably in the Lip and the right (north) side of the Center Bowl. Other adjacent areas like the Sluice and the upper Chute weren’t left out, but are a bit behind the previously mention locations. 

Because of our field time yesterday in the Sluice area, loading since then, and the visuals at dawn, I believe we are on the upper end of the Moderate rating bumping against the next rating level, Considerable.  Two main issues are driving this for me today. One being new cold slabs (0 to +5F) reactive to a human trigger being strongly possible; and two, warm solar gain building on some of these slopes that have a southern component due to clear sunny skies and low wind speeds this morning.  Of these the main concern is for human triggers moving through the Lip area and over to the Center Bowl.  However I have a slight lingering concern for enough heat to build in the Sluice and over towards the edge of the Lip area to feel natural potential may be on the cusp of moving from unlikely towards possible.  So,  I believe the best rating to reflect the situation today is Moderate, but understand we are at the ceiling of the rating particularly on the northern half (right) of Tuckerman.  In areas post at Low wind scouring and hard conditions prevail although a few isolated pockets do exist, like in the mid section of Hillman’s, below the “Y” and near the top of the Lobsterclaw.  In Huntington, the gullies didn’t hang on to much snow, but a few exceptions exist.  The bottom half of Central has the most new snow of any forecasted gully, hence the Moderate rating.  Other locations have varying degrees of scouring with a pocket or two here and there, but certainly nothing that isn’t covered in the Low definition.  Although the gullies were stripped of new snow it has been deposited in a number of protected approaches near the top of the “Fan”.  Areas under Yale, the Harvard Bulge, and across the Ravine under South gully are a few examples.  Clear conditions are expected today, tonight, and tomorrow with temperatures between 0 and 15 degrees.  Outside of protected southern aspects I would expect new slab instabilities not to settle much over the next 48 hours.  Another issue to keep in mind that Jeff discussed yesterday and which was supported by field work yesterday is the numerous layers including 5 different crusts from thaws and wet precipitation events.  New avalanche activity would quite plausibly step down to one of these crusts in the upper 6.5 feet (2m) due to the facet growth weaknesses around them.

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 8:55a.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

2012-02-08 Print Friendly