Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:20a.m., Tuesday, March 1, 2011

(Gulf of Slides is apparently closest to Tuckerman Ravine. Although Tuckerman and Huntington are
not far apart either and can still have differing advisories and danger levels.)

Tuckerman Ravine has CONSIDERABLE avalanche danger today.  Natural avalanches are possible and 
human-triggered avalanches are likely.  The only exception to this rating in Tuckerman Ravine is 
the Little Headwall which has Low avalanche danger.  In this area natural and human-triggered a
valanches are unlikely.

Huntington Ravine has MODERATE avalanche danger today.  Natural avalanches are unlikely and 
human-triggered avalanches are possible.

Good morning March.  We hope that you can give to us what February lacked.  We didn’t have a 
single day that we picked up more than 10?(25cm) of snow and our precipitation’s liquid equivalents 
for the month came in at about half of the historical average.  We hoped that February would end 
with a bang but yesterday’s storm didn’t pan out quite like we expected.  Then again how often do 
they?  I’m not hating, just stating the facts my friend.  As predicted yesterday we received snow 
and then mixed precipitation and then some more snow.  Where the forecasts seemed to diverge from 
what actually happened is in the snowfall accumulation department.  Most forecasts were calling 
for 8-10?(20-25cm) but the Observatory only recorded 1.9?(5cm) from midnight until midnight and 
then an additional 1.1?(3cm) from midnight to 6AM this morning.   At Hermit Lake we picked up 
4.1?(10.5cm) with an average density of 16% and at the Harvard Cabin we found 4?(10cm) of fresh 
snow with a slightly higher density. New snow was blown in on winds that wrapped from the S through 
the W and eventually to the NW.  This progression has allowed significant wind loading to take place 
on all aspects and if we could see more than a stone’s throw I’m sure we’d be looking at some good 
debris piles and fracture lines.  Wind speeds climbed during this clockwise progression and once 
they made it to the NW they started holding steady around 90mph(145kph) with gusts over 100mph 
(161kph).  These speeds often scour some of our slopes rather than load them with new windslab 
and we expect this phenomenon to have occurred to a degree in Huntington.  One factor that is 
present and limits scouring is the high density nature of the snow.  Much of what we received was 
perfect snowball snow with a high water content that packs together nice and tight.  During the 
early hours of the storm moderate winds deposited dense windslab that is resistant to wind erosion.  
For this reason I don’t believe scouring will be as widespread as it would have been with lighter 
and drier snow.  If you venture into avalanche terrain today you’ll likely find stability issues 
no matter where you travel but scoured areas of exposed old surface may provide a route to avoiding 
these issues.  Natural avalanches will continue to be a threat through the morning hours especially 
in the areas rated Considerable that have a SE aspect such as the Center Bowl, Lip and Sluice in 
Tuckerman.  As winds die down to 60mph (97kph) later today we’ll see loading diminish and the threat 
of natural activity will drop.  The potential for human-triggered slides will remain especially 
with forecasted temperatures that will only reach the single digits (F). 

The Sherburne Ski Trail picked up some good snow from this storm but a rain crust topped it off 
yesterday afternoon.  Although freezing rain and drizzle were reported all the way to the summit 
the crust that developed at mid elevations is definitely thinner than what you’ll find on the lower 
parts of the Sherburne.  Consider doing a couple laps on the upper section and then chopping up the 
lower section once you’ve got your game on.

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.
    * This advisory expires at midnight. A new advisory will be issued tomorrow.

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