Avalanche Advisory for Wednesday, March 11, 2015
Expires tonight at 12:00 midnight
Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and the Chute
have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Evaluate snow and terrain carefully and identify features of concern. All other forecast areas have Low avalanche
danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. These pockets of
instability exist.
Huntington Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely except in
isolated terrain features. These pockets of instability exist.
AVALANCHE PROBLEM: Wind slabs are the primary concern today. These vary in size, thickness, and
overall level of the threat. Yesterday’s intense heating and clear skies did cook new slabs with a S facing component.
However as you wrap from E to N facing slopes slabs retained their cold snow nature compared to S aspects. The
main concerns are once again from the Sluice to the Chute in Tuckerman. A trace to 2” expected today may
create some pockets of new wind slab that should bond poorly to crusts that developed from yesterday’s solar
gain.
WEATHER: A cold front moving into the area will drop temperatures through the day, hitting the teens F above
treeline. This will be associated with snow showers potentially accumulating up to 2” (5cm). High winds will
return, expected to crawl to 100mph (160kph) during the overnight. The mercury will drop below 0F (-18C) tonight
and approach -10F (-23C) before rebounding slightly tomorrow.
SNOWPACK: Yesterday, glorious blue skies dominated in the mountains. Copious sun effect could be seen on
smiling faces. This sun effected snow as well. Roller balls on sheltered S facing slopes and a moist upper snowpack
were the result. By midday, 0C snow could be found between10-15cm down from the surface depending on exact
density and the facing aspect. This general theme played out on S facing slopes resulting in a crust once
temperatures cooled off. On N aspects you should find slight evidence of a warm day as air temperature soared to
6C at Hermit Lake, however heat penetration was much more limited than on S slopes. Overnight areas with warm
moist snow refroze, gaining some strength back after going through a period of instability yesterday. Icy surfaces
are now poised to create a slick bed surface for future new snow, particularly if it comes in cold. Current fog,
clouds, dropping temperatures, and high winds with continue to pull heat out of the upper snowpack day. Some new
snow is expected this afternoon, and although scant at a trace to 2” (5cm), watch for some pockets of snow to
develop. In areas already posted Moderate this should have minimal effect on your travel mitigation and strategies
as you are already planning for instability. However in areas posted at Low there may be some additional pockets to
contend with as you transition back and forth between stable and potentially unstable snow. This will exacerbate the
situation of existing pockets that are already pepper the Ravines such as in upper Hillmans, below the ice in Central,
high in Pinnacle, the middle of Odell, and the top of the Escape Hatch.
The next couple days will feel much more like winter compared to yesterday. This is all in prelude to perhaps a
snowy weekend. We’ll say more about this weather maker tomorrow.
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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 8:30 a.m. Wednesday, March 11, 2015. 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