Avalanche Advisory for Sunday, March 15th, 2015

This advisory expires at Midnight.

Tuckerman Ravine will have Considerable and Moderate avalanche danger today. The Lobster Claw, Right Gully, The Sluice, Lip, Center Bowl, Chute and Left Gully will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanches conditions exist.  Careful snowpack evaluation and conservative decision making is essential. Hillman’s Highway and the Lower Snowfields have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger.

Huntington Ravine will have Considerable and Moderate avalanche danger today. North, Damnation, Yale, Central, Pinnacle, and Odell will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanches conditions exist.  Careful snowpack evaluation and conservative decision making is essential. South Gully and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wind Slabs are the primary concern today with Dry Loose following behind in very steep terrain.  This dry loose sluffing problem is likely to mix with spin drifting in locations like the Huntington gullies.  Wind Slabs currently exist from Thursday’s storm and new snow that started yesterday afternoon.  New wind slab will build today with up to another 4″ falling associated with a building and shifting wind.  Expect new cold snow to load into mostly E, SE, and later S facing slopes creating a wind slab problem that should peak in instability later this afternoon.

WEATHER: Precipitation started a bit later yesterday than expected, but eventually snow began in the afternoon mixed with a potpourri of frozen grains. This compacted to a heavy 1.5″ by midnight before transitioning to a more consistent snow crystal type that we like.  It’s been snowing since that occurred, giving about another inch by dawn.  This theme should continue today, delivering 2-4″ of additional snow during daylight hours.  I would expect crystal type to change, becoming lighter in density, as an upslope regime begins producing fluffier snow.  As the system moves out and creates this low pressure system wrap around moisture, the temperatures will fall into the singles F ( -16C).  Winds will increase to hurricane force, gusting to 80-85mph (128-136kph) with a shift from the NW to the N this afternoon.  This will increase instability and generate new wind slabs.  Expect poor visibility above treeline.

SNOWPACK: With the delayed precipitation start, only a very brief period of liquid drizzle, and light snow accumulation areas did not reach their Considerable ratings in Tuckerman, or Moderate in Huntington yesterday.  With what is lining up I believe that will change today.  Snow is likely to continue according the multiple forecasts and sources causing natural avalanche potential this afternoon.  Over the last hour winds have moved to the NW and are moving at a velocity between 35-40mph (56-64kph).  This is transporting some overnight snow, but is creating limited new slabs compared to what is likely this afternoon.  If the precipitation forecast plays out, you can anticipated more instability issues to develop this afternoon on SE and S facing slopes.  Examples include the exits in North, Damnation, Yale, most of Central, and the approach and exit of Pinnacle and Odell in Huntington.  In Tuckerman, the Lobsterclaw, Right Gully, Sluice, and Lip are good examples of slopes being loaded by a NW and N wind. This is all based on the weather forecast playing out giving us a storm total of 4-6″ (10-15cm) and NW>>N winds to hurricane force. In very steep locations you can expect sluffing to come off of water ice pitches in Huntington creating dense new slabs at their base.  Watch out for this hazard potential on the Ides of March. Conservative travel that a Considerable rating definition recommends is near impossible in steep narrow gullies and could leave you asking…..”Et tu Mount Washington”

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 7:45 a.m. March 15, 2015. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2015-03-15