Avalanche Advisory for Sunday March 2, 2014

Expires at Midnight

Tuckerman Ravine will have CONSIDERABLE and MODERATE avalanche danger.  Right Gully, The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillmans Highway will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and careful route finding is essential.  Lobster Claw and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The only exception to this is the Little Headwall, which has Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and careful route finding is essential.   All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEMS: Problem number 1 is the new Wind Slab development we expect today.  This will layer over areas of unstable wind slab that has been the main problem over the past several days.  All of these wind slab layers are building over early facets under and above the frozen (ZR) crust from 9 days ago.  Old wind slab has started to go to early facets and is now what we would consider problem #2, a Persistent Slab.  The facet development is greatly influenced by how deep the crust layer is buried due to more wind loading in some locales and less in others.  A small Dry Loose sluff, as problem #3, or a new wind slab failure could step down into this persistent slab. In the case of a human triggered avalanche the initial failure would probably be in the upper wind slabs, but would possibly step down to facets as well.

WEATHER: Today new snow is expected to bring up to 2” (5cm) on a high W wind from 60 to 80+mph (96-128+kph).  Winds will drop in the afternoon along with the temperatures.  Over the past several hours the mercury drop has begun, expected to reach -10F ( C) today and -20F ( C) tonight.

SNOWPACK:    Over the past 7 days we keep getting small amounts of snow keeping a consistent fresh wind slab for us to consider.  You will find multiple wind slab layers of varying hardness due to vastly different daily snow densities and wind speeds.  This is all over the ZR crust layer developed on 2/21.  This layer varies in depth from the surface, therefore has been subject to different levels of temperature gradients.  This in turn influences the degree of facet development so keep this in mind as you travel.  Once again, frequent stability assessments will be important to give you a good sense how the snowpack varies as you move.

The biggest factor for us to consider in relation to ratings is the amount of snow we receive today.  A trace to 2” is expected. Scant amounts you say? Yes it is true that this is not much, but if we get towards the 2” mark coupled with 60-80mph winds we will have new wind slabs that will create new instabilities.  This is particularly true beneath protected areas in the terrain below ice bulges, cliff bands, and buttresses.  The Considerable postings are in place primarily taking this in account. If new snow amounts remain on the lower side today, expect areas to struggle getting out of the upper end of Moderate.  Either way, depending on how precipitation places out, sticking with the “Considerable” mindset would be smart.  Consequently, careful snowpack evaluation, cautious rout finding and conservative decision making will be essential.  Expect the returning cold air moving in to increase the facet growth rate around the ice crust, depending on its proximity to the surface.

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 825a.m. March 2nd, 2014. 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

2014-03-02 PRINT