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

Avalanche Advisory for Saturday, March 1, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. The Sluice and Lip have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall is an exception to the ratings described above. It is at Low avalanche danger. Natural and human triggered avalanches are unlikely.

 Huntington Ravine has MODERATE and LOW avalanche danger. Yale, Central Gully, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. North and Damnation Gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. However, watch for unstable snow in isolated terrain features in these areas.

 AVALANCHE PROBLEM: Recently formed wind slabs are avalanche problem number one. These formed predominantly on lee aspects facing to the east, with cross loading on other aspects facing more to the S or to the N. Because of this distribution pattern, we have a wide range of avalanche danger that includes both Considerable and the upper end of the Moderate range in areas of Tuckerman. Some forecast areas of Huntington also sit in the upper end of Moderate, e.g. Central and Odell. Other locations fall more toward the lower end of the Moderate range, such as Yale Gully or the Lower Snowfields. There is potential for additional wind loading later, therefore the potential exists for increasing avalanche hazard today. Keep an eye on the ridgelines for signs of new loading. 

WEATHER: Currently, the weather is as good as it’s going to get today. While valley temperatures were sub-zero early this morning, we’re already seeing double digits above zero at the ravine elevations. Factor in the relatively light winds right now, the increasing winds as the day progresses, lowering clouds, and the possibility for some light snowfall late in the day, and you’ll see that travel conditions will be deteriorating steadily the longer you are out.

The recent weather that has created our avalanche problems was the 6.3” (16.5cm) of new light density snow that fell on the mountain over the course of a few days in the middle of this past week. Strong westerly winds have blown most of this snow into the ravines already, but we are seeing some airborne plumes of snow in a couple locations this morning, even with relatively light winds. 

SNOWPACK: Within the snowpack there is a very notable feature, the freezing rain crust from February 21. Until it was buried, this breakable crust had been making travel off the beaten path very painful on the shins. Now, we are dealing with some early faceting beneath the crust in what had been a layer of light density snow topped with ice pellets. Above the crust we are seeing a variety of soft wind slab layers that have formed over the past week. There was a recent wind slab avalanche in the Center Bowl on Wednesday night that ran on top of the crust. This is a great indicator of instability especially on similar slopes or in adjacent locations. Note that the Lip, Sluice, and Chute, all adjacent to the Center Bowl, and they did not avalanche but did grow in size during this period. These are all the areas I’d be most concerned with if I were looking to travel in Tuckerman. Other areas such as Left Gully and Hillman’s have sections that developed similar slabs, but not to the extent that the areas near the Lip did. In Huntington, the area of most concern is easily Central Gully, with portions of Odell and South Gullies in a dead heat for second place.

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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin.
  • Posted 8:35a.m. 03-01-2014. A new advisory will be issued tomorrow.

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

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