Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:00a.m., Monday, February 28th, 2011

Tuckerman and Huntington Ravines have HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely.  Travel in avalanche terrain is not recommended. The only exception to this rating is the Little Headwall in Tuckerman Ravine which has Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

We have a high degree of confidence that today’s conditions will result in numerous natural avalanches in both Ravines.  A winter storm is forecasted to dump 7-10″ (18 to 25.5 cm) of snow and sleet in the mountains before changing over to freezing rain this afternoon.  Winds are forecasted to be out of the S, shifting to the SW and increasing to 50 to 70 mph (80 to 113 kph) during the day.  Tonight, winds will continue shifting until finding a home out of the NW and increasing  to 70 to 90 mph (113 to 145 kph) with gusts forecasted over 100 mph (161 kph).  There are a number of blatant clues telling us that snow stability will be poor today.  The snow that is falling right now is landing on yesterday’s snow that totaled around 2-3″ (5 to 7.5 cm).  Yesterday’s snow was remarkably light with a density around 4%.   This will provide an ideal weak layer for the first round of avalanches today.  As much as I hate to accept it, warm air will be nudging its way into the mountains causing today’s snowfall to increase in density and ultimately transition to sleet.   This will continue the theme of an upside down snowpack with lighter snow becoming buried by increasingly heavier snow.  Wind loading aside, this is a red flag when it comes to snow stability and will be an issue on all aspects.  I suspect these details will be subtle in comparison to the dramatic effect wind loading will have on snow stability today.  The shifting and increasing winds will transport copious amounts of new snow onto all aspects of the ravines and create wind slabs of increasing density as the day wears on.  When you put all of these variables together it is hard to figure a way that avalanches won’t occur.  The fun doesn’t end there!  Freezing rain could create some intense glazing later this afternoon which will make you wish you were wearing a house rather than your fancy parka.  Depending on how much freezing rain accumulates, some of the snow could become encapsulated by a crusty layer.  The increasing winds should do a good job at ripping this to shreds overnight but we will have to wait and see how it all plays out.  It is worth noting that today’s avalanches could step down into older wind slabs that were deposited on Friday and Saturday resulting in some sizable slides.

The warm air that will move in today will be quickly booted out by very cold air once the winds shift to the NW.  Tomorrow’s summits forecast is calling for mostly sunny skies but winds will still be quite strong and temperatures will struggle to reach the single digits F.   Aside from a minor weather disturbance on Wednesday, it looks like the rest of the week will be quiet with plenty of cold air.

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.

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

Printable Advisory

Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:20a.m., Sunday, February 27th, 2011

Tuckerman Ravine has Considerable, Moderate and Low avalanche danger. The Chute, Center Bowl, Lip and Sluice have Considerable avalanche danger.   Natural avalanches are possible and human triggered avalanches are likely. Hillman’s Highway, the Lower Snowfields, Left Gully, Right Gully and Lobster Claw have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  The Little Headwall has Low avalanche danger.  Natural and human triggered avalanches are unlikely.

Huntington Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

There are two primary stability issues to focus on today.  The first pertains to wind slabs that are left over from Friday’s snow storm that caused several natural avalanches in both Tuckerman and Huntington Ravines.  The second is new snow that will continue falling into the afternoon and the potential for this new snow to form soft slabs that could push a number of areas to the upper end of their forecasted ratings.  Starting with the first concern I mentioned, Friday’s storm brought between 6 and 8.5″ (15 and 21 cm) of snow to the mountains and it was accompanied by winds that shifted counter-clockwise from the SE to the W.  Wind transported snow created unstable wind slabs and natural avalanches occurred in many of our forecast areas.  Ongoing wind loading from west winds continued into yesterday leaving wind slabs behind of varying density and size.  These wind slabs fall within the Moderate rating and it is possible you could cause one to fracture and fail resulting in an avalanche.  These can be found in just about every forecast area with the Center Bowl, Lip and Sluice being the most unnerving representatives of this stability issue.  Some areas, particularly in Huntington, have more spatial variability so good route finding skills can provide you some reasonable alternatives to climbing on this suspect snow.  That being said, limited visibility will make it difficult to pick out a good line.

The second stability issue will be developing as the day progresses.  The formation of touchy soft slabs is possible today as winds from the SW shifting to the W between 10 and 25 mph (16 and 40 kph) gently transport new light density snow into the start zones and other lee areas of the ravines.  These new slabs could be pretty reactive to people making them easy to trigger and cause an avalanche. We are expecting up to 2″ (5 cm) of new snow today which makes us comfortable with many areas being posted at Moderate.  If we exceed the forecasted snow totals some areas posted at Moderate may push into the Considerable rating due to the potential for these new slabs to avalanche on their own. This is a key piece of bulls-eye information you will need to monitor if you plan on being in avalanche terrain today.  Either way, expect to find a variety of snow out there that is waiting for you to test the balance between strength and stress of the snowpack.  The ability to evaluate snow stability and employ safe travel techniques will be important for anyone traveling in avalanche terrain today.

A significant storm is lined up to provide  us with a messy Monday.  Accumulating snow is forecasted to give way to freezing rain and possibly rain tomorrow.  Expect this miserable weather to be complimented by elevated avalanche danger in both ravines.

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.

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