Avalanche Advisory for Monday, December 31, 2012

Expires at 12:00 midnight, December 31th, 2012.

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

Huntington Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

The pundits today may all be focused on Washington, but personally I think what’s going on here on Mt. Washington is more interesting and newsworthy. It’s been a while since we’ve seen winds sustained at such a strong speed, staying from the NW at 90+mph (145kph) for well over 15 hours with gusts up to 117mph (188kph). The forecast is for wind speeds to stay quite strong through today and this will play a significant role in snow stability during this forecast period. In case you’ve been hibernating for the last two weeks, winter has come on strong here, bringing December’s summit snowfall total to almost 70″ (178cm). About 22″ (56cm) of this has fallen in the past 4 days. How the wind has been moving this snow across the terrain is the reason for the difference in ratings for the two ravines.

In Huntington, I strongly suspect that the winds last night were able to scour and wind-hammer all of the forecast areas. This generally leaves behind either old surfaces, such as the December 21st rain crust, or very hard and strong windslab. However there is an exception to this. In locations that were heavily sheltered from the winds, relatively softer slabs may have developed, and these may be unstable.  Be watchful for any areas where you see signs of wind loading, for example an increase in the depth of your boot penetration may clue you in to snow with less strength. Further, as winds diminish late in the day there is a chance that what snow is left to be blown may actually stick to the slopes and create isolated areas of unstable slab. The bottom line for Huntington is to stay aware of the potential for isolated areas of unstable snow amidst a generally stable snowpack.

In Tuckerman a slightly different story is playing out. This ravine is more protected from the winds and less prone to scouring than Huntington, so concerns exist about ongoing loading of snow onto steep slopes. After Thursday’s storm, areas such as Right Gully and the Lobster Claw had about as much snow them as they did at their peak last season. The headwall area, Left Gully, and  Hillman’s were still a little bony, but snowfields were growing and connecting to one another. Virtually all other areas also had growing bed surfaces. I suspect that many forecast areas had avalanche activity yesterday, so slide paths are growing as well. Add all this to the continuation of blowing snow landing in the ravine, and you need to be thinking about the potential for naturally triggered avalanches to take place.

Although we are only expecting a trace amount, it’s worth mentioning that snow is currently falling at Hermit Lake. If we get more than a dusting, expect avalanche danger to be increasing and potentially exceeding the rating, particularly for Huntington.

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 8:45 a.m. December 31, 2012. 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

12-31-2012 Print Friendly

Avalanche Advisory for Sunday, 12-30-2012

Expires at 12:00 midnight, December 30th, 2012.

All forecast areas of Tuckerman and Huntington Ravines have HIGH avalanche danger. Natural avalanches are likely; human triggered avalanches are very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended.

It appears as though 2012 will go out with a bang…or maybe more like the roar of a freight train passing by. Not only has there been above average snow over the last two weeks, but the weather conditions over the next 36 hours or so will be especially fierce. These are conditions that should make you seriously consider (or reconsider?) taking a trip above treeline. Winds today will be steadily on the rise, reaching sustained speeds over 100mph (162kph) before dark. During this time, temperatures will continue to fall to below zero F (-18C). In the evening the trend continues, with even stronger winds and colder temperatures.

As you can probably imagine by now, spending time up high on Mt. Washington today has the potential to be a very challenging experience. So while there may not be a lot of people moving around up there, snow certainly will be on the move today. As far as avalanches go, what will happen today seems pretty clear. It’s an almost perfect setup situation for numerous avalanches in many areas.

Last night about 6″ (15cm) of light density snow fell during a period with summit winds generally less than 30mph (48kph). This new snow blanketed any existing snowfields and lower angle ice bulges, creating a nice layer of weak snow as the first step toward this avalanche cycle. Next, winds shifted to the NW and began to rise. As the newly fallen snow was in the 5-6% density range, it didn’t need much wind to start loading it onto the weaker layer. Continually increasing winds overnight and through today are going to keep layering heavier, denser slabs on top of softer, weaker layers. We expect this scenario to play out in most forecast areas today, so although the size of the avalanches are not expected to be very large, there is a strong likelihood that a single avalanche path may slide several times today. As if last night’s snow wasn’t enough, today’s winds will be strong enough to pick up any and all available snow from the windward side of the mountain and load it onto the eastern slopes as dangerous windslabs.

Today is a good day to stay out of avalanche terrain. This includes venturing very far up onto the floor of Tuckerman. Yesterday I saw avalanche debris in Odell Gully that had run almost to the flats of Huntington. Despite what I said about expected avalanches to not be very large, there is no reason to believe today’s avalanche activity will not run into low angle terrain at the base of slide paths.

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 8:15 a.m. December 30, 2012. 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