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