Expires at 12:00 midnight Monday 12/23/2013
All forecast areas of Tuckerman and Huntington Ravines have Low avalanche danger today. Natural and human triggered avalanches are unlikely except in isolated terrain features.
AVALANCHE PROBLEM: The lump of coal that Santa delivered us in advance of Christmas came in the form of a late December thaw event. The peak period of instability related to the warmth and rain is now behind us, leaving behind a snowpack that will be in the process of locking up in ice later today. While you wait patiently for temperatures to fall, you should be thinking about the chances for lingering wet slabs to release. The chances are unlikely that any unstable slabs still exist, but remember that unlikely does not mean that same as impossible. The consequences of a slip, trip, or fall in current conditions can be dire.
Outside of avalanche problems, there are other hazards you ought to be thinking about. The first is generally nasty hiking conditions, especially if you go off the beaten path. We highly recommend crampons for travel in steep icy terrain or other traction for travel on hiking trails. Another problem you may encounter is ice dam formation. As temperatures drop, drainage channels get plugged with ice, causing water pressure to build behind the ice. This can be annoying or it can be very dangerous, but you never know which until you release the pressure with your ice tool or crampon.
Finally, there is a chance for a small amount of snow late today. This may load into small pockets of unstable windslab late in the day. This problem will only form after the changeover from rain to snow, which isn’t forecast to happen until late afternoon.
WEATHER: The summit recorded over an inch of rain in the past 48 hours with the heaviest period of rain falling Saturday afternoon. The cold air damming that resulted regionally in widespread freezing rain played out in the mountains as warmer air aloft that allowed more of the precipitation to fall in liquid form. Fog and freezing fog will reduce visibility throughout the day with rain transitioning to snow as the low pressure currently in place is pushed out to sea. Liquid equivalents (QPF) of .25” are forecast which will fall as rain, freezing rain then snow as temperatures drop. Expect a wide range of weather conditions today.
SNOWPACK: Our snowpack took a beating from the rain. Summit measurements showed 12” on the ground 48 hours ago reduced to 1” by yesterday afternoon. Snow surface conditions will remain soft for the forecast period until lockup due to falling temperatures through the day and into tomorrow. It is unlikely that you’ll find cold dry snow anywhere except low in the deepest wind-loaded areas. Peak instabilities due to rain on snow have peaked and we are in a stabilizing trend as percolating water delivering heat into our thin, early season snowpack slows.
- 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 7:30 Monday 12-23-2013 A new advisory will be issued tomorrow
Jeff Lane/Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856