Avalanche Advisory Monday 2-18-2013

This advisory expires at 12:00 midnight, February 18, 2013

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

All forecast areas of Huntington Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely except on isolated terrain features.

Hopefully if you’re reading this advisory today, it’s from the warmth and comfort of an indoor facility. Current conditions on the mountain are exceptionally brutal. Due to clouds and blowing snow, visibility is near zero.  Temperatures are just above zero F at Hermit Lake. Some trees are swaying back and forth like hippies at a Grateful Dead show, while other trees look more like headbangers at a Metallica concert. Don’t be fooled by the diminishing winds and clearing skies forecasted for today; the wind will only decrease 80-100mph (130-160kph) and you should expect airborne snow to be acting as a sandblaster until well after dark today.

Yesterday, the summit recorded 3.6″ (9cm) of snow with increasing wind speeds reaching a crescendo this morning. They’re currently 115mph (185kph) with gusts pushing close to 130mph (210kph). What is this doing for snow stability? The easier ravine to forecast is Huntington. Sustained winds overnight have likely scoured out and wind-hammered the gullies into stable hard slab and old exposed crust. There may be small and isolated pockets of unstable snow in the most well-protected locations, so as always, be vigilant to changing conditions. We have yet to get a view of the ravines, so there is some uncertainty to the rating, but I am fairly confident that it would be difficult to find stability problems in Huntington.

Tuckerman is a little different story. It’s less prone to scouring than Huntington due to its being more protected from strong winds. There is currently wind transport of snow taking place in all locations of Tuckerman. The snow moving around is likely from yesterday morning’s snowfall as well as older snow being picked up from the other side of the mountain. The Considerable forecast for many areas is due to the potential for slabs building in lee areas, creating the possibility of naturally triggered avalanches in these areas. Any slab being formed today will be hard and dense, which are typically quite strong. However, if these hard slabs do fracture and fail, the destruction left in their wake can be impressive. Overall I suspect that many of the areas are being hammered by the wind so strongly that they will be strong enough to not avalanche, but until we can confirm this, the safe bet is to go with the reliable data rather than the assumption. In this case, I know for certain that snow will continue to be transported into Tuckerman at a good rate today. The areas posted at Considerable are the strongest contenders for unstable snow. In areas posted at Moderate, remember that “unlikely,” which is used in the definition for naturally triggered avalanches in Moderate hazard, is different from “not possible,” which is not part of any danger rating definition but is commonly how we see people act in avalanche terrain. The lesser rating reflects the overall hazard compared with other forecast areas, but Moderate avalanche hazard is still dangerous, particularly when active loading is taking place.

Winds have created some good drifts on the Tuckerman Trail. My hope is that they also filled in the Little Headwall. We may find out more later today. The Sherburne will have some icy scoured locations and a few deep drifts to play around on.

 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 8:35a.m., February 18, 2013. A new advisory will be issued tomorrow.

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

2013-02-18 Print Friendly