Avalanche Advisory for Wednesday, March 1, 2017

This advisory expires at Midnight.

 

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features. The Little Headwall is no longer forecast this season as it is now an open river.

AVALANCHE PROBLEM: With the temperature warming and rain falling, Wet Slabs will be the main problem today. These will develop as the wind slab that formed Sunday is saturated with rain and melting snow. The largest pockets of this are just under the rollover in the Bowl in Tuckerman and can also be found in sheltered areas of terrain features in other locations. Wet slabs are very difficult to predict.  They can be triggered by the added weight of water to an existing slab; alternately, meltwater can lubricate a potential sliding surface within the slab or at the interface of the old surface. As rain continues to fall and increases in intensity, the possibility of triggering this layer will increase. However, the amount of rain forecast is light and will be spread out through the day, likely allowing the snow to absorb the water and remain in place. The rest of the snowpack spent much of last week above freezing and should handle the water today with no real problems.

WEATHER: Precipitation began last night and has delivered .06” of water to the Summit. Southwest winds of 40mph will shift to the W and increase to 65-80mph. All elevations are above freezing this morning with Hermit Lake already above 40F. The warm front setting up over the region may drive the Summit to the mid-40sF by the afternoon, possibly setting a new record high today. Rain will be light for most of the day with about 0.1” falling by dark and another 0.2” tonight.

SPRING HAZARDS: Warm temperatures are creating spring hazards sooner than usual. If recreating today, be on the lookout for the following:

  • The freeze/thaw over the past 48 hours will loosen rocks in exposed cliffs. This time of year is notorious for rock fall in steep terrain. The ice flows that formed over the winter are delaminating from the rock. Be aware of ice fall.
  • Ice dams – water flowing down Huntington gullies can build up pressure behind ice and burst naturally or more likely from the whack of an ice tool or crampon.
  • Glide cracks, moats and crevasses have opened and will increase in size with the melting taking place. The largest ones at the moment are under the cliff that separates the Sluice from the Lip, at the top of the early season ice climb called the Open Book, and on the approach to Central Gully near the climb called Cloudwalkers.
  • Undermined snow over stream channels can be a problem in gullies but more of a danger lower in the tributaries. The generally warm winter so far hasn’t allowed many streams to freeze so this undermining is emerging early this year. The Little Headwall is mostly open water, making exiting the Bowl on skis difficult.

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  8:10 a.m., Wednesday, March 1, 2017. A new advisory will be issued tomorrow.

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

2017-03-01