Avalanche Advisory for Sunday, February 19, 2017

This advisory expires at Midnight.

Huntington Ravine has LOW avalanche danger today. All forecast areas in Huntington Ravine have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger today.  Lobster Claw, Right Gully, Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain carefully. Left Gully, Hillman’s Highway, Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Today, the avalanche problem will differ depending on the slope aspect. The likeliest hazard today will be Wet Loose avalanches. These will remain a threat until the snowpack refreezes tonight. Slopes of most concern for wet loose will be S and SE facing slopes such as Lobster Claw, Right Gully, and Sluice. Other slopes may have the potential for wet loose depending on how long temperatures remain warm. Wet Slabs may come into play today if the warm temperatures penetrate deep enough into the snowpack or if thinner slabs are encountered. Again, this is most likely on S facing slopes. Areas that remained in the shade yesterday and have more recently started to warm still harbor characteristics of Wind Slab. While less likely that these would be triggered by a human than a wet loose slide, the size and destructiveness of a wind slab avalanche today would be far greater.

WEATHER: Temperatures on the Summit have stayed over 20F for 24 hours and hitting the freezing mark yesterday for a few hours in the afternoon. Currently, it is 24F on top and 35F at Hermit Lake. Today, the temperature should approach 30F on the Summit and remain there until mid-afternoon. Winds will decrease slightly from the current W 75mph to the 60mph range and shift to the NW. Summit fog will likely remain for the day with periods of clearing in the Ravines possible. A chance of snow (trace to 2”) exists today and tonight.

SNOWPACK: Strong winds Friday and Saturday transported much of the snow that fell over the past week. Evidence of this wind can be seen as scoured areas like the north wall of Huntington, smoother wind loaded slopes like the Lip and Center Bowl area of Tuckerman, as well as large sastrugi formations in Odell, South, and Left Gully. Temperatures around the freezing mark yesterday along with periods of sunshine allowed the sunnier (south facing) slopes on both ravines to warm. This warmth seemed to be limited to the top 10cm of the snowpack and was not creating any issues yesterday. Areas that saw no or very little sun remained cold. Overnight temperatures dropped very little, leaving us this morning with the same 10cm of wet snow. Today, temperatures will increase slightly, allowing this warmth to continue penetrating into the snowpack. With forecast cloudy skies, this likely will not get very deep, keeping the main hazard for skiers and climbers to wet loose avalanches. If the clouds break for a period and the snow receives rapid solar gain combined with the warm temperatures, the potential for wet slabs will increase. As the uppermost wind slab is quite thick in places, this is unlikely; however if the skies clear, this may rapidly change.

With a busy weekend in progress, be prepared for crowds. Having an alternate travel plan in mind will make today safer.

 

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., Sunday, February 19, 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

2017-02-19