Avalanche Advisory for Sunday, February 23, 2014

This advisory expires at 12:00 midnight.

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

Huntington Ravine has Moderate and Low avalanche danger. Central and South have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEMS: Wind Slabs is the main avalanche problem today. The most likely avalanche today would be from new snow that fell at the end of the rain event which drifted into pockets. These slabs were easily reactive to human triggers on isolated steep slopes yesterday. The next problem would be the new snow that cascaded down steep ice and snow which has piled up above and below the rain crust.  Basically, loose dry sluffing that has created new slabs.  These have grown quite thick in the past week or so and are hard to trigger, but would be dangerous if they did slide.  Central Gully, Center Bowl and Sluice leap to mind as examples of these sluff piles. Deeper wind slabs are also scattered around and are still a concern in some areas. Areas rated Low share most of these concerns though to a lesser extent so safe travel techniques, careful route finding and avalanche safety gear continue to be recommended.

WEATHER: Mild temperatures and relatively moderate winds today are a welcome break from the conditions that have dominated the past few weeks. Clouds may obscure visibility at times today with a possible snow shower to improve the mountain ambiance. No weather conditions are forecast today that will affect our avalanche situation other than flat light due to the overcast and potentially reduced visibility if the cloud cap descends into our terrain. Spotting the areas of new wind slab on the ice crust is much easier in the sun and shadow than in flat light or fog.

SNOWPACK: It is remarkable what little effect the rain and freezing rain had deep within our snow pack. The ice crust formed on sleet and ice pellets which fell on 8 or more inches of the sweet fluff that skiers dream about. That powder stills exists but is guarded by a thick breakable crust. Yesterday in Huntington, I observed several lunch tray sized chunks of the ice crust blowing through the sky over South Gully. This was the first indicator to me that our new slab issues were probably being fed by more than the recorded 1.5″ of snowfall. Once the crust protecting the underlying soft snow was ripped up, more snow became available to build the new wind slabs forming our primary concern today. The ice crust is easily breakable over this soft snow but is adding tensile strength to the otherwise weak layer beneath. The rain crust will be something to watch this week as cold temperatures return and begin affecting the snow grains above and below the crust. Currently, the grains beneath the crust are sugary ice pellets doing a convincing impression of facets. With any luck they won’t have time to become a widespread weak layer.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:30a.m., February 23, 2014. A new advisory will be issued tomorrow.

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

2014-02-23 Print friendly