Avalanche Advisory for Friday, February 27, 2015

This advisory will expire tonight at 12:00 Midnight.

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

All forecast areas of Huntington Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. Recent very cold air in place has stressed some of the ice features and caused some recent ice dam ruptures.

AVALANCHE PROBLEM: Old wind slabs, which have become Persistent Slabs, are the primary avalanche problem to consider today. We have only received about an inch of new snow in the past 3 days, however continued cold weather has kept old wind slabs which formed earlier this week from bonding to bed surfaces. While the likelihood of triggering an avalanche is trending more towards unlikely, the size of a potential avalanche in the moderate rated areas is what is driving our rating. The steepest sections of slopes, wind loaded sidewalls of gullies and thin sections of slab are the most likely potential trigger points. Avoiding the steepest parts of gullies is relatively easy, knowing where thin spots exist is much harder. Assess for potential faceting and weak interfaces between slabs within the snowpack if you choose to travel in this terrain.

WEATHER: Continued cold temperatures today with a high around -10F (-24C) on the summit will likely feel warmer in the Ravines if periods of sunshine pan out. A NW wind in the 25-40 mph (40-65 km/h) range will increase a bit to 35-50 mph (55-80 km/h). This wind will have no effect on stability and will make for a fairly pleasant day in the lee areas of our Ravines despite the cold ambient temperature. Ridgelines will obviously feel colder so be prepared to cover exposed skin. Clear but cold conditions will persistent early this weekend as high pressure takes the stage.

SNOWPACK: Howling winds on Monday dumped quite a bit of snow into Tuckerman Ravine but scoured out most of Huntington. The Sluice through Chute area has large, smooth expanses of snow. We know that historically the Lip and Center Bowl area can fracture in a big way and generate a really large avalanche. There are no bright red flags today, but a combination of snowpack concerns keeps us from dropping these areas to low. The continued cold, a buried crust, and thick wind slabs are the drivers of current ratings and should give you something to think hard about before center-punching a big slope. Lobster Claw and Right Gully share some of these snow structure concerns but are much smaller slopes and allow more options to avoid unstable areas. Field work today should help resolve some of these snow structure questions and help us understand the scope of these potential problems.

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 8:30a.m. February 27, 2015. A new advisory will be issued tomorrow.

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