Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. North, Damnation and Yale have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.
Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. The exceptions to this rating are the Lower Snowfields and Little Headwall which have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.
AVALANCHE PROBLEM: Wet slab avalanches may slide naturally without a human trigger today. As rain and warm temperatures continue to reach deeper into the snowpack, the likelihood and size of an avalanche will increase. While relatively slow moving, this avalanche type is particularly dense and potentially destructive. The floor of Tuckerman Ravine is particularly threatened by a natural avalanche from the Headwall area.
Additionally, higher volume watercourses such as the main waterfall in the Lip as well as Central and Pinnacle Gullies in Huntington, among other streams, will undermine snow and create fall or drowning hazards. It is likely that the main waterfall/Open Book area will open up today along with the Little Headwall stream course. Both of these areas have been the scene of serious or fatal accidents.
WEATHER: Another day of warm temperatures and rain are on tap today. As is often the case on the mountain, precipitation amounts vary widely by elevation and location. Hermit Lake received only a trace of rain in the past 24 hours with .42” falling on the summit during the day yesterday and more last night. Another ¾”-1” of rain at minimum is expected to fall through the daylight hours with the heaviest rain falling later this morning and in the afternoon. Current temperatures are 40 F on the summit, 45 F at Hermit Lake, and high 40’sF at Ravine elevations on the Auto Road. Southwest winds will increase to the 70-90 mph range with gusts over 100 mph then diminish a bit in the afternoon. Temperatures will begin to fall later tonight and dip below freezing by sunup tomorrow.
SNOWPACK: Our snowpack had some soft slabs in lee areas of a northwest wind day before yesterday. These slabs were first to saturate and may have already avalanched in some areas. Beneath that snow a firmer pencil hard slab was widespread through the terrain. It seems likely that this part of the snowpack will be the bed surface along with some isolated areas of ice crust that have survived the avalanche cycles since the December 23-24 freezing rain event. It is also possible that our snowpack adjusted to the increased stress of rain saturated and heat weakened snow with no avalanches occurring anywhere. Such is the nature of this type of avalanche problem. In either case, there are plenty of reasons to avoid traveling in avalanche terrain today, the least of which may be the potential for avalanches.
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 Harvard Cabin.
• Posted 7:35 a.m., Friday, January 12, 2018. 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