Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch 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 exception to this rating is the Lower Snowfields which have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. The Little Headwall is likely a raging river with avalanche danger being the least of your concerns.
AVALANCHE PROBLEM: Wet Slab and Wet Loose avalanches will continue to be our primary avalanche problem until our snowpack solidly refreezes later today or tonight. Peak instability, with possible natural avalanches and likely human triggered avalanches, may have already passed since this warm and wet storm started early yesterday. That said, the nearly 1” or rain in the past 6 hours could be causing continued instability. Temperatures that are currently dropping will allow our avalanche danger to decrease significantly through the day. If rain switches to snow early and pushes the higher end of forecast snow accumulation, we could see areas of new snow instability develop by the end of the day, though other hazards like undermined snow and firm snow conditions will likely be of greater concern.
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 along with the Little Headwall waterways have opened up. Both of these areas have been the scene of serious or fatal accidents.
WEATHER: The past 24 hours has brought nearly 2” of rain to the mountain, with nearly an inch in the past 6 hours. Though temperatures are currently hovering around 32F at elevations 4000’ and below, with warm air near 40F holding at the summit, our snow surface has yet to freeze. It will become increasingly cold from now until tomorrow morning with lows around 0F tonight. The timing of this cold air will determine what form our continued precipitation will take as it falls. If the current rain turns to snow sooner than later we could see several inches of snow or more by the end of the day. If warm temperatures hold a few more hours, we will likely see much less snow accumulation.
SNOWPACK: The heavy rain over the past 24 hours will be drastically altering our snowpack. A lack of visibility into the terrain since this storm began limits our ability to identify specific changes to our surface snow. We expect that wet avalanches have occurred naturally and may continue until a solid freeze later today. Prior to the rainstorm, layers of varying density though mostly firm wind slab existed across much of our terrain. A buried crust formed Dec. 23rd was also continuing to hang around in areas it had not been ripped out by avalanches. Rain and meltwater percolating through the snowpack will first be the cause of natural wet slab and wet loose avalanches, but by the time our snowpack refreezes this water will likely have resulted in greater uniformity.
• 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 7:50 a.m., Saturday, January 13, 2018. A new advisory will be issued tomorrow.
Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856