Expires 12:00 midnight, 1-28-2012
Tuckerman Ravine has Moderate and Low avalanche danger. Right Gully, the Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Left Gully and Hillman’s Highway have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted.
All forecast areas of Huntington Ravine have Low avalanche danger. Natural avalanches and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
One of the first lessons an avalanche student learns is that hazard evaluation is a constant process. One needs to be continually open to new information and questioning every assumption. Coming up the trail from Pinkham this morning, small amounts of new snow drifting into protected areas of the trail caused me to question my own expectations for the day. After temperatures yesterday climbed above freezing at all elevations for several hours, including many hours of freezing rain and rain, I expected a crust to be the prevailing surface in the lower elevations. So where did the new snow come from? One suspected source is the wind. Last night, west winds ramped up to the 100mph+ mark for several hours. This likely ripped up the crust that formed above treeline and exposed the colder, drier, underlying snow from Thursday night to the strong winds. The other source, the one I wasn’t expecting, was new snowfall last night. For a couple hours, just prior to the winds maxing out, there was light snowfall at the summit with totals of about an inch in their collection can. This is what I believe is the source of the drifting down low, and is contributing to stability concerns for today.
In Huntington, as well as the areas in Tuckerman that are rated Low, the new snow will have had a difficult time holding onto the slopes during the sustained strong winds. While most of the surfaces will be scoured down to an older crust, you may find pockets of unstable snow in strong lee areas within the Low rating today. The other areas of Tuckerman have a Moderate rating today based on their ability to hold windloaded snow even during strong wind events. Clouds have prevented me from seeing it firsthand today, but I suspect there will be a mix of conditions in these forecast areas. Some places where wind was able to get at it more, you’ll find relatively stable snow. But in locations that are more protected, the new snow mixing with bits of old snow picked up by last night’s wind, you may find slabs with sufficient elastic energy to propagate a fracture. The Lip and Center Bowl stand out as the most protected locations, but smaller areas such as the mouth of Right Gully and above the narrows of the Chute are also well protected. Beneath any new slabs you’ll find a variety of crust layers, giving a handful of potential bed surfaces. To add more complexity to the forecast today, snow is currently being blown around above treeline. This should subside soon as wind speeds decrease, but remember that if active loading continues it will increase the avalanche hazard.
The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk.
- 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 8:25am. A new advisory will be issued tomorrow.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856