Posted 8:55a.m., Saturday, January 22, 2011
Tuckerman Ravine: Lobster Claw, Right Gully, the Sluice, the Lip, Center Bowl, and Chute all have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine: Central, Pinnacle, Odell, and South gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger today. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
Throw an extra pair of long underwear in your pack, it’s going to get chilly this weekend. A cold snap will take hold today and last through Tuesday. Summit temperatures are potentially going to be colder than they have been in four years. Add reasonably strong winds and you’ll be facing some very challenging conditions over the next few days. Know all your options in advance so you don’t need to spend unnecessary time above treeline figuring things out. Enough about that, let’s get on to the avalanche discussion…
Yesterday the winds on the mountain shifted to the WNW and began to ramp up steadily through the afternoon and evening. They peaked at 101mph (162kph) from the W before coming down to their current speeds in the 60mph (97kph) range. This transported plenty of snow into Tuckerman Ravine, which set off a round of avalanches in numerous areas, followed by more loading that happened after the maximum wind speeds had been reached. As if the mountain wanted to show that it means business today, it just released a pretty good sized avalanche in the Center Bowl as I was writing this advisory! One of the first things taught in most avalanche classes is the idea that recent avalanche activity is a red flag indicating unstable snow. With natural avalanche activity taking place before our eyes, it’s not at all a stretch to say that the snowpack might be a little sensitive today. Cold temperatures tend to keep the elastic energy in the slabs, which allows fractures to propagate through them. The areas rated Considerable harbor the most unstable snow, due to continued reloading since the last avalanche cycle. As loading subsides with further diminished wind speeds this afternoon, the threat of naturally triggered avalanches will decrease as well, but the potential for human triggered slides will remain elevated thanks to the cold temperatures and snappy slabs. Left Gully has a stepped crown line below the narrows, with sufficient hangfire to warrant a Moderate rating. Obedience to safe travel rules is a must for anyone entering avalanche terrain today, including just going to the floor of the ravine for a look around.
In Huntington there is a mix of Moderate and Low danger. The winds created a variable snowpack, with the Moderate rated areas having some scouring, but more areas where reloading took place after any avalanche activity occurred. Human triggered avalanches are possible here. In the areas posted at Low, you’ll need to be watchful for unstable pockets. One example is the top of the fan below Yale Gully, but anywhere you find deeper slabs on steep terrain you should be watchful.
- 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.
- This advisory expires at midnight. 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