Posted at 8:30 a.m. Thursday 4/21/2011
Tuckerman Ravine has Low avalanche danger. Natural and human-triggered avalanches are unlikely but you’ll want to watch for unstable snow on isolated terrain features. Keep an eye on snowfall accumulations; more snow than forecasted may increase the avalanche danger today.
Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when using avalanche terrain in Huntington Ravine. A danger of falling ice exists and will persist until it all comes down.
Don’t let the 3-4mm stellars falling from the sky fool you today. The amount of upslope snow we’re expecting isn’t going to give us a Utah-style powder day. However, snow is currently falling and beginning to accumulate in the icy boot prints around the courtyard. Despite the current conditions, neither the Observatory nor the National Weather Service is predicting significant snow accumulations today, but they are both forecasting strong WNW winds. We know this can move tiny accumulations of snow into deeper slabs in strongly sheltered areas. So as far as snow stability goes, you’re going to need to watch accumulations throughout the day and adjust your plans accordingly. If the snowfall rate we’re currently seeing keeps up for the duration of the day, I’d expect to see stability problems grow in numerous areas. Aspects facing E and SE, such as the Sluice, Lip, and Center Bowl, would be the first to move up beyond the Low rating, with other areas having smaller pockets to watch out for. On the other hand, if the current snowfall slows down and accumulations remain light, overall stability will remain quite good with maybe a small pocket of unstable snow here or there. My confidence in modern weather forecasting makes me think the latter is the more likely scenario, but you should be paying attention to the actual weather conditions regardless of what I think. Even under the Low rating, you should watch for growing isolated pockets of unstable snow.
Over the past couple days, rain and warm temperatures followed by the drop in temperatures have made conditions very slick. In steep terrain, this icy crust will make slips and falls very dangerous. It will be incredibly difficult to stop yourself once you gain a little speed. Do yourself a favor, bring an ice axe and crampons for climbing steep slopes. Being skilled in their use is also very important, as is paying attention to what might be in your fall line and choosing routes with fewer objective hazards. There are a couple other hazards to know about today. First is the waterfall hole near the Lip. With icy conditions and poor visibility today you’ll want to avoid the area near this hole at all costs. Also, exiting the ravine via the brook and Little Headwall is quite difficult, and not without hazards of its own. Undermined snow, steep-icy-bumped-up glades, open waterfalls below narrow traverses, etc. all will need to be navigated safely just to get to the top of the Sherburne. You’ll probably find it faster and more enjoyable to hike out of the Bowl. With the strong winds, cold temperatures, limited visibility, blowing snow, and icy conditions, you might want to ask yourself if you can save the adventure for another day.
You might be hoping to develop a cough or sore throat this afternoon, or maybe catch a 24-hour bug, so you can take a day of “R&R” tomorrow. The weather looks to be sweet on Friday before an ugly weekend. We’ll keep you posted for the weekend in tomorrow’s morning advisory and the Weekend Update in the afternoon. Expect icy bumps with bare spots on the Sherburne Ski Trail.
- 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 or the AMC at the Pinkham Notch Visitor Center and Hermit Lake Shelters.
- 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