Posted 8:40a.m., Friday, January 21, 2011
Tuckerman Ravine has HIGH avalanche danger today. Natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended. There are only two exceptions to this rating. The Lower Snowfields have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Little Headwall has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
All forecast areas of Huntington Ravine have HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended.
Another winter storm is hitting New Hampshire! As you can see from today’s High danger rating, this storm is expected to significantly impact snow stability on the mountain. The Observatory forecast is calling for 5-7” (12-18cm) of snow to fall today, and as the snow winds down the winds will ramp up and shift around clockwise from the S to the NW. By the end of the day wind speeds will be gusting over 80mph (130kph). This will load snow into all forecast areas and create very dangerous avalanche conditions. New windslab will build in an upside-down pattern. It will start with lighter densities from the lower wind speeds, but as the winds begin to pick up slab densities will increase and lay heavier slabs on top of the lighter, weaker slabs. This is the notoriously unstable upside-down snowpack effect. In some locations slabs will start building on top of a very touchy soft slab surface layer left over from previous events this week. In addition to the new snow today, we expect the strong winds to be able to pick up and move snow that was already sitting above treeline from previous snowfalls this week. The bottom line is that very dangerous conditions will be developing today; travel in avalanche terrain is not recommended.
A lot is happening today in addition to the High avalanche danger. First, we have switched over to the Lion Head Winter Route. This route follows steep terrain; we highly recommend mountaineering skills and equipment for safe travel on the route (i.e. an ice axe and crampons.) Second, we have forecasted the Little Headwall and Lower Snowfields today. They had previously been “not posted.” The danger in the Lower Snowfields today comes primarily from above, with natural avalanches possibly running from the Duchess down into the Lower Snowfields proper. Although there is enough snow to warrant a forecasted rating today, the Little Headwall is not a good option for descending from the Bowl. The stream above is a long way from being filled in and skiable and the Little Headwall itself was only recently an open waterfall. Third, Arctic weather is coming in for the weekend. Check the Mt. Washington Observatory’s Higher Summits forecast discussion for the details. Testing yourself against the coldest temperatures we’ve seen here in a few years may sound glorious, but it doesn’t leave a big margin for error. Be conservative with your decisions this weekend. We’ll let you know more in the Weekend Update section of our website later this afternoon or evening. And finally, the John Sherburne Ski Trail has good coverage from top to bottom.
- 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