Posted 8:30 a.m., Monday, March 7, 2011
Tuckerman and Huntington Ravines have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The only exception to this rating is the Little Headwall in Tuckerman Ravine which has Low avalanche danger. Recent heavy rain has undermined this slope so use caution if you opt to travel in this area.
As an observer from the Mt. Washington Observatory said this morning, “this one isn’t playing nice”. A massive storm system has dumped rain, sleet, freezing rain, more sleet and even some snow on the mountain since Saturday morning. Yesterday was pretty much a wash out with rain falling through the day totaling 2.6” (6.7 cm) at Hermit Lake. YUCK! This finally transitioned to frozen precipitation last night and since then the Summit has recorded 11.8” (30 cm) and Hermit Lake recorded 6.9” (17.5 cm). This is a mix of snow and sleet so it has a high density. Sadly, it has currently transitioned back to rain in the Ravines and freezing rain near the Summit. This is resulting in numerous wet loose slides within the new snow and sleet. Blowing snow has come to a halt up high as freezing rain has encapsulated the new blanket of frozen stuff. Colder air is near by and we expect temperatures to drop and allow precipitation to transition to snow for the remainder of the day. This squirrely weather maker has been difficult to forecast the specifics but we are expecting accumulating snow in the mountains today. There is about 0.4” (1 cm) of water left to wring out of this one so several inches of snow can be anticipated. Today’s snow stability issues are starting with the rain on the new snow and the loose wet avalanche activity we are experiencing. Later in the day the focus will be on snow that falls during the day and subsequent wind loading by shifting and increasing winds. SE winds will shift to the NW and increase to 60 to 80 mph (97 to 129 kph) late today. These winds will easily transport today’s snow into the Ravines creating new wind slab. Depending on how much new snow we pick up, this could result in most forecast areas being at the upper end of the Considerable rating due to the increasing potential for natural slab avalanches. If today’s winds start mining out the heavy snow and sleet that is encapsulated by an ice layer, you can expect more significant avalanche problems today.
The recent rain has created a warm snowpack that does not have any interest in supporting your weight. If you plan on being off the heavily packed trails, you’ll need skis or snowshoes to get anywhere. Tonight temperatures could dip below 0F and free water in the snowpack will lock up. Expect some ice dam issues to develop in the gullies in Huntington as a result of this.
- 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.
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856