Expires tonight at midnight December 27th 2012.
Tuckerman and Huntington Ravines will have HIGH avalanche danger today. Natural avalanches are likely and human triggered avalanches are very likely on a variety of slope angles and aspects. Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended.
It’s no secret that a major weather maker is impacting the area as we speak triggering a “Winter Storm Warning” until tomorrow morning. Forecasted snow totals have vacillated back and forth a bit with each weather model run, but currently the mountains of NH are expecting 12-18” (30-45cm) with potential more in localized areas. This precipitation is being delivered on high ESE and E winds gusting in the 90-100mph (144-160kph) range this morning. This will back off as the day progresses being a more effective loader of snow in our terrain versus the current scouring agent. Our greatest concern today is the cross loading of N and S facing aspects which will become more unstable into the afternoon. Although east facing aspects, such as the Tuckerman Headwall, will receive a much higher degree of scouring small terrain features on these aspects will also receive some cross loading depending on the exact wind direction. Because of this it is important not to generalize too much concerning what aspects might being getting completely scoured.
It’s early in the season so there are a number of the typical locations that have limited bed surfaces. The Lobster Claw, high in Right gully, North gully and South Gully are some examples of thin couloirs with multiple anchors scattered through their terrain. They will take longer to reach the “High” forecast and may sit in the “Considerable” range for a good portion of the storm event flirting with the High danger definition. However, copious amounts of low density snow rapidly loaded by high snowfall rates and wind will eventually make many anchors in these areas moot, hence the High rating. The blanket rating today for the two Ravines is greatly hinged on the potential for far over a foot of snow. Given the potential for atypical avalanche activity in locales that were a bushwhack yesterday, very high winds, and near zero visibility travel in avalanche terrain is certainly not recommended. Depending how this storm event plays out we may return to not forecasting for some areas due to the lack of bed surfaces. We’ll have to see how much snow we end up with and the exact duration of high velocity winds.
As this system moves into the Maritimes winds will wrap around through the NE, N and eventually out of the NW tomorrow. As this move begins to occur overnight we expect South facing aspects to receive additional loading. As our prevailing winds from the NW get settled in Friday morning a potential for new elevated avalanche concerns should develop tomorrow for aspects with an E and SE component. Be sure to take a look at the latest avalanche information updated daily and, for a prelude to the weekend, our first Weekend Update on www.mountwashingtonavalanchecenter.org late Friday afternoon.
- 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 6:40a.m. December 27th, 2012. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856