This advisory expires tonight at 12:00 midnight.
Tuckerman and Huntington Ravines have Low avalanche danger. Natural and human-triggered avalanches are unlikely, but watch for unstable snow in isolated terrain features. It is important to realize these pockets do exist and can produce smaller avalanches in remote steep locations. This is a greater concern in Tuckerman than in the wind scoured gullies of Huntington.
AVALANCHE PROBLEM: Persistent Slabs are the primary avalanche concern today. These slabs exist as both as hangfire from the natural avalanche cycles on Sunday and as pencil hard slabs from the wind loading on Tuesday. These are most likely to be found beneath the highly wind protected upper ice flows in the Tuckerman Headwall area. The second threat is from softer wind slab that developed as winds died down on Tuesday. Look for these smaller, but touchier slabs (1F hardness) behind terrain features in strong lee areas such as lookers left at the top of Right Gully, and along steep buttresses.
WEATHER: Weather will start transitioning late today from the clear high pressure system to increasing clouds with the approaching low pressure from the south. However, nice weather will continue for a day in the mountains and should not affect snow stability. An increasing wind may move just a little alpine snow, but not enough to load in as a new problem. Late tomorrow and into the early Sunday morning we will pick up some new snow, albeit scant.
SNOWPACK: Field time yesterday and a lot of discussion led us to settle on a Low rating today despite the fact that Persistent Slabs more often than not for us earn a Moderate rating. The main driver behind the Low rating is that the persistent weak layer of facets in question was discontinuous in nature even before this last avalanche cycle. Persistent slabs are typically hard, stubborn and therefore resistant to a human acting as a trigger. Although this is true for our current situation we also have limited weak layers keeping us from moving our concern to a higher rating. In addition, we believe the tensile slab strength of varying depth is bridging over an occasional deeper facet layer or isolated graupel pool. Intense spatial variability and the discontinuous nature of the slabs and weak layers lead us to believe isolated pockets of concern most accurately describe our snowpack. While you may find some smooth Q2 shovel shears among the wind slab layers you will generally find them “hard” and stubborn. There is a lot of bridging power in hard slabs like these. That said, I would be careful of any of these slabs sitting on top of ice flows such as in the Center Bowl area. As always, mitigate your exposure to avalanche threats by careful route selection.
Look for more terrain/conditions photos today on our Facebook page and possibly the new Flickr account if all goes well on the technology front. The Sherburne is not particularly enjoyable skiing unless you like hard snow and water bars. It is currently plagued with a brutal frozen rain crust on it’s upper half. Right Gully saw a half dozen skiers yesterday on firm but smooth and carvable snow. Many other areas such as Left Gully were much more bumpy due to wind whipped sastrugi. Chris is writing what may be his last weekend update today….look for that later today.
- 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 8:40 a.m. January 23, 2015. A new advisory will be issued tomorrow.
Frank Carus/Chris Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856