Frank Carus

Jan 242015
 

This advisory expire at midnight.

All forecast areas of Tuckerman Ravine and Huntington Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow, terrain and weather conditions carefully. Dangerous avalanche conditions may develop after dark and overnight!

AVALANCHE PROBLEM: Be thinking about Persistent Slabs scattered around in the Ravines as your primary avalanche hazard if you are planning to thread the weather needle today in the Ravines. This hazard earns a Low rating this morning. New snow on increasing winds beginning around noon will begin to create a Wind Slab hazard. The rate of new snowfall will determine the likelihood and size of the new, unstable wind slabs as well as how soon we reach the Moderate hazard rating. As the day progresses, the likelihood of natural and human-triggered avalanches will become increasingly possible, particularly in lee areas such as Central and Pinnacle Gully and where the Tuckerman Ravine trail enters Tuckerman Ravine (the Lip and Sluice forecast areas). We may reach a Considerable danger rating after dark.

WEATHER: Clouds will thicken and descend this afternoon as the storm system to our east brushes by the area. 1 to 3” (2.5 to7.5 cm) of new snowfall is forecast this afternoon and evening followed by 1-3” more snow overnight. NW winds will ramp up as the storm moves through, building unstable wind slabs in the process.  Temperatures will drop back towards 0F (-18C) tonight with strong winds complicating travel.

SNOWPACK: A generally hard, wind packed surface (P) in most areas is bridging over discontinuous areas of weak layers (4F-F) on some benches and in some lee areas which were not scoured out by avalanche activity last week end or Tuesday morning. Also, some pockets of softer slab that developed on Tuesday may remain in lee pockets. It is also worth remembering that the wet snow Sunday may be hiding some ice flows and may not be well bonded, at least in areas that did not already avalanche on Sunday. Skiers in Right Gully and Hillman’s the last couple of days have found the surface carvable but firm and worthy of crampons on the ascent. Overall, the snowpack is pretty thin with lots of ice still exposed in Center Bowl and around the Open Book. The recent avalanche activity in Huntington has covered more shrubs on the approach to Odell and the firm snow has made for good cramponing and easier approaches. Ice is still somewhat thin on Pinnacle Gully.

The Sherburne Ski trail is icy on the upper half due to the freezing rain last weekend. Lots of bumps and waterbars are still around. A “dust on crust” situation will develop as the afternoon wears on. We are running the snow cat on the Tuckerman Ravine trail to Hermit Lake and part way into Huntington to try to improve SAR access so please be aware that a large steel object may be descending in the middle of the trail this afternoon.

Please Remember:

  • 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, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2015-01-24

Jan 232015
 

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.

Please Remember:

  • 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

2015-01-23 print friendly