Avalanche Advisory for Sunday, February 9, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. North, Damnation, and Yale have Low danger. Natural and human triggered avalanches are unlikely. In these locations, watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEMS: Wind slab is the primary avalanche problem today. This problem is compounded by additional slab that has developed by sluffing and spindrifting snow. In places, persistent slabs deeper in the snowpack may exist, though locating where exactly this issue exists would be challenging. The new wind slab and sluff slab problem contributed to a human triggered avalanche in the Center Bowl area yesterday afternoon. I suspect more locations have similar issues, especially those places where sluffs have added significant load, such as underneath pitches of ice (e.g. below Pinnacle) or in areas that transition from very steep to slightly less steep (e.g. under the Chute or Center Bowl). In strong lee areas such as the Lip, expect touchy slabs sitting on top of softer weak layers. This situation, in this particular location, is quite dangerous and is pushing the upper boundaries of the Moderate rating.

WEATHER: The most noticeable weather feature today is a lack of strong winds. This is a welcome change from yesterday when winds averaged 5omph (80kph) from the W with a peak gust of 80mph (130kph). Temperatures will still be cold, hovering in the low single digits above zero F at the summit. Late today, we are expecting the mountain to become engulfed in fog and for snow to begin falling. The Observatory has forecast 1-3″ by midnight tonight. I don’t expect this to cause too much trouble for backcountry travelers today, but if you’re out after dark you should be prepared for snow and limited visibility.

SNOWPACK: Spatial variability should be on your radar. Yesterday I traveled into Chicken Rock Gully (between the Open Book and Lunch Rocks) immediately after a group of four skied it with very little regard for safe travel techniques and apparently no snowpack analysis. What I found was alarming–a layer of slab (6-12″ deep) sitting on top of a very weak layer of unconsolidated snow. In one extended column test, the block failed as I placed my shovel on it. The upside down layering was everywhere in this area, but tests in other spots did not have quite so much scare factor. However, with this info, I abandoned my hope to go closer to the Lip based on what I’d just seen. Instead, I headed down and back up the lookers’ left side of the Center Bowl. As I started to climb up, I felt much more confident about the strength of the hard slab underfoot than I had moments ago in a more sheltered location. While digging a pit to try to learn how deeply the persistent slab and facet layer was buried, I triggered the slide mentioned above, which broke off about 100′ uphill of my location. This caught me completely off guard, and I can say I was fortunate that the slide broke out only in one direction above me, allowing me to quickly escape to the side. The moral of this story is this: instabilities currently exist in the snowpack, weak points are not always obvious, and these harder slabs can propagate a crack a long distance. Be careful out there!

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 8:15 a.m. 2-9-2014. 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

2014-02-09 Print friendly