Expires at midnight 2-10-2013
Tuckerman Ravine has LOW, MODERATE and CONSIDERABLE avalanche danger. The Lobsterclaw and Right Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Sluice, Lip, and Center Bowl have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Chute, Left Gully, Hillman’s Highway, the Lower Snowfields and the Little Head wall have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Huntington Ravine has LOW, MODERATE and CONSIDERABLE avalanche danger. North Gully, Damnation, and Yale have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Central and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Odell, South, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
What a mental rollercoaster it’s been over the past 24 hours. First, the precipitation storm totals played out as forecasted with the summit picking up 24.5” (61cm) of low density snow. Next, the expected wind speeds of 110-115mph did not occur, but did reach peak gusts into the 80’s mph for a few hours. Then, I was anticipating widespread slabs in both Ravines that we would need to deal with and forecast for in today’s advisory. Finally, what we found once in the Ravines was truly a classic Mount Washington scenario.
High winds from the NE and N yesterday loaded up south facing aspects causing avalanches in Huntington and Tuckerman. Those same winds slapped directly into north facing slopes, easily removing the light 4-5% density snow clean off the old slick rain crust. Odell, South Gully, and the Escape Hatch in Huntington, and the Chute, Left Gully, and Hillman’s in Tuckerman have very little evidence of new snow in them. Of these locations, Left Gully does have some pockets to pay attention to, but generally they are all down to the slick icy dirty layer from our last thaw. As you transition towards easterly facing aspects there are variable surface conditions with new slabs of concern in areas like the right side of the Center Bowl under the Lip and in Huntington’s Central Gully.
By far the big concern is south facing aspects that have been reloading since the last avalanche cycle by N winds in the 70 mph range early this morning. Although they are currently seeing some loading, clearly evidenced by plumes against a clear blue sky, the main concern is human triggered avalanches compare to natural potential. The current light loading should shut down as winds drop through the day potentially as low as 25mph. The existing slabs mountain travelers will find are cold at about -18C (0F) and harbor denser layers over softer weaker ones from early in the storm. Also, during stability assessments they will find all this is sitting on the old slick surface. Our primary concerns on the mountain right now are these south facing slabs, hence their Considerable rating. Areas in strong lee areas, where slabs were protected from wind packing and hardening, will be more sensitive and reactive to human triggers. Although several of these slopes are on the lower end of the Considerable rating a good approach would be to be conservative and make careful snowpack assessments. Cold unstable slabs will dot the landscape across the start zones of these south aspects and in usual safe locations in the trees. Areas in the trees picked up a lot of new snow so be cautious even in the smallest of snowfields possessing new fist and 4 finger hard slabs. Winds will continue to shift overnight and come from the SW tomorrow gusting high into the 80’s mph. Be ready for another loading event mixed in with more new snow elevating avalanche danger again for Monday.
Traveling down low and in the trees will be slow going due to deep soft snow. Snowshoes or skis will be very helpful. Unfortunately the long slide fall issue on slick hard icy surfaces is still a concern so, as always, assure you have the right gear to travel safely in steep terrain. The Sherburne ski trail is doing quite well.
- 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 8:53a.m. 2-10-2013. 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