Tuckerman and Huntington Ravines have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist making conservative decision making essential. Huntington’s Escape Hatch has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Tuckerman’s Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.
Over the past 32 hours the summit has received 6 inches (15cm) of snow brought in on strong NW and W winds. Over the last several hours winds ramped up quickly gusting to 118mph (190kph) from the WNW before falling as rapidly back to the current of 85-90 (137-145 kph). In addition to the snow already received the forecast is expecting an additional 1-3” (2.5-7.5) this morning. This entire scenario has brought us to similar discussion points we entertained yesterday.
Friday’s winds have loaded new snow into many E and SE aspects and crossloaded a number of others giving us concerns about natural avalanches in almost all of our forecast areas, hence the Considerable rating. High winds, particularly this morning, brought above treeline snow and new snow falling from the sky into strong lee areas. Areas in Tuckerman harbor more of these protected locations than in Huntington so we believe our number one avalanche concern today spans between the Sluice through the Center Headwall. Other lee locations of W and NW winds currently have instabilities, but not to the extent of the aforementioned areas.
High winds over the century mark this morning have undoubtedly scoured a number of areas particularly in the Huntington gullies, and Tuckerman’s Left gully and Hillman’s. However our rationale for a Considerable rating in these locations is due to a dropping wind speed and continued loading from alpine areas and additional snow. As winds fall through the day, eventually getting as low as 40mph this evening, new slab will deposit over older scoured locations. Some gullies, especially those being cross loaded will struggle to meet the “considerable” definition but as the day continues should get there nonetheless.
Bulls-eye points and considerations:
**Generally expect a high degree of variability as you move through the terrain with the potential of being on hard old surfaces one second and fresh unstable slabs the next.
**In Tuckerman we have the most concern of natural avalanches coming from the Center Headwall over to the Sluice followed by the top climber’s left of Right Gully and the top climber’s right of Left Gully.
**In Huntington we have the most concern about the protected approaches of climbs, most notably the bottom of Odell, Pinnacle, and Central. These areas pick up frequent sluff deposition creating new slabs. As winds fall some higher start zones should pick up some new snow through the morning.
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 8:30am, 1-5-2013. 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