This advisory expires at midnight.
Tuckerman Ravine has HIGH, CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is NOT RECOMMENDED. Right Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, Lower Snowfields and the Little Headwall have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Huntington Ravine has HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is NOT RECOMMENDED. The only exception is the Escape Hatch which has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.
AVALANCHE PROBLEM: Wind Slab will be the primary hazard today. The ultralight density Storm Snow deposited yesterday and overnight around the range will be picked up and moved into both ravines and deposited in lee areas and will quickly form reactive, weak Wind Slabs. Widespread sluffing will continue and will form slabs beneath steep pitches of ice and rock such as below the ice in Central, Pinnacle and Odell as well as in areas beneath steep slopes (over 40 degrees) such as in and below the hourglass in Chute. Danger level will increase to the rating levels through the day as winds ramp up.
WEATHER: This storm was an atypical event for the Presidentials. Rarely do we get such low density snow from a moving weather system, or synoptic event. The 6″ (15cm) that we received by midnight had an average density of 2.8% with more falling since then. This came on very low wind velocities from the WSW, S, SE, E, NE, N, and now the NNW. During this march around the compass rose winds were between 8 and 20 mph since yesterday morning until 4am today. As winds moved from the NE to come from the N velocities picked up quickly and are currently gusting to 36mph (58kph). Winds will continue to shift and should be from the NW later this morning and continue picking up to over 60mph (96 kph) this afternoon. This will create whiteout conditions as the champagne fluff still sitting above treeline gets whipped into a disorienting melee. All this translates into an excellent snow loading scenario causing widespread instability. While all this occurs temperatures will plummet reaching -20F at the upper elevations and close to -30F in local valleys.
SNOWPACK: As the winds shift and increase over the next 2-3 hours snow instabilities should quickly rise. The very low densities, already mentioned above, that fell yesterday on very light winds created a blanket of unconsolidated snow that should act as the main weakness for the first avalanche cycle. Winds will load a soft slab over this even lighter unconsolidated snow over the next several hours making for a very weak and unstable upper snowpack. Slabs should be very delicate and easily triggered. We should see more than one avalanche cycle for areas in the lee of NW winds. Steep areas may release thin slabs multiple times, perhaps creating some new denser slabs lower down or on major benches. This has happened historically due to dry loose and spin drift snow moving down slope. Today’s very light slabs may act similarly, particularly during an early cycle before densities increase this afternoon. Expect an elevated avalanche danger as we enter the weekend due to even higher winds Saturday morning creating some new slabs and leftover instabilities from today that survive in place.
- 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 8:25am Friday, January 3, 2014. A new advisory will be issued tomorrow.
Frank Carus/Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856