This advisory expires at Midnight.
Huntington Ravine will have EXTREME and HIGH avalanche danger today. North, Damnation, Yale, and Central will have EXTREME avalanche danger. Natural and human triggered avalanches are certain there. All other forecast areas have HIGH avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely.
Tuckerman Ravine will have EXTREME and HIGH avalanche danger today. Sluice, Lip, Center Bowl and Chute will have EXTREME avalanche danger. Natural and human triggered avalanches are certain there. All other forecast areas have HIGH avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely. The only exception to this rating is the Little Headwall which has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible there.
Very dangerous avalanche conditions will exist today. Avoid all avalanche terrain later today as wind speeds begin to increase. Large avalanches in many areas will be likely.
AVALANCHE PROBLEM: This morning, there is Considerable danger of Storm Slab avalanches from 17” of new snow last night. Diminishing wind speeds at the start of the storm deposited this snow in our entire forecast area with little wind effect. Steep terrain this morning also has significant Loose Dry avalanche potential with Wind Slab concerns in upper start zones. As wind ramps up from the north, rapid loading of slopes with a southern through eastern aspect will occur and build large and dangerous wind slabs. These slabs will release naturally and most likely run far into flat areas like the floor of Tuckerman Ravine and the Fan in Huntington, as well as through avalanche paths in adjacent areas like the Gulf of Slides.
WEATHER: Summit wind speed is currently blowing near 40 mph from the northwest. Hourly forecast models indicate that winds will continue to increase through the day and shift to the north and northeast. The 17” (43cm) of new snow is light density (4% water) and will be easily transported by winds increasing to the 65-85 mph range from the north. Moisture in the lower atmosphere will continue to produce fog and upslope snow showers with another 2-4” of new snow falling through the day. Visibility will diminish through the day with ground blizzard conditions making navigation difficult.
SNOWPACK: Beneath all this new snow, you’ll find mostly firm snow with pockets of softer, newer snow along with a dense ice crust in steep terrain. Hard slab debris from a natural avalanche that occurred in the Lip on Wednesday contained a fair amount of this ice crust as well as the old sleet beneath. While it’s hard to say for sure whether today’s avalanche will step down into this layer, it doesn’t really make much difference in terms of the danger level. Today’s avalanches will likely shift from medium to large size as the day progresses and then to potentially much larger avalanches as slabs grow thicker. Crossing avalanche paths or entering Tuckerman or Huntington Ravine will put you in the crosshairs for multiple avalanche paths.
- 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 8:00 a.m., Monday, February 13, 2017. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713