This advisory expires at Midnight.
All forecast areas in Huntington Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Cautious route finding and conservative decision making is essential.
Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Chute and Left Gully have High avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely. Very dangerous avalanche conditions exist. Lobster Claw, Right Gully, Sluice, Lip, Center Bowl and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. The Lower Snowfields and Little Headwall are not rated due to lack of snow.
AVALANCHE PROBLEM: The primary avalanche problem today is Wind Slab. These slabs will grow throughout the forecast period as wind loading moves 4-6” new snow falling today, along with the 16” that fell yesterday. Natural avalanches will become more likely through the day as new slabs build over yesterdays low density snow. Areas with a high rating have more well developed bed surfaces from early season snowfall. All slabs are likely to be sensitive to a human-trigger as well. This type of avalanche could break above you either naturally or with you as a trigger. Combined with rocky, early season snow coverage, getting involved in any avalanche will likely lead to injury or worse.
WEATHER: Upwards of 16” of new snow fell on the mountain in the past 24 hours. Unlike valley and southern locations, this snow remained fairly low density through the storm and will be easily transported by increasing west winds through the day. By noon, west-northwest winds will reach into the 50 mph range and gust to 70 mph. These wind speeds are prime for moving snow into our start zones. Winds will continue to increase through the day and continue the loading process. Visibility will be challenging as upslope snowfall and snow on the ground are blown around. Navigating in these conditions and staying out of avalanche paths will be difficult due to these ground blizzard conditions.
SNOWPACK: I was a little gunshy about using a High rating today since our terrain is still discontinuous and rocky due to the lack of snow so far this season. Despite that, many red flags exist for natural avalanches to occur this afternoon in many areas of our terrain. Though these avalanches may not be large, only a few areas in our terrain are really capable of producing large avalanches. The critical point is that the consequences of travelling into or below these avalanche paths will be very dangerous. These avalanches will certainly be able to bury and kill you regardless of the overall dimensions of the avalanche paths. Rocks, cliffs, and bushes will make being captured and carried by an avalanche particularly dangerous. Many terrain traps exist in our current snowpack, especially in the floor of Tuckerman Ravine, beneath the Tuckerman Ravine Trail and at the start of ice climbs in Huntington and Tuckerman.
The Tuckerman and Huntington Ravine Trails pass directly through avalanche terrain and are serious mountaineering objectives. The summer Lion Head trail remains the safer direct route to the summit from the east side of the mountain. The Sherburne ski trail has greatly improved due to the boot top snow depth that fell yesterday. Beware of lurking rocks.
• Safe travel in avalanche terrain requires training and experience. This bulletin 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., Wednesday, December 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) 466-2856