This advisory expires tonight at 12:00 midnight.
Tuckerman Ravine has Considerable and Moderate avalanche danger. The Lip, Center Bowl, Chute, and Left Gully will have Considerable avalanche danger. Natural avalanche are possible, human triggered avalanches are likely in these locations. The Sluice has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lobster Claw, Right Gully, Hillman’s Highway, Lower Snowfields, and Little Headwall have no rating, due to the overall lack of snow in these areas; however, watch for signs of unstable snow in isolated steeper locations and larger areas of continuous snow.
Huntington Ravine is under a General Avalanche Bulletin. General Bulletins are issued when instabilities are isolated within forecast areas and are issued every three days or earlier if conditions warrant. Forecast areas in Huntington have less well developed bed surfaces for avalanches to run on. However, bed surfaces do exist, particularly in Central, Pinnacle, and Odell gullies. For today, expect wind slabs to develop in many areas. Winds will continue to strengthen tonight and remain very strong through Tuesday. As wind speeds rise towards 100mph, expect a significant amount of wind scouring to take place, eroding most, if not all, of the new snow from the gullies.
AVALANCHE PROBLEM: Wind slabs are the primary threat today. These currently exist in many locations and with the expected weather, they will be growing through the day. Expect an increasing hazard as snow falls and wind velocities rise today. The areas of greatest concern are in the headwall area of Tuckerman, such as the Lip, Center Bowl, Chute, and Left Gully. Any avalanche encounter is dangerous but the potential for traumatic injury increases due to the many small cliffs and boulders exposed by our thin snowpack.
WEATHER: A strong low pressure system well to our east will continue to send bands of snow showers to the the mountain. As the low strengthens and moves east, it will draw an arctic cold front across our terrain. This cold air mass will bring much colder air and high winds to Mount Washington and generate a protracted period of upslope snow shower activity lasting into Tuesday. This front has a strong squall line on its leading edge which may produce a brief but intense period of snow showers today. Expect winds to reach 75mph by sundown and near 100 mph tonight and into Tuesday. These strong winds, coupled with temperatures near 0F, will create challenging travel conditions today and tomorrow. 2-6″ of new snow is possible today.
SNOWPACK: We have been watching the avalanche terrain slowly fill in with snow, increasing the size of bed surfaces but are still well behind schedule in terms of a normal winter. Even the forecast areas that now carry a five scale rating are discontinuous in nature and contain snowfields which, in the grand scheme of things, could be considered pockets of unstable snow. But even smaller slabs of snow can produce dangerous avalanches, especially in our steep terrain where the force of a sliding mass of snow combines with gravity to push people where they don’t want to go. Yesterday morning, we found fresh debris from two avalanches (Chute and Center Bowl) and then later there were two human triggered avalanches (Chicken Rock Gully, which is the small area left of Lunch Rocks and beneath the Lip, and Chute, a second time). Fortunately, these did not end in significant injuries but the outcome could have been very different.
New snow with increasing winds today will create new wind slabs which will have the classic “upside-down” structure to it. This creates a dangerous situation where a slab rests over lighter, weaker snow. We expect today’s wind loading to exacerbate both the previously existing slabs, which have probably been slow to stabilize, as well as the newly created ones.
- 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 8:25 a.m. January 18, 2016. A new advisory will be issued tomorrow.
Frank Carus/Helon Hoffer, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856