This advisory expires at Midnight tonight.
Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. North, Damnation and Yale Gullies have Low avalanche danger. Natural and human-triggered avalanches are unlikely.
Tuckerman Ravine has MODERATE and LOW avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely.
AVALANCHE PROBLEM: The primary avalanche problem today is Wind Slab. High winds yesterday transported snow into our forecast zones and built wind slabs in many areas. Most of the terrain remains discontinuous due to a shallow early season snowpack but larger bed surfaces exist, particularly in Center Bowl, Chute and Left Gully. Those areas likely harbor the most reactive and larger wind slabs in Tucks. The snowpack in gullies like Central, Pinnacle and Odell in Huntington and Hillman’s Highway, which were in the lee of yesterday’s wind grew in size, while North, Damnation and Yale lost snow to scouring action. In short, it is a mixed bag of wind slab densities and distribution out there, so bring your A game if venturing out. Avoid large, smooth pillows and smooth, steep slopes that you may find until you can safely make an assessment of stability. Cracking and hollow sounding areas should be avoided until these slabs gain more stability. Additionally, be aware that some slopes may be further stressed by loading from wind deposited snow later this afternoon.
WEATHER: Lingering fog and some blowing snow continue to flatten light and hamper visibility this morning. The wind is currently blowing out of the west in the 60 mph range and will slowly ramp up through the day. Skies should continue to clear but temperatures will remain near -10F on the summit. Yesterday and overnight, west and west-northwest winds howled near 80 mph on the summit for a 12 hour period. Gusts hit 100 mph and scoured south aspects of Huntington. Expect the wind to slacken tomorrow with temperatures warming to around 0F.
SNOWPACK: Limited visibility and flat light obscure signs of avalanche activity in Tuckerman but the amount of ice, cliffs and boulders that remain visible point to the generally thin snowpack. Low density snow yesterday was easily picked up and carried by the wind and began to fill in voids above treeline and in the lee of terrain features. Areas where these slabs were built on top of the new, soft snow are the features to assess or avoid. The firm wind slabs that we frequently deal can create the illusion of safety due to their stubbornness. Practice safe travel and do lots of probing and digging to assess these slabs. You can likely seek out a path through scoured or heavily sculpted snow on climbs in Huntington Ravine and avoid questionable slabs above you.
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 and some bare sections due to wind scouring.
• 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 8:30 a.m., Thursday, December 14, 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