Posted 8:40a.m., Sunday, December 26, 2010
Tuckerman and Huntington Ravines have both LOW and MODERATE avalanche danger today. Natural and human triggered avalanches are unlikely in areas posted at Low and natural avalanches are unlikely and human triggered avalanches are possible for areas posted Moderate. We have not begun forecasting for the Escape Hatch, Lower Snowfields, or Little Headwall due to a general lack of snow in these areas. Forecasting will begin for these areas when conditions warrant although avalanche activity may occur before this point.
Tuckerman: Hillman’s Highway, Left Gully, Chute, and Center Bowl have Low avalanche danger. The Lip, Sluice, Right Gully, and the Lobster Claw have Moderate avalanche danger.
Huntington: South, Odell, Pinnacle, and Central have Low avalanche danger. Yale, Damnation and North have Moderate avalanche danger.
Temperatures from the teens to mid twenties F over the past 2-3 days are allowing some slow changes in our snowpack towards a stabilizing trend, but not quite enough to drop any forecast ratings from Moderate to Low. The start zones of southern aspects that were loaded Thursday into Friday morning still harbor the instability issues of most concern. Slopes with southern aspects like the climbers right side of the Lip, the Sluice, Right Gully, Lobster Claw, Yale and Damnation and North continue to have softer slabs than areas with other aspects posted at Low. In much of both Ravines outside of these south facing slopes, anchors and the broken nature of snowfields are assisting most slabs to remain in place, but as you move through a patchwork of snow, bushes, rock and ice re-evaluate slab stability constantly. Due to spatial variability, particularly across the Center Bowl in Tuckerman, expect changes in slab quality and strength.
The big news on the horizon is we are in a WINTER STORM WARNING beginning later today through Monday. Some showers may begin in the mountains during daylight hours, but the real onslaught is expected to start after dark. Expect blizzard like arctic conditions with very limited visibility making above treeline travel tonight and tomorrow quite severe and not recommended. I would consider planning today’s mountain adventure such that you do not end up benighted; a little conservatism would be prudent. The general trend is for temperatures to drop allowing colder lower density snow to fall while wind will begin from the ENE/NE and walk over to the NW and increase to a freight train roar. 8-12” (20-30cm) are expected with localized higher amounts. The initial problems and potential for natural avalanche activity will be on south aspects because of direct loading from the NE and N and terrain protected east slopes due to cross loading. By daybreak tomorrow we should be gusting to 100mph (160kph) as we move from the N to the NW. Northwesterly winds should directly affect the majority of our avalanche terrain, loading aspects not as influenced by the earlier NE direction. Summit temperatures should drop about 20 degrees F from the current of 15F (-10C) to -5F (-21C) tomorrow. All of this should translate into multiple cold dry snow avalanche cycles tonight and tomorrow if accumulation predictions and winds play out. Century winds have not been seen in a long time on Mount Washington so I would expect a fair amount of snow currently sitting above treeline to be moved into the Ravines along with new snowfall. I would anticipate elevated avalanche danger ratings tomorrow likely hovering around “High” for many areas. Powerful winds should also do their fair share of scouring in addition to avalanche creation. As always, it will be very important to read the avalanche advisory over the next couple of days as you may see rapid increases, and perhaps decreases, in avalanche potential.
- 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.
- This advisory expires at midnight. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856