Posted 8:30a.m., Tuesday, February 08, 2011
Tuckerman and Huntington Ravines will have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The only exception to this rating is the Little Headwall in Tuckerman Ravine which has Low avalanche danger. Natural and human triggered avalanches are unlikely in this forecast area.
Active weather continues to keep us on our toes up here on Mt. Washington. Today’s weather will bring snow, dropping temperatures and increasing winds which will work together to create new avalanche issues in the Ravines. The extent of these issues will depend on how much snow accumulates on the mountain today. The Mt. Washington Observatory is forecasting for 1-3” (2.5 to 7.6 cm) of snow today with another trace to 2” (5 cm) overnight. This seems to be playing out but I can’t ignore the National Weather Service’s forecast that is calling for up to 6” (15 cm) of new snow today in higher terrain. What snow does fall will be accompanied by winds out of the NW that will be increasing to 70 to 90 mph (112 to 144 kph) with higher gusts. These winds will transport new snow into the ravines creating wind slab that will increase in density as the day progresses. The increasing slab density will occur as winds ramp up, blast snow crystals apart and pack them into cohesive layers (wind slabs) in lee areas of NW winds. Today’s winds will exceed velocities the mountain has seen since our most recent storm on Saturday night and Sunday. These winds could find snow that is lingering from this last event to transport into the Ravines, adding to today’s snow stability issues. If we max out the forecasted snow totals, reaching 6”, I expect there will be numerous areas that will have natural avalanches. If we stay on the lower end of the forecasted snow totals, some locations will struggle to reach the Considerable rating today. Aside from what is going to change today, most areas in Tuckerman Ravine currently have wind slabs that fall within the Moderate rating. Justin and I spent time in the field yesterday evaluating the aftermath of Sunday’s avalanche cycle. At least four gullies avalanched in Huntington. In Tuckerman, Hillman’s Highway ran pretty big and the Bowl took the prize with a large avalanche that fractured from the Chute to the Lip. It is worth noting that no significant activity was observed in many of the other forecast areas in Tuckerman and they are pretty loaded up with wind slab. Some of these could get ripped out if we start having natural avalanches today.
Cold weather is working its way into the mountains with temperatures expected to drop to -20 F (-29 C) over night with winds exceeding 100 mph (160 kph). Tomorrow temperatures are forecasted to top out at -10 F (-23 C) and westerly winds will still be cranking between 65 and 85 mph (105 and 137 kph) making for prime ice cream headache conditions. Take this challenging winter weather into account when planning tomorrow’s outing.
- 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.
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856