Posted at 7:30 a.m. Wednesday 4/20/2011
Tuckerman Ravine has Low avalanche danger. Natural and human-triggered avalanches are unlikely but you’ll want to watch for unstable snow on isolated terrain features.
Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when using avalanche terrain in Huntington Ravine. A danger of falling ice exists and will persist until it all comes down.
Although the mountain has been hanging onto winter during the month of April it keeps us guessing what kind of mood she’s in, winter or spring, and today’s no different. Every time we melt a little snow we get a little snow. In the end we are losing more than we are gaining but the cold temperatures and freezing nights have made our losses quite slow. Today will be another example of the concept 1 step forward, 1.1 steps back. During the overnight the higher elevations received a minor shot of snow which recently began to change over to mixed precipitation. As the summit temperature steadily climbs today from the teens into the upper thirties F moisture will move from sleet to freezing rain to rain. Wind velocities are expected to shift from the SSE to the SW and increase from around 30 mph to 70 later today as the front hits the mountains. Forecasts are expecting around 0.5” (1.25cm) of QPF or expected melt water. This amount should be split between the frozen form and plain liquid. Any concern today is related to how precipitation will affect the snow already on the slopes that was deposited over the last couple of days. Generally, the existing new snow is easily recognized by its fresh white appearance against the old dirty background. These areas vary in size tremendously from a patchwork in some locales to larger coverage in spots like the narrows of the Lip or below the Headwall ice. Rising ambient temperatures yesterday and solar gain on many slopes rid new snow of most propagation potential. Rain later today may generate some sluffing particularly in the steepest pockets of snow, but any slab release is unlikely. Although we do believe slab avalanches are unlikely, a slightly deeper isolated pocket in a few strong lee areas with an E aspect may have resisted complete consolidation in Tuesday’s warmth. Some elastic energy may still be contained in these drier slabs beneath their upper portions that settled from the sun. These areas are quite isolated and their potential to avalanche is remote enough that they still fit within the Low rating, but it’s something to keep in mind as rain picks up later today. Temperatures will drop again tonight which should bring more snow to the mountains.
Old surfaces will remain pretty hard through the day making sliding falls a real concern. An ice ax and crampons are always important to travel safely in steep terrain and I would highly recommend them. You’ll also want to identify and avoid the waterfall hole in the Lip which has been partially obscured by new snow. The waterfall feeds a river under the floor of the ravine. Falling in there is bad, how bad? REALLY bad! Bad enough that if you were alive with significant injuries, you’d be a lucky individual. Rain and melting later today will begin to increase the water volume again in this area which has slowed a bit over the past 24 hours. I would be also be concerned about the flowing river in the streambed which most people use as the ski out of the Ravine. Increased water volume will begin to weaken and further erode the strength of the remaining snow bridges so use caution.
The Sherburne Ski Trail is bumped up for you mogul junkies. When it is frozen it is hateful. When it is soft it may make you smile. Watch for water ice, vegetation and the occasional rock poking through the snow. If your legs allow you can still make turns all the way to the parking lot!
- 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 or the AMC at the Pinkham Notch Visitor Center and Hermit Lake Shelters. 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