This advisory expires at midnight Thursday 1-26-2012
Tuckerman and Huntington Ravines have Low avalanche danger today. Natural and human triggered avalanches are unlikely except in isolated features. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted. Recognize avalanche activity may occur within these areas before forecasts begin.
Conditions haven’t changed too much from 24 hours ago as clear overnight conditions and just a little snow have left the mountain looking pretty much like yesterday. Over the past 2 nights we have gone through a bit of diurnal recrystalization in our snowpack underneath the surface crust. Basically a strong temperature gradient in the snow from the rain event, dropping air temperature, and clear skies allowing for good radiation wave movement has “dried out” the snow under the porous crust. Grabbing this snow quickly it initially feels like dry powder. Under further examination it’s actually faceted crystals that morphed from the wet rounds they were 2 days ago. I mention all this because it means that the surface crust likely will not increase in strength, it may possibly get weaker making for difficult off trail movement without floatation. Snowshoes or skis will make life easier is most places. Use caution descending steep terrain and be ready for sudden posthole plunges through the crust. Snow stability-wise we have widespread Low danger with avalanches being unlikely, watch for some very small pockets (what Joe likes to call “pocket lint”) of new snow from yesterday in a few places.
As I mentioned yesterday ice climbers should anticipate the problem of “ice dams” which usually occur after a mid-winter rain or thaw. Freezing temperatures begin creating new ice at choke points which puts water flow under increasing pressure looking for a way out. Often this way out is your ice tool or crampon hole which can unleash an eruption of ice and water. This phenomenon has blown numerous ice climbers off their stance over the years. This hazard generally dissipates with time but can be persistent in isolated areas for many days and is unrecognizable beneath the surface.
The big news is another pre-weekend storm is upon us tonight and tomorrow. 5-8” (12.5-20cm) is forecasted for the mountains, but warm air will infiltrate during the event making precipitation more dense and heavier. Icing and sleet is almost assured in the surrounding valleys possibility making it to the rain form. We may be spared from some of this pain, but an inverted snowpack with heavy on lighter snow is probable. Anticipate an increasing avalanche trend late tonight and into daylight tomorrow and cross your fingers for quiet snow on the landscape and not like some kid hucking gravel on a metal roof.
The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail had decent coverage, but nothing erodes snow faster than a rainy and foggy night. I expect it will be quite icy by the end of the day with numerous exposed rocks.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856