This advisory expires at midnight, Thursday 2-23-2012
Tuckerman Ravine will have CONSIDERABLE and MODERATE avalanche danger today. The Sluice, Lip, Center Bowl, and Chute will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, Right Gully, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow, but are getting closer. Forecasts for these locations will begin when conditions warrant.
Huntington Ravine will have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Over the last 24 hours the summit picked up 1.6” (4cm) of new snow delivered on W winds peaking at 77mph last night around 10pm. Today’s avalanche ratings are taking this accumulation and the 2-3” (5-7.5cm) forecasted for today into account. Light snow recently began right on schedule with the 2-3” expected mostly to fall this morning and in the early afternoon. As this system gets ushered off to the East, winds will accelerate, gusting over 80mph later today. As all of this occurs a wind shift will also transpire, moving from a SW direction early this morning to the NW. If this forecast comes to fruition new snow will be deposited in all our primary avalanche start zones in both ravines as winds walk a full 90 degrees on the compass rose. This new loading will commence first with those aspects having a north facing component, moving through eastern aspects during the late morning, and then finishing with southern faces later today when winds move to the NW. I would expect gullies facing towards the E and SE, such as the Center Bowl, Lip, and Sluice in Tuckerman and Odell, Pinnacle, Central, and Yale in Huntington to move to the upper end of their rating definitions if we end up on the high side of the expected snow totals and wind velocities. As this occurs a number of Moderate danger forecasted areas will increase their potential for natural avalanches so we maybe running the fine line between the words “unlikely” and “possible” later today. A slow transition from the end of one danger rating into the beginning of the next can be hazy so evaluate stability continuously today and be ready for an increasing avalanche danger. In steep locations I would expect sluffing to occur beginning later this morning building up snow below sections of water ice such as under the Headwall ice in Tuckerman and the ice in Odell and Pinnacle gullies in Huntington.
Tomorrow the higher elevations will get more snow while the valleys likely deal with a lovely mix of snow and rain. On Mount Washington and the rest of the Presidentials the potential for some respectable snow accumulations is becoming more certain with each weather model run. The latest data is expecting 6-8” (15-20cm) with some locations getting upwards of 10” (25cm) associated with a SE and S wind. Total melted water from precipitation over the next 48 hours should total between 0.8 and 1.0” (2 and 2.5cm). Expect an increasing avalanche danger with a good chance for some areas posted at “High”. At this point, with the forecasted snow and the drop in temperatures expect a number of lingering avalanche problems into the weekend. In addition, until widespread snow covers the hard icy surfaces expect some challenging travel in steep terrain without traction devices for your feet. Crampons, an ice ax and good self arrest skills are necessary for safe travel. Many fall lines are peppered with rocks, brush and other unfortunate body stoppers so consider your travel routes well and think about who might fall above you this busy holiday week.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856