Expires at Midnight Saturday 2-11-2012
Tuckerman and Huntington Ravines 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. Forecasts for these locations will begin when conditions warrant.
Today’s avalanche forecast is mostly based on the expected light snowfall today and an increasing wind. New snow, which just started over the past hour, is forecasted to give the higher summits 1-2” (2.5-5cm) by later this afternoon. Light winds this morning from the W will shift to the NW and increase with gusts to 40 mph (65kph) late in the day. If this weather maker plays out as forecasted, the initial new snow should lay as a thin blanket across the mountain due to the very low wind speeds (8mph/14kph) this morning. As winds increase light slabs may build over this loose unconsolidated layer that would possibly act as the new weak layer of concern. Any new thin slabs would most likely be found near the tops of gullies and snow fields, in the strong lee of both ravines, due to the relatively gentle winds for Washington. For most locations, particularly N and NE facing aspects, this process and concern will take most of the day. Therefore areas that were posted at Low yesterday, like all of Huntington, will remain there through most of the morning until winds pick up and start moving areas into Moderate danger. Areas in the lee of WNW and NW winds will have new slab concerns first, with others trailing behind.
In Tuckerman, high in the Right Gully, Sluice, Lip, and under the Headwall ice will build slabs before areas like Hillman’s Highway. In Huntington, Yale, Central, Pinnacle, and Odell will develop slabs before South Gully and the Escape Hatch. This entire issue today all depends once again on EXACTLY how much snow we get and what the winds actually increase to this afternoon. Our forecaster’s discussion this morning highlighted how just a small amount of differences could substantially change the reality on the ground. A half an inch (1.25cm) with winds to 30mph (48kph) will be very different from 2.5” (6.25cm) and 45mph (72kph) velocities. On the low end, areas will struggle to achieve the Moderate rating. On the upper end, or surpassing the weather forecasts slightly, may push a number of areas to the upper end of the Moderate rating. Watch the accumulations closely, think ahead to where you might be this afternoon and consider your bail out options. The slight nuances will make a difference today. Before these new snow issues came into the picture our last lingering concern yesterday was some slabs in the Chute, Center Bowl and Lip of Tuckerman. Although these were barely above “Low” we did have some concern for a large impact ripping out a slab deposited from earlier in the week. This concern exists today with any large sluffs, or perhaps a slab avalanche, which may step down creating a bigger moving mass of snow.
As this weather system moves out late in the day winds will increase overnight to 70mph (112kph) associated with a drop in the mercury. Temperatures below zero will start overnight and continue to fall all day on Sunday and into Monday morning. Expect full on arctic conditions tomorrow with high winds and negative numbers in the teens F (-26C). Finally, reports from the people who have tried to get into an out of the Little Headwall indicate that the slope itself is reasonably good skiing, but getting in and out of the area makes the experience not a worthwhile endeavor.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856