Posted 7:23a.m., Tuesday, February 1, 2011
Tuckerman Ravine: The Sluice, Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway will have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, Right Gully, and Lower Snowfields will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine: South, O’dell, Pinnacle and Central gullies will have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The Escape Hatch, Yale, Damnation and North gullies will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
All I’ve heard for the past few days is “the storm,” “the storm.” Settle down everyone! It is true that we’ll be seeing some decent snowfall tomorrow and upslope snow showers are expected to continue into Thursday. And then there’s the system that appears to be tracking our way for Saturday…Oh boy! Instead of getting too far ahead of ourselves let’s not forget that we currently have instabilities that are worthy of mention on their own. Yesterday we had essentially all of Tuckerman rated at Considerable and all of Huntington posted at Moderate. The conditions that drove these ratings still exist for the most part although the threat of naturally-triggered avalanches has temporarily subsided since winds dropped off and blowing snow no longer fills the air. This will change later in the day. The layers of windslab that were created over the past couple of days are made of what started as light density snow. As the slab was laid down in wind-sheltered areas it topped loose unconsolidated powder with some of the lowest densities we’ve seen this season. The combination of the two layers created a decent avalanche cycle though most of the debris was soon wiped out by strong winds. What remained in place is today’s primary concern. Temperatures dipped down below 0F (-18C) Sunday at midday and have only recently moved back into the positive numbers. Arctic temperatures do a fine job of preserving energy stored in the snowpack and instabilities can persist far longer under colder temps. Up to 3in (7.5cm) of new snow today will add additional load and therefore stress to these weaknesses. The day’s wind is expected to shift from the W to the SW with speeds at the lower end of what’s needed for measureable wind transport. The National Weather Service is calling for slightly stronger winds and if we meet their forecasted speeds of 40mph (64kph) with higher gusts we could see areas pushing the upper end of their forecasted ratings by late in the day. If the wind stays just a bit lower loading will be minimized and the stress applied to the slopes by the new snow should be largely uniform.
In Tuckerman, the areas of most concern are the Sluice, Lip, Center Bowl and Hillman’s Highway. All of these areas received loading through the morning yesterday and they’re also well positioned for additional loading if the winds reach the upper end of their forecasted speeds. In Huntington it’s the bottom of South Gully and above the ice bulge in Central that concern me most. South had more loading occurring yesterday morning than anywhere else in that ravine and Central had avalanched but only the section below the ice bulge. Plenty of hangfire remains in place above. Scattered around both ravines you will find a fair amount of old surface that was uncovered by recent wind or avalanche activity. It provides the most stable travel option so watch for old tracks and a difference in surface texture as clues to where it’s exposed prior to new snowfall.
- 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.
Justin Preisendorfer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856