Posted 8:30 a.m., Sunday, March 20, 2011
Tuckerman and Huntington Ravines have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
Today’s weather will start spring off on the right foot. Sunny skies, relatively comfortable temperatures and light winds will make you happy that you had today free and chose to be in the mountains. Climbers and mountaineers have an abundance of good options for their activities today, while skiers and snowboarders will have to be a bit picky about where they travel. Balancing the desire to ski soft snow with the reality that isolated areas of unstable snow exist along with lots of crust will be the primary challenge this crowd will need to manage. Yesterday’s weather brought 1″ (2.5 cm) of new snow to the Summit with slightly more at Hermit Lake. WNW winds gently blew this small amount of snow into lee areas creating a band of soft slab in the Headwall through the Sluice in Tuckerman Ravine. Just as the clouds were lifting, we observed three human triggered avalanches in this band of soft slab. One was in the Sluice, one in the Lip and the other was a pocket between these two areas. They were all relatively small but a great reminder that safe travel and on-going stability assessments are critical, even under a Low rating. Over in Huntington Ravine, some climbers recognized a pocket of unstable snow on the top of Diagonal. After poking and prodding it they were able to trigger an approximately 10′ x 10′ slab that ran down the gully and onto the Fan. Based on the light amount of accumulation we received yesterday, the size and distribution of new wind slab remains on the small side; however, it is critical that you realize that isolated areas of unstable snow exist. These are easily avoided with good route finding skills. If you opt to venture onto new wind slab you may trigger an avalanche. While the size of these has proven to be on the small side, consider the consequences. Are you going to get swept of a cliff? Will a slip result in a high speed sliding fall on the crust? Are there rocks in your run-out? The majority of the new snow is in the Headwall, Lip and Sluice in Tuckerman. It is a band that goes across this area with old surface above and below and in places, in the middle of this band. You can also find smaller pockets in lee areas of WNW winds including the top of Damnation and the top of South in Huntington. As I mentioned, skiers and snowboarders will be tempted to stay on new wind deposited snow because the icy crust isn’t any fun. If you do, make sure you take the time to check the stability of this new snow and consider the best way to manage the hazard.
Sunny skies and warm temperatures will give us some hope for softening conditions on south aspects. Until this occurs, expect very icy conditions to persist that make the potential for long sliding falls real. Crampons and an ice axe are needed to travel safely on the icy surface. If things do soften up today, expect them to lock right up as soon as they go into the shadows. It looks like we will be getting about 2-4″ (5 to 10 cm) of new snow tomorrow with another 1-3″ (2.5 to 7.6 cm) tomorrow night. Winds will be shifting from the SSW to the W and increasing. Expect increasing avalanche danger tomorrow as a result of this weather.
- 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.
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856