This advisory expires at midnight Saturday 2-04-2012
Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. The Lip and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecasted areas of Tuckerman have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Included in the Moderate rating for the first time this season is the Lobster Claw. The Lower Snowfields and Little Headwall remain not posted due to a general lack of snow. Forecasts for these areas will begin when conditions warrant.
All forecast areas of Huntington Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.
Another small snowfall should be keeping you on your toes today. While our avalanche forecaster friends in western states might chuckle at the idea that an inch of snow can create bona fide avalanche concerns, that’s the reality of Mt. Washington. Don’t let the amount of snow fool you into complacency. Yesterday the summit began recording light snow at about 3pm. This continued through the overnight, leaving about an inch (3cm) across the mountain by daybreak. Currently, the snowfall rate is around 1cm per hour with brief heavier bouts. How long this continues will play a role in how far up the danger scale we go today. Even if it were to stop snowing completely, 50-70mph (80-113kph) W winds this morning will be able to transport the freshly fallen and readily available snow into the ravines from elsewhere on the mountain. Late in the day winds will decrease into the 35-50mph range, but this should still be able to carry the light density snow (6-7%) into avalanche start zones. The weather trend for later today is for at least partially clearing skies and the diminishing winds already mentioned.
What this is adding up to is a situation in which avalanche danger is creeping upward this morning. In many areas, we expect to reach the upper end of the Moderate rating due to new wind loaded slabs. This rating defines human triggered avalanches as “possible” and naturally triggered avalanches as “unlikely”, but we want you to keep in mind the potential for natural avalanches as you travel around today. Not only is the trend for increasing instability due to ongoing loading, but it is also a Saturday morning with lots of people on the mountain and poor visibility. If you’re hit with an avalanche as you’re walking into the Bowl to “take a look around” or “check it out”, I’d bet you won’t care so much whether it was triggered naturally or by another person trying to find their way through the fog. Knowing the trigger will take second fiddle to wondering if anyone actually saw you get buried and assessing the extent of your injuries. In the areas we believe naturally triggered avalanches are most possible, we have posted a Considerable rating. If new snow continues to fall for longer than forecasted or adds up to more, expect other areas to surpass the Moderate rating and move into Considerable territory. Bear in mind that in order to get to adjacent areas with a Moderate rating, you may be crossing the runouts of these higher rated slide paths.
As you can see, the primary threat today is related to new snow and wind loading that is currently taking place. Second to this concern, there are older instability issues that you should also be aware of. Snow that came on the heels of Wednesday’s warm rain and mixed precip event was being blown about all day yesterday. Much of this was sluffing downhill and piling up onto various terrain features. In some areas it was blown into pockets of reactive, energetic slabs, and some of these were sitting on deep pools of graupel. Overall, this would have been enough to keep a lot of areas at a Moderate rating even if it weren’t currently snowing. Any avalanche activity today might very well step down into deeper layers creating a larger avalanche than you might expect from new snow alone.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856