This advisory expires at midnight, Saturday 4-14-2012
Tuckerman Ravine has 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 to identify features of concern. The Lower Snowfields and Right Gully have Low avalanche danger. The Lobster Claw and the Little Headwall are not posted due to lack of snow. Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when using avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down
Let’s get right into today’s hazards for Tuckerman Ravine.
AVALANCHES: We spent the day in the field yesterday and our predictions were right on the money. Cold slabs harboring instabilities exist in many of the upper elevations of the Ravine. The areas we are most concerned about exist from the Left Center Headwall through the upper Chute to the south. Other isolated cold instabilities can be found in the Lip region and more prominently in the Chute variations, the top of Left Gully and the top of Hillman’s. The weak layer in most areas is a layer of graupel (little snow ball bearings) of varying thicknesses. This was the failure layer in several Extended Column Tests with results in the single numbers indicating areas of unstable snow. Cold snow instabilities will be the primary avalanche issue this morning, but as the day wears on intense warming should affect all aspects as winds slacken and summit temperatures move into the thirties F. Our local valleys will see temperatures into the 70’s F. What this translates into is some wet slab issues later today. South facing slopes will get the warmest today, but have already been through some heating over the last couple of days. Therefore they should be able to handle today’s warming a little better than other aspects that still possess cold slabs. As solar gain increases there will likely be a period trending towards increasing stability, however eventually may turn back in the other direction as the sun bakes out snow cohesiveness. I believe “Moderate” addresses the issues today better than Low or Considerable, but if slabs heat up enough and thinner portions lose strength the danger may be on the upper end of the Moderate rating. Although natural slab avalanches are unlikely I wouldn’t say they’re impossible, particularly in the steepest of terrain. I would expect sluffing snow to occur, especially by skiers late in the day. If this happens from up high, the entrained snow could have enough impact to trigger a lower slab. The last avalanche concern relates to the number of triggers that may be out in the terrain today considering it’s a sunny Saturday. Therefore expect numerous potential weaknesses to be tested by skiers, riders, and mountaineers. Be very cautious about what slopes you are under with instabilities and people above. Realize avalanches can run down the length of the Ravine floor so sledding, sliding, hanging out, etc. under these avalanche paths puts you at risk of burial.
FALLING ICE: We saw a number of ice chunks fall yesterday from the Headwall. This should increase today with the heat hitting the highest point since last month’s record heat wave. The greatest icefall hazard exists from the Center Headwall and the Sluice ice above Lunch Rocks. Both these areas pummel Lunch Rocks with ice, so sitting there should be avoided. Many injuries and some fatalities have occurred in this area. Icefall is one of the most difficult hazards to predict and time, but realize it can happen fast and can be enormous, shattering ice in multiple directions. Sitting and hanging out down to the left on the opposite side of the Ravine, out of avalanche paths, is a safer option to avoid ice.
CREVASSES AND HOLES: The Center Bowl and Lip area have numerous deep crevasses from earlier warm weather that is now being hidden by new snow. You will not be able to assess this hazard safely because of their hidden nature. Many of these deep slots possess weak snow bridges that can collapse under your weight. Because the consequences of falling into one of these crevasses are severe we recommend avoiding this area entirely. Hikers should not use Tuckerman Ravine to access the alpine zone and the summit of Mt. Washington. Also, you should not descend down from these areas into the Ravine.
- 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 Mount Washington Volunteer Ski Patrol, and the AMC at Pinkham Notch or Hermit Lake. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service, White Mountain National Forest