This advisory expires at midnight, 4-13-2012
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 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
Finally a sunny day on the mountain! Today marks the first day without precipitation for the month of April. The summit has received 33” of snow since the 1st, of which 24” fell since last weekend. Once again the mountain is deciding when it’s over and when winter is still her fancy. Settlement of unstable slabs has been slow, but a trend towards stability has been occurring due to the diurnal warming and cooling. As on Wednesday, yesterday the Hermit Lake mercury climbed into the high 30’sF (3C) just after 3pm before falling below freezing again overnight. This has allowed a steady consolidation of slabs in Tuckerman, keeping the snow up on steep slopes with very little avalanche activity since the initial heavy accumulation on Monday. Above Hermit Lake, up to the Ravine rim, temperatures did get above freezing, but barely as you get to the upper reaches of avalanche terrain. Because of this expect more stable conditions down low than up in the traditional avalanche start zones, especially those less affected by the sun. Some examples of colder slab concerns are up high in the Chute, Left Headwall, as well small buttress shoulders in terrain that point to the north and are shadowed later in the day.
A number of aspects, particularly south facing slopes, are showing evidence of intense rollerballing or snowballing from periods of sun yesterday with low winds. I would expect this to intensify as we will likely see the warmest, sunniest day all week today. Strong lee S and SE facing slopes sheltered by the NW wind in the direct sun will get the warmest today, which does bring some concern of instability issues created by rapid warming. The last 2 days of warming are comforting so southern slopes will be able to handle some warming, but be wary of intense long-duration baking today. If your assessments determine you feel comfortable on these slopes I would consider getting on them in the first half of the day and giving them some room as heating intensifies. We are already exceeding the forecasted wind speeds today with current gusts hitting the 50mph mark from the NW. This will help keep a number of slopes cool, likely hanging on to cold slabs that are exposed to winds from the northwesterly direction such as high in Left gully, and the Chute.
To summarize, we have two very different avalanche issues today. We will be in the field assessing and posting any information we garner to the Weekend Update this afternoon. First, we have cold slabs up high and on some mid-elevation slopes that aren’t directly impacted by direct sun influence that will need your caution and evaluation. Stability will change as you travel due to the thickness of slabs, the differing age of surface slabs, the cooling effect of wind exposure, etc. Therefore anticipate variable problems and potential weaknesses reactive to you as the trigger. And second, we have the potential for excessive warming causing some wet slab issues on SE and S slopes like the Sluice and Lip area. Areas that are reasonable options to be in are the lower half of Hillman’s and Left Gully as long as there are not human triggers above you in more unstable snow. This can often be difficult to see and determine.
Falling ice hazard will begin increasing today and through the weekend. The Center Bowl and Lip area have numerous deep crevasses from earlier warm weather that is now being hidden by new snow. Expect all of these to be covered visibly by new snow, which makes for weak bridges that can collapse under your weight. You will not be able to assess this hazard safely because of their hidden nature and 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