Posted 8:45am Friday 4-22-2011
Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, The Lip, Center Bowl, and the Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist so it is important to evaluate snow and terrain carefully. The Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely but you’ll want to watch for unstable snow on isolated terrain features.
Huntington Ravine is under a “General Advisory”. You will need to do your own snow stability assessments when using avalanche terrain in Huntington Ravine. A danger of falling ice exists and will persist until it all comes down.
Spring, winter, spring….winter, and back to spring again. Ah… “spring” in the high Presidential mountains continues to be what many generations of New Englanders have witnessed, unpredictable fickleness. Blowing snow, graupel-ball bearing snow, and upslope energy on Thursday have given us new cold slabs in Tuckerman, ergo the Moderate avalanche danger rating for many areas. New snow reported on the summit and Hermit Lake was quite light at under 2”, but very high winds from the West loaded an impressive amount of snow into East facing slopes. New snow blankets the entire main bowl from the Chute over through the Sluice. Some isolated old surface is showing, but new slab dominates the terrain. How deep are those slabs? Well, we’re not sure, but Jeff and I will spend some time this morning figuring that out when we get into the field. Generally slabs should be fairly thin due to the limited new snow accumulations, but I would expect the thickest slabs to be in the most protected lee areas, high under the Headwall ice and under the Lip. Because of this, coupled with a mostly hidden main waterfall hole these two areas are the primary locations of concern. A cold start to the morning will allow new snow to propagate a fracture until it begins going through some settlement as the day progresses and the sun delivers some intense solar radiation into the Ravine. A clear day is forecasted today with diminishing winds which will allow some fairly rapid change in the new cold snow by midday heating. Could we see some wet sluffing and sun rollers today? Yes probably. Will we see a natural wet slab avalanche on S and SE facing aspects? It is unlikely, but not completely impossible. Snow stability issues this morning should be a totally different animal compared to late in the day as cold dry slabs transition to heavier spring mashed potatoes. Stability issues will change, but all will fall within the Moderate rating with a slow trend towards being more stable at the end of the day than this morning.
Besides the aforementioned avalanche concerns we have a very hard, cold, icy bed surface in all areas which currently are either showing or hidden under the new snow. Areas posted at Low today have the most widespread icy surfaces. In steep terrain, this icy crust will make slips and falls very dangerous. It will be incredibly difficult to stop yourself once you gain a little speed. Do yourself a favor; bring an ice axe and crampons for climbing steep slopes. Being skilled in their use is also very important, as is paying attention to what might be in your fall line and choosing routes with fewer objective hazards. It is possible that these surfaces will soften, but be weary about the some icy layer nearby that may lie under some thin new snow that the sun isn’t getting to. We will certainly be wearing, or at least carrying, crampons today. Lastly, I would stay well away from the main waterfall hole near the Lip proper which opened last week and has been somewhat hidden by new snow and ice over the last few days. Falling in here…. well, it is not good. Frankly it is very very bad. Give it plenty of berth and distance.
Today is beautiful, but tomorrow…that’s another story. Rain is anticipated for the day after a start of mixed precipitation and freezing rain. We’ll have more on this in the weekend update later this afternoon and of course in tomorrow’s avalanche advisory.
- 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.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856