This Advisory expires tonight at midnight.
Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation and conservative decision making is essential. Some areas are not yet posted due to the overall lack of snow. These include the Lobster Claw, the Lower Snowfields, and the Little Headwall in Tuckerman and the Escape Hatch in Huntington. Forecasts for these locations will begin when conditions warrant.
We started yesterday with some interesting mid-elevational warm bands encompassing both Ravines. Temperatures quickly spiked from the freezing point around 5 am to 35F (2C) and back to freezing all within a 3-4 hour window. As this occurred light precipitation fell, vacillating back and forth between wet snow and light rain eventually adding up to 2.7” (7cm) with a water equivalent of 0.42” (10mm) on the summit. The periods of freezing rain and mixed precip account for the high water content. Temperatures dropped, changing all new precipitation to dry snow and limiting the development of crust at the mid-elevations. Winds were reluctant to wrap from the SE to the W as forecasted, but did so eventually late in the day and then raged like a tempest during the overnight. Winds peaked between 8 and 11pm Friday night with a maximum of 110mph (176kph) from the W. Velocities have diminished, currently gusting to about 70 mph, and are slowly moving from the W to the NW. Speeds are expected to drop just a bit more along with the temperatures which are expected to fall to -10F (-24C) through the day.
As winds finally shifted and increased last night large volumes of snow were delivered by the “Western Express” hitting the century mark over a 4 hour period. Undoubtedly, some terrain in the lee saw some natural avalanche activity, others saw some scouring, and some saw both. Since midnight winds have diminished but continue to transport snow from the alpine zone into the Ravines. This is in addition to upslope snow showers that are mixing into our loading situation. Because the Ravines are engulfed in clouds and blowing snow we cannot confirm what has avalanched, what is still loaded, and what has become scoured. With new additional loading through at least the morning, we cannot rule out the possibility of natural avalanche activity hence the “Considerable” rating. Additionally, I believe a fair degree of spatial variability exists due to the blend of scouring and loading that has occurred. The rating definition for human triggers being “likely” takes second fiddle to our unease for natural avalanches that may come from above. You may be on hard old surface down low on your route with no chance of triggering an avalanche, but above you in a strong lee slope loading may release a natural avalanche. This issue is compounded by low visibility this morning not allowing you to see the entire route. The dynamic conditions that have transpired over the last 24 hours have clearly created some unknowns, so it will behoove you to be conservative with your choices until new facts come into play. Once clearing occurs we may be able to ascertain more of the conditions the Ravines are currently holding secret.
Travel above treeline over the next couple of days will be rugged as full conditions will prevail. Winds will continue to drop a bit into tomorrow but temperatures will fall to about -20F by Sunday morning. Above treeline travel will need a high attention to detail and preparedness. The best arctic mountaineering equipment is necessary for safe travel. Mittens, goggles, facemasks, excellent double boots, insulated water bottles, insulated over parka, etc. are all items we have seen lacking in past accidents. As in avalanche terrain, be conservative and remember if you make the summit you’re only half way home.
- 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.Posted 8:20am. 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