This advisory expires at 12:00 midnight.
Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger today. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Natural avalanches are possible and human triggered avalanches are likely. The only exception to this rating is the Little Headwall, which has Moderate avalanche danger. In this location, natural avalanches are unlikely and human triggered avalanches are possible.
AVALANCHE PROBLEM: Wind slab or storm slab? Who cares what you call it today? What’s really important is that we are starting with an elevated level of avalanche danger, and this will be increasing throughout today due to wind loading. Expect danger to be pushing the upper end of the Considerable rating, moving in the direction of High avalanche danger. This is the case for all forecast areas, although the greatest potential for us to exceed the Considerable rating is in the Lip and Center Bowl of Tuckerman. Other areas on the flanks of the ravines will still sit solidly in Considerable danger. In all areas, avalanche paths have been growing large in recent weeks, and have the ability to push avalanche debris well down into low-angled terrain. You don’t need to be on a steep slope to be at risk!
WEATHER: This has been a great stretch of weather up on the mountain for snow enthusiasts. In the last four days, the summit has reported 21.2” (54cm) of new snow, which has pushed us up over the average total for the month of March. The depth of snow in the woods at Hermit Lake has increased from 111cm to 160cm over the last two weeks.
We are starting today with a little more snow in the air than we expected due to an arctic front passing through the region. Currently the snowfall rate is about 1cm per hour. Keep your eyes on total accumulations. Expect very strong winds above treeline today, ranging from 50-70mph (80-113kph). Following the passage of the front, snowfall should taper, temperatures will continue to plummet, and high pressure may begin to clear the clouds off the mountain. Personally, I wouldn’t recommend waiting around for the end of the day in hopes of getting some better weather up high.
SNOWPACK: Wind loading today is the driving force behind the avalanche danger. Although winds were fairly strong yesterday, they weren’t able to remove all the snow from above treeline and they obviously couldn’t have already transported the new snow that’s currently falling. From what we’ve historically seen, 50-70mph NW winds with an ample supply of snow to draw from can create very deep slabs in the ravines, and produce some large avalanches. Densities of the recent snow are such that I’d expect large slabs to be able to build before releasing.
While we have seen evidence of recent avalanche activity (e.g. Left Gully sliding to the opposite side of the floor of Tuckerman and Dodge’s pushing into the approach path to Hillman’s), we have also seen evidence of significant reloading of slide paths. Figuring out which weak layer to be concerned with should be an academic exercise today, rather than one with meaningful implications on your travel routes. You’ll do a lot better today to identify avalanche terrain and do your best to avoid it.
- 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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin.
- Posted 8:45a.m. 03-23-2014. A new advisory will be issued tomorrow.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856