Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully and Hillmans’s Highway will have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. The Lobster Claw, Right Gully, Lower Snowfields and the Little Headwall all have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully, Pinnacle, Odell, and South will have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. North Gully, Damnation, Yale and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
If you haven’t already seen the pictures Jeff posted yesterday on our website please do so. These are a testament that a picture is worth a 1000 words in regards to how much snow we lost in our recent thaw. The result of several days of melt is a variety of left over snow fields that differ in size from the football field to the postage stamp bushwhack. How does today’s expected 3-5” (7.5-12.5cm) of snow effect this new situation? Well, all of these areas have similar icy bed surfaces that new snow will be challenged to bond with at the interface. Although current surfaces are textured and rough in most locales, the new snow falling with temperatures in the teens F will be cold enough to limit much adhesion. The true bulls-eye data today will be a combination of total snowfall, what aspect your slope is facing, its size, and the amount of anchors that exist. Today’s SW winds will bring new snow mostly into NE aspects. The obvious locations would usually be a watch out situation for the top of Odell, and South Gully in Huntington and the tops of The Chute, Left Gully, and Hillman’s in Tuckerman. However they are currently very broken up with multiple anchors in the form of bushes, rocks and Cliff walls. This will limit the problem compared to the same weather event under better conditions, but due to the poor bonding I would use caution on all steep slopes that receive newly loaded snow. The potential of a human triggered avalanche is possible in many areas albeit it a smaller slide than under traditional mid-winter conditions. With this said no matter what the size I would not want to be swept off my feet at the top of any gully right now as a full pin-ball environment exist pretty much everywhere. This hazard pertains to a fall on icy slopes as well. If you fall anywhere expect to gain speed quickly and hit earthly objects because clear run-outs just don’t exist.
The key points today and tonight:
1.**Snow pit stability tests will likely give you poor stability results in newly deposited windslab. This should give you a good heads up for potential hazards. But realize there will be great variability in triggering potential within the Moderate rating depending whether you go to large open slopes such as the Tuckerman Headwall or bushy small slopes like the top of South Gully.
2. **Although many bed surfaces are quite small 3-5” of new snow today with an additional 1-3” tonight will create new instabilities on the mountain. Precipitation associated with SW winds from 15-40mph, shifting to the W tonight, ramping to 90mph will give us an “upside down” snowpack with denser new slab over lighter unconsolidated snow in a variety of locations.
3. **Expect an increasing avalanche danger from Low, as of 7am today, through Moderate and perhaps towards CONSIDERABLE tonight. The Center Tuckerman Bowl followed by its outlying neighbors, the Chute and Lip should be the leaders in today’s instability and concern. Watch snow fall amounts, expect frequent sluffing on steep slopes and building up on mid-slope benches, and anticipate many areas to be at the upper end of the Moderate rating definition this afternoon. A greater potential for natural avalanches being possible before the overnight hinge on the snow intensity rates, if the forecasted snow amounts are exceeded, and more importantly exactly how fast winds become today and the timing of the shift to hold from the W. The later you are out today the more you will need to be wary of increasing danger.
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 7:23a.m. 1-16-2013. 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