Posted 8:58, Thursday March 10, 2011
Tuckerman Ravine has CONSIDERABLE AND MODERATE avalanche danger. The Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, Right Gully, Sluice, and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger.
Huntington Ravine has CONSIDERABLE AND MODERATE avalanche danger. Central, Pinnacle, Odell, South, and the Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation, and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
After a beautiful sunny day on Wednesday another weather maker is upon us with snow, a New England wintry mix, and rain. Between 1 and 2am this morning light snow began on the summit giving them only about a half an inch by 7am with winds out of the south between 50 and 60mph. Down at the base of the ravines we have received approximately 2” (5cm) when blending the Hermit Lake and Harvard snow plots. Precipitation intensity should continue at the current rate which will give us in the area of 4” (10cm), which would exceed the forecast. Temperatures will slowly rise increasing new snowfall density, eventually changing over to a wintry mix in avalanche start zones around the 5000ft level later this afternoon. After dark it will continue getting warmer making its way towards rain tonight. Today’s weather will load slabs of increasing density predominately on N facing aspects due to winds from the S between 45-55mph, rising temperature, and new snow. As the mercury rises it will generate a heavier slab over lighter ones underneath increasing stress and strain within the newly forming upper snowpack. This scenario will be playing out on a hard slick crust from the last storm that ended in rain and ice pellets. Surfaces are not quite as slick as they can get on Mount Washington, but the bonding between the crust and the new snow should be poor. New snow began this morning with temperatures in the teens which created some low density snow. On a number of aspects this snow likely was blown off the crust, but it undoubtedly survived in numerous locations protected from direct S winds.
All of these above issues will create an increasing avalanche danger through the day raising our concerns for natural avalanche activity being possible, hence the Considerable rating in a majority of forecast areas. If we exceed the snow total forecast of 3” (7.5cm) and move closer towards 4” (10cm) followed by mixed precipitation you can expect slopes pointing due N to being pushing the upper end of the Considerable rating. The start zones in Hillman’s Highway and Left Gully in Tuckerman and the Escape Hatch, South, and Odell gullies in Huntington have some significant N facing terrain and are the focused gullies of concern today. Although some other locations carry the Considerable forecast as well many of these have a predominately E facing component to their slopes causing them to be cross loaded instead of receiving direct snow deposition. This will have them linger behind the aforementioned locations in terms of developing instabilities. All of these problems will be slowly progressing through the day so your risk will be greater this afternoon than later this morning. Obviously how much actual snow we get today will be critical whether or not natural avalanches occur today. If the snow backs off from this morning’s rate and creeps along giving us just a few inches the ratings will come to fruition, but barely. Be aware of snow totals today because an additional inch or two will make all the difference. Once rain begins you can expect the avalanche danger to rise quickly although this card isn’t expected to be played until the overnight.
Tomorrow won’t be pretty. Rain…heavy at times. UHG!- Here we go again. It is quite clear at this point that it will rain all the way to the summits tomorrow causing an elevated avalanche danger. If you like to get wet and cold and plan on being in the mountains on Friday be sure to check the avalanche advisory before venturing into angled terrain
- 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