Avalanche Advisory for Tuckerman and Huntington Ravines

 Posted: 8:52 a.m., Thursday, December 20, 2007

 Tuckerman Ravine has CONSIDERABLE, MODERATE and LOW avalanche danger
 today. Hillman's Highway, Left Gully, the Bowl, Headwall and Lip have
 Considerable avalanche danger. Natural avalanches are possible and
 human triggered avalanches are probable. Unstable slabs are probable.


 Be increasingly cautious in steeper terrain. Right Gully has Moderate
 avalanche danger. Natural avalanches are unlikely and human triggered
 avalanches are possible. Use caution in steeper terrain. All other
 forecast areas in Tuckerman Ravine have Low avalanche danger. Natural
 avalanches are very unlikely and human triggered avalanches are
 unlikely except in isolated pockets. Normal caution is advised.


 Huntington Ravine has CONSIDERABLE AND MODERATE avalanche danger
 today. The Escape Hatch, South Gully, O'Dell's, Pinnacle, and Central
 Gullies have Considerable avalanche danger. Natural avalanches are
 possible and human triggered avalanches are probable. Unstable slabs
 are probable. Be increasingly cautious in steeper terrain. Yale,
 Damnation, and North Gullies have Moderate avalanche danger. Natural
 avalanches are unlikely and human triggered avalanches are possible.


 Use caution in steeper terrain.


 Yet another snow event is upon us! Expectations for this weather maker
 have been all over the board during the last couple of days. Forecasts
 have gone from 3 (7.5cm) to 12 (30cm) and back to 4-8 (10-20) as the
 trough and system track moves around. As of 7am our accumulated snow
 and water equivalent data is fairly consistent between the manual snow
 plots on the Summit, at Hermit Lake and over at the Harvard Cabin. We
 received between 3.5-4 (9-10cm) of new snow with densities between
 7.7-8% for all locations. We will continue to get snow through the
 afternoon with an additional 2-4 (5-10cm) expected. This would give us
 between 7-8 (18-20cm) for the entire event. Snowfall through the
 evening has come in on S winds around 20mph (32 kph). Over the past
 hour the wind has shifted and is now coming from the SE as it slowly
 moves to an easterly direction for most of the day. Winds will stay
 light between 20-25mph (32-40 kph) for this avalanche advisory period
 which will keep loading light although densities are a bit below
 normal. With this said expect the most direct loading and cross
 loading on northern aspects with some cross loading on southerly
 aspects later in the day. Some deep-gullied east-facing slopes with
 sheltering buttresses like the Chute may have picked up some loading
 on last night's S winds. We know that snow accumulation will continue
 but an inch one way or the other wont be the absolute critical
 bulls-eye data as much as exactly what speeds wind will reach today.


 All forecasts are putting the higher summits up to 25 mph (40kph). If
 we begin to exceed this by as little as 5mph loading should pick up
 with our light density snow. So keep a very close eye on what SE to E
 winds are doing while youre in, or below, angled terrain today. Expect
 all areas to climb through their ratings as the day progresses and be
 prepared for some northerly aspects to be on the upper end of their
 definitions if we reach the maximum weather forecast parameters for
 precipitation and wind speed. As the Considerable rating says--Natural
 avalanches are possible.


 Winds are anticipated to stay from the E into Friday as high pressure
 drifts in and overtakes the region though Saturday before Sundays
 weather system moves in. With all this snow you thought you were
 dreaming and living in Utah, huh!?! Well back to reality youre a New
 Englander so here it comes--our beloved wintry mix and.....yup rain.


 Well get into all the nasty dreaded conversation about this system
 Friday night in the Weekend Update and the Saturday advisory.


 The John Sherburne Ski Trail is open with continuous snow from top to
 bottom, however this trail has also been hammered by the wind. THE
 LION HEAD WINTER ROUTE IS NOW OPEN. This is a steep and challenging
 route for mountaineers. Crampons, an ice axe and the ability to
 properly use this equipment are recommended for safe travel on this
 route.


 Please Remember:
 o It is impossible to accurately predict natural events, such as
 avalanches, in every instance. This Advisory is one tool to help you
 make your own decisions in avalanche terrain. It should be used along
 with safe travel techniques, snow stability assessments, an
 understanding of weather's effect on the snowpack, and proficiency in
 avalanche rescue.


 o You should obtain the latest weather forecast before heading into
 the mountains. Anticipate a changing avalanche danger when actual
 weather differs from the National Weather Service forecast.


 o For more information, contact the U.S. Forest Service Snow
 Rangers or the AMC at Pinkham Notch Visitor Center or Hermit Lake
 Shelters or the HMC caretaker at the Harvard Cabin. This advisory will
 expire at midnight.


 Christopher Joosen, Snow Ranger
 USDA Forest Service
 White Mountain National Forest