Avalanche Advisory for Thursday, December 18, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Sluice, Lip, Center Bowl, Chute and Left Gully have High avalanche danger.  Very dangerous avalanche conditions exist.  Natural avalanches are likely and human triggered avalanches are very likely. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.  Natural avalanches are possible and human triggered avalanches are likely.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. Central, Pinnacle, and Odell Gullies have High avalanche danger.  Very dangerous avalanche conditions exist.  Natural avalanches are likely and human triggered avalanches are very likely. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.  Natural avalanches are possible and human triggered avalanches are likely

AVALANCHE PROBLEM: Wind Slab today will create widespread avalanche hazard in both ravines. A strong northwest wind will continue to grow in velocity and with it, Wind Slab will grow in size. Areas rated High are likely to avalanche naturally at some point today due to the weak layer, comprised of yesterday’s new snow. Very dangerous avalanche conditions will exist today and travel in avalanche terrain or onto the floor of either Ravine is not recommended. This includes the area around Lunch Rocks, the Tuckerman Ravine trail and the Fan in Huntington Ravine. Our avalanche paths survived the recent warmup and are large enough to generate avalanches which could easily bury and kill a person. Some forecast area avalanche tracks are certainly less developed but are still capable of producing a dangerous avalanche.

WEATHER: Forecasted NW wind with speeds today in the 50 mph range, gusting to 85 mph, will be ideal for loading our slopes and gullies with snow. Snow will taper to snow showers this afternoon and will continue to add to the snow available for wind loading. Visibility will be strongly diminished through most of the day due to this classic weather pattern that frequently comes with the passage of a Low pressure system. Freezing fog will further hamper visibility through the day. Some clearing tomorrow will allow for snowpack assessment, but anticipate elevated avalanche danger tomorrow as well.

SNOWPACK: Yesterday was a good example of how important it is to stay on your toes and make decisions based on new information from Mother Nature.  We had an uneasy feeling about the weather forecasts, hence the discussions about an increasing avalanche danger if weather differs from forecasts.  Sure enough, by 1045 am Wednesday morning between 6-7” (15-18cm) had fallen from a SE direction, more than the entire 24 hour forecast.  As snow continued, adding up to 9.5” (24cm) of 9.9% density by midnight, the avalanche forecast remained accurate because the forecasted wind increase occur remaining in the teens mph.  This is all changing as current weather screams avalanches!  Since midnight snow has continued and is expected to give us another 2-4”, giving the alpine zones about a foot (30cm) for the ramping NW winds to transport.  Overnight NNW wind speeds in the 40’s began to move snow into the ravine, but over the past several hours gusts are into the 60’s from the NW.  Velocities are expected to increase to 80-85 mph today which will move large volumes of snow into eastern aspects.  This is a fairly straight forward, watch out situation.  We expect natural avalanche activity in our forecast areas to be between possible and likely.  Building winds should develop slabs of increasing density over the low density layer from yesterday afternoon.  Slabs will develop with cold snow that fell between temperatures of 25 and 28F Wednesday morning to the current of 12F.  Certainly a day to give the terrain a wide berth. We’ll stay out of the terrain today, but look forward to assessing conditions tomorrow if the hazard decreases for a good Weekend update Friday afternoon on www.mountwashingtonavalanchecenter.org

Please Remember:

  • 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 7:45 a.m. December 18, 2014. A new advisory will be issued tomorrow.

Frank Carus/Christopher Joosen, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-12-18