Avalanche Advisory for Thursday, 03-29-2012

This advisory expires at midnight, Thursday 3-29-2012

Tuckerman Ravine will have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.  Heightened avalanche conditions exist on specific terrain features.  Evaluate snow and terrain carefully to identify features of concern.  The Lobster Claw, Right Gully, the Lower Snowfields, and the Little Headwall are not posted due to lack of snow.

Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when using avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

As of Wednesday morning at dawn the summit picked up a quick 3.3” (8.4cm) of snow during the previous 8 hours.  There was little snow movement down into the Ravine due to the light to moderate winds through mid afternoon.  Later, wind speeds ramped up, gusting into the 60’s mph (96kph), with a 24 hour maximum of 70mph (112kph) around 7pm.  This 6 hour high velocity window moved some snow down into the lee of W winds before subsiding again over the past 9 hours, while shifting from the W to the NW.  Light snow showers have been falling since about 2am and are expected to continue through the morning.  This precipitation should taper to snow showers giving us an additional 2” (5cm) of snow today.  While this falls wind will increase from the current of 35mph (56kph) to over 60mph (96kph) later today, moving any new snow mostly in lee areas of NW winds.  Today’s “Moderate” avalanche forecast is due to loading that occurred around dark last night and in anticipation of additional snow today along with an increasing NW wind.  Some patches and pockets of new snow have already filled in some of the irregular surface texture allowing for a smoother bed surface for future loading.  If today’s full snow loading potential does play out there will still be extensive old hard surfaces in Tuckerman.  In reality hard icy conditions will prevail as the majority of coverage compared to new snow.  Therefore, be ready for both very hard old surfaces and unstable cold snow.  New snow issues should develop particularly near the horizon of prominent gullies or under strong terrain features of W and NW winds from the Sluice over to through the Headwall.   Clouds and fog will obstruct quality views making good assessments of the terrain from a distance difficult.  Because of this you’ll need to visualize the spatial variability, or differences, of snow conditions.  Poor visibility should continue until clearing conditions occur tomorrow.  We will spend time in the field Friday morning to have the best information for the weekend.  Looking ahead to the next couple of days, cold conditions will continue with the summit potentially breaking the March 30th low temperature record 24 hours from now.  This, after smashing the high records last week, ah…the ying and yang of mountain weather.  If you can’t convince yourself to love the diversity it will drive you crazy, I guarantee it.

Due to frozen surface conditions long sliding falls are a significant threat to all mountain travelers in angled terrain. The slick icy surface will allow for rapid acceleration down slope potentially sending you into numerous obstacles below you.  Exposed rocks, chunks of ice, trees, and moguls that feel like rocks all make the sliding fall potential much more hazardous. An ice axe, full 10-12 point crampons, and real mountaineering boots are absolutely critical for climbing in these conditions safely.  Because the current surface conditions have made most steep slopes “no fall” territory the experience and skills to use this equipment is imperative.  If you have to rent them I would think twice.

Undermined snow and crevasses have emerged in recent weeks. Overall, the worst of the crevasses can be found in the Sluice, through the Lip and into the Center Headwall. Undermined snow can be found in many locations, including Hillman’s and Left Gully. Cold temperatures this week have strengthened snow in relation to these issues, but you’ll still want to know where they are so you can avoid them. Realize falling into an open crevasse from above is potentially more likely due to the icy surface conditions and fog than when it’s soft and clear.  We recommend climbing up what you plan to descend so you can learn about these hazards.

Falling ice should remain in the back of your mind as well. Below-freezing temperatures generally pose less risk than very warm days, but the freeze-thaw cycles can work to dislodge rock and ice from steep terrain, sending it down onto anyone or anything in the runout.

The Harvard Cabin at the base of Huntington Ravine will be closing for the season this weekend.  Saturday night is the final evening for overnight accommodations.  The Sherburne Ski Trail, full of icy bumps, is open about 1/3 of the way down.  Cross over to the hiking trail at the closure rope.  There is a lot of newly frozen water ice on the hiking trails. Traction devices on your feet will be very helpful.

 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.  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

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