Avalanche Advisory for Sunday 12-29-2013

This advisory expires today at midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. Lobster Claw, Right Gully, Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.  These Low areas are mostly a bushy rocky landscape lacking any sizable slopes for unstable slabs or traveling.

Huntington Ravine has MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM:  Today we continue to have a combined avalanche problem of left over Storm Slabs and Wind Slabs.  Although many bed surfaces in our terrain are still broken up by rock cliffs, turf, and ice bulges limiting their size they are large enough to harbor unstable slabs sensitive to a human trigger.  This was tested last night when 2 hikers came down from summiting Washington and traveled into “the Lip” at dark and triggered an avalanche carrying them down to the floor of the Tuckerman Ravine.  They miraculously survived but sustained injuries requiring rescue during the overnight.  Through history there have been a number of very lucky people in the world, they are now 2 more of them.  More information will be posted in our accidents page later today.  Variability in our snowpack stability is still substantial.  In many areas you will find old hard surfaces such as down low in Left Gully, Central Gully and Odell while in many others such as the Sluice, Center Bowl and the Chute you will find unstable wind slabs with poor to fair strength.  If you transition from stable old surfaces to new slab of varying depth, I would be very skeptical about their strength.  A potential initial failure in their weaker thin areas may rip into deeper sections.  These problems will be complicated by the Winter Storm moving into the mountains this afternoon.

WEATHER: Winds will shift to the SW and decrease to 25-35+mph today in prelude to a WINTER STORM moving into the region later this afternoon.  The current NWS issued WARNING begins at 4pm this afternoon.   We expect 4-8″ of new snow before it wraps up Monday morning. Winds will shift briefly to the S before returning to the W and raging during the early morning hours approaching 100mph (160kph).  Expect new loading on a variety of aspects based on the shifting wind.

SNOWPACK: There are a number of locations such as Central and Pinnacle in Huntington that may take all day to reach their forecasted rating.  This is due to generally stable old surface conditions that exist this morning.  They are starting the day at Low although isolated pockets of instability exist.  This will change late in the day due to the incoming afternoon snow.  Other areas particularly E facing slopes in Tuckerman have a solid Moderate rating this morning and will be bumping the ceiling of their definition, hedging towards Considerable late in the day.  This likely won’t happen till after dark, but it is all something to keep in mind in your decision making today.

Icy conditions still exist. Crampons and an ice axe are required for safe travel in steep terrain and other traction footwear for travel on low elevation hiking trails.  Generally speaking microspikes are for lowland trail travel and not suitable for mountaineering terrain and alpine zone conditions.  Sherburne ski trail coverage is very thin with last night’s rescue snowcat tracks.  Although a bit bumpy the grinding of the icy surfaces helped it and will hold the storm snow much better than yesterdays’ ice. Long sliding falls are possible. Realize that in locations scoured by high winds such as Left or Central Gully, and in locations where snow is thin, the icy surface with be hard to self-arrest on making it very difficult to stop yourself if you fall.

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 0855. 12-29-2013. 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

2013-12-29 print friendly