Avalanche Advisory for Friday, March 18, 2016

All forecast areas of Tuckerman and Huntington Ravines have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, the Lower Snowfields, and Little Headwall are not posted due to a lack of snow in these areas.

AVALANCHE PROBLEM: Today’s main avalanche problem is Wind Slab.  Another 2-3″ of snow overnight and an additional few hours of snow this morning, potentially heavy at times, will create new wind slab on specific terrain features. These locations are most likely to occur near ridges in the upper start zones or below terrain features a bit lower.  In your travels you can expect mostly hard old surface conditions and low visibility.  As you move upslope stay tuned to changing conditions, other individuals that may be triggers, and realize you may be in the runout of wind slab from above.  Late in the day winds will rage, triggering another loading event, so expect new wind slab development to wax this morning, wane a bit midday, and then wax again later.

WEATHER: As of midnight last night, the summit recorded another 2.5″ (6cm) of snow as we continue a recent nickel and diming trend.  Over the past 4 days the Observatory has recorded 6.1″ (15cm) of new snow with some additional icing and rain.  This morning a period of heavy snow is expected briefly before a clearing trend begins to develop.  Winds will pick up substantially, expected to gust over hurricane force, hitting close to 90mph late in the day.  Temperatures will also fall getting close to -10F (-23C) tonight and only climbing to about 0F (-18C) on Saturday. This will create hard icy conditions in the vast majority of locations.  Although we have had a lot of spring recently, Winter is in charge over the next few days!  Expect anything but a t-shirt sun soaking weekend

SNOWPACK: Last week’s melting and rain followed by cold conditions has created a situation that doesn’t have us too concerned about deep instabilities.  The main focus for us is new snow over the past 48 hours and additional accumulation this morning.  Although socked in with clouds and blowing snow, historically similar events tell us we can expect some thin new slabs to develop, primarily in upper start zones.  Snow on Wednesday began warm so generally the early bonding was good.  Anticipate weakness, leading to failure, to be within snow density changes above the interface with the old surface.  Saying this we don’t believe instabilities are widespread, but expect a high degree of spatial variability.  You will be on hard old surface one second and into some slabs the next.  Some forecast areas barely meet the criteria of a Moderate rating while others such as the Lip, Center Bowl and Chute may reach the upper end of the definition.  This depends on how much snow we receive this morning and the timing and velocity of afternoon winds.

 Other typical spring hazards include:

  • Long sliding falls – Crampons are highly recommended in steep terrain. Snowshoes and microspikes are no substitute. Spring weather brings variable snow surface conditions that change by the hour and by aspect. Arresting a fall on an icy 30+ degree slope is practically impossible.
  • Crevasses, moats and waterfall holes – Warm water flowing under the snow pack creates holes and thin spots in surface snow that are deep enough to injure or kill you. New snow can obscure the openings.
  • Falling ice – Cold temperatures are putting this hazard on the back burner for the weekend.

TRAILS INFO:

  • The Tuckerman Ravine Trail uphill from Pinkham to Hermit Lake is mostly wall-to-wall ice. Traction devices or crampons are necessary for reasonable travel on this trail.
  • The Lion Head Summer Trail is open. The winter route is now closed.
  • The Sherburne Trail is closed about 2/3 mile up from the parking lot. Please respect the closure by walking over to the Tucks trail at the rope to reduce erosion on the ski trail.

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 8:05a.m., Friday, March 18, 2016. 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

2016-03-18