Avalanche Advisory for Thursday. April 23, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine will have Considerable and Moderate avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches will be likely. The Lobsterclaw, Right Gully, and the Lower Snowfields will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches will be possible. (The Little Headwall is falling apart and is not recommended. See posted video on our website if reading this hardcopy). Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: All areas are starting today a rating lower than the posted danger level. However, this should change as we move through the morning and into the afternoon. Because of last night’s snow, in addition to another couple of inches forecasted today, expect Wind Slabs to exist and more to develop through the day.  Anticipate the most instability in the lee of W and NW winds, such as in the Sluice, Lip, Center Bowl/Headwall and Chute. Slabs and the avalanche problem will grow today if the weather forecast plays out. As this occurs anticipate the avalanche danger to creep into the posted ratings depending on timing of additional snow showers. This is most probable later this afternoon.

WEATHER: Well the heavy snow we hoped for did not occur.  As of 7am the summit received 3.7″ of snow with an additional 1-2″ expected today, ultimately giving us a potential 5-6″ available for wind slab development.  During the onset of snow yesterday a moderate S wind blew for 8 hours before transitioning to a 40-55mph W wind very early this morning.  Over the last 2 hours winds are starting to move towards the expected NW, gusting to 60mph.  Winds may drop off a bit to 45mph today, but will continue to be decent loading speeds for slab growth. Temperatures are beginning at 16F this morning and only rising slightly through the day.

SNOWPACK: A rising temperature yesterday, peaking at 30F on the summit in the early afternoon, allowed for decent ski conditions and a bonding surface for snow that began around 1pm.  The initial S wind should have created some thin slabs on N facing start zones near the ridge. Portions in the upper climber’s left of Hillman’s and Left Gully are some good examples. Overnight, W winds likely began loading our more dominate aspects facing E, such as the Chute, Center Bowl, and Lip.  Current obscure skies and blowing snow make visual confirmation difficult, but historically thin slabs have resulted in similar conditions.  Consistent NW winds and another couple inches of snow will slowly increase avalanche danger through the day.  The ratings are posted with the anticipation of this to become reality.  If we fall short in accumulation expect all areas to struggle reaching their forecasted danger levels. With the potential of 5-6″ available between last night and today, with good W and NW loading wind speeds, a Considerable rating is appropriate.   Based on the nuances of moguls, melted out brush and exposed rocks above treeline new slab development will not be as consistent or large as mid-winter.  Expect a variety of conditions and realize hard old surface down low doesn’t mean you will find the same up high. With the history of wind over the last 24 hours I would expect most new slab to be in the upper elevations of each forecast area.

OTHER HAZARDS: The typical springtime hazards have emerged. You should be aware of the potential of falling ice, crevasses, and undermined snow. The best you can do to mitigate the risk from these objective hazards is to avoid them, especially during times when they are more probable. Falling ice is the hardest to predict and should be given a lot of respect and room. Because of this unpredictability, we generally recommend hazard avoidance as a primary strategy. As an example, Lunch Rocks or “Icefall Rocks” is right in the bulls-eye and has been the scene of many accidents over the years, so avoid this location. Other hazards such as emerging crevasses may be hard to recognize, due to being hidden by new snow.

The Little Headwall has suffered from a collapsed section. We are no longer recommending this as a route out of the Bowl. The Sherburne Ski Trail is closed from the lower switchbacks to the parking lot due to mud.  Please cross over to the Tuck trail at the arrow sign and walk the short distance to your car.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 8:10a.m., Thursday, April 23, 2015. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713

2015-04-23