Avalanche Advisory for Sunday, March 10, 2013

Expires at midnight Sunday, 03-10-2013

Tuckerman Ravine has MODERATE and LOW avalanche danger. Lobster Claw, Right Gully, Sluice, Center Bowl and Chute have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features, particularly on sunny aspects. Exceptions to this rating are Left Gully, the Lower Snowfields, Hillman’s Highway and the Little Headwall which have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine has LOW avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

Yesterday temperatures on the floor of Tuckerman Ravine reached well into the 30’s F. I recorded 38F at around 1:30 pm under intense sun and calm winds which occasionally gusted to 5 mph.  The intense solar radiation reached into the upper most 4-6” of snow on south facing aspects and weakened the snow by melting bonds between grains. Around 2pm two skiers entered the steeper entrance to Right Gully on the skiers right and unintentionally triggered a small wet slab avalanche about 50’wide with a crown which tapered down from 10” to 3 or 4”. Though small, the debris ran 850’ through the mouth of the gully.  I mention this to illustrate several issues involving our instabilities as well as the issues surrounding travel in our terrain. First, the solar gain we experienced yesterday will most likely be ratcheted up a notch later in the afternoon as forecasted temperatures and high thin clouds may warm all aspects more equally and reduce the intense solar gain on southerly ones compared to yesterday. We are starting out at Low hazard in most areas after cool temperatures last night, but afternoon heating may loosen bonds in areas of windslab in lee aspects where snow pillowed during the ENE winds that we experienced 48 hours ago. Southerly aspects such as North, Damnation and Yale in Huntington Ravine may push up towards Moderate if the thin clouds do not materialize today so be on the lookout for wet snow and sluffing indicating deteriorating stability. Lobster Claw, Right Gully and Sluice may push higher into their rating if the thin clouds hold off and the sun cooks lingering weak interfaces that we have been looking at for that last 10 days.  This brings me back to the skier triggered avalanche in Right Gully yesterday. Several signs existed to alert savvy backcountry skiers yesterday of potential instabilities. Several parties ignored the most obvious one…recent avalanche activity. No sooner had the debris stopped moving than several skiers and a splitboarder began skinning directly up the runout and through the debris apparently disregarding the acres of easily skinnable terrain between the mouth of Lobster Claw and Right Gully which would take overhead triggers off the list of concerns. Several parties skied the East Snowfields and more will probably do so today so don’t be surprised if someone drops in above you unannounced.  Low hazard doesn’t mean no avalanche hazard particularly on steep terrain where fairly shallow moving slab can sweep you off your feet and push you into the exposed ice and rocks which are numerous this year.

To summarize:

1)      Solar gain may hit hard this afternoon, making some slabs unstable.

2)      Cloud cover and breezes may keep southerly surfaces a frozen nightmare of death cookies until things warm up.

3)      People above you could trigger a pocket in some locations.

Shady aspects will be pleasant climbing today though “postholing” may slow travel if the snow heats up due to the solar gain.

 

 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 9:00am, March, 10th 2013. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2013-03-10 Print friendly

Coming Soon: Upslope Snow on Mount Washington

Stay tuned coming soon in the Pit will be “Got Upslope #2” by our partners on the mountain.  The Mount Washington Observatory summit crew know our local weather like no others and are excited to help us discuss and learn about upslope snow.  We look forward to it!!

Upslope snow