Avalanche Advisory for Wednesday 2-1-2012

This advisory expires at midnight Wednesday 2-1-2012

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger.  The Lip, Center Bowl, and Chute have High avalanche danger.  Natural avalanches are likely and human triggered avalanches are very likely.  Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended. This includes runout paths of avalanche activity. Right Gully, The Sluice, Left Gully, and Hillman’s Highway have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

Huntington Ravine has CONSIDERABLE AND MODERATE avalanche danger.  Yale, Central, Pinnacle, Odell, South, and the Escape Hatch have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. North and Damnation gullies have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

Growing up in New England we never stopped hearing “…if you’re getting bored with the weather just wait a minute”.  Staying on our toes is a daily priority so we don’t fall asleep at the wheel.  On the drive in this morning I hit periods of rain hitting my windshield,…it was 22F degrees.  Yes rain, not freezing rain, rain.  This of course began freezing on contact.  It was pretty obvious a warm layer of air had infiltrated and was likely just above the 2000ft level.  2 minutes later I parked and 10 minutes later it was 37 degrees.  Temperature sensors up the mountain are now reading between 35 and 37 degrees from 2000 to 4500 ft. with elevations above and below getting warmer as mixing occurs.  So you’re likely wondering what does this mean for avalanches today.  Yesterday light snow fell through the day adding up to 3.4” (8.5cm) on the summit with W winds at about 40mph (64kph) through the morning and increasing to 50-60mph (80-96kph) gusting 70mph (112kph). This loaded E facing aspects directly and cross-loaded a number of other locations facing more S or N.  All of these slabs are now being affected by today’s warm precipitation and many areas in Tuckerman have already released wet loose avalanches. Hillman’s has a sizable debris pile in the dog leg down low with signs that the wet loose snow stepped down into an earlier 20m x 20m wind slab deposit.  Chute, Center Headwall, the Lip and Sluice all have wet loose debris. The period of freezing rain and rain in avalanche start zones, mostly between 4500 and 5200 will add load, weaken bonds and percolate into Tuesday’s cold slabs.  Weather models are expecting a total water equivalent between 0.1 and 0.25” (2.5-6.25mm).  For the slabs of concern in both Ravines this should fall as both rain and mixed precipitation before changing back to snow showers late this afternoon preceding a cold front hitting us around 5pm.   Expect snow instability to increase through the day with avalanche danger hitting a peak this afternoon before cold air begins to stabilize slabs.  Realize freezing temperatures won’t instantly reduce your risk, but it should end the instability trend.  A caveat to this is if we get both warmer temperatures and more rain than anticipated.  This would cause in an increase in free water percolation down to an impermeable lens below.  This scenario can delay the peak instability until after the freezing begins on the surface.  This is not a likely scenario today, but keep an eye on precipitation and ambient air temps in avalanche terrain today.  New snow loading through most of the day should be limited due to moderate wind speeds for Washington and a developing wet snowpack above treeline.  Late in the day snow showers and an increasing wind may begin snow transport to E aspects.  This shouldn’t add up to much for today’s date however Thursday may be a different story.  To summarize, expect a rapid rise in instability and the likelihood of naturally triggered avalanches due to rain and warm air.  Rain adds load, melts bonds that were contributing to slab strength, and can percolate down to a buried crust, lens, or blue water ice and lubricate this potential bed surface.  In addition to snow stability issues it will generally be an unpleasant day for mountain travel and a good one for the hot tub.   

The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail should be wet and grabby for today and freezing up tonight.  Expect a frozen surface crust of a thickness and strength yet to be determined, but don’t expect it to be pleasant.

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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 8:20am. 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