Avalanche Advisory for Tuesday, April 8, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravine have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wet Loose Avalanches are the primary threat today. The standard definition of Moderate danger says that naturally triggered avalanches are unlikely. With today’s loose wet problem, this is not the case. Expect rain today to trigger small wet loose avalanches across many different aspects. Steeper slopes will be more susceptible to this problem. The expected size of these allows the danger rating to be Moderate, whereas Considerable is usually the more appropriate rating when naturally triggered avalanches are possible.

If rain falls heavier than we currently are expecting, avalanche danger may rise further due to the threat of wet slab avalanches. You need to be your own weather observer for this one. If you see heavy rain and not so much frozen precipitation today, consider recreating outside of avalanche terrain.

WEATHER: As one former Snow Ranger used to say…today is a good day to be wearing a house. It’s currently 37°F at Pinkham Notch. The summit is several degrees below freezing, and Hermit Lake sits right at the freezing mark. So the upper portions of the mountain are receiving mixed frozen precipitation, at least for now. Temperatures are expected to rise this morning which will bring rain to all elevations. In the afternoon, precipitation will transition from steady to showery. Temperatures will be falling during this time, so we will begin to see snow showers again in the afternoon. Overnight the summit has received a few inches of heavy dense snow and ice pellets. We will need to wait to see how much more falls before a transition to rain showers.

SNOWPACK: The last two days have turned out to offer good snow conditions for skiing and riding. Yesterday’s warm temperatures helped the snowpack continue on its path to being fully isothermal. However, last night the temperatures only slightly dipped below freezing, so there is going to be some refrozen snow grains near the surface but deeper in the snowpack you would likely still find warm moist snow.

Today’s primary avalanche problem stems from rain landing on two different snow layers. The older one fell on Saturday night with strong NW winds which landed on slopes with an easterly or southeasterly component. Much of this has been skied over, so wet slab concerns are minimal in these locations, but the loose snow that remains can still get moving enough to be a concern. The more recent layer is 3” or so of wet snow and sleet that fell overnight and early this morning. Winds were from the SSE, but the wetness of this snow leaves me thinking it’s blanketing all aspects, not only those in the lee of SSE winds.

OTHER HAZARDS: Swollen streams today may increase the hazard of undermined snow. We’re also beginning to think about falling ice as a potential concern.

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.
  • Posted 7:45 a.m. 4-8-2014. A new advisory will be issued tomorrow.

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

2014-04-08 Printable