Avalanche Advisory for Saturday, 4-20-2013

This advisory expires at 12:00 midnight.

Tuckerman Ravine has LOW avalanche danger. Natural and human triggered avalanches are unlikely.

A General Advisory is currently issued for Huntington Ravine. We are done issuing daily avalanche forecasts for Huntington for the remainder of the season. You will need to do your own snow stability assessments when using avalanche terrain. A danger of falling ice exists and will persist until it all comes down.

Over this past week, Tuckerman Ravine has changed quite a bit. Melting conditions, though not excessively hot, took a toll on many locations. Yesterday, these changes were taking place before our very eyes. Hillman’s Highway sprung a leak just above the dogleg, the Lip waterfall opened up and triggered a wet slab avalanche, friends reported booting through running water up high in the Chute, and the stream bubbled up through the floor of the ravine near the bottom of Left Gully, running over the top of the snow. And this was all before the rain fell last night!

Today’s weather is not looking good for springtime recreation. Temperatures will be falling through the day and winds will remain strong. This will create a situation where the snowpack will be freezing from the surface layer downward. There is currently a lot of heat and moisture in the snow, which means the snow beneath the developing ice crust will be soft and mushy. I can already hear my knee ligaments screaming at me to take it easy today.

SLIPPERY TRAIL CONDITIONS should be expected today. Where there had been snow and slush there is now clean water ice, like the great Zamboni in the sky cleaned it all off in preparation for a new day. Traction devices such as microspikes and ski poles are recommended for travel to the bowl.

UNDERMINED SNOW is a significant concern today. As mentioned, many areas had water running beneath the snowpack. The snow that bridges these streams has been weakened in the past several days. You do not want to be the reason for one collapsing. In many cases you’ll simply be wet and uncomfortable, but in the worst case you may be swept  underneath a channel in the ice. Today, I have yet to see the area in the bowl where water was percolating through, but nevertheless I recommend staying well away from this area.

FALLING ICE is another concern. Warm temps and rain have weakened the bonds that hold the ice to the rock faces. Although today’s temperatures are going to fall below freezing, there is still going to be a chance for icefall to take place. If visibility is poor, you stand little chance to see it coming, let alone protect yourself somehow. Minimize the amount of time you’re in icefall zones, such as the middle floor of the ravine and near Lunch Rocks.

CREVASSES/OPEN HOLES have been growing. Yesterday’s avalanche area and the Lip itself is a great area to avoid. The waterfall is open, there are crevasses growing on either side of the Lip, and the waterfall has punched another hole in the snow down low in the Lip, to the lookers left of the Open Book area. Other areas to avoid include the Little Headwall and the stream leading out of the ravine. Also expect problems near any exposed rocks, where moats may have been created from the snowpack’s downhill creep.

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 at 7:10 a.m., April 20, 2013. 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

2013-04-20 Printable