Avalanche Advisory for Sunday, February 17, 2013

This advisory expires at 12:00 midnight, February 17, 2013

Tuckerman Ravine has Considerable, Moderate and Low avalanche danger. Right Gully, Sluice, Lip, Center Bowl, Chute, and Left Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lobster Claw, Hillmans Highway and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger.

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

Avalanche danger in all forecast areas will be increasing from yesterday’s ratings through today!

Today’s impending wind event was apparent this morning as I got in the car in Brownfield, Maine. A steady wind and distant dull roar brought memories of near misses by hurricanes as a young lad growing up in the South. The big low pressure system, now southeast of Cape Cod, will remain too far away in the Gulf of Maine to bring the snow that the area desperately needs. However, pressure differentials will be deep enough to generate significant winds with 1-3” (3-8cm)of new snow today and a trace to 2” (5cm)tonight. The new snow, which is in the 4-5% range so far, will be transported by wind which will increase through the day. Currently, winds are blowing from the N at 35-50 mph (55-85 kph) but will shift to the NW and increase in velocity through the day to the 100 mph (160 kph) range this afternoon. This will load the upper avalanche start zones near the top of Damnation, Yale, Central and crossload other areas in the same gullies as well as Pinnacle, Odell, and South. North and Escape will also receive crossloaded pockets of snow but natural avalanches are unlikely there due to the scarcity of continuous snowfields and abundance of anchors. Lookout for the light density snow piling up into sizable slabs at the base of steep ice and rock features. In Tuckerman Ravine, the wind and new snow will also conspire to build new slabs in Right Gully, Sluice, Lip and crossload other areas particularly across the bowl in the Center Headwall Left Gully and even Hillmans Highway. Lobster Claw and Hillmans are rated at Moderate due to the smaller size of snowfields there but careful travel there is still warranted. The lower half of Hillmans is mostly ice chunder with a veneer of snow due to the huge ice dam slush burst during our last thaw.

If the forecasted snow totals pan out, the possibility of natural avalanches is definitely there in both ravines. If snowfall is lighter than expected, we still have two issues to consider. One is the cold slabs remaining from Monday and Tuesday.  These slabs are fairly stubborn, both in their longevity and their resistance to triggers. Hard wind slabs are tempting due to easier travel and consistently carvable skiing but the softer layer which exists below can spell doom when some unlucky soul finds the sweet spot that fractures and fails the slab.  Several skiers, including Joe and I, found thick slabs over one hardness step lighter snow in Central, Left and South over the course of the last two days. These slabs would take a large trigger, a new heavy load or a particularly well aimed trigger in a thin spot between rocks, for instance.  A natural avalanche of today’s storm snow could also step down into this layer creating a larger than expected problem.

Difficult off trail travel will make bailing off of usually packed out trails on the ridgetops a significant challenge.  The high windspeeds and low visibility will add to the challenge today. Speedy ascents will be the best option today to get off the mountain before the white witch unleashes her dragon. Remember that 60-75 mph (95-120 kph) NW summit winds make walking increasingly difficult and accidents more and more likely. Windspeeds will increase beyond that to upwards of 120mph (190 kph)tonight so wise climbers will adjust turn around times accordingly. Coupled with a plunging mercury to -15F (-26C) will make for unforgiving brutal conditions.

 

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 8:45a.m., February 17, 2013. A new advisory will be issued tomorrow.

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

2013-02-17 Print friendly