Avalanche Advisory for Wednesday, March 26th, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. The only exceptions to this is the Little Headwall in Tuckerman which has Low avalanche danger.

AVALANCHE PROBLEM: Avalanche problem today is Wind Slab.  These are slabs that formed from last week’s storm and then mostly from snowfall and loading over the weekend.  Cold air in place since then has slowed the consolidation pace, but several locations have been moving towards stability.  As typically occurs, the most concerning instabilities can be found in the middle of Tuckerman, between the Sluice and the Center Bowl. New Wind Slab is problem #1B Later today some snow showers are possible which will likely produce some thin slabs in lee areas of N and NW winds.  You will likely begin seeing us discuss persistent slabs very soon.

WEATHER: Well winter continues.  The day is starting at about 0F (-18C) and will fall through daylight hours to about -10F to -15F (-23 to -26C) tonight.  Winds will also go in an unfavorable direction, from a current of 30mph from the NE, to the NW gusting to 110mph (176kph) tonight.  Alpine zones will get quite uncomfortable this afternoon as winds creep towards the 100mph (160kph) mark late in the day.  This will come with snow showers delivering up to 2” (5cm) of new snow.  Two winters ago we finished March almost 10degreesF above the 30 year average, the warmest in at least the previous decade. Conversely, this year March will hit about the same in the other direction with an average of +/- 9 to 10F below the long term averages.  Continue to expect and plan for extremes, it seems to be the new normal.

SNOWPACK: Snow pits and stability tests are highlighting the multiple snowfalls from the past week.  As Jeff alluded to yesterday when you dig a hole, isolate the stack of snow layers, and give them a load it’s like knocking over a book shelf at home.  Multiple layers are popping out, demonstrating all the loading events we endured from 5 days of snow from this past Wednesday through Sunday.  Graupel seems to be the snowpack’s culprit of choice for failure potential.  This fell among Friday’s snow and although they weren’t the perfect smooth little ball-bearings we can see, their fuzzy rimed nature is still not bonding well with neighboring crystals.  Look for this in your stability tests today.

In Huntington, the northern side of the Ravine has some snowpack issues to negotiate down low to their mid sections, while on the south side the concerns are more from their mid to upper reaches.  Some location’s like Hillman’s, Left gully, and Huntington’s Pinnacle are starting the day at a Low rating. However they are posted Moderate, based on new loading potential this afternoon due to new snowfall forecasted and potentially some icy crystals loading from alpine zones.  The wide snowpack temperature gradients, yesterday’s cold air, and low winds make me believe some diurnal recrystallization/faceting has occurred.  This may fall victim to the very high winds we are expecting today sending icy particles down into the Ravine mixed with new snow.  This is a possibility later today, hence all areas at Moderate, but is more plausible during the overnight as winds move above 100mph.

In summary, expect some lingering instabilities from recent wind slabs created over the weekend and then new instabilities that layer in on an increasing N wind shifting from the NW later.  Initial moderate wind velocities may produce a soft slab first followed by stiffer, harder slabs overtop later.  I would envision this initial soft snow to be a potential weak layer for the thin hard slabs waiting for a trigger. Saying this, with the scant snow fall expected these new slabs should be thin and isolated, so continue to expect variability across our terrain and not widespread consistent problems. Due to this irregularity make careful snowpack assessments and conservative choices to avoid potential instabilities. There are recreational options out there if you’re flexible and willing to play on the mountain’s terms.

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 755a.m. 3-26-2014. 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

2014-03-26 Print