Avalanche Advisory for Thursday April 30, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these locations. Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington.

AVALANCHE PROBLEM: We are continuing to trend slowly towards stability as all the new snow in upper elevations settles down. Warm ambient temperatures yesterday wet the snow and a period of freezing temperatures last night contributed to stabilization. Deeper areas of the new snow are rated Moderate due it’s depth and concerns that further heating today, coupled with some rain showers, will make these areas more prone to human-triggered Wet Slab or Wet Loose avalanches.

OTHER PROBLEMS/HAZARDS: Be aware of the potential for crevasses to be hidden underneath the recent snow. These slots have been growing in the Lip and are beginning to grow in other locations extending from the Sluice over to the Chute. Also anticipate the potential for falling ice today.  These issues will grow in intensity over the next several days due to the expected warming trend.

WEATHER: Yesterday was the 13th day in a row for new snow on the Mount Washington summit.  Recently, scant precipatation amounts have had little effect on the avalanche problem, but has maintained some lingering stability concerns over the past week.  This, in addition to cold temperatures, has kept conditions changing very slowly. Frankly it feels more like the end of March than April.  The prolonged period of low pressure systems that have plagued the higher terrain should give way to sunny skies over the next 24 hours. However, we will go through a round of snow, sleet, freezing rain and rain in avalanche terrain today before conditions improve on Friday. Summits will be in the clouds with a chance of mixed precipitation associated with a NE wind from 5 to 20 mph (8-32 kph). Temperatures will increase from the current of 24F into the mid-thirties.

SNOWPACK: Areas posted at Low danger today did not receive very much loading from recent snowfalls. The surfaces in these locations are as close as you’ll get to typical springtime corn snow. In the Sluice through Chute, conditions vary by aspect, but they all have a similar bed surface of old melt-freeze crust above mostly isothermal snow. New snow from this week has gone through a number of changes as the temperature hovered just above, and dipped below, the freezing point. Today’s warming trend will continue the melting/rounding process of the snow grains which will make for sloppy snow in the upper snowpack. It is the deeper areas of snow, such as the bowl like feature below the ice in Sluice, under the ice in Center Bowl and in the Chute where we have the most concerns for avalanche activity today. If you recall, the early days of our continuing period of unsettled weather, which brought 14” of snow in the last week, was cold with light winds. These weather conditions allowed the snow to fall somewhat undisturbed and though this snow bonded well to the warm crust beneath, it was a fairly weak layer in itself. While the upper snowpack went through a lot of changes since that time, suffice it to say that none of these changes was a dramatic, penetrating cycle of heating and refreezing. This melting and refreezing cycle would normally take most avalanche concerns off our radar this time of year. It is important to understand that while we have fair to good stability in Moderate rated areas, the potential for a wet slab avalanche remains enough of a concern that you should continue considering this hazard in your travel choices and trip planning. I’ll be carrying my beacon until I see a hard refrozen snowpack without the potential for these wet slabs. The upcoming warm weather will ensure that I’ll be carrying it at least through the weekend if not till the end of the season.

The Little Headwall has open holes of water and undermined snow, but it continues to be a skiable option for descending from the Bowl. Use extreme caution if choosing this route. Another alternative is to hike down to Hermit Lake, although expect an icy trail making microspikes and ski poles handy. The Sherburne ski trail is now closed at the #5 crossover, 1 mile up the Tuckerman Ravine Trail from the parking lot. At the rope, please avoid the muddy descent and cross to the hiking trail and walk down. Do not ski on the hiking trail.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 8:15 a.m., Thursday, April 30, 2015. A new advisory will be issued tomorrow.

Frank Carus/Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713