Avalanche Advisory for Saturday, February 10, 2018

Huntington Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Careful snowpack and weather evaluation and cautious route-finding are essential.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. Chute and Center Bowl have High avalanche danger. Travel in the floor of the Ravine is not recommended. All other forecast areas have Considerable avalanche danger. Careful snowpack and weather evaluation and cautious route-finding are essential. Little Headwall has Low avalanche danger.

AVALANCHE PROBLEM: The new and reactive wind slabs developing today will contribute to existing avalanche problems by adding stress to the older wind slab. Prime conditions for wind slab development on Wednesday and Thursday spawned a large natural avalanche that ran to the mouth of Tuckerman Ravine in the early afternoon Thursday, with another crown observed left of the Harvard Bulge in the snowfield to the right of the Fan in Huntington. Many other areas did not avalanche during that cycle and still contain the weak layer and slab above. Today, new snow, wind slabs and natural releases of dry loose snow will strain the snowpack and the weak layer beneath. High rated areas hold the greatest potential for a large avalanche due to the thicker wind slabs in place before today’s snowfall. Considerable rated areas hold similar concerns, though avalanches in these areas are likely to be a bit smaller or less likely to fail naturally due terrain configuration or a lower angle. No matter the rating, you’ll need to bring your A game to this tournament if you want to make it to the next round.

WEATHER: Harvard Cabin recorded 2” (5.5cm) of new snow at 6:30am with around 4” recorded on the summit. Snow will continue today and bring another 2-4” new snow to higher terrain. Wind from the WSW is currently in the 50-60 mph range on the summit with higher gusts. These wind speeds will move enough snow to create reactive and soft wind slabs. New snow and fog will reduce visibility on and off through the day. Today’s weather pattern is remarkably similar to Wednesday when lots of natural dry loose avalanches and one skier triggered wind slab occurred.  Summit temperatures will rise to 25F from the low 24 hours ago of -9F. Hermit Lake was 24F at 6:30am.

SNOWPACK: Warming temperatures will be another red flag on display today. The deeper instabilities, mentioned above, that create our greatest risk for a large avalanche will be subjected to warm temperatures for the first time since their development. Weak, poorly bonded snow that fell Wednesday on pre-existing firm slabs led to the large avalanche in Tuckerman Ravine. This was evident by the lack of ice crust visible at the bed surface, though a few areas of slab stepped down to that layer. Lots of wind slab was observed in our terrain yesterday with large smooth pillows in the Fan in Huntington and very large smooth wind slabs in the Chute. The upper portions of Right Gully, Sluice and Hillman’s Highway have grown in expanse and Lobster Claw is continuous and wider now with an ugly terrain trap at its bottom. To make a long story short, winter is showing up again today and brought a dynamic snowpack with it. Today is a good day to keep it well on the conservative side of the line.

The Sherburne Ski Trail is a great alternative to skiing in avalanche terrain today.

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 Harvard Cabin.
• Posted 8:10 a.m., Saturday, February 10, 2018. A new advisory will be issued tomorrow.

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

2018-2-10