Avalanche Advisory for Wednesday, February 1, 2017

This advisory expires at midnight.

 

All forecast areas of Huntington and Tuckerman Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision making are essential. The only exception to this is Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Wind Slab formed over the past few days and new wind slab will form today. Avalanche danger will increase today as winds increase and snow accumulates. The terrain above the ravines contain plenty of snow available for transport. This will start blowing into the Ravines as winds shift and increase today. Even if the snowfall today is at the lower end of the forecasted 2-4”, we will likely see widespread new wind slab due to wind transport. This will make for limited visibility which will hamper route-finding.

WEATHER: Late Monday night, winds shifted to the NW and blew close to 50mph for a short period. Tuesday was cold and clear with SW and W winds 15-30mph. Snow showers started last night and so far have produced a trace of new snow. The approaching clipper system has moisture to give and will drop somewhere between 2-4” of snow today. As the center of the system passes us, winds will calm for a brief period before shifting to the W and picking up in intensity to 60mph by dark. Tonight, temperatures will drop below 0F with W winds increasing to 75mph and another possible inch of snow.

SNOWPACK: Due to shifting winds and 4” of 5% density snow over the past 48 hours, the snow surface is variable and tough to read. The slight wind shift to NW 50mph for two hours Monday night moved much of the light density snow that fell on Sunday. This can now be found as firm slab, soft pockets, and scoured melt-freeze crust. Signs of slab avalanches from this wind shift were visible in the Lip vicinity of Tuckerman and below the ice bulge of Central in Huntington. Similar aspects to these like Sluice, Lip, and the snowfield below the ice in Pinnacle are of greatest concern at the moment. However, expect pockets of one-finger (1F) wind slab over four-finger to fist (4F-F) snow scattered around our terrain. While these pockets were resistant to human-triggers yesterday, new snow today may be the tipping point. The upside-down trend will continue as current winds from the SW at 40mph calm mid-morning and then shift to the W and increase to 60mph. With up to 4” of steady snowfall forecast, wind slab will likely form on many aspects. Mild winds since this past Saturday along with 5” of light density snow created deep soft slab that in many places are still clinging on to slopes. Be aware that even a small wind slab that releases today could entrain a significant amount of snow. The floor of both Ravines have many avalanche paths above that will be hard to see today and once there, you will be in the runout zone. Cautious route-finding will be key today.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. Please be on the lookout for machine traffic on the Sherburne.

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  8:10 a.m., Wednesday, February 1, 2017. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2017-02-01