This advisory expires at Midnight.
Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. Central, Pinnacle and Odell have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other forecast areas in Huntington have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, Right and Left Gullies, Hillmans Highway and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The only exception to this rating is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely there. Open water and water ice remain exposed in the Little Headwall and the creek above. It is skiable but people have been occasionally punching through into water beneath.
AVALANCHE PROBLEM: Wind slab avalanches will continue to be a problem. Recent wind speeds and available snow have been ripe for the growth of these slabs, especially in the strong lee areas of a westerly wind where larger slabs have developed. Anticipate smaller but still potentially dangerous areas of wind slabs in moderate rated areas with a highly variable snow surface from firm barely edge-able snow to softer drifts. Careful snowpack evaluation and cautious route finding are essential today.
WEATHER: The temperature is currently 3F on the summit and 18F at Hermit Lake. The summit recorded an inch and a half of new snow in the past 24 hours with blowing snow observed at most every hourly observation during the same time period. Predominately west winds in the 70 mph range with gusts near 80 mph have hampered visibility but reports indicate that there was plenty of snow in the alpine zone yesterday to continue the slab building process in the Ravines. These higher wind speeds have begun to diminish into the 40-55 mph range in the past few hours and will remain in that range through the day. The forecast shows a cold front approaching the region later in the afternoon and evening with increasing wind speeds and falling temperatures. Continued westerly wind will wring out moisture from the clouds today and bring up to 2” of upslope snow showers. Low visibility will continue through the day.
SNOWPACK: Variable density wind slabs exist throughout the terrain. Recent snow has generally been very low density and easily transported. These wind slabs have shown clean shears between layers with generally good bonding to the old, heavily rimed melt/freeze crust that developed over the sleet event on January 24/25. Though that crust is exposed near the tops of gullies, it has been well buried at mid and lower elevations. The sleet beneath this crust has spooked many by masquerading as a facet farm but those layers have not been a player in the several avalanches cycles since the sleet fell. Of primary concern are the multiple layers of wind slab that developed since. Within areas covered by a moderate rating today, new and reactive wind slab is most likely to be located on aspects with a NE or E component. If you choose to enter avalanche terrain today, continue to respect the loaded slopes above you and approach slopes cautiously since current conditions indicate the potential for natural activity to some degree. While wind speeds and loading will diminish a bit today, the possibility of human-triggered avalanches being on the larger side elevates our danger rating today.
- 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 8:20 a.m., Thursday, February 2, 2017. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713