Avalanche Advisory for Saturday, February 14, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. Sluice, Lip and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other forecast areas except the Little Headwall have Moderate avalanche danger.  Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain carefully.  Little Headwall has Low avalanche danger where natural and human-triggered avalanches are unlikely.

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human –triggered avalanches are possible. Evaluate snow and terrain carefully to identify features of concern.

AVALANCHE PROBLEM: Wind slabs which developed yesterday should be your primary avalanche concern today. The wide distribution and variable resistance to human-triggering of these slabs, along with the variable integrity of weak layers beneath, will make ongoing assessment of your chosen route a critical task. High wind speeds yesterday morning moved around 11” (28cm) of low density snow from storms earlier in the week. These winds scoured many areas while building firm, and less firm, more sensitive wind slabs in others. Pre-existing weak layers of soft snow and poor bonding to icy older surfaces contribute to the potential for areas of this firm wind slab to fracture some distance from your feet and even above you. The potential exists for small areas of new unstable wind slab to develop later this afternoon and certainly tonight as heavier rates of  snowfall develop while the approaching winter storm settles into the region.

WEATHER: The low pressure system that is approaching as already begun to influence our visibility on the mountain. An aerosol of very light snowfall and flat light are current harbingers of more significant snow developing later this afternoon and overnight as the latest major Winter Storm affects the area. While the new snow is not expected to generate much in the way of avalanche problems during daylight hours, it certainly will overnight and tomorrow.

SNOWPACK: Strong winds yesterday appear to have generated a fair amount of avalanche activity in our terrain. Even now with much lighter winds, signs of continued loading are evident. As I alluded to in the avalanche problem section, lots of spatial variability is the defining feature of our upper snowpack. You would find icy old surface, softer slabs from low wind speeds, as well as hard stubborn wind slabs during an ascent of any of our forecast areas. Careful travel and assessment with a strong suspicion of someone dropping in from above, particularly later in the day, would be the advice I’d give to anyone venturing into avalanche terrain today. A 5-minute window of reasonable light this morning allowed us to see surface features in Tuckerman Ravine. Surface textures, debris, and almost buried crown lines indicate that the lower Lip (at the choke), Chute and Left Gully avalanched yesterday and have since reloaded with smoother and likely sensitive slab. The bowl beneath the ice of Sluice looks ripe with newly loaded snow while the upper part, as well as most of the higher slopes at the rim in the rest of Tuckerman, is mostly scoured or covered in heavily wind sculpted snow (sastrugi). Solar effect on south facing slopes on Tuesday and particularly Wednesday resulted in a melt freeze crust on those slopes which resulted in breakable, read horrendous, ski conditions on those aspects.

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 8:35 a.m. February 14, 2015. 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

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