Avalanche Advisory for Sunday, March 9, 2014

This advisory expires 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. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine has Moderate and Low avalanche danger. Central Gully has Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely, except in isolated terrain features.

AVALANCHE PROBLEMS: With the lack of recent snow, our avalanche problem discussion has moved toward persistent slabs. In reality, the true problem is the interaction between the weak layer beneath the slab and the slab itself. The snowpack generally has a good amount of strength, which decreases the probability of triggering a slide. However, an avalanche triggered in a Moderate rated area could be large and carry significant consequences. The locations where we have the greatest concern for this problem are on east-facing, strong lee slopes such as the Lip, Center Bowl, and Central Gully. In some isolated terrain features, you may also encounter pockets of wind slab from earlier this week. These will likely be smaller in size and have good stability, but treat them as you would any isolated pocket of wind slab…with an appropriate level of caution.

WEATHER: So far, March has been a lackluster month for snowfall. The Observatory has recorded a mere 3.6” in the first 9 days of the month. Thankfully, we might start to get some refreshment this week with snowfall on Monday and possibly a large storm on Wednesday. For today, you can expect fair weather for being out on the mountain (fair as in slightly worse than good, not the fair that implies sunny skies and pleasantly warm breezes.) Winds will pick up late today and clouds will be dropping over the mountain as well, so if you’re out late, be prepared for poor visibility.

SNOWPACK: On the whole our snowpack has good stability. This is true not only for locations that have exposed crust such as Left Gully, but also for the areas with stiff pencil-hard slabs at the primary surface (e.g. Hillman’s). Additionally, I would go so far as to say the areas rated Moderate today have good stability, but this statement comes with a strong caveat. That is, while it may have good overall strength, if you were to trigger a slide it would be deep and large and full of blocks of hard slab. This is not the type of avalanche you want to be involved with. So far this season our snowfall has been lower than average, which means that many rocks and ice bulges in the ravines are not deeply buried. In the vicinity of these hidden features you will often find weak points in the snowpack. Triggering these hard slabs would most likely be done either at a weak point or by a large impact (e.g. dropping an ice cliff, taking a tumbling fall, etc.).

We’ve been watching the freezing rain crust pretty closely over the past couple weeks. It is changing over time and its characteristics are becoming more variable. The key point to remember is that there is a weak layer just beneath the crust, and this would be the most likely failure layer for avalanche activity 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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin.
  • Posted 8:10a.m. 03-08-2014. A new advisory will be issued tomorrow.

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

2014-03-09 Print friendly