Avalanche Advisory for Wednesday, April 29, 2015

This advisory expires tonight 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. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these locations. Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington.

AVALANCHE PROBLEM: Today we are transitioning from wind slab avalanche problems to wet slab or wet loose avalanche problems. Overall the snowpack has been doing a good job working toward stabilization, but some areas still pose a threat due to the prolonged warming of near-surface layers. Expect avalanche danger to increase slowly but steadily through the day as temperatures creep upward. Though we are in the more stable end of the Moderate range, wet avalanche problems can be quite unpredictable and difficult to assess through snow pit stability tests.

OTHER HAZARDS: Be aware of the potential for crevasses to be hidden underneath the recent snow. These had been growing in the Lip more than other areas, but we typically see these in various locations from the Sluice through the Chute. Icefall is also a possibility today despite there being plenty of cloud cover.

WEATHER: Much of the snow that has fallen near the end of April has not fallen at ravine elevations. It has fallen above 5000’ and up to the summit. Today we expect mostly cloudy conditions with temperatures staying above freezing for most of the day. You may even get spit on by snow or rain (in fact, it’s snowing lightly as I write). Diurnal fluctuations have not been strong (i.e. nighttime lows are staying fairly warm) which means that the snowpack is mostly moist down to the older melt-freeze crust from mid-April.

SNOWPACK: Areas posted at Low danger today did not receive very much loading from recent snowfalls. The surfaces in these locations are as close as you’ll get to typical springtime corn snow. In the Sluice through Chute, conditions vary by aspect, but they all have a similar baseline of the old melt-freeze crust from over a week ago. Above this layer, you’ll find a mostly “rightside-up” snowpack in the Chute, so expect loose wet avalanches to be the primary threat here. Over closer to the Sluice, we found a 4-5” thick shin-bruising breakable melt-freeze crust at the surface over softer snow that was either moist or dry depending on the thickness. Stability was generally good yesterday, but this was primarily due to the bridging effect of the crust on top. As this layer loses strength today, the potential exists for wet slab avalanches. This will be greater in locations harboring cold dry weak layers underneath, such as in the Lip or tucked in deeper pockets under the ice in the Center Bowl. The likelihood of triggering a slide has been moving from possible to unlikely. However, we’re not quite there yet. Additionally, the size of a potential slab or loose avalanche that you can expect today could be large. These factors lead us to continue with a Moderate rating, and should be considered in your own decision making today as well.

The Sherburne is now closed at the #5 crossover, which is about 1 mile up the Tuckerman Ravine Trail from Pinkham Notch. At the rope, please cross to the hiking trail and walk down. Do not ski on the hiking trail.

The Little Headwall has some open holes of water and undermined snow, but it continues to be a skiable option for descending from the bowl. Use extreme caution if choosing this route. Another alternative is to hike down all the way to Hermit Lake, but when icy this has proven challenging to many and presents it’s own unique hazard.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 8:25a.m., Wednesday, April 29, 2015. A new advisory will be issued tomorrow.

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