Avalanche Advisory for Tuesday, April 11, 2017

This advisory expires at Midnight.

 

Huntington Ravine has MODERATE and LOW avalanche danger today. Central Gully has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain to identify features of concern. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger today. Sluice, Lip, and Center Bowl have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain to identify features of concern. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features. Be aware of open water holes in the Little Headwall.

AVALANCHE PROBLEM: Another warm day following no overnight freezing temperatures will further the wet avalanche problem. Loose-wet avalanches are more likely to occur from skier induced slough rather than naturally occurring. Evidence of this can be seen from the skier-triggered wet slide that came out of The Duchess yesterday morning. These are more likely to occur on steeper slopes that have seen little to no traffic. While these often can be managed, getting caught in this mass of cement-like snow can take someone over a cliff almost in slow-motion. As the day progresses, temperatures will rise and the chance of rain will increase. Wet slabs are another problem today. When meltwater and rain start to lubricate the freezing rain crust below the surface slab in Moderate rated areas, these slabs will rely on tensile strength to stay in place. The Lip presents a specific hazard as the waterfall hole is now open and this area will now see undermining. Warm temperatures are awakening spring-time hazards. Glide cracks are sure to be developing and will become visible soon if not today. Undermined snow exists in the Little Headwall and will be appearing in other places as well. Keep an eye on what is above you when moving around today as icefall is starting to occur.

WEATHER: Bluebird sky and warm temperature was the theme of the day yesterday. The high recorded on the Summit was 47F. Today will see similar temperatures if not a few degrees warmer. Approaching low pressure will usher clouds in this morning. Low level moisture associated with this system will likely create rain this afternoon. Total rain for the daylight hours today should stay below a tenth of an inch. Tonight, rain should continue at a light rate, totaling close to 0.2” by tomorrow morning.

SNOWPACK: Wind slab that formed over the past weekend has now seen 36-hours straight of above freezing temperatures. In many areas, this slab has become saturated entirely. Yesterday, several skiers reported the freezing rain crust being impermeable to meltwater during the morning. Continued warmth should start to break this crust down, except in areas where the slab is thicker (lee areas of NW wind) and the warmth has yet to reach the crust. These are the areas where the slab is the most continuous and could produce a wet slab release. With increased skier traffic in some forecast areas, the saturated snow is being pushed around, revealing some of the freezing rain crust. The warm temperatures are softening this to produce some corn snow, however this is not widespread. Expect variable conditions that will require good slough management. 

The Harvard Cabin is closed for the season. We will continue posting advisories there as long as it is logistically feasible or until the ice melts out. Be sure to check the date of the advisory when you read it!

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 caretaker at Hermit Lake Shelters.

Posted  8:15 a.m., Tuesday, April 11, 2017. A new advisory will be issued tomorrow.

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

2017-04-11