Avalanche Advisory for Sunday, March 26, 2017

This advisory expires at Midnight.


Huntington Ravine has MODERATE and LOW avalanche danger. Damnation, Yale and Central Gullies 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.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice and Lip will rise to the upper end of Moderate avalanche danger today. Lobster Claw, Right Gully, Center Bowl, Chute, Hillman’s Highway and Lower Snowfields will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Left Gully and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: Today’s avalanche problem will be driven by heating of the snow by sunshine and warm temperatures. Areas with the most soft wind slabs like Sluice and Lip in Tuckerman Ravine and Central in Huntington have the greatest potential to produce a human-triggered avalanche. As sun warms the snow this morning, the soft snow will become heavy, begin to saturate with water and produce loose wet sluffs and possibly wet slabs large enough to push you around. Today’s warming is not extreme enough to create large wet slabs but skiing will become challenging in the variable “mashed potato” snow and firmer old crust. Areas of old, hard icy snow in Tucks are not widespread but can be found in Left Gully and low in the Chute. This icy surface is generally discontinuous and will create some travel challenges going up or down. Hillman’s Highway has a mix of firmer slabs and softer slabs so expect heavier snow there as well as things heat up.

WEATHER: It’s a blue sky morning, with a current summit temperature of 20 degrees F and WNW winds blowing at 21 mph. Overnight, a low of 14 degrees F was recorded with NW wind reaching 50 mph. Blowing snow was not observed at the summit, suggesting wind transport has not significantly altered our surface conditions since yesterday. Today, temperatures will rise to the mid-twenties and wind will remain light, below 20 MPH, and shift to W and then SW by noon. The ravines will be slightly warmer with less wind. Clouds will build throughout the day as a warm and wet system approaches, but sky cover should remain below 50% through late afternoon.

SNOWPACK: Surface snow conditions remain mixed across our forecast areas. If variety is what you’re after, this is the place to get it. The new snow of mixed forms, including pellets, which fell and drifted late Friday is soft and sluffy in places. While sensitive yesterday, this slab has limited capacity to propagate a crack. This layer exists primarily on south and southeast facing aspects and so is primed for solar warming. Heat and resulting melt water will add to cohesion of the slab and increase potential for a human triggered avalanche as the day progresses. Firmer (1 finger hardness) snow with greater stability that was deposited in the middle of last week is present in much of our terrain. An icy old rain crust, now nearly a month old, is still exposed in wind scoured pockets including nearly half of Left Gully. Beneath these varied surfaces, the snowpack is quite stable. Fun skiing and climbing can certainly be had today. Travelers in our avalanche terrain would do well to retain a level of caution, bringing a partner or two, their beacon, shovel, probe, and critical decision making skills, and avoid sunny aspects if they warm significantly this afternoon.

If you are wondering what a wet slab in Tuckerman Ravine looks like, here is one captured on video that was triggered April 24, 2009. This one was small, but it is events like this that make it so disconcerting when we see people bringing small children into avalanche terrain during periods of elevated danger, as they did yesterday.

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 Harvard Cabin.

Posted 8:10 a.m., Saturday, March 26, 2017. A new advisory will be issued tomorrow.

Frank Carus/Ryan Matz, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856