Avalanche Advisory for Tuesday, March 28, 2017

This advisory expires at Midnight.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. The Sluice and Lip have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The exception to this is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: The avalanche problem today will be wet slab. The hazard will increase today slowly due to temperatures remaining only just above freezing and cloud cover remaining in place. With minimal precipitation forecast today, the hazard will lie largely in meltwater lubricating a layer within the snowpack rather than a rapid additional load. The greatest hazard for the day will be in places where the wet slab is the thickest, such as the Lip or Central Gully, as these areas have the potential to produce larger avalanches than other forecast areas. As wet slabs act as liquid concrete once they release, bear in mind that even a thin wet slab can push people into potentially hazardous terrain.

WEATHER: Precipitation ended yesterday in the early afternoon with the heaviest period of freezing rain in the early morning. All told, the Summit recorded 0.37” of water that came primarily as freezing rain and ice pellets. Current temperatures around the mountain are 28F at Pinkham Notch, 40F at Hermit Lake, and 33F on the Summit. The wind is currently 33mph from the W and should remain there for most of the day, shifting slightly toward the NW tonight. Cold air is dammed between very slow moving systems this morning which will cause clouds and summits fog to linger. A cold front is approaching and should arrive this evening. The highest chance of rain is associated with this front tonight, bringing up to 0.1” of water, possibly mixing snow flurries later tonight.

SNOWPACK:  Our terrain has seen above freezing temperatures since yesterday early afternoon, but as these temps were only just above freezing, the rate of saturation of the snowpack has been slow. The period of instability due to a rapid addition of water weight has passed as we will likely see very little precipitation during the day today and only a minor amount tonight. Today’s concern for wet slabs will be due to the slow percolation of meltwater through the snowpack and lubricating layers within the old wind slab or the interface of the wind slab and old ice surface. It is unlikely that the meltwater will impact a layer beneath the old surface due to the amount of melt and previous strength of this layer. Predicting the release of a wet slab today will be very difficult indeed. The trend of the snowpack today will be slowly moving toward instability as the meltwater continues to move deeper, but weather conditions today will keep this rate of change very slow. Heightened avalanche conditions exist 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 Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.

Posted 8:20 a.m., Tuesday, March 28, 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

2017-03-28