This advisory expires at Midnight.
Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale and Central Gully 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 CONSIDERABLE, MODERATE, and LOW avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely in Sluice, Lip and Center Bowl. Careful snowpack evaluation, cautious route finding, and conservative decision-making are essential. Lobster Claw, Right Gully, Chute and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Left Gully, Hillman’s Highway, and little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely.
AVALANCHE PROBLEM: The warming snowpack will make loose-wet and wet slab the avalanche problems today. This hazard will increase as the day progresses and temperatures continue to rise. Firm wind slab that formed from strong NW winds moving 12” of snow on Saturday will see rapid warming today. The interface of this slab and the old freezing rain crust becoming lubricated will create our wet slab problem. This slab is the biggest in Considerable rated areas and with enough warmth today, may release naturally. Slough created while skiing or riding can often entrain a good amount of snow and if improperly managed, can carry a person over a cliff or into rocks. Runnels exist in the Headwall region of Tuckerman and as these funnel slough, expect them to become deeper as the day progresses. In addition to avalanche problems today, extreme warmth may create icefall. Be aware of this, particularly in Huntington Ravine.
WEATHER: Although skies were clear with ample sunshine yesterday, the temperature remained just at the freezing mark for most of the day. This, combined with wind speed remaining above 40mph until mid-afternoon created colder than expected conditions. As of 8pm yesterday evening, the Summit temperature hit 32F and has steadily been increasing. This upward trend will continue for most of the day with a good chance of cresting 50F in the afternoon. Current wind speed is 48mph from the W and should remain around here for most of the day.
SNOWPACK: Last Thursday, 0.7” of liquid fell in the form of rain and freezing rain. This was followed by slow cooling on Friday, allowing this liquid to penetrate into the snowpack. As the cooling process was slow, only the top few inches of this refroze before approximately 12” of snow fell Friday night and Saturday. This blanket of new snow insulated the snow beneath, allowing the wet snow to remain saturated and keep it from freezing. Strong NW wind on Saturday created firm wind slab in lee areas, the largest being the Sluice, Lip, and Center Bowl. Huntington also had this slab develop in Central and the northern gullies, though not as large due to the nature of the terrain. Some warming occurred yesterday with the top 2-3” of snowpack becoming wet in S and SE facing aspects. East and N facing aspects saw this to a very minor degree and areas that went into the shade quickly may have remained cold and dry. Today, all slopes will warm due to high temperatures. Slope aspect will also play a factor with S and SE facing slopes seeing the most solar gain. As these aspects also have the most new snow, the threat of avalanches is higher in these areas. Older surface, which is identifiable by its dirty appearance, should provide the more consistent ski quality and the least amount of slough management problems.
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!
• 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 8:10 a.m., Monday, April 10, 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