Latest avalanche advisory for Mount Washington’s Cutler River Drainage – Tuckerman and Huntington Ravines

Avalanche Advisory for Thursday, March 23, 2017

This advisory expires at Midnight.

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Natural avalanches are unlikely but human-triggered avalanches are possible. 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. Sluice, Lip, Center Bowl and Chute 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.

AVALANCHE PROBLEM: Wind slabs remain the primary avalanche problem. Low rated areas are a mix of scoured old surface with areas of heavily wind sculpted and eroded sastrugi snow. You may encounter unstable snow in isolated areas but options to travel on the stable, icy old surface will be plentiful in low rated areas. Stubborn and firm wind slabs may provide easier travel but will also harbor a low probability risk of triggering a stubborn, hard wind slab. Moderate rated areas contain much more smooth wind slab. This typically means that the area was dominated by deposition throughout the wind and snow event. Anticipate firm, continuous thicker slabs in these areas that will also be stubborn and fairly strong but with weaker layers of new snow beneath that bring a higher probability of fracture and failure. As is often the case, these slabs have good bridging power but the possibility of finding and triggering a thin spot in the slab remains. In general, our moderate rated areas are at the lower end of the moderate rating while low rated areas are nudging towards moderate unless you are on the icy, old surface.

WEATHER: The needle on the gauge has once again swung around towards winter. The current temperature on the summit is -17F with 9F at Pinkham Notch. High pressure to our west will keep winds elevated from the northwest, though at a bit lower velocity than yesterday and last night. Expect 70 mph northwest winds to gradually diminish through the day, ultimately blowing around 50 mph with higher gusts, by dark. Temperatures will increase to around 0F during that same time frame. Expect another cold day on the mountain as the epic battle between winter and spring continues.

SNOWPACK: The 5” of snow recorded on the summit on Tuesday night and early Wednesday morning was blown around the mountain and redeposited by the usual, prevailing nuking winds that grace Mount Washington in winter. Several hours of sustained NW winds in the 80’s mph flanked by 18 hours of winds in the high 60’s and 70’s mph tend to beat up snow particles and either blow them out of our start zones or pack them into firm slabs. A combination of fairly low density snow, high wind speeds and a poor bonding surface in the form of the old, icy surface allowed the snow that fell 24-36 hours ago to be scoured and transported through, and out of, many avalanche start zones. That said, remember the forecasters rule of thumb that a typical ridgetop wind can double or quadruple the amount of snow deposited on a lee slope. Our ridgetop is atypical with a large flat expanse in the Alpine Garden that provides enough snow to easily quadruple and more likely octuple (yep, that’s a word) the amount of snow in wind slabs on lee slopes. Again, expect these slabs to be tough and challenging to trigger in most areas but the hard slab that would result would make for a harsh ride downslope. Stay tuned, winter ain’t over yet!

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 8:23 a.m., Thursday, March 23, 2017. A new advisory will be issued tomorrow.

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

2017-03-23

Avalanche Advisory for Wednesday, March 22, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravine have CONSIDERABLE and MODERATE avalanche danger. In Tuckerman, Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Central, Pinnacle, and Odell Gullies in Huntington Ravine have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential. All other forecast areas of both Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. The only exception to these ratings is the Little Headwall, which has Low avalanche danger. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEM: Wind Slab formed overnight is the primary avalanche problem today. With a currently upside-down, firm over soft nature, this surface layer will be particularly sensitive to a trigger this morning. A lack of visibility hampered morning observations, but we expect this slab to be thick in places and widespread over Chute, Center Bowl, Lip, and Sluice in Tuckerman as well as Central and lower Pinnacle and Odell gullies in Huntington. Pockets in lee areas of west through northwest winds will hold this wind slab in Moderate rated areas. Increasing wind speeds throughout the day will cause this instability to peak this morning or mid-day, decreasing as we approach wind speeds that should scour Huntington and create pockets of very firm slab in Tuckerman

WEATHER: It’s cold and windy up here. The summit is currently recording -2 F, with sustained northwest wind nearing 60 mph and gusts to 70. Throughout the day, this wind will increase, nearing 100 mph, and temperatures dropping to -20F. Snowfall and cloud cover is tapering off as this wind increases and temperature drops, remaining partly cloudy with no precipitation this afternoon.

SNOWPACK: We’re seeing a significant amount of new and blowing snow on the mountain, with 3.5 inches of snowfall recorded at Hermit Lake and 5 inches at the summit in the past 24 hours. Underneath this new snow, a mix of relatively stable surfaces exist. This ranges from pencil to 1 finger hardness wind slab over much of the terrain as well as areas of previously scoured old rain crust. The melt-freeze cycles over the past few days, with current temperatures well below freezing, have facilitated bonding between this wind slab and underlying layers. Snow that fell yesterday and last night arrived on West winds in the mid-40 mph range that shifted this morning to the Northwest and increased, with gusts to 70 mph. This transport of new snow from our largest fetch zones for Tuckerman Ravine has likely deposited a significant amount of snow in the Chute, Center Bowl, Lip, and Sluice. In Huntington, Central Gully should hold the largest wind deposits, both above and below the choke point, with Pinnacle and Odell having quite a bit of similarly deposited snow below the ice.  The wind slab formed in the aforementioned areas will display increasingly upside-down characteristics, with softer deposits made by the light to moderate overnight winds sitting underneath the more dense snow loading under the current winds.  Accordingly, the growing wind slab will be increasingly sensitive to a trigger.  Winds are forecast to increase through the day, with peak summit gusts around 100 mph late today, so we’re likely to see a morning or mid-day peak in instability as this high wind begins to erode the newly formed surface slabs, decreasing their size and sensitivity to a trigger.  Sensitive wind slabs could remain, though, in lower and more sheltered pockets of our considerable rated areas.

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 the Harvard Cabin.

Posted 9:20 a.m., Wednesday, March 22, 2017. A new advisory will be issued tomorrow.

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

2017-03-22