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

Avalanche Advisory for Friday, April 20, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is no longer forecast due to open holes in the snowpack and is not recommended as an exit from the Bowl.

AVALANCHE PROBLEM: Six inches of new snow overnight arriving on increasing NW wind makes wind slab our avalanche concern today. No visibility this morning adds a degree of uncertainty to today’s forecast. We expect the snow to struggle to adhere to the ice crust which will act as today’s bed surface. This highlights a key characteristic about today’s avalanche problem; wind slab will likely be touchy to human triggers. In Moderate rated areas, the combination of wind and the slick bed surface may allow scouring to take place leaving areas of bed surface exposed. Considerable rated slopes, those in the lee of our fetch, should hold much larger areas of wind slab with limited to no old surface exposed. The potential for large avalanches exist in these areas with the possibility of natural avalanches due to continued loading through the day. The floor of Tuckerman Ravine today will be avalanche terrain as we have seen avalanches run far this year on well-developed slide paths. The hard bed surface will demand the use of crampons and an ice axe for those choosing to travel in avalanche terrain.

WEATHER: Low pressure centered over Nova Scotia will continue to send bands of winter weather to Mount Washington today. After a midday lull yesterday in wind speed combined with a spike in temperature to the mid-20s on the summit, snowfall began along with an increase in wind and a drop in temperature. Winds bottomed out at 5mph around noon yesterday and by midnight were above 40mph. As of this morning, the summit recorded 5.2” of snow while just under 6” fell at Hermit Lake. Today, temperatures will remain in the 20’s F in avalanche terrain with the summit reaching the upper teens. Winds should stay in the 40-55mph range from the NW. Snow is likely; 0.25” of SWE is forecast to arrive by this evening which could amount to another 2+” of snow. Wind and temperatures tonight should remain similar to today with another possible 2” of snow by tomorrow morning.

SNOWPACK: Over the past week, 10” of mixed precipitation arrived with a SWE of 3”. This was followed by cold temperatures that allowed a thick ice crust to form. On Wednesday, this crust was 4cm thick in places with moist snow beneath. With continued cold Thursday and last night, this crust will remain thick and strong, limiting avalanche concerns to the surface wind slab. We expect the new wind slab to vary in size from small to large depending on terrain and aspect. The uncertainty of wind slab size today comes from a combination of weather and snowpack factors compounded by no visibility. This same visibility challenge will make safe travel decision difficult today, as seeing avalanche start zones will be difficult. Days like today, which have a degree of uncertainty, are best for choosing low consequence terrain. The Sherburne will ski well today with top to bottom coverage.

Bear tracks were seen around the Fire Road and Tuckerman Ravine Trail. Please use the bear boxes and keep your camp clean if staying overnight at Hermit Lake. The Harvard Cabin is closed with no camping allowed anywhere on the east side of Mount Washington except at Hermit Lake Shelters or adjacent tentsites.

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.
• Posted  8:00 a.m., Friday, April 20, 2018. 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

2018-04-20

Avalanche Advisory for Thursday, April 19, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. 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.  Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall has open water in the steep section as well as the stream bed above. It is not a recommended route out of the Bowl.

AVALANCHE PROBLEM: Due to the rugged ice crust on the mountain, you’ll find two distinct threats to safe travelling in steep terrain. The recent sleet storm finished with freezing rain which created a thick ice crust over top of a widespread glaze of sleet, wet snow and ice. New snow fell at the end of the storm on Tuesday afternoon and was able to stick in some areas, but not very well. Due to scouring of the snow, wind exposed, scoured areas above tree-line will require crampons for safe travel while many lee areas have collected enough snow to build some wind slabs. Low visibility, and other duties kept us from gathering many observations yesterday and this morning, but it seems that the ice crust will be the dominant surface in steep terrain. In areas where the new snow adhered to the ice, hand shears low in Hillman’s Highway showed that the new wind slabs failed easily in the new snow. Only a small amount (2-3”) of the recent snow was light enough to be carried by the wind and blown into our terrain but the icy bed surface will up the ante if you get swept off your feet. Human triggered avalanches are unlikely today unless you seek out these areas of wind slab. Additionally, light winds may allow the 1-2” of new snow that falls to build into small but more sensitive, new wind slabs. If we receive the upper end of the forecast amount, human triggered avalanches will become more likely and increasingly widespread.

WEATHER: Just 0.7” of snow fell on the ice encrusted summit yesterday. This snow was light enough to be carried by the wind, like the inch or two which fell at the end of the storm on Monday and Tuesday. That storm brought a generous coating of sleet and ice totaling 10” of mixed frozen types and over 3” of water equivalent. A low pressure system will pass to the south today and spawn snow showers and some fog. Expect another wintry day with a high temperatures near 20F. Snow surfaces are unlikely to soften despite the warmish temperature and low wind speeds. More new snow toight and tomorrow may create more significant avalanche concerns tomorrow and Friday.

SNOWPACK: Instabilities in the snowpack are limited to recent snow. Yesterday, 8” or more of moist rounds were found beneath a rugged 3-4cm ice crust. This ice crust was more ice than crust and was just barely bootable on sub 20 degree slopes. Anything steeper required crampons or a stubborn desire to link skin-able sections of wind deposited snow. Lower on the mountain, the Sherburne was recoated with the sleet which has covered the bare spots on the trail that had begun to emerge. The trail is very skiable all the way to the parking lot at Pinkham Notch.

Bear tracks were seen around the Fire Road and Tuckerman Ravine trail. Please use the bear boxes and keep your camp clean if staying overnight at Hermit Lake. The Harvard Cabin is closed with no camping allowed anywhere on the east side of Mount Washington except at Hermit Lake Shelters or adjacent tentsites.

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.
• Posted  7:30 a.m., Thursday, April 19, 2018. A new advisory will be issued tomorrow.

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

2018-04-19