Frank Carus

Apr 252015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. Natural avalanches are possible and human-triggered avalanches are likely in The Sluice, Lip, Center Bowl, and the Chute and are rated CONSIDERABLE as a result. All other areas have Moderate avalanche danger. Natural avalanches are unlikely but human-triggered avalanches are possible in Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, and Lower Snowfields. The only exception is the Little Headwall which has Low avalanche danger but has some open holes in the waterfall area. Use care if riding this and start from Connection Cache down the trail from the floor of the Ravine. Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington.

AVALANCHE PROBLEM: A surprising amount of recent new snow and ideal wind speeds for loading lee slopes have built Wind Slabs in Tuckerman Ravine. These wind slabs are likely to generate medium to large size avalanches, sensitive enough to be triggered by a skier, rider or climber and will have the ability to propagate a crack a long distance. They will be more than capable of burying a person and killing them by suffocation or trauma. This is true in Moderate as well as Considerable rated areas. Lower angle areas with bushes and rocks may be less prone to avalanche but could still be swept by debris from avalanches starting higher in the terrain. Once you pass the first aid cache on the way into the Ravine, 15 minutes up from Hermit Lake, you are in avalanche terrain.

WEATHER: Low visibility is expected to be a problem all day. Flat light and fog will make identification of critical snowpack details, as well as spotting people in avalanche start zones above you, a significant challenge today. A trace to 2” (TR to 5 cm) of new snow will further complicate things and add to our stability concerns. Cloud cover will keep temperatures below freezing even as the ambient temperature rises to the low 20’s F on the summit. Expect a windy, cold winter-like day.

SNOWPACK: A grainy and textured bed surface of refrozen corn snow allowed the initial new snow falling on it a few days ago to bond. The snow just above is our weak layer due to it being deposited during very low winds. Think of this layer as generally intact snowflakes with weak arms trying to hold the overlying firmer wind slab in place. These flakes are currently quivering and shaking due to the strain of holding up the wind slab which is likely to be thick in many of our start zones. In total, 9” (23 cm) of new snow built this wind slab on 40-60 mph (65- 95 km/h) W and NW winds. The wind slab is soft enough to crack easily and depending on the location will be finger to pencil hard. We have not been able to verify what has naturally avalanched, what has potentially been reloaded and what is harboring the thickest wind slabs. Because of this we need to assume all locations still possess substantial hazard and instabilities. Looking ahead, keep in mind the weakening affect that heat and filtered sunshine will have on this slab.

OTHER HAZARDS: The typical springtime hazards have become less of a problem with the recent freeze-up. You should be aware of the potential of falling ice, crevasses, and undermined snow. The best you can do to mitigate the risk from these objective hazards is to avoid them, especially during times when they are more probable. Hazards such as emerging crevasses and holes in the Little Headwall may be hard to recognize today and tomorrow, due to being hidden by new snow. The greatest hazard today is the threat of avalanches, and debris running on to the floor of the Ravine. The Sherburne Ski Trail will have the lower section closed. You can ski (mostly) to the #3 crossover, then pack up the skis for the 3/4 miles of hiking down the Tuckerman Ravine Trail.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 8:30 a.m., Saturday, April 25, 2015. A new advisory will be issued tomorrow.

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

2015-04-25 Print friendly

Apr 202015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Low avalanche danger. Natural and human-triggered avalanches are unlikely.

Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: Temperatures will hover around the freezing mark in our Ravines today with wet snow and rain creating the potential for wet loose avalanches. Keep a close eye on the type and rate of precipitation since it will determine if more significant avalanche problems will develop. It is conceivable that the 3-6” (7.5-15cm) of snow and sleet forecast for the summit will create wet slab issues as rain begins to fall on the new snow. This could push our rating into a Moderate danger rating with human triggered avalanches becoming more likely in the steepest terrain.

OTHER HAZARDS: The usual spring hazards are in full bloom this week.  Large flows of ice have numerous areas where horizontal cracks are forming and the Sluice ice, above Lunch Rocks, is already missing some chunks. Rain will undoubtedly spawn more falling ice as it weakens the ice-to-cliff bond and melts channels through ice columns. Reduced visibility due to summit fog, flat light and snow will challenge navigation as well as your ability to identify and manage objective hazards. Additionally, the snowpack is slowly gliding downhill as a unified mass and is pulling away from cliffs, creating crevasses and moats. These may change quickly, and though many filled in with sluff debris yesterday, they will now doubt grow larger with this week’s weather. Undermined snow is creating challenges for exiting the Bowl and will become more undermined and more dangerous with increased meltwater and runoff. While the Little Headwall is still skiable, there is open water both above and below, with large moguls throughout. The safer exit from the Bowl is to carry your skis down the hiking trail to HoJo’s where you can easily pick up the Sherburne Ski Trail. As of yesterday, it was just possible to make it to the parking lot, though the riding involved threading the needle through bare patches while raking your bases over exposed rocks. It may be best to cross back over to the Tuckerman Ravine trail as the snow disappears. Please respect our advice when we string the rope across the ski trail…foot traffic damages the trail and leads to erosion.

WEATHER and SNOWPACK: After perfect spring conditions yesterday, the weather is taking a turn for the worse. Precipitation will start around lunch time with wet snow before changing to sleet, freezing rain and then rain tonight. High winds and fog will challenge visibility and make for unpleasant above tree-line travel, but I don’t expect this wet snow to be moved along the ground and drift into the wind slabs that you would see in colder, drier winter conditions. A slushy surface is the most likely conditions you will find today with firm and less edge-able snow beneath in some areas. Unsettled weather is on tap all week with proverbial April rain and snow showers expected most days.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 7:45 a.m., Monday, April 20, 2015. A new advisory will be issued tomorrow.

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

2015-04-20 print friendly