Apr 222015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine will have Moderate and Low avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches will be possible. All other areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely except for small avalanches in isolated terrain features. 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: All areas are starting today with a stable snowpack and Low avalanche danger. Mixed precipitation and snow this afternoon with a W, SW, and S wind from 25-40 mph will create Wind Slab primarily in upper start zones. Slabs may be dense and heavy due to the possibility of a mixed crystal type until early evening. If a prolonged period of a “New England wintry mix” hits us it will consume the available water, giving us quite a bit less than the max 4″ of snow forecast. Conversely, if we get mostly snow, expect the danger to move into the upper end of the Moderate danger later today. Eventually, around midnight ratings will likely beyond Moderate for most areas.

WEATHER: Precipitation amounts during the past 36 hours were impressively diverse. Close to 2.5” of rain fell near Conway while not much more than 0.1” fell north of the Presidentials. The snowpack, holding plenty of free water, froze hard overnight from the upper half of the ravines to the summits, however at Hermit Lake the mercury only fell to 31F    (-1C). Another wet shield is heading our way with snow beginning this afternoon. Expect snow to become heavy at times, producing up to 2-4″ today with a W wind shifting to the S. Heavy snow tonight will add to another 4-8″, perhaps generating up to a foot (30cm) by tomorrow, being delivered on a W wind approaching 70mph (112kph).

SNOWPACK: As the snowpack drained overnight and began to freeze from the surface down, overall stability increased. At the 3800’ Hermit Lake level the ambient air temperatures fell to 31F (-1C) freezing the surface, but snow temperatures at 10 and 20 cm down from the surface are still a warm 0C (32F). The summit falling to 21F early this morning insinuates a deeper freeze took place at higher elevations. As snow falls this afternoon and into the overnight a number of skier produced nooks, crannies, and moguls will help create some anchoring, such as in the Lip. However with recent warm air and rain most areas have settled and are smooth making a slick bed surface for the afternoon snow event. If precipitation begins as a wet mix, some bonding between layers can be expected.

OTHER HAZARDS: The typical springtime hazards have emerged. 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. Falling ice is the hardest to predict and should be given a lot of respect and room. Because of this unpredictability, we generally recommend hazard avoidance as a primary strategy. As an example, Lunch Rocks or “Icefall Rocks” is right in the bulls-eye and has been the scene of many accidents over the years, so avoid this location. Other hazards such as emerging crevasses may be hard to recognize late today and tomorrow, due to being hidden by new snow. The vast majority can be found in the Lip towards the Center Bowl.

The Little Headwall has suffered from a collapsed section. We are no longer recommending this as a route out of the bowl. The Sherburne Ski Trail will have the lower section closed beginning today. 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 8:40a.m., Wednesday, April 22, 2015. A new advisory will be issued tomorrow.

Christopher Joosen /Jeff Lane, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713

2015-04-22

 Posted by at 8:47 am
Apr 212015
 

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Low avalanche danger. The Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely except for small avalanches in isolated terrain features. 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: Rain today will create conditions that can lead to wet slab avalanche releases. In the Lip and Center Bowl, the problem stems primarily from the potential for runoff to overwhelm the waterfall’s existing drainage channels. This has led to very large destructive avalanches in past events like it. Other locations posted at Considerable have received new snow in the past 24 hours, which may have been capped off with freezing rain. As we warm further and transition to rain, there is a potential for this new snow to slide as either a wet slab or a wet loose avalanche. As precipitation changes back to snow later today, the problems created by rain on surface slabs will subside, but percolating water coursing down through the snowpack and into the headwall may still keep alive the chance for a waterfall blowout.

WEATHER: Put simply, today will be a nasty day in the mountains. Seriously, if you are reading this before leaving from Pinkham, I encourage you to think about how much you enjoy being soaked to the bone with temperatures in the 30’s F. Unless this is just your cup of tea, you might want to find an alternative to hiking to the bowl today. We’ve had a lot of precipitation fall on the mountain in the last 24 hours. Precipitation began as snow across much of the higher terrain, leaving a little more than 3” of snow at the summit before changing over to freezing rain. I don’t yet have a rain total for Hermit Lake, but at home in Conway I received 1.85” of rainfall by 5am. The potential exists for another 0.25” to 0.5” of rain to fall on the mountain today, possibly heavy at times this morning. As is always the case in the mountains, weather can come faster and heavier than the broader synoptic scale forecasts may indicate. It looks like more snow at the upper elevations in the coming days, so pay attention if your plans involve a trip to the mountains this week.

SNOWPACK: Today’s Considerable rating might be on the conservative side for areas such as Hillman’s. 3” of dense snow may not be much, but I do suspect some loading took place while winds were strong from the SSE and temperatures were below freezing. Rain on this new snow layer may simply be absorbed, or it may produce smaller wet loose avalanches. In the worst case scenario, an upside down slab may have developed that could release. Over in the Lip and Center Bowl, the concerns are much more serious. The hazard potential there is virtually unpredictable. There are no reliable tests or other ways to detect whether or not the waterfall will blow out a deep slab. Traveling into the bowl, even just into the flats near the bottom, puts you in the line of fire from this type of avalanche.

OTHER HAZARDS: The typical springtime hazards have emerged and it will be challenging to protect yourself from them today. You should be aware of the potential for falling ice, crevasses, and undermined snow. These objective hazards exist and to a large extent are beyond your control. My advice for today is to avoid the potential hazard entirely.

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 6:35a.m., Tuesday, April 21, 2015. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713

2015-04-21

 

 Posted by at 6:31 am