Avalanche Advisory for Thursday April 30, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these locations. 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: We are continuing to trend slowly towards stability as all the new snow in upper elevations settles down. Warm ambient temperatures yesterday wet the snow and a period of freezing temperatures last night contributed to stabilization. Deeper areas of the new snow are rated Moderate due it’s depth and concerns that further heating today, coupled with some rain showers, will make these areas more prone to human-triggered Wet Slab or Wet Loose avalanches.

OTHER PROBLEMS/HAZARDS: Be aware of the potential for crevasses to be hidden underneath the recent snow. These slots have been growing in the Lip and are beginning to grow in other locations extending from the Sluice over to the Chute. Also anticipate the potential for falling ice today.  These issues will grow in intensity over the next several days due to the expected warming trend.

WEATHER: Yesterday was the 13th day in a row for new snow on the Mount Washington summit.  Recently, scant precipatation amounts have had little effect on the avalanche problem, but has maintained some lingering stability concerns over the past week.  This, in addition to cold temperatures, has kept conditions changing very slowly. Frankly it feels more like the end of March than April.  The prolonged period of low pressure systems that have plagued the higher terrain should give way to sunny skies over the next 24 hours. However, we will go through a round of snow, sleet, freezing rain and rain in avalanche terrain today before conditions improve on Friday. Summits will be in the clouds with a chance of mixed precipitation associated with a NE wind from 5 to 20 mph (8-32 kph). Temperatures will increase from the current of 24F into the mid-thirties.

SNOWPACK: Areas posted at Low danger today did not receive very much loading from recent snowfalls. The surfaces in these locations are as close as you’ll get to typical springtime corn snow. In the Sluice through Chute, conditions vary by aspect, but they all have a similar bed surface of old melt-freeze crust above mostly isothermal snow. New snow from this week has gone through a number of changes as the temperature hovered just above, and dipped below, the freezing point. Today’s warming trend will continue the melting/rounding process of the snow grains which will make for sloppy snow in the upper snowpack. It is the deeper areas of snow, such as the bowl like feature below the ice in Sluice, under the ice in Center Bowl and in the Chute where we have the most concerns for avalanche activity today. If you recall, the early days of our continuing period of unsettled weather, which brought 14” of snow in the last week, was cold with light winds. These weather conditions allowed the snow to fall somewhat undisturbed and though this snow bonded well to the warm crust beneath, it was a fairly weak layer in itself. While the upper snowpack went through a lot of changes since that time, suffice it to say that none of these changes was a dramatic, penetrating cycle of heating and refreezing. This melting and refreezing cycle would normally take most avalanche concerns off our radar this time of year. It is important to understand that while we have fair to good stability in Moderate rated areas, the potential for a wet slab avalanche remains enough of a concern that you should continue considering this hazard in your travel choices and trip planning. I’ll be carrying my beacon until I see a hard refrozen snowpack without the potential for these wet slabs. The upcoming warm weather will ensure that I’ll be carrying it at least through the weekend if not till the end of the season.

The Little Headwall has open holes of water and undermined snow, but it continues to be a skiable option for descending from the Bowl. Use extreme caution if choosing this route. Another alternative is to hike down to Hermit Lake, although expect an icy trail making microspikes and ski poles handy. The Sherburne ski trail is now closed at the #5 crossover, 1 mile up the Tuckerman Ravine Trail from the parking lot. At the rope, please avoid the muddy descent and cross to the hiking trail and walk down. Do not ski on the hiking 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 8:15 a.m., Thursday, April 30, 2015. A new advisory will be issued tomorrow.

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

2015-04-30

Avalanche Advisory for Wednesday, April 29, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these locations. 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: Today we are transitioning from wind slab avalanche problems to wet slab or wet loose avalanche problems. Overall the snowpack has been doing a good job working toward stabilization, but some areas still pose a threat due to the prolonged warming of near-surface layers. Expect avalanche danger to increase slowly but steadily through the day as temperatures creep upward. Though we are in the more stable end of the Moderate range, wet avalanche problems can be quite unpredictable and difficult to assess through snow pit stability tests.

OTHER HAZARDS: Be aware of the potential for crevasses to be hidden underneath the recent snow. These had been growing in the Lip more than other areas, but we typically see these in various locations from the Sluice through the Chute. Icefall is also a possibility today despite there being plenty of cloud cover.

WEATHER: Much of the snow that has fallen near the end of April has not fallen at ravine elevations. It has fallen above 5000’ and up to the summit. Today we expect mostly cloudy conditions with temperatures staying above freezing for most of the day. You may even get spit on by snow or rain (in fact, it’s snowing lightly as I write). Diurnal fluctuations have not been strong (i.e. nighttime lows are staying fairly warm) which means that the snowpack is mostly moist down to the older melt-freeze crust from mid-April.

SNOWPACK: Areas posted at Low danger today did not receive very much loading from recent snowfalls. The surfaces in these locations are as close as you’ll get to typical springtime corn snow. In the Sluice through Chute, conditions vary by aspect, but they all have a similar baseline of the old melt-freeze crust from over a week ago. Above this layer, you’ll find a mostly “rightside-up” snowpack in the Chute, so expect loose wet avalanches to be the primary threat here. Over closer to the Sluice, we found a 4-5” thick shin-bruising breakable melt-freeze crust at the surface over softer snow that was either moist or dry depending on the thickness. Stability was generally good yesterday, but this was primarily due to the bridging effect of the crust on top. As this layer loses strength today, the potential exists for wet slab avalanches. This will be greater in locations harboring cold dry weak layers underneath, such as in the Lip or tucked in deeper pockets under the ice in the Center Bowl. The likelihood of triggering a slide has been moving from possible to unlikely. However, we’re not quite there yet. Additionally, the size of a potential slab or loose avalanche that you can expect today could be large. These factors lead us to continue with a Moderate rating, and should be considered in your own decision making today as well.

The Sherburne is now closed at the #5 crossover, which is about 1 mile up the Tuckerman Ravine Trail from Pinkham Notch. At the rope, please cross to the hiking trail and walk down. Do not ski on the hiking trail.

The Little Headwall has some open holes of water and undermined snow, but it continues to be a skiable option for descending from the bowl. Use extreme caution if choosing this route. Another alternative is to hike down all the way to Hermit Lake, but when icy this has proven challenging to many and presents it’s own unique hazard.

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 8:25a.m., Wednesday, April 29, 2015. A new advisory will be issued tomorrow.

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

2015-04-29

 

Avalanche Advisory for Tuesday, April 28, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The only exceptions are Hillman’s Highway, the Lower Snowfields, and Little Headwall which have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these locations. 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: As winter refuses to release Mt. Washington from its grip, wind slab avalanches are the primary threat again today. Yesterday’s snowfall brought yet another round of snow into Tuckerman, which was likely transported on northerly winds into aspects that have a southerly-facing component. Expect the greatest avalanche danger to be found on the looker’s right side of Tucks as well as in the Lip and Center Bowl. In these areas you may find very stable snow near the bottom or middle, but unstable snow near the middle or top. Be careful of what you are traveling underneath.

WEATHER: Throughout yesterday, snow showers brought about 3” of snow to the summit. Down at Hermit Lake we received only a trace. Given the temperature trends, I strongly suspect the snow that fell above the ravines is cold enough to have been moved by overnight winds. These winds came from a NNE direction and increased in speed from 40mph at 6pm to gusts in the 70mph range around midnight. Winds today will diminish slightly, forecasted to be from the N at 45-60mph. Ravine temperatures may hover around the freezing mark again today while uppermost elevations should remain below freezing.

SNOWPACK: This stretch of weather has been interesting from an avalanche forecasting perspective. Snow totals and winds do not tell the complete story of what’s taking place. The relatively warm temperatures are one prominent factor keeping things interesting. With the ravine temps hovering around freezing, the ability of the new snow to move toward better stability is much greater than is typical in mid-winter; this is happening in the absence of the usual springtime melt-freeze cycles. I expect that this process is underway, especially within the 3” of snow that came in the week prior to yesterday, we do not have enough evidence yet of stable snow to forecast Low avalanche danger. This means that your ability to carefully assess the snowpack will be critical to your decision of whether or not to travel on a certain slope today. You should also be paying attention to the amount of solar energy penetrating the snowpack. This can help stabilize some thinner slabs, but if it doesn’t reach deeply enough in thicker slabs, it might only serve to weaken the uppermost snow, which makes human triggered avalanches more likely.

If you want to avoid much of the new loading hazard, stay away from the right and center of Tuckerman. Hillman’s Highway and the Lower Snowfields have much less risk and have been providing enjoyable skiing for many people in the last few days. Remember though that Low avalanche danger does not mean “No Danger.” Stay alert for isolated slabs and be wary of traveling in the avalanche path below others.

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 8:15 a.m., Tuesday, April 28, 2015. A new advisory will be issued tomorrow.

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

2015-04-28

Avalanche Advisory for Monday, April 27, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. Lobster Claw, Right Gully, Sluice, Lip, Center Bowl, Chute, and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Hillman’s Highway, Lower Snowfields, and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely except 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.

AVALANCHE PROBLEM: Avalanche danger will be increasing today as wind slabs form during daylight hours. The danger will increase most quickly on slopes such as Right Gully and Sluice. Prior to new snow, areas such as the Lip and Center Bowl hold the greatest hazard and will receive cross-loading of new wind slab today. Should temperatures in the ravine stay on the warm side and precipitation falls as rain, there is the chance for either wet loose avalanches or wet slabs. The location for both of these wet avalanche problems would be across all forecast areas in locations that have collected snow from the previous week.

WEATHER: Another round of light precipitation is expected to fall today. Liquid equivalents in the 0.10” (2.5mm) range will bring another 1-3” (2.5-7.5cm) of snowfall to the summit. We expect this to fall as snow at the elevation of Tuckerman and higher, but temperatures will be very close to the point where it may fall as rain. This precipitation will coincide with an increasing wind from the N and NE, rising to 50-65mph (80-105kph) with higher gusts.

April has been a very snowy month on the summit, though unfortunately not all of this snow has fallen on lower elevations. This is very normal at this time of year, and it means that the weather you are experiencing at Pinkham Notch or at Hermit Lake may not be representative of what’s taking place above treeline. Today will be another example of this, and it’s the higher elevation weather that will play a role in the avalanche conditions more than what’s down below.

SNOWPACK: Today’s concerns are driven by two sets of factors. First are the pre-existing conditions. Were it not for incoming snow and increasing wind, there would probably be more areas rated at Low danger. The recent snowfalls have had some time for some stabilization, and in some locations the snow did not completely blanket the terrain in new slab. Areas such as the Sluice, Lip, and Center Bowl did show smooth blankets of new slab, while Hillman’s, Right Gully, and Lobster Claw have many locations with exposed old surfaces. If you’re venturing out into the right or left side of the ravine, be wary of areas of deeper snow. This is an indicator that wind loading has taken place and the snowpack might be unstable.

The second set of factors is related to the new snow coming today. We’re expecting some loading to take place on aspects facing south through east. How quickly this develops will depend on how much snow we receive and the wind’s ability to transport it from upper elevations down into the avalanche start zones. You’ll need to monitor this carefully, especially later in the afternoon.

OTHER HAZARDS: 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. Recent cold has kept these in check to some extent. Emerging crevasses in the ravine and holes in the Little Headwall may be hard to recognize today 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.

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 8:15 a.m., Monday, April 27, 2015. A new advisory will be issued tomorrow.

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

2015-04-27

Avalanche Advisory for Sunday, April 26, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The only exceptions are the Lower Snowfields and Little Headwall which have Low avalanche danger. 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: Wind slabs exist throughout much of the ravine, providing snow stability conditions from the upper end of the Moderate range right down through the lower end of the range. Your terrain choices will certainly play a role in how much exposure you have to the avalanche hazard. Remember, by the time you have reached the floor of Tuckerman, you have already entered avalanche terrain and are at risk of an avalanche hitting you and your group from above. The areas of greatest concern are in the Sluice, Lip, Center Bowl, and Chute, as well as in the flat terrain beneath these areas.

WEATHER: Today will be much like yesterday as far as weather is concerned. We currently have some visibility, but with the forecast as it is, I think the prudent thing would be to expect thick fog to obscure sight lines at elevations above Hermit Lake. If visibility gets better, we should consider ourselves fortunate. There is a chance for a light snowfall to bring a trace to 2” to the summits, though I doubt if we get this it will affect snow stability to a great degree. Temperatures in the ravine will rise to somewhere near the freezing mark, but the fog and humidity makes things feel much less comfortable than a typical 30-35F day.

SNOWPACK: The story of the snowpack begins with a buried melt-freeze crust layer that is still holding heat and moistening the snow immediately above it. However, you don’t have to look far above the crust to find cold dry snow with a layer of weak rimed crystals mixed in. Slab that built from the recent snow on top of this weak layer is denser and dry. If you are on foot, you’ll feel the discomforting “upside-down” snowpack, which should raise the hairs on the back of your neck. If you’re on skis, you might not notice this underfoot, but a couple pole-probes should alert you to the presence of weak snow under strong snow. The majority of the new wind-loaded slab has built in the mid-elevations of the ravine, such as directly above and below the ice in the Center Bowl. Hillman’s has old surface showing in places all the way to the top, but the narrow section just above the fork appears to be holding deeper slab. Where we poked around under Right and Lobster Claw, the slabs were between knee-deep and thigh deep, but there are pockets of old surface showing here and there as well. This leads us to believe that there is a wide variety of stability falling within the Moderate range throughout all areas.

OTHER HAZARDS: 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. Recent cold has kept these in check to some extent. Emerging crevasses in the ravine and holes in the Little Headwall may be hard to recognize today 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 is open about 2/3 of the way down. You’ll see the rope across the trail directing you back to the Tuckerman Ravine Trail, where you will need to hike 3/4 mile down to the parking lot.

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 26, 2015. A new advisory will be issued tomorrow.

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

2015-04-26

Avalanche Advisory for Saturday, April 25, 2015

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

The White Wolf? Weekend Update 4-24-2015

Talk about full on winter!  It’s really hard to believe it’s almost May with the full on conditions today.  No visibility, temperatures in the teens, and 8.3” of snow in the past 48hours as made for more like a February afternoon than a typical spring day.  We are most concerned about the increasing avalanche danger that has developed over the past 24 hours with some areas currently bumping the upper end of the Considerable rating.

Fine grains are mixing in with average sized crystals which are producing a high water content per inch of snowfall packing into some fairly dense slabs.  As we expected the main weaknesses can be found above the old surface in lower density slabs created yesterday during periods of light wind.  Snow should taper overnight, but forecasts expect continued low visibility and temperatures in the high teens, perhaps reaching 20F on the summits. A blustery morning should give way to a diminishing wind in the afternoon, but currently it appears a chance of precipitation will keep all of us on our toes for the day.

With the information I’m seeing right now, along the weather that was slapping my face today, there is no way to sugarcoat or get around the reality that we will have avalanche issues tomorrow.  Expect to see an elevated avalanche danger rating for a number of areas with some “Considerable” slats probable.  Avalanche experience, skills, equipment and a history of good conservative decision making will be important.  If you have these skills and abilities several other issues and challenges would run through my mind.  1. With potential low visibility, and being a Saturday in April, I would have a fair amount of angst for triggers above me that I can’t see.  Expect some users coming in from multiple locations like hyenas converging on desired prey   2. Will someone adjacent to you, seemingly far away, trigger an avalanche that will propagate to your location.  Or 3. To ski something safely will ‘ski cutting’ a slope to clear it send snow down onto others below.  Frankly, slab instability and lots of people just don’t mix in the confines of an alpine cirque with avalanche paths that converge in multiple locations.  It is very difficult to mitigate the multiple hazards that are reasonable during a quiet day midweek versus dealing with a busy Saturday.  It can spell a disaster mixing hazards and crowds.  I don’t say these things lightly, but I think it’s important to accurately portray the potential situation tomorrow.  And although it’s not lining up as the cover shot of the “Worst Case Scenario” books it might be found on page 5 or 6.

Okay that was important to get across. Now how could it be not all that bad?  Loading and snowfall today has me believing that we are fully in the midst of Considerable avalanche danger.  This means that natural avalanches are possible.  If this occurs in numerous slide paths today/tonight we may rid ourselves of a good deal of hazard.  Although this is hard to plan or count on, it’s a possibility.  If snow shuts down overnight the concern for natural avalanches will dissipate a bit tomorrow which may leave us with a number of areas potentially being Moderate on Saturday.  This is quite plausible, but we will undoubtedly have concern for human triggered avalanches.  “Moderate” means a lot of different things to people.  Read the full meanings, size, and potential destructive forces for “Low”, “Moderate”, and “Considerable” in the scale below.  For a minute, focus only on the definitions for LOW and CONSIDERABLE.  There’s a pretty big gap between them isn’t there!!??  Well that’s the hole MODERATE is trying to fill.  So in reality there is a difference between instability that is just a bit above Low versus just below Considerable.  I think tomorrow’s Moderate will be just coming off of Considerable.

danger-scale-english

I recognize these are hard things to plan around for coming to the mountain or not, but for what I’m seeing it may not be the best Saturday to head for east facing higher terrain from the Gulf of Slides to the Northern Presidentials.  Some improvement for Sunday is likely, but anticipate some lingering avalanche instabilities.  Truthful and accurate reporting is important to us and I frequently ask myself the self-monitoring question “Am I crying wolf?”.  Although I do believe things can play out a number of ways overnight the above discussion reflects a high likelihood of how it will all play out tomorrow.  Be sure to check the Avalanche Advisory each morning before heading up into avalanche terrain.  See Jeff’s video post about descending from the Ravine.  We’ll see you in the hills or on the internet. Chris

Avalanche Advisory for Friday, April 24, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. The Lobsterclaw, Right Gully, and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. (The Little Headwall is falling apart and is not recommended. See posted video on our website if reading this hardcopy). 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:  As of midnight the summit received 6.7″ (17cm) of snow during the previous 36 hours.  Since then it has been snowing lightly each hour which will continue through the day with up to another 2″ (5cm) forecasted. Therefore, expect Wind Slabs to exist and more to develop into the afternoon.  Anticipate the most instability on lee slopes of W and NW winds rated at “Considerable” such as the Sluice, Lip, Center Bowl/Headwall and Chute. Also be ready for areas posted at “Moderate” to be on the upper end of the rating’s definition, hedging towards Considerable this afternoon. With an increasing wind anticipate new layers near the surface to be denser than the layers deposited yesterday creating a classic, unstable and “upside down” wind slab.

WEATHER: The unsettled period of weather over the past couple of days, which will linger into the weekend, has been delivering a consistent slow steady snowfall.  6.7″ (17cm) of snow recorded in the past 36 hours, coupled with 2-5″ (5-13cm) expected over the next day, will continue our avalanche danger concerns into the weekend. Wind speeds over the past several hours have increased into the mid 60’s mph (95+kph) from the NW. This trend will dominate the day with velocities crawling towards 70+mph (112+kph)this afternoon. Summit temperatures are beginning the day at 12F (-11C) and will not move up much making for a cold winter experience.  Be ready for all these factors to work together limiting visibility in the alpine zone.

SNOWPACK: On Thursday snowfall began on a S wind and shifte d from the W during the last 4″ (10cm) of accumulation. W winds were moderate, blowing in the upper 30’s mph (50kph) for the vast majority of daylight hours.  Since midnight, speeds increased and have been gusting over 60mph (95kph) this morning. This general theme will create an unstable snowpack situation by building dense slabs with smaller wind beaten particles over lighter layers that developed yesterday.  These lighter less dense slabs should be the weak layer to look for in your stability tests.  I think you will find this above the interface with the old hard surface as initial bonding was fairly good.  Today requires avalanche experience, training, and a history of good decision making in unstable snow.  We are not in spring and have new cold snow instabilities to deal with that currently exist and will continue to build into tonight.   The avalanche hazard has increased from yesterday, although still within the Considerable rating, due to additional snow and higher wind speeds.  We are not yet at peak for these instability issues so expect an increasing hazard as the day wears on.  We’ll discuss the prognosis for Saturday and Sunday in the Weekend Update that will come out this afternoon.

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.  The move back into winter over the past 48 hours has limited the development of these problems.  However, expect emerging crevasses and some undermining hard to recognize, due to being hidden by new snow.  The avalanche dangers listed above lead today’s objective hazards with crevassess and undermining following behind.

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 is closed from the lower switchbacks to the parking lot due to mud.  Please cross over to the Tuck trail at the arrow sign and walk the short distance to your car.

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 7:50a.m., Friday, April 24, 2015. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713

2015-04-24

Avalanche Advisory for Thursday. April 23, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine will have Considerable and Moderate avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches will be likely. The Lobsterclaw, Right Gully, and the Lower Snowfields will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches will be possible. (The Little Headwall is falling apart and is not recommended. See posted video on our website if reading this hardcopy). 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 a rating lower than the posted danger level. However, this should change as we move through the morning and into the afternoon. Because of last night’s snow, in addition to another couple of inches forecasted today, expect Wind Slabs to exist and more to develop through the day.  Anticipate the most instability in the lee of W and NW winds, such as in the Sluice, Lip, Center Bowl/Headwall and Chute. Slabs and the avalanche problem will grow today if the weather forecast plays out. As this occurs anticipate the avalanche danger to creep into the posted ratings depending on timing of additional snow showers. This is most probable later this afternoon.

WEATHER: Well the heavy snow we hoped for did not occur.  As of 7am the summit received 3.7″ of snow with an additional 1-2″ expected today, ultimately giving us a potential 5-6″ available for wind slab development.  During the onset of snow yesterday a moderate S wind blew for 8 hours before transitioning to a 40-55mph W wind very early this morning.  Over the last 2 hours winds are starting to move towards the expected NW, gusting to 60mph.  Winds may drop off a bit to 45mph today, but will continue to be decent loading speeds for slab growth. Temperatures are beginning at 16F this morning and only rising slightly through the day.

SNOWPACK: A rising temperature yesterday, peaking at 30F on the summit in the early afternoon, allowed for decent ski conditions and a bonding surface for snow that began around 1pm.  The initial S wind should have created some thin slabs on N facing start zones near the ridge. Portions in the upper climber’s left of Hillman’s and Left Gully are some good examples. Overnight, W winds likely began loading our more dominate aspects facing E, such as the Chute, Center Bowl, and Lip.  Current obscure skies and blowing snow make visual confirmation difficult, but historically thin slabs have resulted in similar conditions.  Consistent NW winds and another couple inches of snow will slowly increase avalanche danger through the day.  The ratings are posted with the anticipation of this to become reality.  If we fall short in accumulation expect all areas to struggle reaching their forecasted danger levels. With the potential of 5-6″ available between last night and today, with good W and NW loading wind speeds, a Considerable rating is appropriate.   Based on the nuances of moguls, melted out brush and exposed rocks above treeline new slab development will not be as consistent or large as mid-winter.  Expect a variety of conditions and realize hard old surface down low doesn’t mean you will find the same up high. With the history of wind over the last 24 hours I would expect most new slab to be in the upper elevations of each forecast area.

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, due to being hidden by new snow.

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 is closed from the lower switchbacks to the parking lot due to mud.  Please cross over to the Tuck trail at the arrow sign and walk the short distance to your car.

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 8:10a.m., Thursday, April 23, 2015. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713

2015-04-23

Avalanche Advisory for Wednesday. April 22, 2015

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