Avalanche Advisory for Friday, February 28, 2014

This advisory expires at Midnight.

Tuckerman Ravine will have CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, and Chute will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.  Lobster Claw, Right Gully,  Left Gully, Hillmans Highway and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.   All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully in Moderate rated areas, most of which are pushing the upper boundary of their rating.

AVALANCHE PROBLEMS: Wind slabs will again be the primary hazard today. These slabs formed from 2″ of light density (4.5%) snow blown in on 35-50 mph (55-80 kph) generally westerly winds. These windspeeds created windslabs in Considerable rated forecast areas that are likely on the touchy side. Avoid steeper areas of windloaded terrain and be alert for continued loading, especially early today.  Persistent slabs due to early faceting above and below the raincrust may contribute to recent wind slab avalanches making them larger than the more obvious surface layers. Slabs formed by sluffing snow beneath steeper pitches of ice and rock are also a concern. Protect yourself well before venturing onto these areas.

WEATHER: Approximately 6.5″ (11.5cm) of snow have fallen on the summit of Mount Washington in the past 4 days as low pressure spawned squall lines across the range. West-northweast winds this morning at 45-60 (70-95 kph) will decrease in speed to 35-50 mph (55-80 kph) and shift to the west. Unseasonably cold temperatures will challenge anyone today recreating in the mountains. High temperatures on the summit are forecast to top out at -15F (-26C) despite clearing skies and some sunshine. Looks like mitten and facemask weather will hang around through the weekend and into next week.

SNOWPACK: A natural avalanche the night before last in the center of Center Bowl about 70 cm thick ran out onto the floor of the ravine. Sluice, Lip, 75% of Center Bowl and Chute were all loaded with the same snow. Central Gully is also ripe with new loading. Clearing this morning may reveal more signs of natural avalanches that occurred last night as snowfall amounts appear to have exceeded forecast amounts. These areas of wind slab are resting on an ice crust which was found to have early stages of a weak layer of facets developing. Though hangfire in the Center Bowl kept me from approaching the crown, it appears as if the ice crust broke out under the wind slab load and then ran on top of the ice crust. The crown line was partially reloaded by yesterday morning and clearing today will give us a better indication  of last night’s loading based on the remains of the crown line. Beneath the ice crust was generally stable pencil hard windslab in the areas assessed from left of Lobster Claw over to the looker’s right edge of Sluice. Field work yesterday near Sluice came to a screeching halt when a large party entered the Ravine for photo ops on the debris pile and proceeded up into Lunch Rocks unaware of the existing hangfire hazard from Center Bowl and Lip not to mention from a Snow Ranger and his partner probing the edges of unstable slopes above. They followed no safe travel protocols, carried no avalanche safety gear and exhibited several classic “human factors”. I felt helpless, like a field biologist watching baby zebras being stalked by lions. If you’re reading this you are probably aware of the intersecting avalanche paths in the Ravines. If you choose not to educate yourself about avalanches, well, good luck with the lions.

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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin. Posted 8:25a.m. 2-28-2014. A new advisory will be issued tomorrow.

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

2014-02-28 Print friendly

Avalanche Advisory for Thursday, February 27, 2014

This advisory expires at Midnight.

Tuckerman Ravine will have CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillmans Highway will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.  Lobster Claw, Right Gully and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, and South Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.   All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEMS: Wind slabs will again be the primary hazard today. Southwest winds will load forecast areas which have a primarily northeasterly aspect today. The degree to which these slopes are loaded depends on the timing of the increase in wind speed and the rate of snow fall in the afternoon. Today’s new wind slab is adding mass to existing wind slabs that developed over the past 3 days. These older wind slabs are a close second in terms of our hazards. These slabs are resting on an icy crust layer and is capable of cracking and producing an avalanche. Persistent slabs should also be on you radar when approaching areas that receive alot of loading from sluff activity, basically where slope angles transition from steep to less steep and allow snow to pile up into deep hard slabs. Cold temperatures and low density snow can be easily transported by today’s forecast windspeed.

WEATHER: Approximately 4.5″ (11.5cm) of snow have fallen on the summit of Mount Washington in the past 3 days as a low pressure continues to spawn squall lines across the range. A trace to 2″ today on southwest winds at 30 mph or so will move new snow and crossload terrain features. Ground level clouds and blowing snow will flatten the light and make snow surfaces more difficult to see and assess. Travelling outside of avalanche terrain, the primary challenge will be the cold temperatures hovering around zero, depending on elevation, as well as a breakable ice crust over softer snow in the woods.

SNOWPACK: Rain crust formed during the mixed precipitation that fell on the 20th is still a big player in our snowpack. Subsequent wind slabs and sluff piles were deposited on this layer which is also potentially generating facet growth. While this ice crust is over hard snow in areas which were previously scoured out by wind such as the lower 2/3’s of Hillman and Left, it is over much softer layers of cold snow in others. If I were out today looking for interesting snowpack features, faceting among the ice pellets below the ice crust as well as just above the crust would be the subject of my curiosity. As mentioned several times in the past week, the ice crust is contributing to the tensile strength of the weaker snow beneath. This strength may be overcome by the increased loading that has occurred during the past several days. Avalanches that occur could step down through the ice crust and entrain more snow than just the surface layers of windslab that grow today. An avalanche occuring in the hard slabs formed by sluffing activity can always be larger than you might expect so consider your options when travelling in these 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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin. Posted 8:30a.m. 2-27-2014. A new advisory will be issued tomorrow.

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

2014-02-27 Print friendly

Avalanche Advisory for Wednesday, February 26, 2014

Expires at Midnight

Tuckerman Ravine will have CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillmans Highway will have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.  Lobster Claw, Right Gully and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, and South Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making and cautious route finding is essential.   All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEMS: Expect new Wind Slab to develop with the forecasted snow squalls today. This will load on top of the wind slabs that have developed since the freezing rain event last week.  Anticipate areas that are most protected from W winds, such as the Lip and Center Bowl in Tuckerman, as well as Central through Odell gullies in Huntington, to be right in the bullseye.   Be suspicious of any new snow that is loaded above the aforementioned crust and perform multiple stability tests as you travel.  Danger ratings posted at Considerable are starting the day one solid step below today’s posting.  They will transition to the Considerable ratings depending on exactly how much squall snow falls as bands move across the region.  It is quite possible that some forecast areas will struggle to reach their rating if we stay on the lower end of the precipitation forecast

WEATHER: Over the past 2 days we have picked up just shy of 3” (7.5cm) on the summit that has been loaded by winds from the W and WNW between 40 and 85mph (68-136kph).  Today, there is a cold front moving our way which will bring a quick hitting system expected to deliver heavy snow squalls at times.  1-3” (2.5-7.5) is anticipated from this event between late morning and dusk, with more upslope snow after dark.  New precipitation will be associated with increased W winds, from the current of 35 (60kph), to 65mph (104kph) this afternoon. This is the dominate weather issue to be paying attention to while in the field.  Exact snowfall intensity, wind velocities, and snow amounts will work together to create the actual level of wind slab problems today.  Watch all three of these factors. A similar squall line is expected tomorrow.

SNOWPACK: As of this morning the dominant feature in the snowpack remains the freezing rain crust. Your primary concern should be focused on new snow above the crust that is not well bonded to this knife hard, and fairly impermeable layer.  The issues will be a mix of older snow from late Friday, new snow from the past 48 hours, and any new snow that develops during today’s squalls. Cold air in place will likely keep new snow densities light making it easy to load with the projected wind speeds.  Expect initial early snow to layer in the deposition of Ravine terrain features more intact due to lighter winds.  This will be followed by denser slab development as new snow crystals become both fragmented and packed in tighter by higher W wind speeds.  This initial lower density snow is the most likely weakness to fracture and fail.  An overrunning avalanche would quite plausibly step down and entrain other layers of slab that we have been discussing over the past several days. Snow beneath the crust also harbors some potential weaknesses, but these will be harder trigger. However, overrunning avalanche load would likely rip out the crust layer particularly in areas of deeper slabs over this lens, like in Tuckerman’s Lip and Center Bowl because of the increased mass.

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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin. Posted 7:10a.m. 2-26-2014. A new advisory will be issued tomorrow.

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

2014-02-26 Print

Avalanche Advisory for Tuesday, February 25, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate avalanche danger in all forecast areas. Natural avalanches are unlikely and human triggered avalanches are possible. The only exception to this rating is the Little Headwall, which has Low avalanche danger. Natural and human triggered avalanches are unlikely in this area.

Huntington Ravine has Moderate and Low avalanche danger. Central Gully has 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 except in isolated terrain features.

AVALANCHE PROBLEMS: Be on the lookout for new wind slab sitting on top of last weekend’s rain crust today. You’ll find this in areas that are strongly protected from westerly winds, such as the Lip and Center Bowl in Tuckerman and Central Gully in Huntington. You’ll also find it in isolated areas around most other forecast areas. Whether you’re in an area rated Moderate or Low, any snow sitting on top of the crust should be seen as potentially unstable. The biggest problems are where larger amounts of snow have been able to collect, whether through wind loading (e.g. in the Lip and Center Bowl) or through deeper pools of sluffs at the transitions from steep terrain to less steep (e.g. on ice routes in Huntington or below the narrows of the Chute.)

WEATHER: You know it’s a cold morning when Joe starts talking about Earnest Shackleton and how thankful we should be to not need to heat the cabin with seal blubber. Currently temperatures at Hermit Lake are hovering in the zero F range (-18C) and while summit winds have diminished into the 30-45mph (48-72kph) range it still feels like they have the ability to suck the heat from you quicker than your body can generate it. Expect a cold day with some clouds and a chance of light snowfall. Yesterday snowfall totals at the summit were 1.5″, though it only a trace landed at Hermit Lake. Maybe it’s just been blown over to Wildcat? There are no major storms on the horizon for us, but we might get smaller snowfalls throughout the upcoming week.

SNOWPACK: The dominant feature in the snowpack remains the freezing rain crust. Your primary concern should be focused on what sits on top of the crust. Where you encounter new snow above the crust, it will be a mix of older snow from late Friday and new snow from last night. The deeper the snow on top of the crust, the more suspicious you should be of it. Beneath the crust there are also some potential weaknesses, but these will be harder for you to trigger. The most likely scenario for these to come into play would be in an area with a large unstable slab sitting on top of the crust. Generally, the crust has a lot of tensile strength and is limiting the ability of any underlying slab to propagate a crack. In the situation where a large slab has buried the crust, the load could be more than the crust can handle, resulting in a large avalanche stepping down into deeper layers.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:20a.m., February 25, 2014. A new advisory will be issued tomorrow.

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

2014-02-25 Printable

Avalanche Advisory for Monday, February 24, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger today. Heightened avalanche conditions exist; evaluate snow and terrain carefully and identify features of concern. Natural avalanches are unlikely and human triggered avalanches are possible. The only exception to this is the Little Headwall which as Low avalanche danger. Natural and human triggered avalanches are unlikely in this location.

AVALANCHE PROBLEMS: Avalanche danger will be rising with incoming snowfall and wind loading this afternoon and evening. New wind slabs will be developing and adding to the existing wind slab problem. We expect danger to slowly rise within the Moderate range today. Expect areas to start the day with danger similar to yesterday, which was mix of Moderate and Low danger. The rise today means that human triggered avalanche are moving from unlikely to possible or simply from possible to “more possible”. With the timing and expected snow totals, we don’t believe we will rise into Considerable before this advisory expires. However, you should be carefully observing snow totals and be thinking about how much this is changing conditions from where they were at the start of the day.

WEATHER: Snow has already begun as of 8:00a.m. The forecast calls for 1-3″ (2.5-7.5cm) by midnight. Winds today will be at an ideal speed for transporting any new snow into all forecast areas in both ravines. West winds 50-70mph (80-113kph) will combine with temperatures falling to -10F (-23C) on the summit to make for a challenging day to be above treeline. Over the past weekend, we had a freezing rain event on Friday in the ravines. This was followed by a light snowfall of 1.5″ on the summit and a couple days of very strong westerly winds. Being a tourist destination, we welcome any and all snowflakes to come visit Tuckerman Ravine. Hopefully they will come by the masses, because we could use a lot more snow.

SNOWPACK: We have an interesting snowpack around the mountain right now, although not an enjoyable one. The most noticeable feature is the nasty crust that formed Friday in the ravines. This is at least a half inch thick, breakable, and sits on top of multiple weak layers that landed earlier in the week. Throughout much of the terrain, this crust is the surface layer, but there are exceptions. Some locations have been able to form new wind slab on top of the crust, or sluffs have formed thicker piles above the crust. In the absence of incoming snow, these areas are the most probable location where you’d be able to trigger a slide. Just beneath the crust, you’ll find a thin layer of round ice pellets and underneath that is a thicker layer weak soft snow. Farther down, the layers get harder and stronger, but there are interfaces here that could act as potential failure layers.

Overall the crust is doing a good job adding strength to the snowpack, so concerns about a person triggering one of these deeper layers exists, but it lives in the back of our minds. The existing slabs on top are more concerning, whereever you can find them. The most concerning issue today is the incoming wind loading on top of the crust. It’s conceivable that the weight of a new slab forming on top of the crust will be enough to overload the strength provided by the crust, thus bringing those deeper layers back into consideration for avalanche potential, especially if this upper slab were triggered by a skier or hiker.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:10a.m., February 24, 2014. A new advisory will be issued tomorrow.

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

2014-02-24 Printable

Avalanche Advisory for Sunday, February 23, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate  and Low avalanche danger. Sluice, Lip, Center Bowl, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. Lobster claw, Right Gully, Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas. Watch for unstable snow on isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Central and South have Moderate 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. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEMS: Wind Slabs is the main avalanche problem today. The most likely avalanche today would be from new snow that fell at the end of the rain event which drifted into pockets. These slabs were easily reactive to human triggers on isolated steep slopes yesterday. The next problem would be the new snow that cascaded down steep ice and snow which has piled up above and below the rain crust.  Basically, loose dry sluffing that has created new slabs.  These have grown quite thick in the past week or so and are hard to trigger, but would be dangerous if they did slide.  Central Gully, Center Bowl and Sluice leap to mind as examples of these sluff piles. Deeper wind slabs are also scattered around and are still a concern in some areas. Areas rated Low share most of these concerns though to a lesser extent so safe travel techniques, careful route finding and avalanche safety gear continue to be recommended.

WEATHER: Mild temperatures and relatively moderate winds today are a welcome break from the conditions that have dominated the past few weeks. Clouds may obscure visibility at times today with a possible snow shower to improve the mountain ambiance. No weather conditions are forecast today that will affect our avalanche situation other than flat light due to the overcast and potentially reduced visibility if the cloud cap descends into our terrain. Spotting the areas of new wind slab on the ice crust is much easier in the sun and shadow than in flat light or fog.

SNOWPACK: It is remarkable what little effect the rain and freezing rain had deep within our snow pack. The ice crust formed on sleet and ice pellets which fell on 8 or more inches of the sweet fluff that skiers dream about. That powder stills exists but is guarded by a thick breakable crust. Yesterday in Huntington, I observed several lunch tray sized chunks of the ice crust blowing through the sky over South Gully. This was the first indicator to me that our new slab issues were probably being fed by more than the recorded 1.5″ of snowfall. Once the crust protecting the underlying soft snow was ripped up, more snow became available to build the new wind slabs forming our primary concern today. The ice crust is easily breakable over this soft snow but is adding tensile strength to the otherwise weak layer beneath. The rain crust will be something to watch this week as cold temperatures return and begin affecting the snow grains above and below the crust. Currently, the grains beneath the crust are sugary ice pellets doing a convincing impression of facets. With any luck they won’t have time to become a widespread weak layer.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:30a.m., February 23, 2014. A new advisory will be issued tomorrow.

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

2014-02-23 Print friendly

 

Avalanche Advisory for Saturday, February 22, 2014

This advisory expires at 12:00 midnight.

All forecast areas of Tuckerman Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. There are two exceptions to this rating: the Lower Snowfields and Little Headwall which have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEMS: Two problems should be on your mind today, wind slab and deeper wind slab. The interaction between these two problems and a crust layer sandwiched between them is where the real story lies. The take home points for today are 1) a freezing rain crust developed midday yesterday, 2) deeper instabilities existed before the crust was formed, 3) the crust will help stabilize slabs beneath it, but fails to eliminate all stability problems, and 4) new wind loading and sluffing may create additional slabs on top of this crust in specific terrain features.

WEATHER: The big weather-related player is yesterday’s crust. I feel bad for the first skiers on the Sherburne today. Hopefully they’re wearing shin guards because the crust here at Hermit Lake is at least a half inch thick and breakable underfoot. The lower part of the ravines only barely and briefly reached above the freezing point for temperatures, so the rain was able to freeze on the snow surface instead of penetrating into the snowpack.

It’s hard to believe that clouds will engulf the summits later this afternoon, because right now it’s about as clear as it gets. Winds are currently finding snow to blow around, which we believe is due to crust being ripped up above treeline, exposing underlying snow to fairly strong winds. Loading may increase as strong gusts above treeline expose more snow through the day; I expect some areas in the ravines will be scoured down to the crust but not below. We’ve had some decent snowfalls, 12.5” (32cm) in the last four days, though very strong winds yesterday and Thursday have already affected this snow to some extent.

SNOWPACK: This freezing rain crust will do some good for adding strength to any slabs that are underneath, however, at the same time it will provide a slick bed surface to any new loading that lands on top of it. Expect varying degrees of hard slab under the crust with generally good stability. But remember that the snowpack is thin right now and potential weak points are only shallowly buried. Taken all together, I’d say we’re in the Moderate range with some locations having better stability than others.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:30a.m., February 22, 2014. A new advisory will be issued tomorrow.

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

2014-02-22 Print Friendly

 

Avalanche Advisory for Friday, February 21, 2014

This advisory expires at Midnight.

All forecast areas in Huntington and Tuckerman Ravine have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route finding and conservative decision making is essential.

AVALANCHE PROBLEMS: Wet Slab avalanches are the primary concern today followed by the Wind Slabs that developed over the last few days. Forecasted warm temperatures and rain will load and weaken the snowpack. The degree to which this occurs will depend on the amount and type of precipitation that falls, and the strength of the slab that it falls on. Thinner areas of slab could react first with less liquid precipitation than areas of thicker slab, but any avalanche could entrain more snow or step down to deeper weaknesses. Wind Slab is also still a hazard today from the last 72 hours of snow loading.  New Wind Slabs may develop in steep, lee areas in the event that precipitation falls as snow and not rain.

WEATHER: Avalanche terrain will see all forms of precipitation today.  Expect a little snow, sleet, freezing rain, and then rain reaching all the way to the highest summits.  Temperatures as of 6am show both Hermit Lake and the Washington Summit at about 27 degrees with a colder band in between.  This could affect varying precipitation types for a short period until full air mixing occurs.  It is possible that the summit could get some rain while areas in the ravines get freezing rain building an ice crust.  In the end, all precipitation forms should melt down to about 0.35″ (0.8cm) of water being brought to the mountains on a S wind building from 30 (48kph) to about 60mph (96kph). Tonight the mercury will fall into the teens F, winds will shift back to the W and increase, and 1-3″ (2.5-7.5cm) of snow should fall. If this does play out, anticipate new cold snow avalanche concerns for Saturday.

SNOWPACK: The main concern today is what rain may do to snowpack stability.  The ratings today are taking into account the potential for upwards of .25-.35″ of rain.  Many areas may handle this fine, particularly locations of deep hard slab.  But we cannot say this about all areas confidently.  Rain adds weight, decreases strength by melting bonds, and can pool on buried ice layers lubricating that potential bed surface.  A Wet Slab avalanche is often destructive and its mass is conducive to stepping down to other weaknesses and becoming larger. The hackles should always go up when rain falls on a cold snowpack. If you have seen the ravines or photos of the ravines in the past several days, you’ve witnessed the substantial growth of our  snowpack. Fans of spring skiing should be elated by this development. The incessant Mount Washington wind has loaded 54″ of new snow into our terrain so far this month. While it is not a banner year for snowfall like our southern neighbors are experiencing, we are at least back on track for a fairly normal looking year. Moving around the terrain now, you’ll notice that our snow surface and consequently our current and future bed surfaces have smoothed out, covering over rocks, boulders and bushes in many areas. This means a couple things. One is that avalanches can grow larger and generally run further than previously. Secondly, these rocks and bushes are no longer in a position to serve as anchors and in fact may create the thin spot in the upper snowpack that helps create a crack, leading to either a natural or human triggered avalanche. Cold weather is returning after this shot of heat and water so anticipate another melt freeze crust to develop after the temperature drops tonight. New snow and high winds will then create a new set of avalanche problems to solve tomorrow.

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 7:15 a.m. 2-21-2014. A new advisory will be issued tomorrow.

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

2014-02-21 Print friendly (corrected day)

 

 

Avlanche Advisory for Thursday, February 20, 2014

This advisory expires at Midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. Lobster Claw, Right Gully, The Sluice, Lip, Center Bowl, Left Gully and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route finding and conservative decision making is essential. Lower Snowfields and the Little Headwall have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

All forecast areas in Huntington Ravine have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route finding and conservative decision making is essential.

AVALANCHE PROBLEMS: Our nemesis the Wind Slab is here again as our primary avalanche problem. West-northwest wind ramped up late yesterday morning and loaded east facing start zones. Somewhere in the neighborhood of 5” of new snow in the past 24 hours yielded plenty of raw material for these slabs to form. Strong winds near 80 mph (128 kph) and gusting into the 90 mph range (145 kph) typically load lower start zones such as beneath the main ice floes in Central and Center Bowl and in the sheltered mid sections of gullies such as South, Escape Hatch, Left and Hillmans. These slabs have grown considerably in the past few days with not a lot of opportunity to stabilize.

WEATHER: Reduced visibility due to a summit cloud cap will hamper assessment this morning, though some afternoon clearing may occur before the next wave of higher clouds and precipitation rolls in tonight. Gusts from the NW this morning are continuing to push into the 90’s mph (140’s kph) and hit 100 mph (160 kph) around 7:30 am, but will shift to the West and slow to the 60’s mph (90’s kph)this afternoon.

SNOWPACK: New loading in the past 24 hours is an obvious concern in the snowpack. This new load is sitting on a grain size change and probably a hardness difference across the fracture plane marked by the wind ramping up yesterday morning. Wind speed has been high enough to create hard slab avalanche potential in many areas and due to the rapid loading we feel that natural avalanches are possible today. These windslabs may be firm (1F) but be sure to consider the softer, weaker layer which may be pretty deep but somewhere within the upper meter of snow. If you are trying to thread the needle today, beware of that layer.  Some softer slabs will also form as wind speeds slow this afternoon though will probably not be all that reactive due to the tired, old wind blown particles packing fairly tightly. Potential bed surfaces grew substantially in the last several days and are much more continuous, most notably in Center Bowl, below Central and below Yale. Mid snowpack density changes could be the weak layer; don’t you be the trigger on larger wind loaded slopes. Yesterday morning showed extensive sluff piles below steep sections indicating further load on the lower start zones. Remember that upper sections of Lobster Claw and Right Gully have filled in and are maturing into legitimate start zones. Lower Snowfields will remain threatened by natural avalanches from above. Though the current wind slab, like any harder wind slab, isn’t touchy in nature, it could sure propagate a crack a long distance and produce a large avalanche. While widespread natural avalanche activity isn’t really on the radar today, a destructive human triggered avalanche certainly is.

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 840a.m. 2-20-2014. A new advisory will be issued tomorrow.

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

2014-02-20 Print friendly

Avalanche Advisory for Wednesday, February 19, 2014

Expires at Midnight

Tuckerman and Huntington Ravines will have CONSIDERABLE avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions will exist.  Careful snowpack evaluation, cautious route finding, and conservative decision making will be essential.

AVALANCHE PROBLEM: Wind Slabs and Storm Slabs are the two main problems.  Later today new Wind Slabs will develop as winds pick up from the current 25mph to around 60mph.  This velocity increase will trigger another round of loading using yesterday’s snow that is sitting in the alpine zone waiting to be transported.  In addition, new snowfall this afternoon will mix in with alpine snow, increasing the volume of available snow. This is the main problem moving the forecast to a widespread “Considerable”.

WEATHER: Over the last 24 hours we have received between 5 and 6” (12.5-15cm) of snow from Pinkham all the way to the Summit.  During the majority of the heaviest snowfall winds were in the 30-40mph range. This did set off a cycle late on Tuesday of very soft slabs and dry loose sluffs, as evidenced by many sluff tracks that terminate mid slope without making a full run.  Today winds will move from the W to the SW and increase to 60mph midday.  Additional snow is expected this afternoon, up to 2” by dark, and another 1-3 tonight.  Winds will then get ferocious, with long sharp canines looking to bite. Winds will climb overnight to over 100+mph.  If that’s not enough for you, Thursday morning winds will increase and start chomping at anything that moves.  Forecasters are taking about 110, 115, 120, >>> and maybe more!  Expect today’s visibility to degrade as clouds, snowfall and blowing snow consume the air.

SNOWPACK: Currently at 730am, most areas sit at a solid “Moderate” rating, but will increase to the posted “Considerable” this afternoon.  Once winds pick up and begin loading new snow that fell last night you will start seeing new slabs develop, primarily in the upper start zones.  As speeds increase, winds will also shift from the W to the SW/SSW. This will load E to NE facing slopes predominately, with areas like Odell and South gully in Huntington, and the Center Bowl through Hillman’s in Tuckerman, being right in the bull’s-eye.  These aspects will reach the Considerable rating first with others lingering behind.  Some of the S facing slopes will struggle to get out of the Moderate rating, but will eventually.  This will all be complicated by additional new snowfall through the afternoon.

If you get out early, before new snow and loading begin, the educated traveler may find slopes that can be negotiated using tactics typically employed during a Moderate rating. Safe travel and route finding, as well as frequent stability evaluations, will be important.  However, you should be in and out of avalanche terrain over the next several hours to avoid new instabilities and an increasing hazards.  Also consider that it’s vacation week so expect a statistically higher than normal amount of triggers running around the mountain.  Be conscience of who may be above and below you.

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 825a.m. 2-19-2014. A new advisory will be issued tomorrow.

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

2014-02-19 Print