Avalanche Advisory for Tuesday, March 31, 2015

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravines have Considerable avalanche danger. Dangerous avalanche conditions exist. Natural avalanches are possible and human triggered avalanches are likely. Cautious route finding and conservative decision making are essential. The only exception to this is the Little Headwall in Tuckerman, which has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible in this location.

AVALANCHE PROBLEM: New and developing wind slabs are the primary avalanche problem today. This hazard is already present but will be increasing through the morning. With the current and forecasted wind speeds and direction, all forecast areas will be on the receiving end of wind transported snow, creating dangerous wind slabs that may avalanche multiple times during this cycle. Hiking beyond the first aid cache at the entrance to Tuckerman will put you at risk of avalanches hitting you from up above.

WEATHER: Current visibility at Hermit Lake is limited to about 50 meters. This is from snow, blowing snow, and fog. Expect this to be the dominant weather pattern through the day. Since yesterday morning, we have received about 3” of 10-12% density snow. This snow event started with rimed particles and graupel, then became mostly non-rimed crystal types but with rimed dendrites and graupel still in the mix.

Today’s weather forecast includes up to another 2” of new snow. Most of this is expected to fall this morning. Although winds are expected to diminish this afternoon, you should be prepared for snow to continue loading into the ravines all day.

SNOWPACK: The most important snowpack information you will need to know about today is the rate of wind loading into the avalanche starting zones. Since you won’t easily get to these upper elevation locations where the slabs are developing, and you can’t see it visually, you’ll need to use other available information and your imagination to form a picture of what’s going on up high. This morning, slabs are likely developing quickly and potentially deeply.

In order to recognize the hazard, you don’t need to know much about potential weak layers or bed surfaces, but here’s my take on the problem. The ravines had a pre-existing instability problem that was demonstrated with multiple avalanches on Sunday. These slabs have had a couple days to settle down, but I don’t believe that’s sufficient to fully stabilize them. A very weak layer of snow over a crust was the problem on Sunday. This was not the case everywhere—some locations were wind scoured and stable. But the riming and graupel period at the start of the most recent snow with winds from a SW direction and lighter than they currently are makes me think that an easily triggerable weak layer may have formed over most aspects. Winds shifted to the W and slowly to the NW with increasing speeds, laying a denser slab on top of this weak layer. If areas have already avalanched, ongoing loading and reloading of the slopes will keep the hazard elevated.

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 8:20 a.m. Tuesday, March 31, 2015. A new advisory will be issued tomorrow.

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

2015-03-31

Avalanche Advisory for Monday, March 30, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. Sluice, Lip, Center Bowl, Chute and Lower Snowfields have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lobster Claw, Right Gully, Left Gully and Hillman’s Highway 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 has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow, weather and terrain carefully. North, Damnation and Yale have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind Slabs developing today, in some areas on an already poor snow structure, are the primary problem. With the exception of the Lip, which was raked down to the bed surface yesterday, Considerable rated areas contain the largest expanses of older wind slab going into today’s weather event. This wind slab was reactive to human triggers yesterday and is most likely still reactive. South facing gullies in both Ravines, though still containing pockets of the older wind slab, benefitted from a period of settlement yesterday due to warming and, in Tuckerman, was also cut up by ski traffic.

WEATHER: Wintry weather continues as a cold front pushes through today bringing some moisture and wind to the region. The main weather factor affecting stability will be the wind. Currently, west winds in the 50 mph range are pushing some snow into east aspects. The wind is expected to pick to the 50-70 mph range later today. These wind speeds are the highest since roughly 6” of snow fell late last week which means that there is enough snow laying around higher terrain to provide the building blocks for new hard wind slabs. Light snow and snow showers through the afternoon hours may contribute 1-3” more snow to the slab building process.

SNOWPACK: Avalanche danger is starting out one rating lower in each forecast area that isn’t already rated Low. The above ratings are based on wind transported snow, plus 1-3” of new snow falling today, which will cause danger to rise.

A crown profile in the 50cm x 20m natural avalanche in the Lower Snowfields revealed that the failure layer of the slab was within soft (4F) snow and rimed snow particles. The overlying harder slab (1F) was softer than we often see due to the light winds that built it being only around 40 mph. This crown thickness and structure is very similar to that in the much larger Lip avalanche and is the same as you might find in other slopes and gullies, only in varying thicknesses and distribution.  In summary, signs of recent avalanche activity in the previous 24-48 hours are one red flag to consider today. Another is active wind loading, as evidenced by snow moving along the ground at the ridgetop and above treeline, A third is a small amount of new snow and a weather forecast that includes wind speeds capable of moving that snow and building wind slabs. It’s pretty hard to miss these signs today, so if you choose to enter avalanche terrain, do so very carefully and limit time spent in avalanche runouts or, better yet, avoid them 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 AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:16 a.m. Monday, March 30, 2015. A new advisory will be issued tomorrow.

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

2015-03-30

Avalanche Advisory for Sunday, March 29, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable, Moderate, and Low avalanche danger. Dangerous avalanche conditions exist. The Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Sluice and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lobster Claw, Right Gully, Left Gully, and Hillman’s Highway, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slabs are the primary avalanche threat today. The main driver behind the Considerable rating for some areas is the low drifting snow currently cascading down steep slopes. This slow loading has caused good-sized avalanches in the past, even on bluebird days like today. It is taking place in the Sluice as well, though as a slightly lesser rate. The Lower Snowfields contains snow with varying levels of stability. I expect the worst to be tight under the rock buttresses. Left Gully and Hillman’s have pockets of new snow loaded into isolated terrain features. Although posted at Low, they may contain unstable snow capable of producing an avalanche. It ain’t spring yet, folks, regardless of what the calendar says.

WEATHER: Blue skies will dominate today, but it will feel more like a nice day in February than the end of March. Expect temperatures below normal. Even south-facing slopes may not get enough heat to moisten the uppermost snow. Westerly winds around 30-40mph will have two noticeable effects. One is to generate additional wind loading, particularly low drifting snow in the center of Tuckerman. The other is to suck the heat away from the snow in south facing slopes, making it harder for the sun to soften the surface. Over the last four days, Mt. Washington has received about 7” of new light density snow, which is at the center of our avalanche concerns.

SNOWPACK: I wrestled with the ratings for Tuckerman today and decided on the higher rating of Considerable for locations where there currently is snow drifting down over the headwall. Today would not be the first time I’ve seen a seemingly small amount of loading trigger an avalanche. I’ll caution you all that as long as this is going on, you will want to be extra cautious. This means that even going into the floor of Tuckerman to access a Low rated area will put you at risk. If it shuts off completely, we’ll be left with a human trigger problem rather than a natural trigger problem. Although this isn’t ideal for recreation, it’s more manageable.

In Lobster, Right Gully, Left Gully, and Hillman’s, the majority of the surface snow is old and stable. However, there are locations where you may find unstable snow, such as the skiers’ left side of Left Gully or hard on the skiers’ left side of Hillman’s. Other examples may exist, too. You’ll need to be alert for these pockets, assess their stability, and determine whether or not you want to pass through them. You may also need to make a decision whether or not you want to be below someone who is making a similar decision!

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 8:23 a.m. Sunday, March 29, 2015. A new advisory will be issued tomorrow.

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

2015-03-29

Avalanche Advisory for Saturday, March 28, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable, Moderate and Low avalanche danger. The Chute has Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. The Sluice, Lip, Center Bowl, Left Gully, Hillman’s Highway and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lobster Claw, Right Gully, and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wind Slab and Storm Slab are the primary concerns today with Dry Loose avalanches also on the list. 3.5” (8cm) of new snow in the past 2 days has created a variety of soft slabs in our terrain. Due to the low wind speeds, the new snow is piling up beneath steeper terrain and forming slabs just cohesive enough to create potentially dangerous slabs. Small avalanches could turn larger by entraining the surprising amount of low density snow laying around.

WEATHER: The Low pressure trough continues to feed clouds and moisture into the area. 1-3” (2.5 – 7.5cm) of new snow is expected today on very lights winds shifting to the North. Expect flat light at best and possibly denser fog to create some challenges for navigating and keeping eyes on the skier. It is likely that the overcast skies above the summit fog will limit incoming solar heating on southern aspects today, unlike yesterday.  The height and intensity of the spring sun is a factor this time of year and could conceivably have a positive effect on stability on these aspects again today. Quite a bit of warming occurred yesterday, in spite of the dense fog.

SNOWPACK: Currently, very low density snow is sluffing off steep terrain and contributed to these slabs. In Tuckerman, Chute holds the greatest amount of soft slab, with boot-top and deeper snow in and above the choke. The narrows of Left, as well as near and above the fork of Hillman’s, were also a concern yesterday. Cracking and increasingly deep snow lead experienced parties to turn around in both locations. 1” (2.5cm) of new snow on even lighter winds last night plus 1-3” more today will contribute to this problem. It is impressive how this paltry amount of snow piles up beneath steep terrain like cliff bands, ice bulges and sidewalls of gullies. Huntington is a mixed bag of Moderate. Greenhouse warming yesterday contributed to stability on south facing aspects so expect more stability concerns from Central to Escape Hatch with more stability from Yale to North.

Field time in Tuckerman confirmed that we still have a dynamic snowpack. Despite cold air temperatures, greenhousing conditions over the past several days have begun to drive heat into the upper 30-40 cm of snow, though the temperatures beneath are far from isothermal. Stability tests yesterday confirmed the new snow was well bonded to the hard surfaces but was slabbing up due to either surface heat gain, light wind effect or sluffing. The older bed surface was just barely negotiable without crampons (2-3cm boot penetration) yesterday but has refrozen more solidly this morning. Expect a slippery, dust on crust surface especially on southerly aspects unless heating occurs. Deeper in the snowpack pooled graupel and a thick, decomposing melt/freeze crust failed cleanly but are well bridged and not much of a concern for the time being.

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 8:23 a.m. Saturday, March 28, 2015. A new advisory will be issued tomorrow.

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

2015-03-28

Avalanche Advisory for Friday, March 27, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravine have CONSIDERABLE avalanche danger. Careful snowpack and weather evaluation, cautious route-finding and conservative decision making are essential.

 AVALANCHE PROBLEM: We are starting out this morning with a Moderate avalanche danger. 3.1” (7.8cm) of new snow on the summit, with probably just a little less in the Alpine Garden and forecast area, and another trace to 2” (TR-5cm) forecast today, creates the threat of Storm Slab avalanches. A small crown line was visible this morning in Center Bowl which indicates that this new storm snow is cohesive enough to avalanche. That said, a highly skilled user could negotiate this hazard with careful terrain management choices with a careful eye on wind, new snow and the snowpack. Wind Slab may become your greatest concern should you choose to venture into avalanche terrain today. Based on forecast wind speeds, these wind slabs are likely to be smaller than we ordinarily see but will probably form high in our start zones. Either type of avalanche could entrain enough snow to carry you and bury you should you be caught. Remember that while the new snow is “right-side up”, it is resting on a firm bed surface which probably only softened a little bit from yesterday’s brief warming and is refreezing as I write this. This firm surface could make escaping an avalanche with your ski edges or self-arrest tool difficult. If wind does not ramp up today, the Moderate avalanche danger formed by existing Storm Slabs, plus a trace to 2” (TR-5cm) more snow, sluff piles beneath steep terrain and some small wind slabs are what you will have to manage.

WEATHER: 3.1” (7.8 cm) of snow and snow pellets (graupel) were recorded on the summit yesterday afternoon and evening on light winds around 30 mph (50km/h). About 2.4” (6cm) of new snow, starting out as mixed wet particles and freezing rain, fell at Hermit Lake. In all likelihood, 2- 3” of 10% snow is available for transport by the wind into our forecast area from the Alpine Garden area above the Ravines. Both Ravines are moving in and out of the clouds.  Challenging visibility will be the story all day. Temperatures have already dropped to the mid-teens Fahrenheit. NW winds will shift to the West, blowing 15-30 mph (25-50km/h) with gusts to 45 mph (70km/h).

SNOWPACK: Currently the snowpack at Hermit Lake is “punchy” in a few areas. This tells me the crust beneath the new snow is beginning to refreeze following yesterday’s warmup to 44F (7C) at this elevation. Limited visibility this morning only gave us a brief glimpse of Tuckerman Ravine but we did gather some information. The steepest terrain like the narrows of Sluice by the water ice, and the Lip, and probably many other similar areas, appear to have gone through a loose or point release avalanche cycle with debris just beneath the start zones and older, textured surfaces currently visible. The small slab release beneath the ice in Center Bowl showed a crown line approximately 8-10m wide by 10-12 cm thick. It is hard to say whether it released spontaneously or was triggered by a sluff off of the ice bulge above. In any case, the slab character is not typical of other areas we’ve seen this morning. The snow at Hermit Lake is only barely cohesive, and remarkably dry…it takes some effort to make a marginally solid snowball.

Tomorrow will defy expectations for spring conditions again. Expect similar conditions as today so remember to bring your good judgment, avalanche rescue gear and well-honed decision making skills if you are headed this way for the weekend. And remember that a back-up plan to skiing or climbing in steep avalanche terrain should be a desirable alternative that is acceptable to the group.

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 8:49 a.m. Friday, March 27, 2015. A new advisory will be issued tomorrow.

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

2015-03-27 print version

Avalanche Advisory for Thursday, March 26, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravine have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible in all forecast areas.  Evaluate weather, snow and terrain carefully to identify features of concern. Heightened avalanche conditions will develop on specific terrain features later today.

Mixed precipitation is expected to get started in the afternoon which will push us higher into the above ratings this afternoon. The ratings above most accurately reflect the daytime recreational period. Anticipate avalanche danger to increase, moving towards Considerable near sundown and more certainly in that rating after dark.

AVALANCHE PROBLEM: Existing stability is generally good to very good in most of the forecast area either because the upper snowpack is wind packed or wind scoured, or because it was exposed to strong solar heating yesterday. Some strong lee areas, like the Chute and the left side of Center Bowl as well as other lee pockets, harbor softer slabs. These softer slabs create the potential for Wet Slab avalanches later today as mixed precipitation falls. Wind Slabs may also develop later in the day. The degree to which these wind slabs will be problematic depends upon the type and timing of the precipitation’s changeover to snow.

WEATHER: The 1/3” of new snow yesterday evening did little to impact our stability. More precipitation is forecast for the afternoon with 1/4″ of water equivalent by dark and another 1/2″ or so through the night. The good news is that it will be getting colder with mixed precipitation on the summits turning to increasingly lighter snow overnight. The bad news is there is some chance for rain, in addition to freezing rain, sleet and snow, in our avalanche forecast area for a period this afternoon. Though not a tremendous amount of precipitation, it may be enough to weaken some existing softer surface slabs or penetrate thinner slabs. The type of precipitation is a wild card due to the position of the melt/freeze line within our forecast area.  Keep a close eye on temperature and incoming precipitation since they will directly impact stability today. As mentioned above, snow this afternoon and evening will increase and grow less dense as the cold front arrives with 2-4” expected to fall on diminishing winds overnight. Favorable conditions for upslope generated snow showers are forecast tomorrow with west winds potentially in the light range. Expect a new wind slab problem tomorrow and a return to wintry weather.

SNOWPACK: Generally firm or hard snow predominates in our terrain due the freeze/thaw cycle that started on Tuesday. Though summit temperatures that day never climbed to the mid-teens, the strong sunshine and dead calm wind in the forecast area allowed significant warming, even in shaded areas. Yesterday, it was apparent that south facing ice climbs in Huntington took a beating and slopes in Tuckerman developed peel away corn snow. Cooler temperatures overnight have no doubt hardened these aspects but the damage to ice features remains. Expect a hard surface requiring crampons and an ice axe in most areas today.  As a reminder, the warm temperatures over the past two days have not created a stable, isothermal spring snowpack.  Be wary of weak layers buried well down in the snowpack particularly in slightly lower elevation, lower angled terrain outside our forecast area.  Deeper weak layers in our terrain also exist but will most likely require more than today’s precipitation to activate.

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 8:26 a.m. Thursday, March 26, 2015. A new advisory will be issued tomorrow.

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

2015-03-26 print friendly

Avalanche Advisory for Wednesday, March 25, 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 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.

All forecast areas of Huntington Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Aging wind slabs are the number one problem today. These began forming on Saturday night and didn’t stop growing until Monday morning when winds slowed. As with the past two days, the primary concerns are in the middle of Tuckerman, from the Sluice across to the Chute. The main issue is in the uppermost layer of the snowpack, which varies in depth but is generally at least 12” deep (30cm). Large avalanches can be produced from these locations. As you enter the floor of the bowl, you will be standing on old avalanche debris from previous avalanches that are smaller than what can be expected currently. Don’t assume the rocks in the floor are out of the range of the avalanche potential!

WEATHER: There is some weather coming in starting tonight, but for most of today, the weather will not affect snow stability to any great degree. Expect winds to be shifting to the south and increasing in speeds. Some light snow or mixed precip may fall this afternoon and evening, but accumulations will be light. The fun stuff will come on Thursday as a warm front surges toward us, bringing rain all the way to the summits.

SNOWPACK: A good portion of the terrain in Tuckerman and Huntington is very firm wind-hammered surfaces. These offer good stability, but not great skiing or riding conditions. If you’re heading into one of these Low rated areas, the climbing will be easier and safer if you have an ice axe and crampons.

In the Moderate rated areas, the upper snowpack is predominantly 1F to 4F hardness windblown slab. Beneath this is a thin layer of new snow that fell prior to the winds ramping up in speeds on Sunday and loading the new slab on top. This weak layer is now buried under the aforementioned slab and waiting for a trigger. Fortunately, the upper slab does have a fair amount of strength to it, so we’re falling short of thinking human triggered avalanches are likely (which would warrant a Considerable rating.) In fact, these are the conditions where you could see several people ski or ride a slope without triggering an avalanche. This certainly does not imply the slope is stable, just that it’s not a hair-trigger Moderate. I can envision a situation where several people skiing the slope could actually be cutting apart the strength of the upper slab, making it a little less stable with every set of tracks. The snow quality in these areas is carvable and alluring, especially compared to the quality you’ll find in the Low rated areas, but don’t allow your desire to have fun influence your risk assessment. Make quality snow stability assessments, think hard about your decisions, and be prepared for the worst case scenario. In these conditions an avalanche could easily kill you, and that would certainly ruin the fun you and your buddies came for.

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 6:30 a.m. Wednesday, March 25, 2015. A new advisory will be issued tomorrow.

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

2015-03-25

Avalanche Advisory for Tuesday, March 24, 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. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

All forecast areas of Huntington Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slab is the primary avalanche problem today. This problem is focused on the midsection of Tuckerman, from the Sluice through the Chute. As far as a Moderate rating goes, the likelihood of triggering a slide is on the lower end of the rating’s range, but not stable enough to warrant a different rating. Additionally, the stakes are raised quite a bit as we would expect the size of an avalanche here to be large and destructive. Other areas rated Low have good stability thanks to very strong winds hammering the slopes into submission. Be watchful for isolated unstable pockets in strongly sheltered areas such as the Lower Snowfields.

WEATHER: Very few people ventured up into the ravines yesterday, and for good reason. Temperatures spent much of the day below zero degrees Fahrenheit while summit winds blew strong throughout the day. From Sunday and into Monday morning, winds had been gusting over 100mph for more than 24 hours. They started to subside yesterday and have come down to near calm levels for this morning. Today you’ll have relatively light winds and sunshine but wintery temperatures will keep it from feeling too much like spring.

SNOWPACK: A good portion of the terrain in Tuckerman and Huntington is firm wind-hammered surfaces. These offer good stability, but not great skiing or riding conditions. If you’re heading into one of these Low rated areas, the climbing will be easier and safer if you have an ice axe and crampons. Speaking of wind-hammered surfaces, the Sherburne trail was scraped clean down to old hard snow for much of its length. My mountaineering boots barely scratch the surface when walking on it.

The focus of the avalanche problems in Tuckerman are found under the ice in the Center Bowl and in the Lip area. The rim of the ravine was blown clean, and the lower angle transition to the floor is a mix of scoured and wind-hammered. It’s the elevation right in the middle where it’s most steep that you will want to be watching. You can expect firm surfaces and strong slabs in the upper layers, but what lurks beneath the surface is where the problem resides. Depending on your exact location, you may see weak interfaces between wind layers, faceting, or recently hidden ice, rocks, or bushes that have created shallower weak spots.

Sunshine may have an effect on steep south facing slopes, but I don’t expect this to be too great or have a significant effect on stability.

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 7:45 a.m. Tuesday, March 24, 2015. A new advisory will be issued tomorrow.

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

2015-03-24

Avalanche Advisory for Monday, March 23, 2015

This advisory expires tonight at 12:00 midnight.

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

All forecast areas in Huntington Ravine have LOW avalanche danger. Natural avalanches and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM:  It is no surprise that Wind Slab is the primary threat today. Hard and stubborn slabs of wind packed snow exist in Sluice, Lip and Center Bowl and probably on the approach to Yale and Diagonal and around areas near the Fan. More sensitive slabs likely exist in the most sheltered lee areas near terrain features and steep bushy areas that create natural wind drift fences. Thin, weak spots in firm slabs like we have now can serve as trigger points in an otherwise strong slab so use caution even in Low rated areas. Due to its low elevation and wind sheltered location, the Little Headwall has collected a lot of snow recently which has buried all the anchors and created a convex surface. Be careful if you are among the first few parties to ski the slope; the terrain traps below are nasty.

 WEATHER:  Again, the wind is raging on the mountain with a peak wind speed of 111 mph (179 km/h) recorded yesterday. Currently, NW winds are blowing at 88 mph (142 km/h) with the mercury standing at -22F (-30C). Temperatures will rise to near 0F (-18C) today as winds decrease to the 45-60 mph (70-95 km/h) range. Expect continued gusty conditions peaking at 105 mph (169 km/h) this morning as well as a challenging experience packing up in the parking lot at Pinkham, not to mention standing and walking above treeline. Conditions should moderate this afternoon but January-like weather will persist over the next couple of days. A warm front on Wednesday could bring a mixed bag of precipitation to the forecast area, the nature of which depends on the exact track of the front.

SNOWPACK: Wind speeds like we are having now created a long, sliding fall problem in addition to the avalanche concerns mentioned above. Though the pencil hard slabs on the surface will allow purchase from a hard boot or ski edge, most people would be comforted by the security of crampons. Persistent slabs are a distant threat on the horizon that may become more relevant this week as temperatures warm and the threat of rain increases. Though not a standout danger due to the strength of overlying slabs and their discontinuous nature, these weak layers of faceted snow are certainly present beneath old layers of wind slab.  In our forecast area, you will most likely find these layers near edges of avalanches paths that have not been swept out by previous avalanche activity or really deep in the snowpack. Other terrain around the White Mountains could also contain these weak layers near old buried crusts so you may want to look for this potentially problematic layer deeper than you would dig for a hand shear. A meter deep pit once in a while could help you make informed decisions and keep your risk acceptance discussions real.

 This last weekend saw an uptick in traffic in both Ravines. As we move into the spring season please remember that the party like atmosphere seems to distract folks from the hard of facts of mountain travel. Legitimate mountain hazards are abundant on, above and beneath our slopes and gullies so prepare carefully, stay alert and help others when you can.

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 8:25 a.m. Monday, March 23, 2015. A new advisory will be issued tomorrow.

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

2015-03-23 print friendly

Avalanche Advisory for Sunday, March 22, 2015

This advisory expires at midnight.

Tuckerman Ravine has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely in all forecast areas. Dangerous avalanche conditions exist.  

 Huntington Ravine has Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify features of concern. Heightened avalanche conditions exist on specific terrain features.

 AVALANCHE PROBLEM: Wind slabs are our primary avalanche concern today. 5” of new snow fell since yesterday afternoon and is currently being deposited in our terrain in the sheltered lee of WNW and NW winds. Hard but stubborn wind slabs will be created by the strong winds today. Expect these slabs to build quickly this morning when peak avalanche instability is likely to occur. Huntington Ravine, being higher and in a more windward location, may see more scouring than loading this morning. Some locations like Central, Pinnacle and Odell may also be sluffing heavily this morning.

 WEATHER: Robins and crocus blooms are nowhere to be seen at Hermit Lake this morning. However, if you prefer wind drifted snow, rimed over conifers and biting arctic winds over the typical signs of spring, you won’t be disappointed. Wind speeds at the summit are gusting over 100 mph (160 km/h) this morning and are expected to hit 130 mph (210 km/h) later today.  Steady 90-110 mph (145-175 km/h) northwesterly winds will make a journey above treeline a fool’s errand even though velocities will abate later to the 80-100 mph (130-160 km/h) range. The 5” (13 cm) of new snow from yesterday is still airborne, along with dense fog, reducing visibility to a few hundred feet at Hermit Lake. Temperatures will continue to fall as the cold front passes, ultimately bottoming out at -25F (-32C) sometime later today.

 SNOWPACK: After the balmy but still winter-like conditions yesterday, the adventurous souls camping around Mount Washington are receiving a brutal wake-up call from weather concierge this morning. Tent flattening wind velocities and face numbing winds would push a quick journey to the nearest coffee shop to the top of my to-do list. Climbing and skiing conditions yesterday, and pretty good crowd of folks enjoyed the firm snow in both Ravines. Snow fall held off until around sundown and bumped new wind slab avalanches off the list of hazards to negotiate. Firm snow (pencil hard) dominated the scene with a few pockets of softer and harder snow here and there depending on aspect and the presence natural drift fences. Today’s wind event is creating similar conditions though I have no intention of venturing into avalanche terrain to verify this today. Expect peak instability sometime this morning, if it hasn’t peaked already, along with brutally challenging conditions for walking, much less for making careful snow stability assessments, group discussions on terrain selection and hazard mitigation.

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 8:25 a.m. Sunday, March 22, 2015. A new advisory will be issued tomorrow.

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

2015-03-22 print version