Avalanche Advisory for Monday, March 31, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche hazard. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions will exist on certain terrain features. Evaluate snow and terrain carefully. Slopes with a southerly aspect may push towards Considerable this afternoon due to an increasing potential to produce natural avalanches. I would avoid larger slopes like the Sluice, Lip, Center Bowl ad Central Gully as well as those gullies with longer paths that have a stronger southerly aspect such as Lobster Claw, Right Gully, Damnation and Yale.

AVALANCHE PROBLEMS: The primary hazard today will be Wind Slab. New snow today, driven by north winds, may build Wind Slabs on slopes with a southerly aspect and crossload other areas. While not particularly large due to the scant amount of snow expected, the potential is there for a large enough avalanche to hurt you. The secondary hazard is the low probability but high risk concern of triggering a Persistent Slab. Recent rain and warm temperatures haven’t reached far enough into the snowpack to stabilize some weaker layers and has added more load to lingering Persistent Slabs. Remain vigilant in avalanche terrain and continue to apply solid avalanche safety techniques.

WEATHER: It appears as though Mt. Washington only caught a glancing blow from the storm that passed yesterday. The bulk of the precipitation we received came as snow early yesterday (2.5″ at the summit). After this, sleet fell lightly before changing over to a light drizzle of rain. Late in the day, ravine level temperatures fell below freezing and stayed there through the night. During this time summit temperatures were much warmer than at Hermit Lake and in the ravines.

Again today, much of the precipitation is falling to our south. We are expecting mixed precipitation turning to snow late this morning, with daytime totals reaching about 0.15″ of water equivalent. The Obs has forecast 1-3″ of snow from today’s precip, most  likely to come late in the day on strong N winds.

SNOWPACK: We have some unanswered questions about the snowpack which complicate the effort to forecast avalanche hazard. First and foremost, how deeply did warmth and liquid precip penetrate into the cold winter snowpack over the previous two days, and does this change at all due to aspect and angle? Also, what avalanched yesterday is a question that will remain unanswered until visibility improves. Weather data for the past 24 hours indicates that the amount of rain and associated warm temperatures were not enough to penetrate deeply into our snowpack. While the snowpack did not go isothermal, a sufficiently thick melt-freeze layer  at the surface now exists to bring down avalanche hazard.  If we receive the upper end of the forecasted snow amounts, we will have new wind slab issues, particularly on S-facing slopes and some cross-loaded E-facing slopes. Pay attention to how much snow has fallen if you’re out and about today. Continued summit fog and new snow will make assessment challenging today. New wind slabs are likely to be touchy on steep terrain and could grow quickly. Persistent Slabs are still a concern. Though the January ice crust and weak facet layer beneath have been mostly swept out of slopes in our forecast area, it is still around as are other weak interfaces between old wind slabs.

OTHER HAZARDS: Undermined and collapsing snow bridges are a potential issue. This is mostly a concern for people looking to ski the Little Headwall or brook above. Be careful around any stream bed today as the snow covering it may not hold your weight.

On today’s project list is completing the report on Saturday’s avalanche on the Southeast snowfield. Hopefully some premature information and otherwise speculative information erupting in social media circles can be corrected and some lessons learned.

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 8:00 a.m. 3-31-2014. A new advisory will be issued tomorrow.

Frank Carus/Jeff Lane, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-03-31 Print friendly

Avalanche Advisory for Sunday, March 30, 2014

This advisory expires at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravines have High avalanche danger. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. Natural avalanches are likely and human triggered avalanches are very likely.

AVALANCHE PROBLEM: If you are heading out to avalanche terrain today, you may want to re-read the preceding paragraph. Wet slabs, wet loose, and persistent slabs are all in the mix as potential avalanche problems today. At the time of this writing, our avalanche paths are sitting well into the Considerable range. Increasing avalanche danger during this weather event will push the hazard up into High danger. There is a fair amount of uncertainty in how much precipitation will fall and exactly what type. But regardless of how this exactly plays out and regardless of where exactly we are on the danger scale, travel in avalanche terrain today would best be avoided.

WEATHER: A wintery mix of precipitation is forecast to fall across the mountains today. This event has already brought a few inches of snow. Currently at Hermit Lake there is a steady stream of sleet pellets falling from the sky. Temperatures are expected to warm through the day, so I expect we will see this turn over to rain at most elevations. The very top of the mountains may have only sleet or freezing rain, but I expect this freezing line to be well above our forecast areas, meaning that the ravines will see a fair amount of rain today.

SNOWPACK: The surface layer is now a few inches of wet snow being loaded further by ice pellets and soon rain. This leads to the potential for wet loose avalanches, particularly in very steep terrain such as the gullies of Huntington. As rain penetrates the snowpack, adding to moisture developed during yesterday’s warmth, we may start to see upper layers of slab releasing as wet slab avalanches. As usual, our snowpack has a variety of layers near the surface. These will continue to lose strength during the day. I would expect any avalanches produced by this problem to be on the smaller side, though the consequences could be significant if you are in the wrong place.

The final piece of today’s puzzle is persistent slab avalanches. These have been in our minds (and in the advisories) for much of the season as back-burner potential problems. Yesterday this potential was realized in a big way. The southeast snowfields of the summit cone were triggered in the afternoon. The failure layer was a layer of facets beneath the January 11 rain crust. In many areas of Tuckerman this layer has been minimized by avalanche activity long ago, but there is a peppering of locations where we believe the layer is intact. The largest of these is the Lip and Sluice, as well as other parts of the Tucks headwall and Central Gully in Huntington. We will hopefully get some pictures and a write up about yesterday’s slide on our site today.

OTHER HAZARDS: Undermined and collapsing snow bridges have snuck up on us as a potential issue. This is mostly a concern for people looking to ski the Little Headwall or brook above. Be careful around any stream bed today.

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 8:30 a.m. 3-30-2014. 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

2014-03-30 print friendly

Avalanche Advisory for Saturday, March 29, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible in all forecast areas. Evaluate snow and terrain carefully. The only exception to this rating is the Little Headwall in Tuckerman, which has Low avalanche danger. Natural and human triggered avalanches are unlikely there. Unstable snow may exist in isolated terrain features.

AVALANCHE PROBLEM: Avalanche problem #1 today is Wet Slab due to saturated snow over dryer, weaker snow. Two inches of snow fell on moderate winds in the 50’s mph yesterday and built wind slabs which may become more reactive to triggering today due to warming temperatures. Problem #2 is deeper Persistent Slab which also may be activated by increased loading from yesterday coupled with warming temperatures.

WEATHER: Diminishing winds and clearing skies are forecast this morning and may lead to heating of the snowpack. The timing of the clearing and warming have will have a direct effect on stability today. If fog lingers and shades the slopes from the sun, our stability concerns will be reduced.  The temperature is forecast to reach 30F on the summit with winds dropping to 10-25 mph (SE) from an already low 25-40 mph (NW). As the fog burns off, anticipate the possibility of rapid warming.

SNOWPACK: Icy conditions exist on the trail due to yesterday’s changeover from snow to rain which froze over the surface. Not only will this make travel more exciting due to the potential for rapid acceleration if you fall, but this ice is a player in our stability today. The wet surface layer, which exists over colder dry snow, is cohesive and relatively strong as long as it stays frozen. When heated, this thin layer of ice crust will lose its strength and create the potential for a Wet Slab or even a deeper weak layer, to release. Warming today is the enemy of stability and areas with the greatest consequences from this effect are those areas with large expanses of slab. These wind slabs developed yesterday in the lee of westerly winds from 1.8” of snow (0.57”SWE). Central, Sluice, Center Bowl and Chute are standouts for large wind slabs. The steepest terrain in Huntington ice climbs would also be vulnerable today as the slab battles gravity. South facing slopes will react soonest to solar gain. I would not expect the typical signs of rapid solar warming to occur today; the pinwheels and wet sluffs you often see in fresh snow will probably be contained by the glaze of ice. The monster lurking in the basement for me is the presence of some weak interfaces between older windslabs as well as some areas of pooled, rimed snow which have been very stubborn, but would have devastating consequences if triggered. Because of this “Scary Moderate” comes to mind. The unobvious nature of these deeper slabs are why we carry beacons, probes and shovels and practice careful travel techniques (minimizing time spent in the fall line of avalanche paths, one at a time travel, etc.). It may feel more like spring today but the snowpack stills tells me that it is winter.

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 8:30 a.m. 3-29-2014. 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

2014-03-29 Print friendly

Avalanche Advisory for Friday, March 28, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack and weather evaluation is essential today. The only exception to the Considerable rating is the Little Headwall in Tuckerman which has Low avalanche danger.

AVALANCHE PROBLEM: Our primary and secondary avalanche problems today are Wind Slab and Wet Slab. Which type of slab carries the most risk depends on temperature and precipitation type and rate. New snow this morning (1-3″) deposited by WSW winds will lead to the development of Wind Slabs. If incoming precipitation falls as rain, which is unlikely but possible, recent wind slab could change into our secondary avalanche problem – Wet Slab. A distant third problem is deeper, Persistent Slabs. Older, deeper wind slab layers could be activated by increased load and warm temperatures today. None of these hazards are expected to generate many natural avalanche releases but given the rapidly changeable nature of mountain weather, a wise traveler will pay close attention to type and rate of precipitation today in case rain shower activity is heavier than forecasted. And although 1-3″ of new snow isn’t much, history has shown this amount can turn into a problematic wind slab.

WEATHER: A mix of precipitation, reduced visibility and increasing winds are on tap for today. A warm temperature band mid-mountain this morning turned snow showers in Pinkham to light rain mid-mountain. Forecasts call for snow before noon with a slight chance of rain before turning to freezing rain in the afternoon. Wind from the WSW at an effective loading speed (45-60 mph, 72-97 kph) will increase a bit in the afternoon before shifting W this evening with the passage of a cold front. A more significant precipitation maker Saturday night has forecasters charged up.

SNOWPACK: Our snowpack is a mixed bag of Wind Slabs in the upper meter of snow. Some temperature crusts also exist, probably with some early faceted snow nearby. The location and depth of these layers varies widely depending your location but expect greater hazard to exist on the very steepest lee areas and slopes with the fewest anchors. The upper snowpack is dominated by hard, ergo strong, wind slabs so they will be stubborn in most locations. Fresh wind slabs, grown yesterday, were pockety and mostly built from highly decomposed snow crystals that packed pretty tightly. Highly textured, wind sculpted sastrugi was widespread. Sluice and Center Bowl had larger areas of more continuous and smooth wind slab and would be areas I would avoid entirely today. High winds in the past 36 hours pushed snow further down into our terrain like the Lower Snowfields and the big slope beneath Damnation and Yale. Though lower angle, these areas are large and continuous and could produce a larger avalanche. Air temperature has increased 36F (20C) degrees in the 24 hour period starting at 7 am so anticipate some weakening of the upper slabs. Ultimately this warming will encourage a breakdown of angular crystals and lead to more stability but we will pass through a period of relative instability to get there.

Spring is in the air this morning but it is not the type of spring day that encourages an outing into the alpine. If I were you, I’d continue to be patient for better weather that must be around the corner. After all, it is Spring. Right?

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 8:30 a.m. 3-28-2014. 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

2014-03-28 Print friendly

Avalanche Advisory for Thursday, March 27, 2014

This advisory expires at 12:00 midnight.

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

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

AVALANCHE PROBLEM: The main avalanche problem today is stiff Wind Slab. Though probably difficult to trigger in most areas, these firm Wind Slabs could propagate a crack and reach a dangerous size in select areas. These slabs are becoming Persistent Slabs as continued cold weather slows the bonding process. Reduce your exposure to these slabs with careful route finding in either Ravine.

WEATHER: High winds yesterday afternoon and overnight have moved and packed snow into slabs and scoured other areas. Northern gullies in Huntington appear to have been pretty well blasted by the wind, although some of the more wind resistant harder slabs certainly may still exist. Drifted snow, bark and branches litter the Tuckerman Ravine trail, clear signs of the harsh wind yesterday which peaked at 104 mph (46.4 m/s or 167 kph) with steadier winds near 90 mph (145 kph) for several hours. Northwest wind blowing near 80 mph (130 kph) will diminish to around 70 mph (113 kph). The wind combined with an air temperature crawling up into the teens will keep conditions noticeably colder than an average spring day.

SNOWPACK: While wind speeds were obviously less in our Ravines than on the summit, you can rest assured that very little soft snow remains. Sluice and Center Bowl escaped the strongest wind, due to their lee location, and are nudging into a more serious, higher Moderate due to the size of the potential slab and steepness. I would place Central Gully in a similar category though it is probably more scoured. The high wind seems to have built these wind slabs lower in our terrain so stay “heads up” to the right of the Fan beneath Damnation and Yale as well as in the lower portions of Sluice through Left Gully. The wind slabs that you may encounter today are certainly firm underfoot but the existence of rimed particle (graupel) layers and clean shear interfaces can leverage the brittle property of this hard slab against you. It is somewhere between difficult to impossible to know exactly where a thin spot lies beneath the upper snow layers, even with an intimate knowledge of the terrain, so your best bet for travel today, if you are going to brave the cold and wind, is to avoid traveling on or below larger areas of these slabs. Remember that although these slabs may have the ability to bridge across terrain features, they are often unsupported from below as they grow thinner downslope, so the slab can be essentially hanging on the slope. Perforating the slab with boots, impacting the slab with the weight of several people or a starfishing skier or just stepping on a thin spot in the right place could leading to failure. Even Low rated areas may contain areas with this sort of concern so ignore the calendar and bring your avalanche safety mind and PPE. 

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 8:40 a.m. 3-27-2014. 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

2014-03-27 Print friendly

Avalanche Advisory for Wednesday, March 26th, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. The only exceptions to this is the Little Headwall in Tuckerman which has Low avalanche danger.

AVALANCHE PROBLEM: Avalanche problem today is Wind Slab.  These are slabs that formed from last week’s storm and then mostly from snowfall and loading over the weekend.  Cold air in place since then has slowed the consolidation pace, but several locations have been moving towards stability.  As typically occurs, the most concerning instabilities can be found in the middle of Tuckerman, between the Sluice and the Center Bowl. New Wind Slab is problem #1B Later today some snow showers are possible which will likely produce some thin slabs in lee areas of N and NW winds.  You will likely begin seeing us discuss persistent slabs very soon.

WEATHER: Well winter continues.  The day is starting at about 0F (-18C) and will fall through daylight hours to about -10F to -15F (-23 to -26C) tonight.  Winds will also go in an unfavorable direction, from a current of 30mph from the NE, to the NW gusting to 110mph (176kph) tonight.  Alpine zones will get quite uncomfortable this afternoon as winds creep towards the 100mph (160kph) mark late in the day.  This will come with snow showers delivering up to 2” (5cm) of new snow.  Two winters ago we finished March almost 10degreesF above the 30 year average, the warmest in at least the previous decade. Conversely, this year March will hit about the same in the other direction with an average of +/- 9 to 10F below the long term averages.  Continue to expect and plan for extremes, it seems to be the new normal.

SNOWPACK: Snow pits and stability tests are highlighting the multiple snowfalls from the past week.  As Jeff alluded to yesterday when you dig a hole, isolate the stack of snow layers, and give them a load it’s like knocking over a book shelf at home.  Multiple layers are popping out, demonstrating all the loading events we endured from 5 days of snow from this past Wednesday through Sunday.  Graupel seems to be the snowpack’s culprit of choice for failure potential.  This fell among Friday’s snow and although they weren’t the perfect smooth little ball-bearings we can see, their fuzzy rimed nature is still not bonding well with neighboring crystals.  Look for this in your stability tests today.

In Huntington, the northern side of the Ravine has some snowpack issues to negotiate down low to their mid sections, while on the south side the concerns are more from their mid to upper reaches.  Some location’s like Hillman’s, Left gully, and Huntington’s Pinnacle are starting the day at a Low rating. However they are posted Moderate, based on new loading potential this afternoon due to new snowfall forecasted and potentially some icy crystals loading from alpine zones.  The wide snowpack temperature gradients, yesterday’s cold air, and low winds make me believe some diurnal recrystallization/faceting has occurred.  This may fall victim to the very high winds we are expecting today sending icy particles down into the Ravine mixed with new snow.  This is a possibility later today, hence all areas at Moderate, but is more plausible during the overnight as winds move above 100mph.

In summary, expect some lingering instabilities from recent wind slabs created over the weekend and then new instabilities that layer in on an increasing N wind shifting from the NW later.  Initial moderate wind velocities may produce a soft slab first followed by stiffer, harder slabs overtop later.  I would envision this initial soft snow to be a potential weak layer for the thin hard slabs waiting for a trigger. Saying this, with the scant snow fall expected these new slabs should be thin and isolated, so continue to expect variability across our terrain and not widespread consistent problems. Due to this irregularity make careful snowpack assessments and conservative choices to avoid potential instabilities. There are recreational options out there if you’re flexible and willing to play on the mountain’s terms.

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 755a.m. 3-26-2014. 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

2014-03-26 Print

Avalanche Advisory for Tuesday, March 25, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. The only exceptions to this are the Little Headwall in Tuckerman and Pinnacle Gully in Huntington, which both have Low avalanche danger. Natural and human triggered avalanches are unlikely. Unstable snow may exist in isolated terrain features.

AVALANCHE PROBLEM: Avalanche problem #1 today is wind slab. The most concerning of these can be found in the middle of Tuckerman, between the Sluice and the Center Bowl. Other areas in Tuckerman, as well as much of Huntington, also fall in the Moderate range. With careful snowpack assessments and conservative choices you may find slopes stable enough to travel through while avoiding potential instabilities. In Pinnacle Gully, the concern lies in the snowfield exiting the route. The climb itself is pretty well wind scoured. Northern gullies in Huntington have potentially unstable snow leading up to the routes as well as in the lower to middle sections. In the gullies to the climber’s left of Pinnacle you’ll find the issues in the middle to upper sections.

WEATHER: Today should be a little warmer than yesterday and with a lot less wind. You should still be expecting a cold day with increasing clouds. Summit temperatures will be in the single digits F (-15C), winds are already lighter than the forecasted 15-30mph range (24-48kph).

SNOWPACK: As I mentioned yesterday, the snowpack in the Center Bowl and Lip area has grown tremendously in the past couple weeks. Within this area, you should expect numerous layers of wind slab. Initial failure of the slope could take place at any one of these, however, I’d put my money on a graupel layer that fell from the sky on Friday as being the weakest of the weak layers. A couple easy compression test results yesterday had the block sliding on this layer, then falling down and breaking up into multiple layers the way a stack of books might look if it fell off the coffee table.

Many areas in both ravines have received a fair amount of wind effect. Left Gully and South Gully are two examples. This hammering of the wind has the potential to add strength and stability to the snowpack, but unless you’ve been able to assess the snow with your own hands, don’t assume a slope is stable simply due to its visual appearance. The surface layer may provide a false sense of security and mask underlying weaknesses.

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 8:00a.m. 03-25-2014. 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

2014-03-25 Print friendly

Avalanche Advisory for Monday, March 24, 2014

This advisory expires at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravines have MODERATE avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. Large avalanches may occur in specific areas. Evaluate snow and terrain carefully. The only exception to this is the Little Headwall which has Low avalanche danger. Human triggered avalanches are unlikely except in isolated terrain features.

AVALANCHE PROBLEM: Wind slab is the primary avalanche problem today. Over the last several days, there has been a lot of wind-transported snow which has created dangerous wind slabs across most of Tuckerman and Huntington. We are just coming down from days with High and Considerable avalanche danger. Depending on where you travel today, you may encounter some areas at the upper end of Moderate based on the likelihood of triggering an avalanche. These locations are also capable of producing large avalanches, so pay close attention to your terrain choices. Being in the flat or low-angled terrain below any avalanche path is a bad place to be if it were to be triggered from above.

WEATHER: Two years ago today, the summit temperature maxed out at +40F (4.5C) during a heat wave. This morning it is -15F at the summit and just below 0F at Hermit Lake. Despite the sunshine, this is a cold winter day. For those who haven’t been paying attention, in the last 5 days, the summit of Mt. Washington has reported 25.5” of new snow.

SNOWPACK: The most impressive thing that stands out this morning is how bloated some forecast areas have become. The amount of wind loading has been very impressive. For example, the rock and ice cliff that has marked the skier’s right edge of the Lip throughout this season is now completely buried under new wind slab, and the ice cliffs that mark the left side are almost gone as well. This bodes well for spring skiing later this season, but very badly for anyone who happens to trigger this slope in the near-term. There is a tremendous amount of slab loaded onto a 50 degree slope. I don’t think it will release on its own today—I think someone would need to travel through there to trigger this path.

Many locations were wind-effected overnight and may have some reasonable travel options for people who are capable of assessing the snowpack and mitigating avalanche hazard with good terrain management skills. Of course, you’d also need to be willing to turn back if you don’t like what you’re seeing in the snowpack. Those savvy travelers who fit this description will have an easy enough time visually figuring out which areas might have good enough stability to venture into. Be honest with yourself and your partners when figuring out if the risk is something you are comfortable with. I will say that the Sluice through Chute is the area of greatest concern. They do not offer good options for terrain management and are the most deeply loaded slopes.

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 8:45a.m. 03-24-2014. 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

2014-03-24 Print friendly

Avalanche Advisory for Sunday, March 23, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger today. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Natural avalanches are possible and human triggered avalanches are likely. The only exception to this rating is the Little Headwall, which has Moderate avalanche danger. In this location, natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wind slab or storm slab? Who cares what you call it today? What’s really important is that we are starting with an elevated level of avalanche danger, and this will be increasing throughout today due to wind loading. Expect danger to be pushing the upper end of the Considerable rating, moving in the direction of High avalanche danger. This is the case for all forecast areas, although the greatest potential for us to exceed the Considerable rating is in the Lip and Center Bowl of Tuckerman. Other areas on the flanks of the ravines will still sit solidly in Considerable danger. In all areas, avalanche paths have been growing large in recent weeks, and have the ability to push avalanche debris well down into low-angled terrain. You don’t need to be on a steep slope to be at risk!

WEATHER: This has been a great stretch of weather up on the mountain for snow enthusiasts. In the last four days, the summit has reported 21.2” (54cm) of new snow, which has pushed us up over the average total for the month of March. The depth of snow in the woods at Hermit Lake has increased from 111cm to 160cm over the last two weeks.

We are starting today with a little more snow in the air than we expected due to an arctic front passing through the region. Currently the snowfall rate is about 1cm per hour. Keep your eyes on total accumulations. Expect very strong winds above treeline today, ranging from 50-70mph (80-113kph). Following the passage of the front, snowfall should taper, temperatures will continue to plummet, and high pressure may begin to clear the clouds off the mountain. Personally, I wouldn’t recommend waiting around for the end of the day in hopes of getting some better weather up high.

SNOWPACK: Wind loading today is the driving force behind the avalanche danger. Although winds were fairly strong yesterday, they weren’t able to remove all the snow from above treeline and they obviously couldn’t have already transported the new snow that’s currently falling. From what we’ve historically seen, 50-70mph NW winds with an ample supply of snow to draw from can create very deep slabs in the ravines, and produce some large avalanches. Densities of the recent snow are such that I’d expect large slabs to be able to build before releasing.

While we have seen evidence of recent avalanche activity (e.g. Left Gully sliding to the opposite side of the floor of Tuckerman and Dodge’s pushing into the approach path to Hillman’s), we have also seen evidence of significant reloading of slide paths. Figuring out which weak layer to be concerned with should be an academic exercise today, rather than one with meaningful implications on your travel routes. You’ll do a lot better today to identify avalanche terrain and do your best to avoid it.

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 8:45a.m. 03-23-2014. 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

2014-03-23 Print Friendly