Avalanche Advisory for Monday, April 23, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Yale, Central, Pinnacle, Odell, and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. North, Damnation, and South have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Right Gully, Sluice, Lip, Center Bowl, Chute, Hillman’s Highway, Lower Snowfields have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. Lobster Claw and Left Gully have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall is the exception with Low avalanche danger and areas of open water.

AVALANCHE PROBLEM: Wind slabs that formed over the weekend will still be our primary concern today. Warming yesterday may have allowed some additional bonding of these wind slabs to the icy bed surface.  While they appear similar, these slabs are variable depths across the terrain.  They proved firm and stubborn to human trigger yesterday however that doesn’t mean they are stable.  We would expect an avalanche today to be medium to large in size, particularly in Moderate rated terrain. Again today’s problem makes it a relatively low probability, high consequence day.  With the rising temperatures today spring hazards should being part of your travel decision making.  The forecast temperature and solar gain for today will help move us toward a traditional spring snowpack.  However, we have not reached this point yet so please continue to bring your avalanche gear and a mid-winter mindset.

 WEATHER: Yesterday the summit reached 20F while Hermit Lake reached 36F.  The wind stayed steady at 30 mph out of the NW with gusts reaching 50. High pressure has set up over the Northeast, with the center moving over us today.  This high will help decrease our winds to 10-25mph and shift them from NW to W.  It will also bring warmer air from the West and help us reach more seasonable April temperatures.  Today the summit should reach the mid 30 F and only drop to the upper 20’s F overnight. Tomorrow warmer temperatures continue with the high on the summit expected to reach 40F.  Cloud cover should increase late in the day with an incoming weather system.

 SNOWPACK: The up to 16” of snow and consistent loading wind speeds have created wind slab across much of our terrain. The bed surface is still the icy, hard crust formed from last week’s mixed precipitation and refreeze.  The slab varies greatly in depth from several inches to multiple feet.  The depth, along with the hardness, is hard to visually assess from the surface.  During observations yesterday we found 2’ thick layer wind slabs in close proximity to 2” of slab on top of a shallow graupel layer, illustrating current spatial variability. Bonding of the slab to the bed surface likely improved yesterday but not to the point of calling it stable.  With the warming temperatures and increasing solar gain today we expect peak instability to coincide with peak temperature. While sun should soften snow on the surface today, don’t expect an instant transition to corn snow from our late season wintry snowpack.  It is always a good idea to choose terrain appropriate to your preparedness and respect avalanche danger.

Be sure to check out our Instagram posts (@mwacenter) for up to date photos and videos. You don’t need an account to view them on your computer!

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.
• Posted  8:10 a.m., Monday, April 23, 2018. A new advisory will be issued tomorrow.

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

2018-04-23

Avalanche Advisory for Sunday, April 22, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Yale, Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. North and Damnation have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, and the Lower Snowfields have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is the exception with Low avalanche danger and areas of open water.

AVALANCHE PROBLEM: Wind slabs that formed since Friday are our primary avalanche problem. Of most concern today will be sun exposed areas holding largest slabs, like Sluice and Lip, where warming will push likelihood for human triggered avalanches toward likely and keep natural avalanches possible. Right Gully and Lobster Claw in Tuckerman and Yale Gully in Huntington should see similar affects though less capable of producing a truly large avalanche. We expect the somewhat firm wind slabs present in most of the terrain to be stubborn to a human trigger but capable of producing medium to large sized avalanches. This sets up a relatively low probability, high consequence day in which it’s plausible for the 5th or 10th skier, snowboarder, or climber rather than the 1st on a particular slope to trigger a large avalanche. Likelihood of triggering an avalanche will be slightly lower today than yesterday, but potential size of avalanches has not decreased, continuing to make the floor of Tuckerman Ravine an inappropriate place to linger.

 WEATHER: Temperatures below 20F on the summit and just above freezing at Hermit Lake yesterday paired with clearing skies and summit wind around 50 mph from the NW for a semi-pleasant day. Today is forecast to be approximately 10 degrees warmer with continued NW wind that should hold between 30 and 45 mph on the summit. Warmer temperatures and clear, sunny skies will make it feel spring like today and more so tomorrow, though the snowpack remains dynamic and more winter-like.

 SNOWPACK: Moisture from mixed precipitation earlier this week refroze and created a hard crust as a bed surface for the wind slabs which have formed since Friday. A few areas of this refrozen crust exist at the surface, but most of our terrain has been smoothed over by wind deposited snow. This means that the wind slab varies greatly in thickness from several inches to several feet, but it looks very similar from the surface. Layers do exist within this new wind slab, with a stiffer layer on the surface remaining reactive, but we would expect avalanches today to ultimately entrain all snow above the refrozen crust. Bonding in this upper snowpack has improved but not to the point of calling anything stable. Further, we expect stability to decrease with warming today, particularly on sunny aspects. A breakable sun crust from yesterday exists on some but not all southerly slopes, with inconsistent cloud cover suspected to be the culprit in variability of this crust. While sun today should soften this crust and affect stability, don’t expect an instant transition to corn snow from this wintry snowpack. Respect avalanche danger today by choosing terrain appropriate to your preparedness. Though avalanches may be less likely than yesterday, they could still be large. Bring your beacon, shovel, and probe along with an ability to use them as you carefully choose terrain. The Sherburne should ski well today and serve as an excellent consolation prize if today is not your day to travel in avalanche terrain.

Be sure to check out our Instagram posts (@mwacenter) for up to date photos and videos. You don’t need an account to view them on your computer!

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.
• Posted  7:40 a.m., Sunday, April 22, 2018. A new advisory will be issued tomorrow.

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

2018-04-22

Avalanche Advisory for Saturday, April 21, 2018

Huntington Ravine has CONSIDERABLE avalanche danger. Yale, Central, Pinnacle, Odell, South, and Escape Hatch have Considerable avalanche danger. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. North and Damnation have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. Lip and Center Bowl have High avalanche danger. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. All other forecast areas have Considerable avalanche danger. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. The only exception to this is the Little Headwall which has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

AVALANCHE PROBLEM: Recent new snow and steady NW wind is elevating the avalanche danger ratings today. Wind slab is likely to be easily triggered and is not bonded well to the soft new snow or the underlying ice crust. With over 16” of recorded snow on the summit since noon on Thursday, avalanches today could be large. Recent avalanche debris in Hillman’s and Dodge’s has been observed so far through the fog and blowing snow. These recent avalanches plus continued wind loading of slopes are obvious red flags for folks considering playing in or below steep terrain today. Well-developed avalanche paths exist, meaning an avalanche today could also run far onto flat ground. Entering the floor of Tuckerman Ravine today is not recommended as this will require crossing numerous avalanche paths that have the potential to avalanche naturally. With most of avalanche terrain offering a high-risk, high-consequence scenario, lower-angled terrain like the Sherburne will be the safe choice today.

WEATHER: Snow began to fall around noon on Thursday, April 19, and has been steadily accumulating, leaving 16.4” at the summit and 8.25” at Hermit Lake. Thursday evening, wind speeds increased to 40-60mph from the NW and have remained at that speed with occasional gusts into the 70mph range. The low pressure system sitting over the Northeast has begun to drift offshore and will allow clearing to take place later today. Before then, low level moisture will likely keep the summits in the fog with upslope snow showers for the morning. Temperatures today will climb to the upper teens F and winds will remain from the NW at 45-60mph.

SNOWPACK: The bed surface for avalanche activity today will be the ice crust that formed earlier this week. Below this ice crust, snow is still moist due to the insulating layer of snow above. Above this ice crust, widespread soft wind slab exists. This wind slab has several changes in density that are interspersed with graupel. Yesterday, this slab was reactive in stability tests, though struggled to propagate a crack. Continuing snow and wind loading today may allow the slab to overcome the minimal friction offered by the icy bed surface. Numerous red flags are present today; ski the snowpack, not the calendar.

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.
• Posted  8:00 a.m., Saturday, April 21, 2018. A new advisory will be issued tomorrow.

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

2018-04-21

Avalanche Advisory for Friday, April 20, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is no longer forecast due to open holes in the snowpack and is not recommended as an exit from the Bowl.

AVALANCHE PROBLEM: Six inches of new snow overnight arriving on increasing NW wind makes wind slab our avalanche concern today. No visibility this morning adds a degree of uncertainty to today’s forecast. We expect the snow to struggle to adhere to the ice crust which will act as today’s bed surface. This highlights a key characteristic about today’s avalanche problem; wind slab will likely be touchy to human triggers. In Moderate rated areas, the combination of wind and the slick bed surface may allow scouring to take place leaving areas of bed surface exposed. Considerable rated slopes, those in the lee of our fetch, should hold much larger areas of wind slab with limited to no old surface exposed. The potential for large avalanches exist in these areas with the possibility of natural avalanches due to continued loading through the day. The floor of Tuckerman Ravine today will be avalanche terrain as we have seen avalanches run far this year on well-developed slide paths. The hard bed surface will demand the use of crampons and an ice axe for those choosing to travel in avalanche terrain.

WEATHER: Low pressure centered over Nova Scotia will continue to send bands of winter weather to Mount Washington today. After a midday lull yesterday in wind speed combined with a spike in temperature to the mid-20s on the summit, snowfall began along with an increase in wind and a drop in temperature. Winds bottomed out at 5mph around noon yesterday and by midnight were above 40mph. As of this morning, the summit recorded 5.2” of snow while just under 6” fell at Hermit Lake. Today, temperatures will remain in the 20’s F in avalanche terrain with the summit reaching the upper teens. Winds should stay in the 40-55mph range from the NW. Snow is likely; 0.25” of SWE is forecast to arrive by this evening which could amount to another 2+” of snow. Wind and temperatures tonight should remain similar to today with another possible 2” of snow by tomorrow morning.

SNOWPACK: Over the past week, 10” of mixed precipitation arrived with a SWE of 3”. This was followed by cold temperatures that allowed a thick ice crust to form. On Wednesday, this crust was 4cm thick in places with moist snow beneath. With continued cold Thursday and last night, this crust will remain thick and strong, limiting avalanche concerns to the surface wind slab. We expect the new wind slab to vary in size from small to large depending on terrain and aspect. The uncertainty of wind slab size today comes from a combination of weather and snowpack factors compounded by no visibility. This same visibility challenge will make safe travel decision difficult today, as seeing avalanche start zones will be difficult. Days like today, which have a degree of uncertainty, are best for choosing low consequence terrain. The Sherburne will ski well today with top to bottom coverage.

Bear tracks were seen around the Fire Road and Tuckerman Ravine Trail. Please use the bear boxes and keep your camp clean if staying overnight at Hermit Lake. The Harvard Cabin is closed with no camping allowed anywhere on the east side of Mount Washington except at Hermit Lake Shelters or adjacent tentsites.

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.
• Posted  8:00 a.m., Friday, April 20, 2018. A new advisory will be issued tomorrow.

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

2018-04-20

Avalanche Advisory for Thursday, April 19, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl and Chute have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall has open water in the steep section as well as the stream bed above. It is not a recommended route out of the Bowl.

AVALANCHE PROBLEM: Due to the rugged ice crust on the mountain, you’ll find two distinct threats to safe travelling in steep terrain. The recent sleet storm finished with freezing rain which created a thick ice crust over top of a widespread glaze of sleet, wet snow and ice. New snow fell at the end of the storm on Tuesday afternoon and was able to stick in some areas, but not very well. Due to scouring of the snow, wind exposed, scoured areas above tree-line will require crampons for safe travel while many lee areas have collected enough snow to build some wind slabs. Low visibility, and other duties kept us from gathering many observations yesterday and this morning, but it seems that the ice crust will be the dominant surface in steep terrain. In areas where the new snow adhered to the ice, hand shears low in Hillman’s Highway showed that the new wind slabs failed easily in the new snow. Only a small amount (2-3”) of the recent snow was light enough to be carried by the wind and blown into our terrain but the icy bed surface will up the ante if you get swept off your feet. Human triggered avalanches are unlikely today unless you seek out these areas of wind slab. Additionally, light winds may allow the 1-2” of new snow that falls to build into small but more sensitive, new wind slabs. If we receive the upper end of the forecast amount, human triggered avalanches will become more likely and increasingly widespread.

WEATHER: Just 0.7” of snow fell on the ice encrusted summit yesterday. This snow was light enough to be carried by the wind, like the inch or two which fell at the end of the storm on Monday and Tuesday. That storm brought a generous coating of sleet and ice totaling 10” of mixed frozen types and over 3” of water equivalent. A low pressure system will pass to the south today and spawn snow showers and some fog. Expect another wintry day with a high temperatures near 20F. Snow surfaces are unlikely to soften despite the warmish temperature and low wind speeds. More new snow toight and tomorrow may create more significant avalanche concerns tomorrow and Friday.

SNOWPACK: Instabilities in the snowpack are limited to recent snow. Yesterday, 8” or more of moist rounds were found beneath a rugged 3-4cm ice crust. This ice crust was more ice than crust and was just barely bootable on sub 20 degree slopes. Anything steeper required crampons or a stubborn desire to link skin-able sections of wind deposited snow. Lower on the mountain, the Sherburne was recoated with the sleet which has covered the bare spots on the trail that had begun to emerge. The trail is very skiable all the way to the parking lot at Pinkham Notch.

Bear tracks were seen around the Fire Road and Tuckerman Ravine trail. Please use the bear boxes and keep your camp clean if staying overnight at Hermit Lake. The Harvard Cabin is closed with no camping allowed anywhere on the east side of Mount Washington except at Hermit Lake Shelters or adjacent tentsites.

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.
• Posted  7:30 a.m., Thursday, April 19, 2018. A new advisory will be issued tomorrow.

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

2018-04-19

Avalanche Advisory for Wednesday, April 18, 2018

Huntington Ravine will have MODERATE and LOW avalanche danger today. Central, Pinnacle, Odell, South and Escape Hatch will have Moderate avalanche danger. Evaluate snow, weather and terrain carefully. Heightened avalanche conditions exist on specific terrain features. Northern gullies in Huntington have Low avalanche danger. Watch for unstable snow on isolated terrain features

Tuckerman Ravine will have MODERATE and LOW avalanche danger today. Sluice, Lip, Center Bowl, Chute, Left and Hillman’s Highway will have Moderate avalanche danger. Evaluate snow, weather and terrain carefully. Heightened avalanche conditions exist on specific terrain features. All other forecast areas will have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall and the streambed above has too much open water to be a good route for exiting the Bowl. Hiking down is the recommended option.

Bear tracks have been seen in the vicinity of the Fire Road and the Tuckerman Ravine Trail. Please be careful with your food. Sometimes “a fed bear is a dead bear” when they become habituated to humans and their food waste. Use the bear boxes located at the Hermit Lake Shelters when camping and be sure your snacks make it into your mouth.

AVALANCHE PROBLEM: The amount of snow available for transport by increasing westerly winds is driving the avalanche problem today. Deeper areas of new snow may be attractive for skiing and riding but bear in mind that the new snow may not be well bonded yet to the old refrozen surface. As wind increase today, be on the lookout for wind slabs growing over a foot thick and may fail on softer new snow beneath. Lower angled terrain may have the best skiing since the icy bed surface will be lurking just below the new snow. The potential for wind slab avalanches in many areas is a reminder that it is not springtime in the mountains yet.

WEATHER: In the past 24 hours, three inches of new snow fell on the summit with 3cm (1.18”) of 13% density snow at Hermit Lake. This disparity is primarily due to the elevation of the freeze line while yesterday’s low pressure system dumped copious amounts of rain that turned to wet snow in the afternoon. Currently, this new snow is refrozen into a thick crust from Pinkham to Hermit Lake with limited amounts of loose snow on the ground at mid-elevations with more likely above in the alpine. Upslope snow showers may continue today bringing a trace to two inches of snow. Wind will shift this morning from northwest to west and increase to the 45-60 mph range. Expect low visibility as lingering moisture produces summit fog along with snow showers. Light snow is falling at Hermit Lake this morning. The temperature on the summit is currently 12F and will rise to 20F.

SNOWPACK: Almost 10” of new snow with 3.4” liquid equivalent has fallen on the summit in the past 48 hours. The mixed bag of precipitation in the past 4 days has generally led to an isothermal and stable deeper snowpack. The return to winter weather yesterday and today brings new avalanche concerns in the form of new snow and new wind slabs. Check for bonding of the new snow to the old and look for signs of continued wind loading today. Continue performing stability tests, traveling with a partner and carrying avalanche rescue equipment including a beacon because it is not spring yet!

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.
• Posted  8:05 a.m., Wednesday, April 18, 2018. A new advisory will be issued tomorrow.

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

2018-04-18

Avalanche Advisory for Tuesday, April 17, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE avalanche danger. All forecast areas in Tuckerman Ravine have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is once again an open stream and is not receiving an avalanche danger rating

AVALANCHE PROBLEM: Wet slab avalanches will be possible to human trigger this morning, with colder temperatures gradually refreezing the snowpack and reducing instability late today into tonight. Multiple layers near the surface may be capable of producing varying sized avalanches. First, sluffing action of ice pellets yesterday proved to create unstable and reactive, though isolated, slabs low in avalanche paths. These and similarly new slabs formed from the mix of sleet (ice pellets), snow, freezing rain, and rain may present pockets of instability in much of the terrain, though wetting from rain overnight has likely reduced sensitivity to a human trigger. Second, deeper slabs which have become increasingly wet could produce large avalanches, also possible to human trigger and unlikely to avalanche naturally, though we’re not ruling out this possibility entirely. Finally, snow falling today and tonight on increasing W wind may build to form new wind slabs by the time this advisory expires at midnight tonight.

 WEATHER: The extreme diversity of precipitation types continued yesterday, with freezing rain showing as the dominant precipitation type in hourly observations but snow, sleet, and rain also falling and affecting the upper snowpack. All told, the summit recorded 3 inches of water amounting to 6.7 inches of snow and mixed precipitation particles. Hermit Lake recorded 2 inches of water and 3 inches of snow and mixed precipitation particles. It’s currently raining lightly from Pinkham up to the base of the ravines, with light snow showers on the summit. Mixed precipitation is forecast to continue today in our terrain, with snow being the dominant precipitation type on the summit. This should gradually trend towards snow as temperatures drop today and tonight from the current 30F on the summit to 15F by tomorrow morning. Snow could total up to 2-4 inches today and 1-3 inches tomorrow. The current S wind under 30 mph on the summit should shift W soon and increase late today and tonight. Tomorrow is forecast to have slightly colder temperatures and continued light snowfall, with W and NW wind in the 40-60 mph range.

 SNOWPACK: Our upper snowpack has become increasingly wet over the past 24 hours, adding to moisture from the weekend and generally thawing the refreeze which occurred Sunday night. The result of nearly every form of precipitation yesterday is wet and dense snow at the surface. Sluffing of ice pellets to pockets low in our avalanche paths accumulated significantly and showed the ability to produce an avalanche. A human triggered avalanche near the base of Hillman’s Highway was triggered from below and from the edge of the slab in terrain possibly below 30 degrees in steepness. Wetting from rain overnight has likely reduced the ability for similar slabs to produce avalanches, as the moisture is slowly making layers more uniform, but layers exist in the new “snow”. Deeper layers could also produce an avalanche, which could be larger though generally less likely. Dropping temperatures today and tonight will ultimately refreeze and lend stability to the snowpack. Precipitation transitioning towards snow from rain today and tonight may ultimately build new wind slabs, but this is unlikely to pose an issue during daylight hours. Those braving the wet conditions today will likely find decent conditions to make turns, with the Sherburne still holding snow coverage.

Be sure to check out our Instagram posts (@mwacenter) for up to date photos and videos. You don’t need an account to view them on your computer!

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.
• Posted  8:20 a.m., Monday, April 17, 2018. A new advisory will be issued tomorrow.

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

2018-04-17

Avalanche Advisory for Monday, April 16, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE avalanche danger. All forecast areas in Tuckerman Ravine have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is once again an open stream and is not receiving an avalanche danger rating

AVALANCHE PROBLEM: Rain, which could be heavy today, will make wet slabs today’s primary avalanche problem. Today’s precipitation type will be the primary driver of instability in the snowpack. If we receive more plain rain, wetting and warming will decrease stability through the day. A greater proportion of frozen mixed precipitation will have a lesser impact on the stability of our currently refrozen and stable snowpack. Today’s Moderate rating is distinctly different than Moderate ratings issued a week ago. Last week, new snow and wind made small avalanches possible in a number of areas. Avalanches were much more likely and much smaller than the large avalanches which are possible but less likely today. It’s a low probability and high consequence kind of day. If the weather doesn’t keep you out of the mountains, be mindful that though natural avalanches are unlikely today, they could be large and run a great distance.

 WEATHER: We’re rolling into day three of mixed precipitation on the mountain, and today should bring the greatest amount with approximately 2” of water. Temperatures should hover near freezing on the summit today. Freezing rain is currently falling on the mountain, though it’s forecast to shift towards plain rain soon. Precipitation should be heaviest this afternoon and evening and continue to flirt with the line between rain and freezing rain. A changeover to snow is forecast to occur early tomorrow morning and result in 2-4” of snow during the day. It will also be a quite windy day today, with current ENE summit wind at 50 mph slated to increase with peak gusts over 100 mph occurring this evening.

 SNOWPACK: New snow last week was followed by a significant melt and refreeze over the weekend, with small amounts of mixed wintry precipitation not resulting in new stability concerns. The upper snowpack is currently stable as a result. Instability should increase as the day progresses due to a significant rain event. While this rain is falling on refrozen surface snow, a number of robust melt/freeze crusts and dry snow exist deeper in the snowpack. This structure presents the possibility for rain water percolating down through the snow to weaken bonds or provide lubrication between layers. It’s unlikely, but a large natural wet slab avalanche could certainly occur today. Large wet slab avalanches are particularly tricky to forecast, and today’s forecast of either rain or freezing rain further complicates this puzzle. Pay close attention to the precipitation type and degree of wetting the snowpack receives as you assess conditions and make terrain decisions today.

Be sure to check out our Instagram posts (@mwacenter) for up to date photos and videos. You don’t need an account to view them on your computer!

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.
• Posted  7:35 a.m., Monday, April 16, 2018. A new advisory will be issued tomorrow.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2858

2018-04-16

Avalanche Advisory for Sunday, April 15, 2018

Huntington and Tuckerman Ravine have LOW avalanche danger. All forecast areas have Low avalanche danger. Generally safe avalanche conditions exist. The exception to this is the Little Headwall which is no longer rated due to a lack of snow and is not advised as a route of travel.

AVALANCHE PROBLEM: We are currently in the freeze portion of a prolonged melt-freeze cycle that began on Friday which is largely eliminating avalanche concerns for the day. With continued below freezing conditions today, long sliding falls will be much more of a hazard today. Crampons, an ice axe, and the ability to use them will make travel in avalanche terrain possible. Climbers should be aware of the potential for ice dams as the current freeze may trap flowing water. This trapped water will be looking for a pressure release valve in the form of an ice tool or screw placement. The thaw over the past two days has also reopened holes in the snow on the Little Headwall, making this no longer an advisable route to exit Tuckerman Ravine. Many skiers and riders were seen removing skis and boards and trying to down climb the combination of refrozen snow, ice, and verglassed rock. Hiking down the Tuckerman Ravine Trail to Hermit Lake will be both faster and safer at this point.

WEATHER: Just about every possible type of mixed precipitation fell onto Mount Washington yesterday. All told, we received 0.35” of water. This came largely as ice pellets, freezing rain, rain, and snow. Winds calmed from W at 45mph yesterday morning to a current N at 8mph this morning. Today, unsettled weather will continue, allowing the temperature to remain around the freezing mark with another 0.2” of liquid precipitation coming in various forms. The wind will wrap from the north through east to SE by early afternoon with speeds staying under 20mph until the evening. If conditions allow and we see all snow today, we could see up to 2”, though it seems more likely that sleet and freezing rain will mix in.

SNOWPACK: Prior to the warm-up on Friday, our snowpack of concern consisted of soft slab of variable thickness, up to 2’ in places, sitting on top of a decomposing melt-freeze crust. Due to warm temperatures and sunshine, this became a wet avalanche problem on Friday into Saturday morning. Earlier than expected on Saturday temperatures dropped and a refreeze began, slowly penetrating into the snowpack and locking things into place. With skier traffic in many areas Friday and Saturday as well as many large roller balls on Friday, the surface of this refrozen snowpack is ugly and likely to provide rough skiing.

The Sherburne saw heavy traffic yesterday from the Friends of Tuckerman Ravine Inferno Pentathlon. Expect large, frozen moguls with icy troughs in between. Some bare spots exist down low, but coverage is remarkably good.

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.
• Posted  7:30 a.m., Sunday, April 15, 2018. A new advisory will be issued tomorrow.

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

2018-04-15

Avalanche Advisory for Saturday, April 14, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features. 

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas in Tuckerman Ravine have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. The exception to that rating is The Little Headwall which has Low avalanche danger.

The Inferno Pentathlon is happening today with the ski leg starting at the upper Sherburne/Hillman’s junction. Use extra caution when driving in the area and know that some folks will be in a hurry hiking on the Tucks trail.

AVALANCHE PROBLEM: Wet avalanches due to melting and liquid precipitation will be possible today. These avalanches are likely to be limited to loose-wet or point release type but a larger, wet slab avalanche is not out of the question in areas that previously had thicker layers of dry wind slab. The Lip, Center Bowl, and Central Gully fit this profile and deserve extra caution. A small wet slab or loose-wet avalanche can also serve as a trigger for a larger avalanche or entrain more snow than expected. Mind your runouts today if you venture into steep terrain and protect yourself and your belayer when climbing into larger snowfields. Avalanche concerns will diminish with the return of freezing temperatures later today and be replaced by slide for life conditions once surfaces have refrozen. 

WEATHER: Overnight, rain and freezing rain fell on our already moist snowpack with temperatures at or just above the freezing point. Hermit Lake collected .4” (1 cm) of rain with no snow on the board in the past 24 hours. A high temperature of 6C was recorded in the same time period. Near but just above freezing temperatures are expected in our avalanche terrain this morning along with a mixed bag of new precipitation types. The new precipitation and warm temperatures will continue to stress and weaken the snowpack until freezing temperatures return later today. Be mindful of the effect that even a degree or two of cooling can have on our snowpack if skiing or riding. 

SNOWPACK: Above freezing temperatures have persisted in our terrain for the past 24 hours. Combined with the overnight rain, these conditions are warming and wetting the snowpack and will continue to until air temperature drops and precipitation returns to frozen forms later today. Prior to yesterday several layers of generally soft slab, totaling up to two feet in thickness, existed above an older melt freeze crust in our upper snowpack. A surface layer observed at only a few inches thick was reactive to skier triggers yesterday. Moisture and warmth are in the process of converting these layers into a singular and more uniform layer of wet snow. This process will increase stability with a refreeze, but as of this morning it creates our wet slab avalanche problem. Also of note yesterday was significant wet roller ball activity in lower terrain and particularly the Lower Snowfields. While we expect the smooth and steep slopes less affected by roller balls to be of greater concern for avalanches today, it’s certainly an indication of rapid warming affecting the snowpack. Roller balls, ski and boot tracks, and generally soft wet snow will all contribute to less than ideal conditions once a refreeze occurs. Expect stability to increase but for the propensity for other injuries to increase, with long sliding falls ultimately becoming a key concern.

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.
• Posted  7:30 a.m., Saturday, April 14, 2018. A new advisory will be issued tomorrow.

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

2018-04-14