Wind slab formed in the past two days covers most of our terrain and is our primary avalanche problem. These smooth surface wind slabs were formed by W to NW wind which either directly loaded or cross loaded most forecast areas. In many areas, this somewhat soft but cohesive surface snow overlies slabs formed late last week that are similar if a little less soft in character. We expect all smooth surface snow to be sensitive to a human trigger today. The connected and consistent nature of wind slab means that such avalanches could be quite large. Upper portions of Left Gully and most of Odell have heavily wind textured snow at the surface that will be fairly hard and more stubborn to a human trigger, hence their Moderate rating. One if not two natural avalanches in Lobster Claw yesterday have reduced snow available to avalanche, though sensitive pockets likely still exist. Moderate avalanche danger means that human triggered avalanches are possible, suggesting that you should evaluate snow and terrain carefully prior to committing to a slope. It’s not likely you’ll be able to avoid the avalanche problem in Moderate rated terrain today. It’s a beautiful day to enjoy the mountains, so carefully evaluate all snow and terrain. Choose to come home safely.
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Wind Slab formed in the past 24 hours is our primary avalanche problem, with older wind slabs from our recent successive storms adding complexity to the upper snowpack. Significant snowfall yesterday combined with westerly winds to transport significant snow into lee terrain and cross load other areas. The resulting wind slabs will vary in hardness and could be large. Expect them to be reactive to a trigger. Human triggered avalanches are very likely in High rated areas. Peak instability likely occurred last night, but we don’t expect these slabs have gained much strength since then. Two known close calls occurred yesterday, including a skier caught and carried in Gulf of Slides by an avalanche that occurred while the party ascended. Shortly after, two skiers were knocked off of their feet at the base of Hillman’s Highway by a natural avalanche. The Hillman’s avalanche is a reminder that low angle areas in our terrain, especially the floor of Tuckerman Ravine, are in the runout of steeper terrain above and should be treated as avalanche terrain. Moving one at a time and carrying avalanche rescue gear is important.
Huntington Ravine has CONSDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Considerable avalanche danger. Dangerous avalanche conditions exist. North, Damnation, and Yale Gullies will have Moderate avalanche danger. Evaluate snow and terrain carefully. Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, Chute, Left Gully and Hillman’s […]
This mix of scouring and deposition of new snow in the terrain makes natural avalanche activity unlikely but human triggered avalanches possible. Move one at a time today when poking into new snow and keep an eye on what or who is above or below you. Visibility will be challenging with flat light and snow showers making assessment and safe travel techniques more difficult. New wind slabs are likely to be largest in Lobster Claw and Right Gully and the northern gullies in Huntington due to their lee position. Hillman’s appears to have a more widely distributed 8″ (20cm) storm slab with less wind effect and fair to good stability. Be on the lookout for signs of wind transport in the afternoon as wind picks up to the 20-35mph range. Northwest winds tonight will ramp up into the range capable of building larger and more dangerous wind slabs. If you have weekend plans that include being in avalanche terrain, know that the forecast wind speed and direction will raise the avalanche danger tonight and tomorrow and build potentially touchy wind slabs in terrain downwind of a northwesterly.
Huntington Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Lip and Center Bowl have High avalanche danger. Very dangerous avalanche conditions exist in those forecast areas as well as on the floor of the Ravine. Travel there is […]
The old and icy snow surface we continue to talk about will be a key player as avalanche conditions develop from the incoming storm, with no deeper instabilities of concern. Slab building on a slick bed surface will likely occur in some areas while the old surface may remain exposed in others. We’re unsure at this time how well new snow will stick to the old surface for a variety of reasons. Slower wind speeds than might normally accompany a winter storm on Mount Washington could result in minimal scouring, but snow today will likely be light and easily transported by wind. Sluffing will also be a significant factor in slab development, as new snow may sluff off of the steepest portions of slide paths before slabs can build in these areas. These variables affecting slab development and distribution in our terrain will determine the number and size of avalanches we may see, with either many small avalanches or fewer large avalanches being potential outcomes of this storm cycle. Regardless, newly forming cohesive slabs should be reactive on the slick old snow serving as a bed surface.
Though we’ve had a few inches of snow in the past week, wind has easily transported it and scoured a majority of our terrain to icy old snow. The multiple melt/freeze cycles which helped form this hard snow surface also stabilized our snowpack, making the pockets of wind slab formed since late last week the only avalanche concern. Avoiding this avalanche problem is straightforward in areas where the grey old snow contrasts the white wind slab, but more challenging in areas like the northern gullies of both ravines where less wind scouring has resulted in less old grey surface. We don’t expect large wind slabs in any terrain. Long sliding falls on the hard, icy old snow remains a key hazard which demands respect. Clearing may allow select sun-exposed slopes to soften slightly but only briefly this afternoon. The current firm conditions which provide good crampon and ice axe travel mean limited options for decent turns, but the John Sherburne Ski Trail has improved and offers decent skiing and riding conditions with a few thin spots.
Wind slab is scattered through the terrain. This initially formed Friday into Saturday and likely developed further thanks to snow that fell overnight. Areas of largest wind slab development are expected in Moderate rated areas due to being lee of prevailing NE winds, though wind slab may still be navigable by staying on old surface. While wind speed will be light by Mount Washington standards, the density of new snow (6% on the Summit and 7.7% at Hermit Lake) should still allow for wind transport and wind slab development in our terrain.
The old refrozen surface is proving difficult for new snow to stick to. As a result, it is the primary snow surface in the Ravines. Pockets of wind slab do exist and we expect generally poor bonding to this icy bed surface, but with visibility you can navigate around these pockets and avoid today’s avalanche problem. Additional snow late today should behave similarly and be easily transported by wind to produce isolated new slabs and leave significant old surface exposed. The series of melt/freeze cycles which formed this icy surface also allowed the deeper snowpack to stabilize and limits avalanche concerns to slabs on the surface. Icy snow surfaces are not uncommon in our terrain, but be aware that this one is particularly hard and smooth which allows a sliding person to accelerate quickly and all but eliminates the possibility of self-arrest. Climbers will find good crampon purchase while skiers struggle to find many options to link turns in edge-able snow. The John Sherburne Ski Trail has improved over the past few days with reports of very thin cover in some sections by generally happy skiers and riders.
Areas of new wind slab are the primary avalanche problem though the primary hazard remains the potential for taking a high-speed sliding fall from steep terrain on the frozen, icy snowpack. Brief windows of visibility into Tuckerman Ravine have confirmed suspicions that much of yesterday’s new snow was scoured off of windward facing forecast zones by high winds from the east-northeast. The high wind speed and easterly direction coupled with very limited fetch, or area of available snow for transport, leads us to our low rating in most areas. Forecast areas that face due east contain much more limited areas of wind slab. These areas should be assessed carefully for sensitivity to human-triggering and consequences of being swept off your feet. More sheltered areas like the long northern gullies in Huntington and Lobster Claw and Right Gully in Tucks will likely harbor larger and harder to avoid wind slab. Human triggered wind slabs are possible where they have developed in steep terrain. Up to an inch of new snow today on continued NE wind will add slightly to existing wind slab.
We are starting the morning with low avalanche danger in all forecast areas. The storm system passing by to the south will likely generate 4-8” of new snow in higher terrain. Easterly wind, shifting to the northeast, will ramp up through the day, building wind slabs that may avalanche naturally in many areas. While wind will eventually reach a velocity capable of scouring lots of the terrain, we will pass through a period of peak instability before we get there. If you choose to travel in avalanche terrain today, remember that the new wind slabs will be forming over an icy bed surface and will be touchy and may fail above you naturally. Due to the wind direction today, wind slab avalanches won’t be large, but they may be large enough to carry you over cliffs or into rocks. Dry loose avalanches may be plentiful as well and will contribute to the volume of wind slab at the base of steep areas. Forecast areas sheltered from NE winds may grow larger wind slabs than usual. Lobster Claw, Right Gully and Sluice in Tuckerman Ravine meet that criteria. The northern gullies in Huntington have limited bed surfaces but their sheltered location could allow wind slabs to grow quickly in steep, upper and mid elevation start zones.
Thin wind slabs, which formed earlier in the week, are scattered throughout northeast facing terrain. These have passed through their unstable phase and should not be of much concern except possibly in the very steepest locations. The old gray refrozen snowpack that makes up most of the travel surface in our forecast area, will be underfoot everywhere due to the thin coating of new snow on top. This surface will create the primary concern for climbing and riding due to its firm and icy nature. Any softening that occurs later in the day in the sun or with warming temperatures will likely be only at the surface. On days like today with temperatures around freezing, passing clouds can allow the snow to quickly refreeze and make arresting a fall difficult at best. Crampons, an ice axe and the ability to use them well will be useful to avoid a long sliding fall today.
Wet weather today may reduce stability in wind slabs formed earlier in the week, making wet slab our primary avalanche problem today. This problem is isolated to areas of existing wind slab which can be visually distinguished from the hard, refrozen snow also present at the surface. Timing of peak instability depends directly on the type and timing of precipitation in our terrain. Watch for precipitation falling predominantly as rain to result in the greatest potential for unstable snow. If we receive less rain and more frozen precipitation particles, expect lesser instability of existing slabs. Bear in mind that significant portions of our terrain have firm, slick, refrozen snow at the surface. The risk of a long sliding fall that would be near impossible to arrest may be of greater concern than an avalanche today. Also remember that “Low” avalanche danger does not mean “No” avalanche danger.
Areas of wind slab exist across much of our terrain amid a more widespread refrozen surface of older snow. Size of this wind slab varies across Moderate-rated terrain and is distributed most widely in Central Gully in Huntington and Hillman’s Highway in Tuckerman. Today provides both an obvious and challenging avalanche problem to deal with for those seeking good turns. The new slab in which it is possible for you to trigger an avalanche is easy to see, appearing very white in contrast with the grey old surface. You can avoid the avalanche problem by avoiding travel on or below this visually apparent wind slab. That said, searching for good turns will lead you to travel on the avalanche problem, as the refrozen old surface will be far less than ideal for skiers and riders. Climbers will find good crampon purchase on the refrozen surface and likely be less tempted to travel on wind slab. This slick refrozen surface will easily allow a long sliding fall that most would struggle to arrest. If a stumble or even the smallest of avalanches causes you to lose your footing, you could take a long high-speed slide with potentially serious consequences. Take care, avoid falls and carefully assess consequence when choosing terrain.
Today’s avalanche problem is wind slab. This hazard will increase slowly through the day as wind continues to transport snow from the fetch into avalanche terrain. Areas of largest concern are those in the direct lee of W and NW wind as those will see the most loading today. Also of concern would be gullies that were in the lee of yesterday’s S and SE wind. Areas rated Moderate today had less developed bed-surfaces prior to yesterday.
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The Mount Washington Avalanche Center is a partnership between the White Mountain National Forest, White Mountain Avalanche Education Foundation and Friends of Tuckerman Ravine and other community organizations. The avalanche forecast applies only to backcountry areas, not operating ski areas, and describes general avalanche conditions which vary locally. The avalanche information provided is the sole responsibility of the USDA Forest Service.