Lawinenlagebericht

Presidential Range

Mount Washington Avalanche Center
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Lawinengefahr

Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

You could trigger an avalanche in wind-drifted snow on steep north, east, and south-facing slopes above 3000 feet today. South and east-facing terrain are also areas that hold a higher potential of triggering a much larger avalanche deeper in the snowpack. Looking out for newly forming drifts and blowing snow to know that the avalanche hazard is increasing.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    What and where is it:

    Old wind slabs formed from 10 inches of light-density snow the past four days on south and east-facing terrain and new wind slabs forming today from 4 inches of snow on north-facing aspects. There is also the unlikely event that triggering a surface wind slab avalanche could have the potential to step down into deeper weak layers and create a much larger and more dangerous avalanche in east and south-facing aspects. At low elevations in steep, isolated terrain it may be possible to trigger an avalanche today.How can you recognize it: 

    New small wind slabs up to a foot thick will be actively developing on north-facing slopes today. You may encounter more reactive conditions as these are forming so red flags to look for will be shooting cracks under your feet, blowing snow at the ridgelines, and deep drifts of softer snow are signs of a wind slab avalanche.

    Old wind slabs are smooth, rounded snow slopes that may be firm and give limited warning signs. These have the potential to produce larger and more destructive avalanches.

    How can you manage it:

    With dynamic weather today and likely poor visibility, it may be challenging to visually inspect terrain for lurking and developing wind slabs. For new snow problems looking for signs of developing slabs like blowing snow or accumulating drifts will help you to assess conditions. The older wind slabs may be covered by new snow, but using a ski pole to probe to understand structure and depth and informal tests like hand shears should help you to assess size and sensitivity. 

    Continue to travel thoughtfully in avalanche terrain. If you're unsure about the sensitivity or location of wind slabs, consider taking an alternate route in simpler, low angle terrain.

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    What and where is it:

    Old hard slabs are sitting on a buried layer of weak snow and could be triggered by finding a thin spot in the snowpack or by the weight of a smaller avalanche. This poor snowpack structure has been found specifically in the Summit Snowfields, gully entrances on the south face of Tuckerman Ravine, and the south aspects of Huntington Ravine and it likely exists in other similar terrain. Additionally, on February 4th a very large avalanche on the Gulf on Slides Southern Snowfields stepped down to this layer and the possibility of this happening elsewhere remains. Note that one of the places this avalanche problem exists is just to the north of where the Lion Head Trail leads to Split Rock on the summit cone and on the Summer Lion Head Trail.

    How can you recognize it: 

    Visually, these dense persistent slabs are difficult to spot, as they will appear and feel very stable underfoot. The unlikely nature of this avalanche problem means a slope could be skied multiple times without triggering it, but the unlucky skier who finds a weak spot in the slab may trigger a large avalanche. Don’t rely on tactile red flags, like "whumping," as a warning.

    How can you manage it:

    Understanding exactly where this problem exists in the terrain will be very challenging. Travel strategically, avoiding high-consequence terrain, and choose conservative terrain. Large triggers, such as surface avalanches or multiple people on a slope, will increase the odds of impacting these layers deeper in the snowpack. As you move through and around avalanche paths, limit exposure to large, open slopes where persistent slabs are more likely to be more dangerous. Stack the odds in your favor by following safe travel protocols and only exposing one person at a time to avalanche hazards.

Avalanche Discussion

An injection of warm air will increase temperatures at all elevations and add a wintry mix to precipitation today. Lower elevations are forecast to warm earlier and longer, but sleet, freezing rain, and snow is forecast for all elevations today. This heavy precipitation will limit the development of new avalanche problems and ice may cap the snow surface limiting any further transport. The moderate hazard of today reflects the impact of this heavy, mixed precipitation that will decrease the sensitivity of wind slabs. In the unlikely event of less than forecast warm air, avalanche problems may remain more sensitive and have the potential to be larger. This would not materially increase the overall hazard, but you would be more likely to encounter reactive wind slabs. 

The most reactive conditions you will likely encounter will be in the morning before snow conditions shift to a wintry mix. Paying attention to the weather and current precipitation will be helpful today to predict the sensitivity of the snow at that time. If snow is still falling expect to find more reactive conditions, as snow shifts to sleet and freezing rain you may find increasing stubbornness.

The old wind slabs were observed by forecasters and professionals to be increasingly stubborn. Slopes are planar, connected, and have the ability to produce large and destructive avalanches, though they may give limited warning signs and appear stable underfoot. While digging into the snow will be the best way to assess their sensitivity, with spatial variability that may not tell you everything. Considering the consequence of a potential slide in many ways may be your best tool, unfortunately, many runouts feed into narrow gullies, and trees which are all classic terrain traps which amplifies consequences. 

OBSERVATIONS: Please consider submitting an observation on our website or in the new Avy phone app of what you are seeing in your travels. Submitting an observation hones your skills, informs other users, and improves our forecasts.

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