Lawinenlagebericht

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Sawtooth Avalanche Center
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Fri
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
2 · Mässig
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Kernpunkte

The chance of natural and human-triggered wet snow avalanches will increase as direct sunshine and warm temperatures turn the snow surface to mush. These slides are most likely on very steep slopes that directly face the sun. Steer clear of terrain where you're sinking deep into a soggy snowpack.

Lawinenprobleme

  • Loose Wet

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

    Yesterday, observers reported a broad spectrum of snow surface conditions from icy, stout crusts and good corn skiing in the morning to sloppy, "survival" and "suction cup" skiing in the afternoon. Today, expect to see a similar spread, with wet snow avalanche concerns rising in the afternoon hours as the snow surface turns to mush.

    The threat of wet loose avalanches will follow the sun around the compass, beginning on E-SE aspects this morning, moving to SE-S facing slopes, and wrapping around to SW-W aspects in the afternoon. As crusts and layers in the middle of the snowpack melt and break down, loose snow slides could gouge into wet snow deeper in the snowpack. These avalanches can be deceptively powerful. 

    Some considerations:

    • Avoid the heat of the afternoon. Hit the trailhead early and hit the tailgate early.
    • If your boards or sled are punching deep into the snowpack, stick to gentle slopes or move to shadier terrain.
    • Expect many sunny slopes where the snowpack is thin (less than about 3 feet deep) to become wet and unsupportable.
    • Pay attention to what's above you. Wet avalanches release on their own much more frequently than dry avalanches. 
    • Things change rapidly. That slope you rode yesterday, or 30 minutes ago, may become an issue.

    ADDITIONAL DISCUSSION:The most prominent weak layers in this zone are depth hoar near the ground (buried 4-6' deep) and crusts associated with facets in the middle of the snowpack (buried 2-3' deep). Wet avalanches discussed above can act as triggers for larger avalanches failing on these deeper layers. The meltwater gradually seeping deeper into the snowpack also adds a layer of uncertainty to the slab avalanche equation. A large, destructive wet slab avalanche occurred in the Sawtooths during the warm-up at the beginning of March (photo here, details here). Steering clear of areas with gloppy, unsupportable snowpacks—including areas below large avalanche paths with mushy snow conditions—is a simple way to minimize the chances of triggering or tangling with large slab avalanches. 

    (3/13/2021) Recent-looking wet slide reported in the Sawtooths. This slide may have released as a wet slab. Photo: T. Harrison

Avalanche Discussion

DIURNAL AVALANCHE DANGER

Today's avalanche danger is diurnal, meaning that it increases during the day and decreases again at night. This has been the case for the past several days. The avalanche danger will begin LOW today and increase to MODERATE this afternoon, driven by the increase in the likelihood of wet avalanches. A better understanding of wet avalanches will not only keep you safer today but will also help you find better snow to enjoy. 

Wet avalanche concerns are driven by meltwater in the snowpack. Wet loose avalanches are simply wet, cohesionless snow sluffing off steep slopes. Wet slab avalanches occur when the meltwater weakens the bond between a slab and the surface below. Meltwater is produced by above freezing temperatures, the heat of the sun, or by adding water due to rain. The most dangerous conditions often occur during prolonged periods of above-freezing temperatures that combine with hot sun or heavy rain. On the flip side, wet avalanche concerns diminish as liquid water in the snowpack is reduced. This can happen as water drains out of the snow or is refrozen.

Today, the avalanche danger will peak during the warmest part of the afternoon on very steep, sunny slopes as the rate of meltwater production is at its greatest. Wet loose avalanches are the most likely (but not the only) problem to consider. Wet loose avalanches have the potential to act as triggers for larger slab avalanches as they move down a slope. Persistent weak layers in the middle and near the base of the snowpack provide potential failure layers, whether they're dry (persistent slabs) or wet (wet slabs).

How can you reduce your risk? Anticipate and limit your exposure to areas that are likely to turn to mush such as:

  • Very steep slopes that increase the amount of heat absorbed by the sun
  • Shallow snow areas, particularly those near rocks and the base of trees
  • Low elevations with warmer temperatures
  • Slopes sheltered from the wind
  • Areas with a weaker overnight freeze (the Soldiers and near the Wood River Valley stand out last night)

A storm will approach this evening. Snow levels will begin around 6,500' and we're likely to see avalanche concerns diverge as low elevations get rain and upper elevations get snow. Check back in tomorrow as we get more info on how this storm develops. 

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