Bollettino valanghe

Sawtooth & Western Smoky Mtns

Sawtooth Avalanche Center
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In sintesi

As the day heats up, small wet avalanches will become possible on steep slopes that face the sun. Pay attention to the surface conditions—avoid slopes where you're sinking into a wet, mushy snowpack. Generally safe avalanche conditions exist on slopes that are shaded from the sun.

Problemi valanghivi

  • Loose Wet

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    • Limite del bosco
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    Probabilità
    Possible
    Dimensione
    1–1.5

    The likelihood of triggering small wet avalanches will increase on sunny slopes as the day heats up. Clear skies and colder temps have provided solid re-freezes the past few nights, and this has helped improve the wet snow stability. Even though wet avalanches have become less problematic, it's still the primary issue you're likely to encounter as you travel through the mountains.

    The snowpack will start out frozen—your job will be to gauge how quickly the surface is melting through the day. Pay close attention to how deep the wet mush is becoming on the snowpack surface. If you're sinking into slush past your boot tops, or if your boards or sled are punching deep into the snowpack, it's time to head for colder (or gentler) slopes. Slopes with a weak, shallow snowpack (less than 3 feet) will turn to a  soggy mess quickly once the surface crust thaws, so pay particular attention in these areas.

    ADDITIONAL DISCUSSION:Weak, faceted snow exists near the base of the snowpack on shady, middle and upper elevation slopes. Triggering a deep persistent slab avalanche on this layer is unlikely, but it's not impossible on very steep (approaching 40 degrees), rocky, wind-affected slopes.

    (2/10/2022) These wet snow avalanches likely occurred on February 9th, when a night of above freezing temperatures was followed by a very warm, steamy day. The failed on a SW-facing slope at 6,500-6,800'.

Avalanche Discussion

It's not even mid-February, yet it feels like April. Today's Super Bowl in L.A. is forecasted to be the warmest ever with a high of 85F predicted at kick-off! While it's not that hot here, it's been warm enough to put wet snow avalanches back on our radar. You'd be forgiven if you've forgotten the finer details of wet snow problems since last spring, so here's a quick refresher.

As warming temperatures, and especially the sun, add energy to the snowpack surface, it begins to melt and produce liquid water. This water melts the bonds that hold the snow grains together, weakening the snow. The more water that exists, the weaker the snow is. If the melt continues, the snow can become a saturated, soggy mess—think 7-11 Slurpee®. Rocks, being darker in color, absorb even more energy from the sun and can transfer that to the snowpack. That's why the snow can be even wetter around rocks, and these outcrops often are the origination point for natural wet slides. 

When the snowpack is deeper and relatively strong, mushy wet snow is often confined to the snowpack surface. The wet surface layer can peel away, either naturally or beneath our board and machine, but the resulting wet slide tends to be fairly small. But when the snowpack is shallow, weak, and faceted, it doesn't take much to make the entire snowpack a hot, soggy mess. Wet slides that occur in these conditions often gouge down to the ground and can entrain large amounts of snow. We've seen a few slides like this at lower elevations where the recent prolonged dry spell has left us with a shallow stack of sugary facets.

For all its complexity, wet snow problems can often be easier to manage. You can avoid the problem altogether by sticking to cold, shady terrain and avoiding traveling on or beneath steep sunny slopes. Timing plays an important role—if you plan to travel on sunny terrain, do it earlier in the day before things heat up. Finally, pay attention to how wet the snow surface is getting. If the slush is getting deeper than about 6-8", it's time to header for colder or less steep terrain. If you find yourself punching through the surface layers deep into soggy snow, you've overstayed your welcome and it's time to go somewhere else—pronto! 

Catch up on what happened this past week in our latest Weekend Update!

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