Bollettino valanghe

East Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Sun
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
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In sintesi

7:30am Update: Increased the avalanche danger to HIGH at mid and upper elevations because we expect more precipitation, increasing the likelihood of large natural avalanches. 

Warming temperatures and rain will make Saturday a dangerous day in the mountains. You could trigger very large wet avalanches that break wider and run farther than you may anticipate. Choose conservative, low-angle terrain and stay well out from under large, steep slopes.

Problemi valanghivi

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    2–3

    If you're headed out into the mountain for a warm and wet day on Saturday, choose lower-angle terrain. Avoid traveling on or near large, steep terrain features. Give yourself large margins of safety from potential runout zones. One of these wet slab avalanches could run further and break wider than you may expect. A good strategy is patience and conservative terrain selection. If you experience whumphing collapses, use extra caution to avoid steep terrain. However, you may not get warning signs before triggering an avalanche. 

    Wet slab avalanches are notoriously unpredictable, but the currently weak snowpack structure and rain up to 7000ft is a perfect setup for these destructive avalanches. Weak, faceted snow over the Solstice Crust continues to produce large avalanches. On Wednesday, the Mission Ridge Pro Patrol reported triggering D2-sized avalanches breaking up to 3 ft deep on the solstice crust in wind-loaded terrain off the ridge. The reported avalanches have only been bigger and more frequent in the neighboring West South zone. The Crystal Mtn Pro Patrol continues to produce very large (D3) avalanches breaking on a similar layer as recently as Thursday. This past weekend, a rider in the Manastash Ridge area remotely triggered one of these avalanches that likely broke on the Solstice crust as well. By adding load to this already weak structure, we anticipate increased avalanche activity on these tricky, persistent weak layers. 

    Wet loose avalanches will also likely be widespread on Saturday. While these are likely to be smaller and more predictable, they have the potential to step down and trigger a much larger wet slab. 

    The last known persistent slab avalanche in the east-south was remotely triggered on January 20th. 

    (1/20/2024) Photo: Chris Ofsthun

Avalanche Discussion

Up to 1.5" of water is forecasted for the East South zone, with snow levels topping out around 7000ft. We are relatively confident that this weather pattern will induce another round of persistent slab avalanches in the Wenatchee Mountains and the northeastern part of East South. It is more uncertain if this will activate the persistent weak layers lurking deeper in the snowpack further west in the zone. Build this uncertainty into your travel plans and choose conservative terrain, even in areas where we have not seen persistent slab avalanches yet. The dry snowpack is still in transition, and with multiple crusts and weak layers, we could see avalanche activity increase significantly in a short period. If you begin to see larger natural avalanches or any indications that smaller wet loose avalanches are initiating wet slabs, increase your margins further from avalanche terrain.On Friday, an NWAC forecaster was out in Ahtanum Meadows near Darland mountain and found the Solstice crust buried over 3ft deep and the 1/2 surface hoar buried 2-3ft deep in a snow profile. While both layers were gaining strength and rounding, the rain and warming could be the tipping point even on these western edges with a deeper overall snowpack. Further east and north, near Manastash ridge, these layers are closer to the surface and could be much easier to trigger. They also found a notably stronger snowpack on southerly aspects versus northerly and easterly.The temperatures were much warmer below 5200ft in the Ahtanum, and the snow has already undergone some warming. With a few crusts in the upper snowpack at these lower elevations, it may take longer for rain to break down the crusts before you start to see wet avalanches. If you get out, let us know what you see by submitting a public observation!

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