Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Sat
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 2 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Although they are becoming stubborn, you could still trigger a massive wind slab. Treat heavily textured or rippled steep E and SE aspects with more than a healthy dose of caution. Shallower wind redistribution should not distract you from paying attention to the very large slabs formed Wednesday night.

Problemi valanghivi

  • Wind Slabs

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

    Strong winds Wednesday afternoon and night formed widespread large to very large slabs. These slabs formed primarily on the eastern half of the compass, most notably on E and SE aspects at upper elevations. By Friday, you can still trigger one of these beasts on steep slopes and heavily wind-rippled snow. You can trigger these avalanches well below ridgelines, particularly on unsupported rollovers. Steep moraine features should be treated with particular caution as you might be buried deeply in a terrain trap if caught. When in doubt, limit the size of the terrain features you engage with and head to lower elevations or more sheltered slopes.

    (2/20/2025)

    Hard slab debris. You don't want to trigger an avalanche and end up in blocky rubble like this.

    Photo: Joe Dellaporta

Avalanche Discussion

Friday will bring a relative break in the weather with ridgeline winds that could move shallow amounts of new snow, particularly if light snow develops late in the day. Warm temperatures could also produce some minor rollerballs and wet loose activity on steep sun-affected slopes.

However, the damage was done Wednesday and Wednesday night. This timeframe brought 6-10" of snow accompanied by strong W and WNW winds. The weather stations showed less snowfall than accumulated in reality. The resultant avalanche activity truly impressed our forecast team. A very large natural avalanche on an E aspect in White River Drainage serves as a stark reminder of the degree of wind loading and was identified by USGS seismographs as occurring shortly after midnight Wednesday night. The 6 ft crown failed 500 ft across at 7800 ft, running 1000 ft of vertical. Multiple size 2-2.5 (large) avalanches were triggered by MHM patrol on E and SE aspects, including this one.

This activity serves as a stark reminder of the degree of wind loading and the potential for these firm deposits to fail lower-density snow that likely corresponds to the 2/13 interface. This interface has been reported to be a new weak layer in other zones further north, and it appears to be problematic in the Mt Hood area as well. The recent snow also sits atop crusts on many aspects.

 On Wednesday, avalanche professionals at Mt Hood Meadows reported one natural, cornice-triggered avalanche and reactive wind drifted snow that released easily with ski cuts. Cornices remain an objective hazard along ridgelines where they can break farther back than you expect and on the slopes below. If they break off with warming temperatures, they could trigger these bigger wind slabs, some of which may be too stubborn for humans to trigger.

You can contribute to the avalanche forecast! Let us know what you see by submitting a public observation here. 

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