Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Mon
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
Senza grado
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Non aggiornato — questo bollettino è scaduto 9 months ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

As you ascend in the terrain, it becomes increasingly easy to trigger a large avalanche in wind-drifted snow on a steep lee slope. Limit your exposure to large slopes beneath upper mountain avalanche paths until the storm cycle runs its course. Rain on snow might saturate recent snow, raising the risk of wet avalanches.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    Dense snow will continue to stack up at high rates, while winds continue to redistribute it throughout the weekend. With multiple days of moderate to extreme winds, this is not your garden variety wind slab Sunday. Anticipate large slabs existing on a variety of terrain features, well below canyon rims, on mid-slope rollovers, but also in the typical locations below ridgelines and fresh cornices. Most of the avalanche hazard exists above 6000 ft, where snow coverage on Mt Hood starts to increase dramatically, and your danger increases further as you ascend. Natural avalanches might descend from wind-loaded slopes within or above NWAC upper elevation terrain as the storm intensifies. Triggering any slab on a large open wind-loaded slope in such a storm would high risk under normal circumstances, but your risk increases markedly due to early season hazards right now. Although slabs are likely smaller and less sensitive to human triggering at middle elevations, your odds of getting raked through rocky terrain increase. 

    Example: Drifts and blowing snow along Pea Gravel Ridge. 

    Photo: Joe Dellaporta

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    Snow may transition to rain as the day progresses, transitioning the wind slab hazard into a wet avalanche one. Rain on snow will destabilize steep slopes rapidly. If you start to see the snow flakes becoming wet and saturated, utilize pre-planned route options to get yourself off of open slopes steeper than 35 degrees. And once again, the early season hazard increases your risk.

    Example: Intentional skier triggered wet loose avalanche on the east aspect of Pea Gravel Ridge near 6000ft

    Photo: Andrew Kiefer

Avalanche Discussion

We're expecting around 1.5" of water equivalent to fall as snow above around 5000-6000 ft on Mt Hood. That's a lot of moisture. It's also coming in with plenty of wind and rising snow levels. Peak avalanche danger is likely during the morning hours due to the heaviest precipitation, but slab avalanches will build throughout the day above the rain snow line. 

Middle and upper elevations on Mt Hood transitioned mostly back to snow on Saturday, picking up 3-4" of really heavy, wet snow with 1-1.25" of water equivalent. Observers noted drifts several ft thick near the Timberline parking lot, confirming that the moderate to strong WSW winds (with extreme gusts) were creating significant wind deposits.  The new snow sits on wet, refreezing surfaces that survived the 3.25-4" of water arriving Thursday night and Friday. Snow levels reached at least 7,300 ft, but likely closer to 9,000-10,000 ft.

Joe Dellaporta visited the south side of Mt Hood during a recent weather window on Wednesday. The new snow likely expanded snow coverage since his tour, but recent gains may be start to wash away below 6000 ft as the day progresses on Sunday. In general, snow coverage increases drastically from around 6000-7000 ft, but thanks to prevailing wind patters, the same lee slopes that have existing snow coverage (smooth slopes) continue to build avalanche hazard throughout the weekend.

These unrelenting WSW winds continue to strip wind-ward slopes and ridgelines, limiting some of your typical safe downhill routes to boot travel. If you don't have a safer low-angled descent route with enough snow to ride, there's no shame in walking back down your safer ascent route. Remember it's a long winter season in the PNW.

With the warm start to the 25-26 winter season, we have less snowpack information than usual to start daily forecast operations. For zones and elevation bands with less snow than needed for avalanche hazard, we will issue a forecast with No Rating. Anticipated avalanche and weather conditions will still be updated daily. NWAC will issue an avalanche danger rating for a zone when enough snow to produce avalanches has accumulated at middle and upper elevations.

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