Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
3 · Marcato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

Dangerous avalanche conditions may develop with a winter-like frontal system building potentially large and reactive slabs above treeline. Look for firm or punchy layers within the storm snow and evaluate similar aspects before engaging with upper elevation start zones. At lower elevations, steer around shallower slabs residing above a rain crust.

Problemi valanghivi

  • Wind Slabs

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

    You can trigger a reactive wind slab at upper elevations where strong winds will have transported more snow. We're expecting 6-8" of storm total snowfall above treeline, but mild temperatures late Monday may limit totals to 4-6" near treeline. As the winds decrease on Tuesday, the surface snow may not appear wind-affected, but remind yourself that much of the slab formation occurred with moderate to strong SSE winds shifting W Monday night. Slabs rest above refreezing crusts (formed by rain to nearly 6000 ft) or breakable crusts (on sun-affected aspects above treeline), but may rest on cold snow on shaded northerly aspects. On any aspect, you should evaluate both the bond with the old snow and any firm over weak snow layering.  If you find 6" or more of snow above the crust, you can trigger a slab and these slabs may be large at upper elevations, particularly on NW-N-NE-E-SE aspects. When in doubt, avoid upper elevation slopes steeper than 35 degrees. Near treeline, you can steer around smaller, shallow slabs near ridgelines.

    Example: Cracking and drifted snow can help you identify and avoid wind slabs in your terrain.

    Photo: Paige Baugher

Avalanche Discussion

Heavy snowfall early last week turned showery toward the end of the week with unusually light winds for Mt. Hood. The final tranche of 6-7 inches of low-density snow arrived on Saturday. In just over a week, the Mt. Hood region picked up nearly 80 inches of snow (4 ft of settled snow) since April 8th.  Snow depths on Hood are 106-110% of normal for this time of year.

No avalanche activity was reported to NWAC on Monday. Professionals traveling in the Tilly Jane area of Mt. Hood on Sunday found 8 inches of cohesionless, low-density snow sitting on a wind-affected old snow surface. Excellent riding conditions were found up to 9000 ft. Winds were beginning to drift snow Sunday afternoon. Small, shallow loose-dry avalanches were naturally initiated by sunshine both below treeline and on steep above treeline slopes in the Pea Gravel Ridge / Wyeast area.

Winds increased as snow levels rose to 5500-6000 ft late Monday with the incoming system, suggesting that cohesionless snow may be harder to find on Tuesday. Rain and snow should peak Monday evening with rapidly lowering snow levels overnight. While this is mid-April, treat Tuesday more like you would a mid-winter storm day as shower activity continues and may reduce visibility at times. Travel cautiously as you move into wind-affected terrain. Evaluate wind loading. And use frequent small test slopes to monitor stability. But also don't forget that the sun angle is significantly higher now, even a 10-minute break in the clouds could initiate shallow wet loose avalanches. If you feel the warm sun, you can bet the snow does as well. Navigate away from steep or sun-exposed slopes above you, particularly where snow might entrain enough to push you into a terrain trap. Lower elevations may have a crust or wet snow under a shallow blanket of fresh snow.

NWAC is aware of a possible avalanche fatality at Mt. Hood Meadows on 4/5. We are actively working with local authorities to gather more information about the incident. This incident involved a solo snowboarder and a multi-day SAR effort. You can read our initial statement here. We will update the statement early next week (week of April 18th). 

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