Bulletin d’avalanche

Mt Hood

Northwest Avalanche Center
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Danger d’avalanche

Sun
Alpin
3 · Marqué
Limite forestière
3 · Marqué
Sous la limite
2 · Modéré
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Périmé — ce bulletin a expiré last year. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

A multi-day storm cycle winds down, but human-triggered avalanches remain likely. Continue to avoid large, potentially reactive wind deposits that extend well below typical start zones on leeward slopes. In sheltered terrain, carefully assess storm slab reactivity, and be prepared to step back from steep slopes if sunshine warms the snow.

Problèmes avalancheux

  • Wind Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1.5–2.5

    Judging from the webcams at middle and upper elevations around Mt Hood there's some serious snow moving. Although the precipitation gradually decreases through Saturday, the winds will linger long enough into the day that slabs will remain reactive on Saturday. We expect plenty of firm, hard slabs that would be stubborn to trigger but lethal. In somewhat more sheltered terrain, slabs will be softer and easier to trigger. Regardless of the variety, it's best to avoid steep leeward slopes at middle and upper elevations because slabs could exist anywhere on the slope. Stick to windward slopes, ridgelines, and slopes less than 35 degrees. Cracking, hollow-sounding drum-like snow, or wind-textured deposits all confirm the issue.

    Example: Heavily wind-affected snow may be present on many slopes.

    Photo: Joe Dellaporta

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    1–2

    The snow was stacking up at 1-2" per hour rates with high water content on Friday, and it needs time to settle. An inconsistent freezing rain crust buried in some areas Friday morning could serve as a failure plane. Mid-storm layers may also remain reactive and might involve a refreezing warming crust from mid-day Friday. The overall trend should be for these slabs to gradually stabilize, but changing temperatures with solar energy can increase the reactivity of the slabs temporarily. Be diligent and evaluate the upper 1-2 ft of the snowpack using quick pits or hand shears as you work through the terrain. If you find cracking or interfaces that shear readily, stay off steep, open slopes or steep, widely spaced trees.

    Example: Storm slab in steep terrain below treeline at Mt. Hood Meadows.

    Photo: Mt Hood Meadows Patrol

Avalanche Discussion

Although we're past peak danger, we're just coming out of a massive storm cycle at Mt Hood Meadows has picked up 82" of snow and counting since March 13th. 10" of that was since 5 AM Friday morning, accompanied by moderate and strong WSW winds. Don't get fooled when the weather relents on Saturday. All the recent snow and wind loading takes time to heal.  Therefore, ease into the terrain, seeking wind-sheltered slopes and trees where the snow quality is likely to be better. If the sun comes out, recent fresh snow will warm quickly and shed off rocks and cliffs, entraining moist surface snow. 

On Friday, an NWAC forecaster on Vista Ridge was finding mid-storm instabilities down 10".  Column tests in the gallery. The snow was significantly denser, creating upside down and difficult trail breaking. This issue may resolve as temperatures drop into Saturday. Wind-affected snow was more supportable above 6000 ft. Dry loose avalanches were also reported within 8" of storm snow above a crust outside the Timberline ski area. The observer also got failures just below the crust. Also on Friday,  Mt Hood Meadows Patrol reported a large wet loose avalanche  on God's Wall, which entrained significant amounts of snow (5400 ft start zone).

On Thursday, Mt Hood Meadows Patrol reported 10-12" of snow above the 12/18 sun crust.  Patrol triggered two large hard slabs (snowcat and explosive triggers) with crowns up to 4 ft deep on S aspects at 7200 ft on Wednesday.

On Wednesday, a rider triggered a size D1.5 cornice fall in White River on Wednesday, which entrained some dry snow, but the rider rode out unscathed. These cornices will remain an issue until warmth or sunshine cut them back.

The recent snow is deep and you should keep Snow Immersion Suffocation (SIS) on your mind. Creeks and tree wells remain dangerous until the snow settles. Ride with a partner and maintain visual and audio contact.

You can help us gather more data by submitting an observation HERE or via the Avy App.

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