Bollettino valanghe

Mt Hood

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
Open full map
Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The most dangerous slabs formed on slopes facing the western half of the compass and they will be most reactive right at the start of the day. Steer around steep, wind-loaded slopes which may include typical aspects as winds shift W in the afternoon. If thin surface crusts break down, reduce your exposure to steep slopes impacted by the sun.

Problemi valanghivi

  • Wind Slabs

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

    Moderate E or ENE winds buffeted exposed near and above treeline terrain on Mt Hood all day Tuesday and will only diminish in the early morning hours on Wednesday. NWAC forecaster Joe Dellaporta was in the Timberline area on Tuesday. He found the winds stripping previously reactive E-facing slopes of recent snow and forming fresh, reactive slabs on the western half of the compass. These slabs were 6-12" deep near treeline, running atop the 3/19 crust. Mt Hood Meadows Patrol triggered notable isolated 2-3 ft drifts (large avalanches) above treeline with some avalanches running on a density interface just above the crust.  Above NWAC forecast elevations, a size 1.5 natural wind slab release at 10,000 ft illustrates an extension of the increase in danger at upper elevations. The larger slabs at upper elevations deserve extra caution, so consider limiting the size and consequence of the terrain you enter at these upper elevations. Expect the possibility for widespread reactive slabs on N-NW-W-SW-S aspects if you're in exposed terrain early Wednesday. By mid-morning, winds shift westerly and may start to re-load more typical start zones, but we expect any avalanches large enough to seriously injure you or worse would remain on the W half of the compass. Take advantage of small test slopes to gauge slab reactivity, noting how easily these slabs release off a crust or a density break just above the crust. Steer around slopes steeper than 35 degrees below fresh, sharp cornices, in areas of textured snow, and if you're experiencing propagating cracks. When in doubt, seek wind-sheltered terrain or avoid the wind slab problem below treeline.

  • Loose Wet

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

    Thin surficial crusts formed early this week. With sunshine and expected light winds early Tuesday, S and E aspects are most likely to experience these crusts breaking down, allowing the dry snow underneath to destabilize. Wind-sheltered sun-influenced terrain above 5000 ft is where you should pay attention for this problem. Expect wet loose avalanches to entrain the recent 4-6" of snow and run efficiently atop the 3/19 crust. Rollerballs are your best clue if the destabilizing slopes in question are above you, putting you at risk. Keep an eye on the slopes overhead and remove the hazard by adjusting your aspect. You could also trigger a small avalanche in sticky surface snow that will be most hazardous where it rakes you into a terrain trap such as a gully or over a cliff.

    Example: Expect brief clearings to easily produced small wet loose avalanches on steep rocky slopes facing the sun.

    Photo: Andrew Kiefer

Avalanche Discussion

The shifting winds might give you wind slab whiplash. West winds accompanied the storm snow on Sunday and Monday, but a switch to E winds Monday night and Tuesday, followed by a shift back to W by Wednesday afternoon have created a complex landscape. If you find mixed signals from cornices about the direction of recent wind loading, and you are confused, take a step back and simply avoid slopes steeper than 35 degrees. Wind slabs can be challenging at times and Wednesday will be such a day. The media gallery shows some of the clues forecasters used on Tuesday to help identify wind slab (blowing snow, textured surfaces, shooting cracks, and actively triggered avalanches on test slopes).

Wednesday is the first full day of spring. We have overlapping cold snow (slab problems) at upper elevations and warm snow (wet loose) problems for another day.  In order to help separate the problem areas, note that wind slab problems occur in wind-affected terrain while wet loose occurs in unconsolidated snow. Although only minor rollerball activity occurred on Tuesday on steep road cuts facing the direct sun (see media gallery), lighter winds Wednesday will give the problem a better chance to develop.

If you get out let us know what you see by submitting an observation!

Regioni coperte