Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Thu
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
2 · Moderato
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In sintesi

The upper snowpack is recovering from another major snow and wind event. Most avalanches will be smaller thickened deposits of stiffened snow that you can steer around. The slight risk of an unsurvivable deeper hard slab keeps us off steep, unsupported rollovers in typical start zones for another day.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1.5–2.5

     Control results on Tuesday at Mt Hood Meadows were impressive. The Accordian Path produced a very large (D3 Avalanche) that went beyond the recent memory of its historical range, releasing 2-6 ft deep on a layer of lower-density snow a foot above the 3/31 crust. More widespread soft slab avalanche activity was in the small to large (D1-D2) size range within more subtly stiffened snow. Wind slabs will become somewhat more difficult to trigger, but remain just as consequential. The outlier avalanche would be unsurvivable. How to handle this tricky problem? We recommend that you continue to avoid large, steep and unsupported slopes on the eastern half of the compass. If you dig down and find firm wind-stiffened snow above the 3/31 crust on a wind-loaded test slope, this will confirm the problem. The less consequential, smaller wind slabs you may be able to visually identify by wind-stiffened or textured snow surface, cracking, or a denser slabby feel. Steer around potential trigger points greater than 35 degrees if you notice any of these characterists.

    (4/4/2023)

    Massive, blocky debris from a very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 

    Photo: Mt Hood Meadows Pro Patrol

  • Loose Wet

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

    There's likely to be a window for wet loose activity as temperatures moderate and before clouds thicken and increase in the afternoon. Surface crusts will need to break down on some aspects before wet loose materializes. Once you start punching through surface crusts or notice snow shedding off trees, rocks, or cliffs, assume wet loose avalanches will follow. Reduce your exposure to steep slopes above you and assume that destabilizing snow surfaces can produce generally small wet loose avalanches on slopes steeper than 35 degrees.

    Example: Wet Loose avalanche on a steep sunny slope. Note how it originated at a point, near trees and rocks.

    Photo: Dallas Glass

Avalanche Discussion

Another massive late-season storm brought 50-60" of snow to Mt Hood along with strong W and WNW winds (particularly on the E side of the Mountains). Intense winds and periods of heavy snowfall finally ramped down rapidly early Tuesday. These stripped a lot of snow off of exposed aspects, forming deposits up to 5-15 ft deep in some areas. The hard slabs overlie less wind-affected and lower-density snow from early in the storm cycle that sits above the 3/31  crust. The Accordian Avalanche released in near treeline terrain on an ESE aspect and was historically impressive, particularly for the elevation of the start zone. It released about a foot above the crust but ran fast and far thanks to the presence of that crust at the bed surface. This melt-freeze crust exists on most aspects (besides northerly) below 6000 ft and may have graupel sitting on it in some locations.

Although the snow continues to settle about 6" per day, we've had some close calls with deep snow safety across the region. Coming out of this storm cycle, deep snow safety remains on our minds. A backcountry traveler was able to rescue his partner from a hole above a creek near Pea Gravel Ridge on 4/2 and although the risk is decreasing by Wednesday, it should still be on your mind too.  

Last week observers reported weak snow associated with a crust that sits several feet below the snow surface. This layer was likely responsible for the isolated whumphs in the Gunsight Ridge area and propagating results( observation) near Vista Ridge. While isolated and unlikely, keep this information in mind especially if you find yourself traveling on higher elevation, northerly aspects.

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