Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Wed
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 4 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Although typical wind patterns have returned to Mt. Hood, your primary concern will be reactive slabs focused on atypical W and S aspects. Identify and avoid smooth, hard snow deposits that may exist near ridges or extend deep into drainages. You can still trigger these slabs on steep slopes with unsupported rollovers.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Extreme NE winds formed stiff, hard slabs on atypical aspects that remain reactive and potentially large on mid and upper-elevation S and W aspects. Professionals found reactive wind slabs on Mt. St. Helens. The one pictured was human-triggered via a crack propagating onto an adjacent slope. Another natural avalanche (see media gallery) released during the strong wind event, likely on Sunday. Both avalanches released on S or SW aspects near treeline, ran on crusts, and produced 1-3 ft crowns that were frequently low on the slope. These avalanches are quite relevant for Mt. Hood. Snow totals have been similar (4-6") above the 1/27 crust in both areas. Winds may have been even more intense on Mt. Hood, potentially producing even firmer (1F to pencil hard) and more widely propagating avalanches. Information from backcountry areas of Mt. Hood remains limited and we suspect large variability exists across the terrain. Some areas may be largely devoid of wind deposition while other areas may have extensive deposits and elevated danger. Despite the high cloud cover in the forecast for Mt Hood, visual clues should help you to identify chalky, pillow-like drifts where you can trigger an avalanche. If this fails, firm and punchy layering or cracking all point to the presence of slabs under your feet. A new round of moderate W winds will begin to move what limited snow remains available for transport onto aspects that were previously scoured to crusts or sastrugi (see media gallery). These fresh slabs are worth paying attention to but we don't expect them to be thick enough to present a problem - just don't let them distract you from the potentially more dangerous slabs on the other side of the ridgelines.  Near and above treeline, anticipate slab formation using visual clues or feel before you end up on steep (greater than 35 degree) or poorly supported slopes.

    Below treeline you can trigger an isolated slab anywhere you find wind-drifted snow 6" or deeper, but expect these areas to be more isolated. These will be most consequential on extreme terrain features or above a terrain trap.

     

    (1/30/2023)

    A skier-triggered Wind Slab avalanche on Mount St. Helens. This Hard Slab failed on a convex feature at mid-elevations, with a crown spanning 150' and as much as 3' deep. It likely ran on the 1/21 interface.  [HS-ASu-R2-D2-I S 4000']

    Photo: NWAC Forecasters

Avalanche Discussion

Temperatures moderated on Monday plenty of sunshine and light winds. This may present as a thin crust on some aspects by Tuesday. Although temperatures will be even milder on Tuesday, we don't think there is much unconsolidated snow remaining for milder temperatures to destabilize.

On Sunday afternoon, Joe Dellaporta experienced bitterly cold temperatures and dangerous wind chills on Mt Hood.  Wind-protected slopes below treeline may still harbor some preserved low-density powder. Most exposed aspects are either exposed to crusts, sastrugi, or wind slabs. Saturday's highly redistributed 3" snow event sits on old wind-affected snow layers or a thin, breakable melt-freeze crust (1/28) that may be present on sun-affected aspects near treeline. Below that, you'll find a firmer and widespread 1/27 crust which now has 4-6" of snow (on average) above it. The MLK crust sits around 2 ft below the snow surface and was the culprit for at least one recent avalanche on Mt. St. Helens. The crust is around 2" thick and partially decomposing with weakening/faceting snow just below it on Mt. Hood. We don't know whether this crust may be a layer of concern at upper elevations on Mt. Hood and we will be looking at it closely over the next several days.

If you get out into the new snow, let us know what you see by submitting a public observation!

 

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