Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

High consequence and unpredictable wet slab avalanches dictate terrain selection. If you take a walk in the mountains, stick to low-angle, low-consequence terrain.  Additionally, reduce your overhead exposure to large avalanche slopes.

Lawinenprobleme

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    2–3

    The atmospheric moisture feed may have decreased and with it, the likelihood of natural or human-triggered avalanches gradually decreases. But it won't decrease rapidly since Monday's unseasonably mild temperatures bring more snowmelt. Therefore, the travel advice remains unchanged. Wet slabs could occur without warning on any middle or upper-elevation slope. The unpredictable nature of wet slabs is their defining characteristic. These avalanches are powerful, with heavy slabs flush with actively flowing water. That water can pool on any one of a series of crusts, potentially triggering massive slabs. A cornice fall-triggered wet slab serves as a reminder that you don't want to be in the wrong place at the wrong time. Continue to limit your exposure to all open slopes 30 degrees and steeper where these avalanches can initiate, run, or stop. We don't anticipate any overnight crust formation to be sufficient to limit the threat. Rising freezing levels on Monday, combined with sunshine could quickly break down any crust formation, but might also trigger wet avalanches on the highest slopes of Mt Hood, which have not experienced above-freezing temperatures in several months. 

    You may also encounter glide cracks, which can produce a surprising and large avalanche on a steep bedrock slope. Once again, keep an eye on the slopes above you. You can also trigger smaller wet loose avalanches within the saturated snow near the surface on slopes steeper than 35 degrees. 

    (1/28/2024)

    Cornice triggered natural size 1.5 wet slab. NE aspect, Vista Ridge, 6200 ft. 

    Photo: Joe Dellaporta

Avalanche Discussion

Monday will be the warmest day of an unseasonably mild weather pattern at Mt Hood. Mt Hood Meadows has also picked up 3.72" of liquid water since Friday morning, bringing the precipitation total to 26.82" since January 1st. Prior to mid-day Friday, much of that moisture arrived as snow, with a series of shorter warmups forming crusts that generally extend into the 6000-8000 ft range.

Riding conditions are not rewarding in the Cascades right now. Deep "glacier blue" rain runnels, open glide cracks, and waterfalls off cliffs as reported on Sunday are all good indicators. A mellow walk outside of avalanche terrain keeps you safe and enables you to enjoy the mountain scenery. But make sure you can identify open slopes and potential start zones that could be a threat. Long canyons are notorious runout paths for a very large avalanche.

Recent heavy rainfall has transformed the landscape. Mt Hood Meadows reported 2-3 large D1.5-D2 natural avalanches on Sunday. The activity focused on NE aspects in the 6000-7000 ft range, but this may or may not be a coincidence. Poor visibility limited observations above 7000 ft.

A very large (D3-4) avalanche reported by seismograph on Friday evening on the Reid Glacier Cirque had a starting zone of around 8000 ft and ran for around 4 minutes. An avalanche of this size would be unsurvivable. While the likelihood of such an avalanche gradually decreases on Sunday, the possibility should make you question your need to travel in terrain connected to very large start zones originating from the upper mountain, particularly during the morning hours. 

In the last week, we have seen multiple very large avalanches shed off the upper mountain (above NWAC's forecast elevation bands). We're unsure what layers these avalanches failed on, but this extended warm-up with periods of heavy precipitation will continue to test the snowpack. If the visibility is poor, it's essential to know what's above you.  Stick to simple terrain without overhead exposure. You may see little evidence of natural avalanche activity at lower and mid-elevations where wet loose avalanches have already run their course.

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