Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

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

Avalanche hazard will rise throughout the day as heavy new snow piles up.  You can trigger the largest avalanche on slopes being actively wind loaded or show signs of recent loading at mid and upper elevations.  Use cautious route-finding and steer around steep slopes, especially if you notice hard over soft layering, see new snow sliding easily, or notice slopes being actively wind loaded. 

Lawinenprobleme

  • Storm Slabs

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

    On Tuesday storm slabs will grow in size and distribution throughout the day.  Temperatures will warm slightly as snow persists, which may create an upside-down layering situation.  Expect these storm slabs to be especially reactive in locations where surface hoar or near-surface facets have been buried.  The largest and most destructive slabs will develop at mid and upper elevations where moderate to strong WSW winds will redistribute new snow into thicker slabs.  You will find these slabs living on the lee sides of ridgelines, below cornices, and scattered near treeline and in the alpine. 

    Use hand pits or small test slopes to assess how the new snow is bonding to the old snow surface.  If you observe hard over soft layering, see cracking in the new snow, or notice recent avalanche activity - avoid steep slopes. 

     

    (4/10/2022)

    Storm slabs like this may be easily triggered as the day progresses. 

    Photo: Public Observation

  • Persistent Slabs

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

    It sure feels like this weak layer went dormant this past week. That being said, observers continue to find this weak layer in test pits and one observer even heard an isolated whumph on Vista ridge on Monday.  This kind of information illustrates that our 12/8 surface hoar layer is still lingering and active. New snow and additional loading may increase the likelihood of triggering a larger avalanche failing on this layer. 

    Currently, this buried weak layer sits under 12-15 inches of snow.  Since its burial, we have been tracking its distribution across the terrain closely.  So far, the most sightings of this layer have been below and near treeline, specifically on open slopes with minimal canopy.  You can locate this layer by using snowpack tests and looking for a thin gray in the upper snowpack. 

    It's been over a week since our last known avalanche on this layer.  As of Sunday (12/18), my partner and I were easily able to still locate this thin gray line of surface hoar in the Vista Ridge area.  The good news is we noticed this surface hoar rounding and becoming harder and harder to fail in snowpack tests.  The bad news is we’re still receiving propagating test results when it does fail.  With that, consider sticking to smaller and lower consequence terrain until this weak layer is proven innocent.

     

    This is the layer of buried surface hoar, which still is producing propagating results, will be worth watching as new snow piles up. 

    Photo: Joe Dellaporta

Avalanche Discussion

Tuesday is shaping up to be a stormy day for Mount Hood.  You may find increasing precipitation rates as the day progresses.  With this, expect increasing avalanche hazard throughout the day.  Leading up to this new snow, a mixed bag of snow surfaces existed.  Observers noted settled, faceting snow in shaded areas, heavily wind affected, firm surfaces above treeline, and sun crusts forming on south facing slopes.  There were numerous observations also pointing at surface hoar existing in more sheltered areas.  As new snow piles up, be sure to check how the new snow is bonding with the old snow surface.  Using quick hand pits or small test slopes as a way to gauge the sensitivity of the new snow. 

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