Lawinenlagebericht

Mt Hood

Northwest Avalanche Center
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Lawinengefahr

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

Kernpunkte

Light snowfall and strong winds will combine to create a fresh batch of shallow wind slabs in exposed areas.  The likelihood of triggering a larger avalanche on buried surface hoar has decreased, however, consider staying off of steep open slopes at mid and lower elevations until this layer is proven innocent. Steer around steep slopes if you observe shooting cracks, hear whumphs, or see new snow actively wind drifting into deeper pockets. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    A few inches of new snow and strong west winds will create a fresh crop of shallow wind slabs in exposed areas. You will most likely find these areas of wind drifted snow at mid and upper elevations, but specifically on the lee sides of ridges, below cornices, and above treeline. If you see blowing snow from the parking lot on Sunday morning, chances are wind slabs will be forming near-by. Use visual clues such as looking for areas where the wind is blowing new snow to help you locate where potential wind slabs are. Avoid steep slopes if you notice shooting cracks, hear hollow-sounding snow, or notice slabs failing easily on test slopes. 

    (12/3/2022)

    Actively blowing snow, freshly building sharp cornices, and textured surfaces. All easy-to-identify signs of wind-loading. Look for slabs to develop on the slopes on the left side of the picture.

    Photo: Dallas Glass

  • Persistent Slabs

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

    The likelihood of triggering an avalanche on the December 8th buried surface hoar has decreased, however, this layer can still be found across the zone. 

    Currently, this buried weak layer sits under 12-15 inches of snow.  Since its burial forecasters, ski patrollers, and observers 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. 

    The last known avalanche on this weak layer occurred last Sunday (Dec 11th)  when we received numerous public observations (thank you for submitting!) reporting close-calls and widely propagating slab avalanches as well as snowpack test results highlighting this layer. 

    As of Thursday (12/15), I found this weak layer in most places that I traveled in the Tilly Jane area.  A key takeaway from this field day is that this weak layer still showed the ability to propagate across a slope. In 4 out of 5 of my snowpack tests,  I received full propagation in extended column tests. Check out my observation here for more details. 

    Time is starting to do its thing and this layer appears to be trending on the more stubborn side with no recent avalanche activity on this layer. That being said, it is not a bad idea to continue using conservative terrain choices and stick to smaller and lower consequence terrain until this weak layer is proven innocent.

    Buried surface hoar propagating in extended column tests on Thursday. 

Avalanche Discussion

Forecasted precipitation amounts are not overly impressive for this storm.  The main story will be the moderate to strong west winds associated with it.  This will bring a small uptick in avalanche hazard, especially in more exposed areas where shallow wind slabs will develop. 

On Saturday observers reported windy conditions and a patchwork of snow surfaces. This new snow will fall on variable surfaces such as preserved cold snow in sheltered areas (including surface hoar and near-surface facets), wind affected snow in the alpine, and a sun crust on steep solar aspects.  As new snow piles up, keep an eye on if surface hoar and near-surface facets are getting buried. This weak surface snow could be tomorrow's weak layer.  Hopefully, strong winds will help destroy these weak grains before they get buried, but they’ll be worth watching as snow continues to pile up throughout the week. 

If you get out into the backcountry,  please submit an observation on our public observation platform!  

 

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