Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Tue
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
2 · Moderate
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Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

New snow and strong winds will form sensitive wind slabs at mid and upper elevations.  If you get unlucky, you may be able to trigger a wide and surprising avalanche near treeline that breaks on a layer of feathery surface hoar.  Monday will be a good day to dial it back and avoid steep, open slopes as new snow piles up.  

 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5–2.5

    Wind slabs will be ripe and sensitive as more precipitation and strong winds (S-SW) are added to the snowpack.  With additional precipitation (up to .75 in) accompanied by moderate to strong southerly winds, wind slabs will continue to grow in size and distribution across the terrain. You will find these wind slabs lurking at mid and upper elevations, specifically on the lee sides of ridges, under cornices, and in exposed alpine areas.  You may also find these slabs forming mid-slope due to strong wind speeds. 

    In specific areas at mid elevations, consider the consequence if you trigger a wind slab that steps down to a potentially buried weak layer of surface hoar. If you do get unlucky, this avalanche will propagate widely and could ruin your day or worse.  

    With continued precipitation and uncertainty of buried surface hoar - steer around wind drifted slopes greater than 35 degrees.  Use visual clues to help you identify these slopes - such as looking for recent cornice formation, pillow-like slabs forming, or wind textured surfaces. Today won't be the day to thread the needle. 

     

    (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

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Storm slabs may start developing below treeline if we receive the upper end of the precipitation forecast, especially during the later hours of the day.  You may find these storm slabs building on slopes greater than 35 degrees.  Evaluate how the new snow is bonding to the pre-existing snow surface. Use small test slopes or quick hand pits to help you identify how this new snow is bonding to the old snow surface.  Steer around steep slopes if you notice the new snow sliding easily.  

    The snow-line has been lingering at 4000 ft, so below you may find rough travel conditions. Snow surfaces are wet and the snowpack is actively melting. Keep an eye out for open creeks and other hidden hazards. 

    (12/20/2022)

    It may be possible for you to trigger storm slabs like this below treeline on Monday.  Use small test slopes or hand pits to evaluate how the new snow is bonding to the pre-existing snow surface. 

    Photo: Public Observation

Avalanche Discussion

After yesterday’s report of a human triggered avalanche in the Gunsight Ridge area   (observation here), I went out to further investigate the possible culprit - buried surface hoar.  Throughout my travels today I didn't find it everywhere, but in the places I did - it showed the ability to propagate across a slope.  Generally, I found this layer of buried surface hoar about 17 inches below the snow surface and above the 12/30 rain crust.  Check out my observation here and the photos in the gallery for more details. 

I’d say we still have a bit of uncertainty regarding the distribution of this buried surface hoar.  So far we have located it on east- northeast facing slopes near treeline (5-6000 ft).  Saturday's human triggered avalanche suggests that it may also be found on northwest facing slopes as well.  With this uncertainty and more forecasted precipitation, Monday will be a good day to take a step back and avoid steep slopes at mid and upper elevations. 

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

 

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