Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

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Out of date — this forecast expired 3 years ago.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

Highlights

Avalanche danger will rise sharply during the morning hours snow as strong winds pile rapidly accumulating snowfall onto lee slopes. The most recent crust may form a reactive interface, so evaluate it on small test slopes before entering avalanche terrain at middle and upper elevations. Rising temperatures during the day will maintain the risk of wet loose avalanches within saturated snow layers.

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    2–3

    Very stormy weather, particularly during the morning hours, will create dangerous avalanche conditions in wind-exposed terrain. Rapid loading with 0.75" of snow water equivalent combined with moderate to strong winds will rapidly increase the size, distribution, and likelihood of triggered avalanches as the day progresses. Once enough snow falls atop the thin 1/23 crust, you can easily trigger a large avalanche at middle elevations. The crust doesn't extend to upper elevations where an isolated very large natural avalanche is not out of the question.  Given the uncertainty of potential natural or very large avalanches at upper elevations, it's really important to avoid exposure to wind-loaded slopes at upper elevations. Stick to the safety of ridgelines less than 35 degrees or wind-scoured slopes. At middle elevations, you'll have to monitor the increasing avalanche danger. Once 3-4" of snow falls, expect drifts on lee slopes in the realm of a foot deep. Average snow depths by the end of the day could be 6-8" over the crust with 1-2 ft slabs ready for human trigger on a wind-loaded aspect. Use obvious signs of wind loading such as active snow transport, fresh sharp cornices, or fat-looking pillows on the slope to identify the problem areas. Navigate away from any wind-loaded slope 35 degrees and steeper and give some extra margin for safety around unsupported slopes where an avalanche could surprise you; or above terrain traps, where an avalanche might be difficult to survive. Hand pits, might help you identify any potentially poor bond to the crust. This interface could create more widely propagating avalanches than you expect, or potentially a storm slab problem if 8" of snow accumulates on top.

     

    (1/22/2024)

    We observed heavy drifting along Pea Gravel Ridge on Monday. Look for wind slabs on the right of the cornice. 

    Photo: Joe Dellaporta

  • Loose Wet

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

    Rain on snow in recent days has saturated the lower and middle-elevation snowpacks. There should be a firm crust at middle elevations by Wednesday morning, but that crust may be very thin or non-existent at lower elevations. Wet snow you can sink into up to your ankle will help you identify the problem; and if you find this snow surface condition stay off slopes steeper than 35 degrees. In some areas, new snow may transition to rain during the day. If this occurs, expect shallow wet loose avalanches that could pick up mass on a long, open slope or push you into a terrain trap.

    (3/25/2023)

    You could see a similar wet loose avalanche on Tuesday. 

    Photo: Public obs

Avalanche Discussion

There has been a lot of avalanche activity on Mt Hood in the last week. While it has been raining or a rain/snow mix at lower and middle elevations, snowfall keeps stacking up at upper elevations. A brief break in the action Tuesday afternoon and overnight with some cooling may or may not be enough to give us a reset on the potential for very large avalanches from upper elevations on Mt Hood. You can see many examples of these avalanches from the last week in the avalanche occurrence database. The most recent of the very large avalanches occurred on Monday - our friends at the USGS reported a seismic signal indicating a very large avalanche (D3) in the upper White River Canyon.

Within the last 24 hours, most of the avalanche activity has been of the wet loose variety at lower and middle elevations as mild temperatures wetted the upper snowpack. However, some cooling on Tuesday formed a zipper crust (see photo in the gallery) from Timberline. That crust now has at least 0.25" of snow on it. With clearing skies this evening perhaps weakening this snow slightly, it could form a touchy interface once the snow starts falling in the early morning hours on Wednesday. With that in mind, take additional precautions to monitor how well the new snow bonds to this crust. Also note the distribution of the crust as you travel and the bond to the heavily wind-affected snow at upper elevations. With the sun coming out on Mt Hood on Tuesday afternoon, the upper elevations of Mt Hood finally came into view, exposing a landscape of heavily wind-stippled snow and old large avalanche crowns. The sun may also have extended the zipper crust to upper elevations on SW-S-SE aspects.

If you head out, be sure to pack the gore-tex and let us know what you see by submitting a public observation!

 

 

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