Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Thu
Alpine
3 · Considerable
Treeline
2 · Moderate
Below
1 · Low
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Highlights

Morning Update: Considerable danger is now anticipated at upper elevations due to stronger than forecast winds.

Increasing winds combined with fresh snowfall will build touchy fresh slabs above a layer of low-density snow. These fresh slabs could propagate more widely than you expect or potentially step down to a recent crust. Build in a margin of safety between yourself and actively or recently wind loading steep slopes, and prepare to dial it back if wind loading is intense.

Avalanche problems

  • Wind Slabs

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

    Morning update: Due to stronger-than-forecast wind speeds, particularly on the eastern side of Mt Hood. The risk of triggering a potentially large avalanche on a steep, wind-loaded slope is now "likely." Avoid all steep, wind-loaded terrain at upper elevations.

    We have a recipe for reactive, even touchy, slabs above the 4-5" of low-density snowfall that fell without much wind on Tuesday. Winds increase late Tuesday night and sustain through Wednesday, coinciding with a fresh 4-6" of snowfall; and there's now low-density snow available for transport on all aspects. To start the day, older firm slabs formed on Monday may be most pertinent, but your attention should quickly shift to the newly built slabs. The size of potential avalanches will also increase as you ascend above the 5500-6000 ft upper limit of the 2/16 crust and into more intensely wind-loaded terrain.

    Your single most important observation will be the degree of active and recent snow transport in your terrain. Actively blowing plumes of snow will give you an idea of how far off a ridgeline snow is depositing and slabs are forming. Fresh, sharp cornices also indicate the same suspect slopes. Also, utilize small test slopes to see whether small pockets of wind-deposited snow show the kind of reactivity they might show.

    While we think much of the fresh slab formation will be in the D1-D1.5 range (mostly small), we can't rule out an isolated avalanche pulling out on or stepping down to a layer of preserved stellars or the 2/7 crust, now 1-3 ft below the snow surface. If you are considering more committing terrain, it would be wise to investigate the bond to the most recent crust at your elevation and aspect.

    Example: The degree of wind transport can help you anticipate the rate of slab formation. If you're seeing plumes of snow like this, then slabs might be growing larger and more connected on the slope below.

    Photo: Joe Dellaporta

Avalanche Discussion

Morning update: Winds are visible transporting significant snow early Wednesday from Parkdale, with reports of sustained moderate wind speeds and significant transport as well at upper elevations around Mt Hood Meadows. With plenty of snow still available for transport and more snow falling, expect to find dangerous avalanche conditions and make conservative terrain choices as you ascend into exposed terrain.

Riders around Timberline and Mt Hood Meadows Patrol reported that slabs were stubborn to trigger on Tuesday. However, that did include one cornice-triggered avalanche. Cold, low-density snow with minimal fresh wind affect created excellent riding conditionswith 4-5" of fresh snow sitting above the more wind-redistributed 6-11 inches of low-density snow that fell Sunday and Monday. At elevations up to 5500-6000 ft, you'll likely encounter a thin 2/16 rain crust. Above that elevation, your next crust is likely to be the 2/13 or 2/7 rain crust.

Another observer around Ski Bowl reported 6" of snow above the 2/16 crust without enough of a slab to form a problem, but noted a poor bond to the crust. 

Avalanche professionals across the region continue to find weak layers in the upper 1-2 ft of the snowpack from our recent high pressure. Here on Mt. Hood, these may range from isolated areas of buried surface hoar or facets adjacent to a crust or a layer of preserved stellars that have consistently shown the ability to fail with snowpack tests. We’re still in the early stages of tracking these layers, so do your homework and approach steep terrain conservatively. 

We could use the observations as winter finally makes a return. Let us know what you see by submitting an observation here or on the AvyApp.

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