Avalanche forecast

Mt Hood

Northwest Avalanche Center
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Avalanche danger

Wed
Alpine
3 · Considerable
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Dangerous avalanche conditions develop by Tuesday afternoon due to heavy snowfall and wind loading. Large and easily triggered avalanches become likely and natural avalanches are also possible. Use active wind-loading, cornice formation, and propagating cracks as a reminder to stay off steep, wind-loaded slopes. In wind-sheltered terrain, expect instability to develop as snowfall rates increase.

Avalanche problems

  • Wind Slabs

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

    Fresh wind slabs will build throughout the day, growing in size and reactivity as heavy snowfall arrives with strong winds. At the start of the day pay attention to small wind-loaded pockets 6" or deeper where you could trigger an isolated avalanche on a steep slope. However, as snowfall intensifies, slabs will fill start zones and grow down onto wind-loaded rollovers. Conditions will deteriorate fast enough that by the afternoon, you can easily trigger an avalanche on any steep, wind-loaded slope, particularly if the slope rolls away below you. And by late in the day, expect the possibility for natural avalanches on the aforementioned heavily wind-loaded features. Adopt a stepping-back strategic mindset, consistently reducing your terrain selection as you see the problem evolve. Always make sure you have a safe exit plan to which you can easily retreat into lower-angle or thickly forested terrain as the storm ratchets up. Active wind-loading will also grow sensitive cornices which deserve a wide berth on ridgelines and serve as a reminder of slab development on the slopes below. Shooting cracks or whumphs also serve as strong warnings of the snowpack destabilization.

    (2/6/2023)

    Multiple large (up to D2.5) slab releases with 1-4 ft crowns in Mt Hood Meadows A-zone. The crown on the right stepped down to approximately 4 ft deep.

    Photo: Mt Hood Meadows Pro Patrol

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1.5

    Heavy snowfall through much of the day (8" or so) combined with a warming trend will create increasingly dangerous avalanche conditions on any steep slope greater than 35 degrees. The new snow sits above more than a foot of right-side-up snow from the last storm. Thus, we're expecting true storm slab characteristics with potential for failure within mid-storm layers or at the new/old snow interface which may have a new thin crust on steep south-facing slopes after Monday afternoon's sunshine. Use simple slope tests on inconsequential steep rollovers as you ascend to evaluate the snow piling up for these storm instabilities. When in doubt, avoid open slopes steeper than 35 degrees.

    (1/8/2023)

    Example storm slab in terrain below treeline.

Avalanche Discussion

Sunday brought strong to extreme winds and heavy snowfall to Mt. Hood. The extreme winds continued Sunday night as snowfall tapered. The photo gallery shows a variety of stubborn, large (to D2.5) avalanche triggered using heavy artillery in the A-zone at Mt. Hood Meadows on Monday. Joe Dellaporta found that these instabilities stabilized quickly with mild temperatures during the day. He dug a pit at 5300 on a wind-sheltered E aspect and found slight reactivity on a storm interface down 10", but expects that interface to mostly stabilize by Tuesday. 14" of snow now sits above the 1/27 crust. On some steeper sun-exposed aspects, you might find a 2/3 melt-freeze crust a few inches above the 1/27. The MLK crust lies around a foot below the 1/27 crust. In shallow snowpack areas such as Tilly Jane, weakening within and around the 1/27 crust may be able to produce a more widely propagating avalanche failing down to that layer with enough snow loading. We don't know if or when such a snowpack could reach a threshold, but if you find yourself in a shallow snow area, Tuesday will not be a good day to be on, near, or under large and rapidly loading terrain features.

On Saturday observers reported fairly quiet conditions, warm temperatures, and 1 inch of new snow. The Timberline Ski Patrol reported finding reactive cornices and the Meadows Patrol triggered isolated wind slabs that broke 4-6” deep. 

 

 

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