Bollettino valanghe

Mt Hood

Northwest Avalanche Center
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Pericolo valanghe

Fri
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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In sintesi

A fresh round of NW wind will add to existing slabs on aspects where you may not expect them. Watch for active snow transport, punchy snow layering, and sculpted drifts to identify and avoid triggering a slab in steep terrain near or above treeline. 

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–2

    A fresh round of moderate winds early in the day and light snowfall throughout the day on Thursday maintain slabs that you can trigger near and particularly above treeline. Drifts will occur more on W-S-E aspects, building upon slabs that have been slow to heal amidst the cold temperatures this week. Low-density powder exists on all aspects and it won't take much to form a small slab.  Active wind transport will be your first sign of instability. Also pay attention to firm over weak snow layering, hollow-feeling snow, and cracking snow surface, particularly on W-S-E aspects.  Some of these slopes melted to bare ground and rock and have shallowly submerged sharp objects that will increase the trauma from any avalanche.

    Cold temperatures have preserved older slabs (up to size 2) longer than you might expect. They should be stubborn to trigger and isolated to heavily wind-loaded, steep, and unsupported N and E aspects. Given the shifting winds, check for firm over weak snowpack layering all the way down to the 2/19 crust. When in doubt, stick to smaller terrain features and lower slope angles.

     

    (2/22/2022)

    Explosive triggered wind slab (D1.5) in Heather Canyon. Failed within the storm snow.

    Photo: Andrew Kiefer

Avalanche Discussion

Wednesday was a beautiful day in the Mt. Hood backcountry with NWAC professionals on Lookout Mountain finding low-density snow on all aspects. They observed wind-affected snow in exposed terrain with slabs 2-4" thick focused on southerly aspects within the 8-16" of snow that sits generally right-side-up and is well bonded to the 2/19 crust. Wind-affected snow was also observed on nearby Pea-Gravel Ridge. The upper slopes of Mt. Hood appeared less wind affected than normal. Below the 2/19 crust, the snowpack is strong and there are no layers of concern. 

Mt Hood picked up 24-27 inches of snow since Saturday evening. Moderate WSW winds were gusting strong as the snow arrived over the weekend. The winds took a break on Monday, but picked back up Monday night out of the NNE, transporting the low-density snow. NE winds will continue to transport snow and drift snow onto unusual and shallow W and S aspects through Tuesday evening.  You might find a consistent density change caused by a wind layer within the storm snow. We suspect most avalanches will not entrain snow down to the well-bonded snow/crust interface buried 02/19.

Cold temperatures have slowed the healing of wind slabs and in spite of strong late February sunshine, wet avalanches and crusts had not formed on southerly aspects by mid-day Thursday. It is a matter of time before temperatures warm just enough to initiate loose avalanches on steep S aspects receiving direct sunshine. Watch for tree bombs and snow starting to melt off rocks and cliffs as a sign to change your aspect or reduce your overhead exposure to steep slopes.

This snow has created great riding conditions, but it won't bury all rocks, tree stumps, and all the other ground hazards that were recently exposed. Ride cautiously in shallow terrain. 

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