Bollettino valanghe

Northern Wallowas

Wallowa Avalanche Center
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Pericolo valanghe

Fri
Alta quota
3 · Marcato
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Upper elevations in the Southern Wallowas have received 12-18" of new snow since the weekend. This new snow combined with increasing winds will drift the light density new snow onto leeward terrain features and build reactive wind slabs 1-3' deep on N-E-S aspects near ridgeline and cross-load ribs and gullies mid-slope. Avoid slopes >30 degrees with recent wind deposit and watch for loose dry avalanches on steep south-facing terrain.

Today's forecast is sponsored by CB Construction.  

Problemi valanghivi

  • Loose Dry

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1–1.5

    The 12-18" of light density snow that has fallen since the weekend is not bonding well to slick melt-freeze crusts on steep (>35 degrees) south-facing aspects. While these slides may be small, they could pick up speed rapidly and take you for a ride into trees, rocks, and over cliffs. Avoid slopes >35 degrees where the new snow is not bonding well to the underlying old snow surface.

  • Wind Slabs

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

    The 12-18" of new snow that has been deposited since the weekend is very light density and will be easily transported by the wind today. Overnight the winds have shifted from the NW to the SW and are currently 8-12mph gusting upper teens on Mt. Howard (8000'). The backing winds have created a wider area of wind-affected snow and riders are likely to find 1-3' reactive wind slabs on steep (>35 degree) on N-E-S aspects near ridgeline and on cross-loaded terrain features mid-slope. Look for smooth rounded pillows below ridgeline and on the leeward side of ribs and gully features mid-slope. It is best for the next few days to avoid steep alpine terrain where reactive wind slabs may lurk.

    Check out WAC forecaster, Nick Burks report from Wing Ridge yesterday.

    (3/1/2023)

    Cracking on isolated features

     

    Photo: Nick Burks

Avalanche Discussion

Protected and Sheltered Slopes Below Treeline

The snow quality on more protected and sheltered terrain is incredible right now. The cold temperatures and constant scud storms have left up to a foot of lovely light density snow in the Southern Wallowa mountains. This is the place to find the best snow quality and stability. There really isn't a good reason to go above treeline - unless you like to punish yourself with variable and more unstable conditions.

Wind Slabs

While great conditions are to be had below treeline, the situation changes dramatically as you move to treeline and above.  The recent north winds and now SW winds are scouring the alpine and creating reactive wind slabs 1-3' thick on leeward terrain features. It is a good idea to avoid steep slopes (>35 degrees) in the alpine for the next few days.

Persistent Slabs

Over the last few weeks the buried persistent weak layers in the upper and lower snowpack have been mostly unreactive to human-triggering and have been gaining strength. I want to stress that pesistent grain types still exist throughout our snowpack. In particular, we have several facet/crust combos in the upper snowpack (top 3 feet) that remain a concern. There are also still some pockets of preserved and buried surface hoar. As our favorite astrologist Carl Sagan said, "The absence of evidence is not the evidence of absence." Be sure to evaluate the snowpack on any slope >35 degrees for buried persistent weak layers. If you see poor structure in the upper snowpack - namely strong over weak - then be sure to test those suspect layers for reactivity. Also, it is good protocol to avoid possible trigger points in the terrain like convex slopes, unsupported slopes above and below cliff bands, slopes punctuated with rocks, and areas in the terrain where the snowpack is shallow, <4' deep.

Loose Dry

At upper elevations in the Southern Wallowas we have 12" or more of super light snow that is not bonding well to any slope that has an old melt-freeze crust or wind scab. In particular, it will be good to avoid steep (>35 degree) south-facing terrain where triggering a point release or sluff may get that new snow moving quickly down the slope, taking you off your feet or sled, and pushing you into terrain traps or stationary obstacles.

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