Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

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

Avalanche danger is limited to areas of recently wind drifted snow in alpine terrain. Conditions vary across the zone - check out the forecasts for Stevens and Snoqualmie Passes if you are traveling near either of those areas. Expect increasing danger through the weekend with a return to heavy snowfall and strong winds.

Problemi valanghivi

  • Wind Slabs

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

    Westerly winds could build new slabs from a few inches of new plus any loose snow still available for transport. This is more or less the same problem as with the last few days. The difference is a shift in wind direction. Though small in size, wind slabs new and old are still big enough to do serious harm if they take you off a cliff, smash you into a rock, or dump you into a gully. 

    The current crop of wind slabs can be identified as stiff, smooth-looking drifts likely surrounded by scoured or otherwise wind affected snow surfaces. You could find these just below ridgeline and also farther downslope on cross-loaded features. Poor visibility could make wind slabs harder to pick out in the terrain around you. Use test slopes to see if you can get the surface snow to crack, collapse, or slide prior to moving into more consequential terrain. When in doubt simply default to simpler terrain with less consequence.

    (3/9/2022)

    Small skier triggered wind slab on the White Salmon Glacier. The avalanche was triggered as a skier traversed across the bottom of the slope (note the ski track entering the debris). He was partially buried. Crown was ~5 inches deep and ~35 feet in width.  

    Photo: Zach Bunch

Avalanche Discussion

Friday marks a transition from cool, high pressure under northerly flow to a much more active weather pattern through the next week. Other than wind slabs up high, you may encounter signs of instability like rollerballs and pinwheels from subtle warming and light precipitation in the afternoon.

The biggest consideration in the days ahead - other than new storm and wind slab layers - is the faceted snow surface. This is by no means a surprise as surface faceting is common during periods of high pressure. How much this layer will affect new snow bonding depends on multiple factors including wind speeds ahead of the storm, precipitation type, etc.  If you identify weak, faceted snow surfaces tomorrow - or even if you don't - help us track this layer by submitting an observation here.

Though signs of avalanche activity can be found throughout the mountains, most observations were of the large slab and wet avalanches from the last major storm over a week ago. Recently triggered avalanches were limited to small and shallow wind slabs in alpine terrain (March 5th, March 9th).

Other than the current snow surface, the upper snowpack is generally strong with no current layers of concern. Human triggered avalanches on the Valentine’s Day crust and the late January crust-facet layers continue to be an issue in adjacent regions (East North and the South Coast and Sea-to-Sky zones in Canada). There were no reported avalanches in West North or Central associated with deeper layers since the natural avalanche cycle in late February/early March.

Regioni coperte