Bollettino valanghe

West Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 5 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Deep new snow can be found in the southern portion of West Central. Expect greater danger in areas where wind drifted snow created unstable slabs. Identify and steer around areas where you suspect wind loading to reduce the likelihood of triggering an avalanche. Be aware of loose snow avalanches starting above you during periods of strong sun and warming.

 

Problemi valanghivi

  • Wind Slabs

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

    Northeast winds will likely form new wind slabs on south and west aspects. These avalanches should be small but easy to trigger as they could be actively building through the morning. New wind slabs may be easy to identify with blowing snow indicating areas of loading. Also, look for scoured ridges with pillowy or lens-shaped drifts on the slope below. If winds are stronger than forecast, anticipate widespread wind slab development and deeper, larger slabs, especially in alpine terrain. 

    Older wind slabs from Saturday’s storm still exist on easterly aspects but were observed to be rapidly gaining strength. Despite heavy traffic across adjacent zones, no new wind slab avalanches were reported on Monday.

    Track the depth of new snow above the crust as you gain elevation. In wind sheltered terrain there is about 2 feet of new snow over the weak crust buried on Saturday. More than 2 feet over the crust? You are probably in wind loaded terrain. You can use simple tests to evaluate the bond of wind slab layers or simply avoid steep, unsupported terrain which you suspect harbors wind slab.

    On Monday northeast winds scoured snow off this slope which was previously wind loaded. This slope loaded (with southwest winds) during the storm on Saturday. The wind slab avalanche was triggered on Sunday.

     

Avalanche Discussion

In addition to slab avalanches in wind loaded terrain, strong late winter sun could overcome cold temperatures and create instability in the new snow. This could include loose snow avalanches and even the rogue storm slab avalanche releasing in new snow layers. These are most likely to occur in steep, sun exposed terrain around or below cliffs and rocky, treed features. 

Saturday’s storm put down 2-4” of precipitation across West Central with up to 3' of new snow in locations favored by the convergence zone. Human triggered wind and storm slab avalanches to D1.5 were reported to the north at Schriebers Meadow/Mt. Baker NRA on Sunday. Small loose snow avalanches, natural and human triggered, were observed across the west slopes of the Cascades on Sunday and Monday. They occurred on both shaded and sun exposed slopes.

Observers in the Mountain Loop today found 2' of right-side-up new snow above a weak crust buried on February 19th. They also found they found 0.5mm facets between this crust and the February 14th/Valentine's crust just below, This weak layer produced sudden results with Compression Tests and propagation with Extended Column Tests.  No avalanches associated with this layering have been reported.

 

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