Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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In sintesi

Strong to extreme winds and a healthy amount of new snow are creating very dangerous conditions at upper elevations. Large natural avalanches could run in the alpine overnight into Tuesday morning, and instabilities may linger through the day. Keep your distance from complex overhead terrain features, and steer around steep slopes with obvious wind drifts and textures at mid and lower elevations.

Problemi valanghivi

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1.5–2.5

    Heavy drifting and over 12" or more of new snow could fall in the western half of the zone by Tuesday. Carefully evaluate the conditions as you gain elevation, and know that danger should be highest in higher, exposed locations. Expect to see some natural activity, with lingering touchy conditions at higher elevations near the crest. Cornices may also be sensitive, and could release and trigger avalanches below. Slabs could be thick enough and wide enough to bury, injure, or kill people. Aside from recent avalanches, look for signs of instability like shooting cracks and feel for hollow sounding snow. Deep drifts, and textured snow surfaces are also clues that wind slabs may exist in nearby terrain. 

    Theres uncertainty with deeper weak layers, but some chances exist that slabs could step down into older facets and slicks crusts. If this does occur, the resulting avalanche could be surprisingly large. Create extra space between your route and potential runout zones from complex, upper elevation alpine terrain.

    Example wind slab with large blocks of snow.

    Photo: NWAC Forecasters

Avalanche Discussion

Avalanche Accident Colchuck Pk, East Central Zone

We’ve received preliminary information of an avalanche incident on Colchuck Peak, SW of Leavenworth, WA. (East Central Zone) The accident occurred on Sunday, February 19 and involved a group of 6 backcountry travelers. Three members of the group are suspected to have been buried and perished in the event. Another sustained injuries and was evacuated by SAR.  Rescue efforts are ongoing. NWAC is working with Chelan County Sheriff’s office and will make updates as more information becomes available.

 Forecast Discussion:

Very stormy conditions are expected overnight Monday into Tuesday morning for the mountains of the East Central. Snowfall should stack up quickly, despite the lackluster storm totals on Monday. Strong to extreme ridgeline winds should heavily drift the new snow, and create dense wind slabs. A round of natural avalanches could occur overnight into Tuesday morning, and we're most likely to see large slides in alpine terrain in the west half of the zone. Further east and at mid and lower elevations, we're likely to see less snowfall. This should lead danger a notch lower in those areas, but conditions may still be reactive with slabs only needing a trigger to release. The danger trend is expected to slowly decrease during the day on Tuesday.

Winds have been redistributing a substantial amount of snow at upper elevation. On Monday observers reported very windy conditions at Mission Ridge, and blowing snow. On Friday observers reported natural, large wind slab activity from alpine terrain near Holden Village. Both in the Salmon la Sac and eastern Highway 2 corridor, we've found the crust from the 13th to be fairly thin and breakable, with weaker snow beneath it. This structure a concern as the storm continues. We may see avalanches break above and below it, and could see slides run on even deeper weak layers. A crust from MLK weekend has been problematic for deeper slab releases in zones to the west. Some large and very large avalanches with wide propagation occurred from the 8 through the 13th in the Stevens Pass and Snoqualmie zones. This storm may act as a good test for this layer.

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