Bollettino valanghe

East Slopes Central

Northwest Avalanche Center
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Pericolo valanghe

Tue
Alta quota
4 · Forte
Limite del bosco
3 · Marcato
Sotto il limite
2 · Moderato
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Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

Expect a heads up day, and very dangerous conditions to develop at upper elevations near the crest with strong wind and new snow. If heading to these areas, create extra space between you and runout zones from avalanche paths, as large slides may run naturally. You may find wet loose avalanche danger at lower elevations with snow turning to rain during the day. 

Problemi valanghivi

  • Wind Slabs

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

    Wind slabs should continue to grow on Monday, and a natural avalanche cycle could occur in alpine terrain near the crest. Further east and in the mid elevations, we may not see natural avalanches, but conditions could become ripe for human triggering. 

    Active wind transport and increasing snowfall rates are clear indicators that slabs are probably forming. Deep drifts and cornices are also clues that wind slabs may exist in nearby terrain. Carefully evaluate the conditions as you gain elevation, and know that danger should be highest nearer the crest. Remember that shooting cracks are also obvious clues to instability.

    There is a chance that slabs could step down into more deeply buried weak layers and become a large, destructive avalanches. Create extra space between your route and potential runout zones from large avalanche paths with this uncertainty as the storm carries on.

    (2/18/2023) An intentionally triggered wind slab avalanche right where all the clues indicated it would be. NE, 5300ft, HS-ASc-D1-R3-I Photo: Dallas Glass

  • Loose Wet

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

    Rain on snow to about 4,500ft should weaken new and old snow surfaces, and could create wet loose avalanche danger. Be cognizant of this possibility on steep slopes, where the wet snow could entrain and pack a punch as it slides downhill. Look for signs of wet loose danger such as rollerballs and fresh fan shaped slides. If you find that you begin to sink into wet snow deeper than you boot top, thats also a good indicator that wet slides could occur.

    Steer around very steep slopes if you find signs of wet loose avalanches or observe that it's raining on freshly fallen snow.

    (1/25/2023)

    You may be able to trigger small wet loose avalanches like this, but on more unusual aspects like East and North as well. 

    Photo: Katie Warren

Avalanche Discussion

A multi-day storm is underway and with a pronounced rain shadow on the east slopes, it's expected to affect the higher elevations near the crest more substantially than areas further east. As such, you'll find the High danger at upper elevations in places like the Salmon la Sac, Teanaway, Icicle on Monday.  The eastern Wenatchee mountains aren't expected to pick up much new snow, but the winds are strong enough that you could still expect to find heightened conditions at upper elevations there. The danger trend will generally be increasing during the day and through the night into Tuesday.

We've been finding anywhere from 2" to 12" of recent snow over the crust that was buried on February 13th. Winds have been redistributing a substantial amount of snow at upper elevation. 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 is cause for concern going into this prolonged storm. We're likely to 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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