Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Mon
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Kernpunkte

Expect increasing danger on Sunday as a multi-day storm begins to affect the area. Wind slabs should grow in size at upper elevations near the crest, and could be reactive on a recently buried weak snow or a slick crust. Take a step back in your terrain selection, identifying large steep slopes in the wind zone that hold questionable stability. 

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–1.5

    Wind slabs should become larger and easier to trigger as the day progresses on Sunday. Higher elevation areas closer to the crest may see heightened danger during the second half of the day as new snow and winds build thicker slabs. You could also trigger wind slabs at mid elevations and sparsely treed slopes as well. You'll generally find lower danger below treeline, and further east in the range where less snow is available for the wind to drift it.

    Look for active wind transport and increasing snowfall rates as indicators that slabs are forming. Use practical tests to check for signs of instability like shooting cracks as you gain elevation. In many areas you'll still be able to avoid the wind slab problem by steering around stiffer and textured pillows, though at higher elevations you might want to avoid entire slopes.

    There is a chance that a slab could step down into deeper buried weak layers and become a large, more destructive avalanche. This problem is particularly concerning in areas near and around Stevens Pass. Although uncertainty exists, similar conditions could also linger in areas further east. With this increased uncertainty, travel with a conservative mindset and consider wider safety margins.

    (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

Avalanche Discussion

We're in for a change, the primary things to convey are that:

1. Snow totals should begin to add up in the mountains over the next few days with strong winds, and

2. Avalanche danger is expected to increase substantially from Sunday afternoon through 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 this recent crust, and could see slides run on even deeper weak layers. Lower elevations hold low danger, but one can still find some nice 'corn' snow, or refrozen grains and a crust that has been freezing and thawing in the sun each day. 

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. These avalanche occurrences are worth noting if you plan to travel along the western edge of the East-Central zone. You should consider the high consequences of triggering a larger and more surprising avalanche. 

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