Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

Tue
Hochgebirge
2 · Mässig
Waldgrenze
2 · Mässig
Unterhalb
1 · Gering
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Veraltet — dieser Lagebericht ist 3 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

The most likely places to trigger a slab avalanche are above treeline, where you find blowing snow and recent wind slabs. Steer around steep slopes below ridges, cross-loaded features, and convex rolls where you find stiffer wind-drifted slabs of snow.

Lawinenprobleme

  • Wind Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Possible
    Größe
    1–2

    Steer around areas of stiffer, drifted snow in steep open terrain at lower elevations. Avalanches could be bigger above treeline and easier to trigger. The best way to keep from triggering an avalanche is to avoid leeward slopes near and above treeline and stick to areas sheltered from the wind and slopes under 35 degrees.  Feel for stiff over soft snow layering and use inconsequential test slopes to identify and avoid areas of unstable wind-drifted snow.  You may find more recent, shallow slabs from east winds. Older wind slabs from west wind may be harder to trigger. Pay close attention to wind direction and blowing snow to identify dangerous leeward slopes. 

    (3/5/2023)

    Cracks in wind-stiffened snow are a sign of wind slab instability. Blewett Pass

    Photo: Matt Primomo

Avalanche Discussion

You may be able to trigger loose avalanches on very steep slopes, especially on sun-exposed, southeast through southwest aspects.

On Sunday, Matt Primomo found some evidence of recently wind-drifted slabs near Blewett Pass. In a profile, (ESE, 5700ft) he was able to identify and get sudden test results on the January 4th surface hoar, however, the layer isn't a current concern for avalanches. Observers in the Icicle drainage reported light wind transport with some fresh wind slab development from easterly wind lower in terrain. The sun was out in the eastern part of the zone, but more cloudy near the Cascade crest. On Friday, an observer in the Icicle Creek Drainage triggered a small slab on a steep convex roll that ran on this recent sun crust. There has been significant snow and winds over the last 3 days throughout the zone. Previously, the highest snow totals were near the Cascade crest where over 1.5 feet accumulated from March 2-4th.

Recent snow is loose and uncohesive in most sheltered locations. On Southerly aspects, snow fell on a slick crust, which could be up to 1-2 feet deep near the Cascade Crest. While this potentially problematic layer may be isolated in distribution, it could produce avalanches as recent snow gains cohesion. At low-elevations and areas further east in the zone, this crust could be Sunday's new/old snow interface.You can find 1-2ft of recent snow sitting over a crust from Valentine's Day, which often presents as a crust/facet sandwich, with weaker snow beneath the upper crust. Observations indicate quite a wide variability in the structure of this layer. There has been a couple of isolated observations of instability on this layer in the Icicle drainage. We have yet to observe avalanche activity on this layer but continue to monitor it as snow adds up. If you get out into the mountains, submit an observation to share what you found.

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