Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Mon
Hochgebirge
3 · Erheblich
Waldgrenze
3 · Erheblich
Unterhalb
2 · Mässig
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Kernpunkte

Recent human-triggered avalanches and additional snowfall should be enough to maintain dangerous avalanche conditions on Sunday. Slides will be more likely in terrain over 35 degrees and could run far distances on a firm crust. Keep an eye on how the dynamic springtime weather is affecting the snowpack, you may have to adjust your mindset as conditions change.

Lawinenprobleme

  • Storm Slabs

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

    You should continue to be leery of open slopes over 35 degrees on Sunday. Multiple rounds of precipitation during this stormy period have resulted in a layered upper snowpack sitting on a crust. Use test slopes or dig down to the crust with your hand or shovel to investigate these potential failure points before committing to terrain. You should also look for heavy snow over weaker snow (upside-down snowpack), cracking of the surface, or recent avalanches as indicators that the snowpack is unhappy. Slabs should be larger as you ascend in elevation or in wind-loaded terrain. Even if the storm snow is not showing much cohesion or failing in blocks during your tests, it could still run far and fast on the underlying crust on slopes over 35 degrees.

    (4/1/2023)

    A skier triggered Storm Slab on a convexity in the Alpental Valley in Big Trees.

    Photo: Andy Harrington

Avalanche Discussion

The peak of this stormy period may be over, but precipitation is expected to continue into Sunday at Snoqualmie Pass. With roughly 15 inches already on the ground at upper elevations, expected accumulations should have us approaching 2 feet of storm snow by Sunday evening. All the recent snowfall is overlaying a crust (3/31 interface) and has an inconsistent bond across the landscape, mostly based on elevation and the stoutness of the crust. 

On Saturday, numerous small avalanches were human-triggered on steeper slopes throughout the zone. Many of them failed at the base of the storm snow, but some failed within. Alpental Pro Patrol reported similar results during their morning mitigation efforts along with some small natural activity. Most of these reported avalanches ran on the 3/31 crust, sometimes traveling far distances. NWAC forecasters found multiple density breaks and plenty of weak graupel within the storm snow. Loose avalanches running on the 3/31 were also observed in steep terrain.

Don’t expect the bond to become much more favorable by the time Sunday rolls around. The added precipitation just means that slabs will be thicker and with more layers for you to investigate. You could encounter periods of heavy convective showers interspersed with more sun breaks than we experienced on Saturday. Even in short spurts, this solar input could start to change the snow surface resulting in it gaining some cohesion and “slabbing up”. You might even see a few rollerballs and Wet Loose avalanches. It’s springtime, so conditions can change rapidly. Be sure to reassess the snowpack consistently throughout the day to see how the dynamic weather is affecting it. 

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