Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

Mon
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

Wind-loaded features will continue to be the most likely location to trigger a slab avalanche on Sunday. Look for shooting cracks and feel for differences in the stiffness of the underlying snow as you travel to help identify potential Wind Slabs. As the temperature starts to creep up ahead of a bigger storm on Sunday night, be leery of overhead cornices or other blocks of snow.

Lawinenprobleme

  • Wind Slabs

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

    You may need to manage Wind Slabs of varying ages on Sunday. To complicate matters, they’ll likely be on an assortment of aspects due to the wind reversing direction multiple times recently. New slabs could build throughout the day as increasing winds drift recently fallen snow onto leeward slopes or other notorious wind-loaded features such as convexities or confined gullies. Look for actively blowing snow, smooth pillow-like mounds, or textured surfaces to help identify the wind-loaded features you should steer around. Additionally, you could encounter lingering slabs from Thursday night’s wind event hidden a few inches below the surface. You’ll need to feel for subtle changes in the stiffness of the snow to identify these ones. They may feel hollow and be more difficult to trigger, but if they fail they’ll likely be larger and could break in more surprising ways. 

    (3/11/2023)

    A skier triggered this slab on a convex slope in the Alpental Valley on 3/11.

    Photo: Jeff Tarshis

Avalanche Discussion

Backcountry travelers were greeted with 4-6 inches of new snow on Saturday morning and found that it had been drifted around by light to moderate winds. A few human-triggered avalanches were reported in the new snow by skiers in the Alpental Valley where the bond to the underlying surface is reportedly poor. Most of these occurred in wind-loaded terrain on convex rollovers or near ridgelines. Alpental Pro Patrol reported similar activity during their morning mitigation work with a few slabs up to 1 foot deep. Sunday should be a similar kind of day, except there will likely be less new snow and temperatures should start to slowly creep up ahead of an incoming storm system. With a cold and clear night forecast for Saturday evening, weak surfaces may develop. 

As temperatures start to climb, be leery of overhead cornices that have grown large during the recent windy weather. They could fail and trigger avalanches on the slopes below. On slopes that see direct sunshine, rollerballing and small Wet Loose avalanches are always a threat if the strong March sun is out for a prolonged period of time.

The past week has delivered multiple small bursts of precipitation at the Pass, yielding 1.5-2 feet of snowfall. Combined with numerous wind events coming from every direction, the upper snowpack now contains subtle storm interfaces, thin sun crusts, and is a bit upside-down in places. Weak grains such as graupel and fragments of surface hoar have regularly been observed by avalanche professionals and recreationalists alike. Some of these grains were at play when larger avalanches occurred within the zone last weekend. While we have maintained that the upper snowpack has been generally right-side-up throughout this period due to the lack of a significant slab, the incoming system on Sunday evening has the potential to turn conditions on their head or finally tip the scales for many slopes.

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