Lawinenlagebericht

Snoqualmie Pass

Northwest Avalanche Center
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Lawinengefahr

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

Avalanche potential will peak on Tuesday as a significant storm impacts Snoqualmie Pass. Look for red flags of instability, such as other avalanches, shooting cracks, or active wind-loading. The snowpack will need time to adjust to the new load, so avoid slopes over 35 degrees for a couple of days.

Lawinenprobleme

  • Storm Slabs

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

    High snowfall rates, fluctuating freezing levels, and moderate winds will all aid in slab development on Tuesday. Slabs will be larger as you ascend in elevation or in wind-loaded terrain. They could overlay weak grains or a firm crust at the 3/9 interface, making them fail easily. Use small test slopes, uptrack tests, and quick hand-pits to gauge the storm snow’s reactivity and bonding. When in doubt, avoid slopes over 35 degrees where triggering an avalanche is more likely.

    (3/8/2024)

    Shooting cracks are red flag signs of instability. This one occurred in wind-loaded terrain, triggering a slab roughly 50 feet away.

    Photo: Micah Hoover

Avalanche Discussion

NWAC will be closed on Tuesday, March 12th, as we gather and grieve following the death of one of our forecasters, Matt Primomo. We will not issue regular avalanche or mountain weather forecasts on Tuesday. We will return to normal operations on Wednesday, March 13th. We appreciate the community's understanding and support during this time.

Discussion:

We saved the biggest storm for last. It should be a doozy and deliver significant snowfall to the Snoqualmie Pass zone, increasing the depth over the 3/9 interface. On slopes that typically receive direct sunshine, the 3/9 consists of a melt-freeze crust of varying thickness. It could be a good sliding surface or result in poorly bonded storm snow. Weak grains, such as near-surface facets and surface hoar, were observed on shadier aspects before this storm parade. Where preserved, they could allow avalanches to fail easily or propagate widely. We expect the majority of avalanche activity to occur above the 3/9 interface.

During this storm cycle, avalanche activity has mainly been confined to wind-loaded features such as confined chutes. Backcountry travelers have reported poor bonding just above the 3/9 interface due to graupel. The distribution of graupel is often difficult to pin down, but it likes to gather in low places such as concavities, the base of cliffs, or where a steep slope starts to mellow out. Because of this, you might encounter slabs in unusual locations. At lower elevations, fluctuating freezing levels have resulted in heavy, moist snow and wet avalanche activity such as rollerballs and pinwheels. This should limit the avalanche potential moving forward at these elevations.

Persistent slab issues continue to wreak havoc in neighboring zones. We do not have any confirmed avalanches at Snoqualmie Pass on the Early February Crust (EFC) or the associated interfaces, but that doesn’t mean it’s out of the realm of possibility.

Outlook (Day 2):

On Wednesday, expect similar avalanche conditions to those found on Tuesday. The storm should be winding down, but there is a possibility of a convergence zone delivering another shot of snow on Tuesday night. Storm snow related avalanches will be more likely as you ascend in elevation or in wind-loaded terrain and should be confined to the snow above the 3/9 interface. The wildcard will be sunshine. With significant sun breaks possible, wet avalanches could follow. Look to the snow surface to help determine if you are dealing with wet or dry avalanche problems. If the surface is getting moist and sticky, head for shadier slopes. 

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