Lawinenlagebericht

East Slopes Central

Northwest Avalanche Center
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Lawinengefahr

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

Significant rain continues to saturate a previously dry and layered snowpack. Wet slabs may release from big steep slopes, and could be very large and destructive. Even roof avalanches could be dangerous on Tuesday, with all the ice buildup. Expect challenging travel with a slick crust, breakable crust, mushy wet snow, and new snow with very strong winds.

Lawinenprobleme

  • Wet Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Likely
    Größe
    2–3

    The snowpack is going through a transition to wet snow, and we could see a variety of dangerous avalanches occur. As water makes its way deeper into the snowpack, widely propagating slabs are possible. Buried layers of small facets, surface hoar, and larger facets near the ground could all act as the weak layer for destructive wet slab avalanches. You may be able to trigger wet loose slides that entrain deeper snow and become large as well. In other areas, you might just find challenging travel with a stout or breakable slick crust.

    The current conditions are a bit unusual, and wet slabs are tricky to predict, so give yourself an extra margin of safety with your travels. This means steering well out from underneath large, steep slopes that have been saturated by rain. Look for recent avalanche activity as the number one bullseye of instability information. Wet, mushy, and unsupportable snow are also good indicators that wet avalanches are possible. 

    Steer clear of roofs that haven't yet released. Roof avalanches could be large and dangerous with all the ice involved. 

    (12/25/2022)

    Example slab avalanche involving wet snow at Snoqualmie Pass.

    Photo: WSDOT, SCR Avalanche Crew

  • Wind Slabs

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

    As snow levels begin a slow decline, westerly winds are expected to become very strong at ridgetop. New snow will be easily transported into reactive slabs at upper elevations. Steer around steep slopes that are actively loading with wind driven snow, or that exhibit instabilities. Shooting cracks are a good sign of dry snow instabilities.

Avalanche Discussion

Another round of rain and snow is expected Monday night and Tuesday. This should be a very wet night and morning for the east slopes of the Cascades. The snowpack is already becoming saturated, so the additional load of heavy rain and snow may be enough to tip some slopes over the edge. The lowest elevations have a thick freezing rain crust, but some water is percolating through, while water is saturating the mid and upper elevations. This makes for a very challenging and complex situation when combined with our previously dry and layered snowpack. Over the weekend, the areas near the crest picked up substantially more precipitation than the Wenatchee mountains. WSDOT reported a number of large natural slides that hit the closed highway in Tumwater Canyon on Sunday. Water amounts near the crest are: 2.2" at Sasse Ridge and 2.7" at Trinity, however these may be much different places at the moment. Sasse likely has a thick freezing rain crust and saturated wet snow. Trinity has 6" of heavy, dense new snow, a freezing rain crust and is later to the party, just now becoming saturated. Many NWAC weather stations haven't registered precipitation well, as they were clogged with sleet. The snowpack has only begun to transition to wet snow near the surface. It'll take time for it to adjust, and in doing so we could see large and surprising avalanches. Keep your wits about you if you do go out into the mountains, it's likely to be a dangerous place on Tuesday.

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