Bollettino valanghe

Snoqualmie Pass

Northwest Avalanche Center
Vedi sulla mappa

Pericolo valanghe

Fri
Alta quota
4 · Forte
Limite del bosco
4 · Forte
Sotto il limite
3 · Marcato
Open full map
Non aggiornato — questo bollettino è scaduto 4 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

The Pass will be impacted by an atmospheric river on Thursday. Snow will eventually change over to rain at all elevations, with multiple rounds of natural avalanches expected. You should avoid all avalanche terrain until this storm has run its course.

Problemi valanghivi

  • Storm Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Very Likely
    Dimensione
    1–2

    This event is supposed to start with precipitation falling as snow. The new accumulation will likely be heavy and wet, overlaying lighter snow that currently exists on the surface. The resulting upside-down snowpack is the perfect set-up for Storm Slabs. This unstable snowpack structure combined with high precipitation rates and some gusty winds will produce very dangerous avalanche conditions. Thursday will not be a day to mess around in the mountains so stay out of avalanche terrain until this storm plays out.

    (12/25/2022)

    This small avalanche occurred in sleet during our last atmospheric river event over Christmas. This a good reminder that precipitation type can vary but still result in slab avalanches.

    Photo: WS DOT, SCR Avalanche Crew

  • Wet Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Likely
    Dimensione
    1–2

    As the day wears on and freezing levels creep ever higher, precipitation is likely to change over to rain. Whenever this occurs, expect another round of natural avalanches. We are calling them Wet Slabs due to the potential failure points in the snowpack. But make no mistake, there will likely be a combination of overlapping wet avalanche problems. It should start with smaller Wet Loose avalanches as a precursor to the bigger and more dangerous Wet Slabs. Even Glide avalanches could occur in isolated locations, which are essentially Wet Slabs with the ground as their failure plane. Categorize these slides however you want, the take home point is that very dangerous avalanche conditions are expected to develop in the mountains and you should avoid anywhere an avalanche can start, run, or stop.

    (12/26/2022)

    Some larger Glide avalanches occurred as a result of our previous atmospheric river event over Christmas. You could see plenty of wet avalanches on Thursday as snow changes over to rain.

    Photo: Alpental Pro Patrol

Avalanche Discussion

This is a tricky forecast for Snoqualmie Pass on Thursday due to uncertainty about the incoming storm and how it will play out. Forecasted water numbers are not impressive by atmospheric river standards, and the flow pattern is not one that typically favors the Pass. Rain should reach the top of the highest peaks in the zone by day’s end, but intensities may diminish by that time. That’s part of the uncertainty. Even if we’re wrong, it probably won’t be a very nice day to be in the mountains, so best to sit this one out and let mother nature do its thing. 

There is currently up to 2 feet of snow over the Christmas Crust at mid to upper elevations. The snow above this interface is generally right-side-up and strong. That said, NWAC forecasters have identified recent storm instabilities and one deeper layer of interest that could come into play during this atmospheric river. Whether they do or don’t we’ll have a hard time ever knowing. Just know that all of the snow above the Christmas Crust is being considered for avalanches during this cycle, and we expect there could be multiple rounds of naturals. We anticipate peeling back the snowpack onion layer by layer as the storm slowly warms and changes precipitation type. 

Regioni coperte