Bollettino valanghe

West Slopes South

Northwest Avalanche Center
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Pericolo valanghe

Wed
Alta quota
2 · Moderato
Limite del bosco
2 · Moderato
Sotto il limite
1 · Debole
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Non aggiornato — questo bollettino è scaduto 3 years ago. Stai vedendo condizioni passate, non il bollettino in corso.

In sintesi

A short-lived storm will bring rain and high-elevation snow to the West South zone Monday night and Tuesday. Warmer and wetter conditions are expected on the volcanoes compared to the crest. Avalanche activity will be more likely on rain-soaked slopes or in wind-exposed areas at upper elevations.

Problemi valanghivi

  • Loose Wet

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    Wherever rain falls on dry snow, small wet avalanches might develop. Higher elevation shaded slopes that have escaped the sun recently come to mind as the most likely locations where these slides could occur. However, with rising freezing levels throughout this event, there might be a narrow band where snow falls initially, only to be rained on later in the day. Look for rollerballs and pinwheels as precursors to wet avalanches and an indication to head for lower-angled terrain.

    (12/16/2023)

    Wet avalanche debris along Van Trump Creek from last week's atmospheric river.

    Photo: John Soltys

  • Wind Slabs

    • Alta quota
    • Limite del bosco
    • Sotto il limite del bosco
    Probabilità
    Possible
    Dimensione
    1

    You might find fresh snow drifting into shallow slabs above the rain/snow line. Look for actively blowing snow or pillow-like drifts to identify wind-loaded features to avoid. These slabs should be small but could be sensitive and break easily on top of the firm crust we have developed in recent days. Convex slopes, rocky features such as cliffs and chutes, or leeward ridgelines are the most likely locations to find these unstable pockets.

    (12/8/2023)

    A small natural wind slab avalanche from earlier this month. It is just below ridgeline.  Crown Point, E, 6200ft, SS-NC-D1-R1-S

    Photo: Dallas Glass

Avalanche Discussion

This storm is really focusing on the volcanoes, but even areas along the crest should expect to get mixed precipitation and some gusty winds on Tuesday. A good guess is that this will be a mostly snow event above 6000 feet with mostly rain below. Of course, there will be temperature fluctuations and local influences that sway the precipitation type one way or the other. So be prepared to make a judgment call based on what is falling out of the sky wherever you may be recreating. 

Any new snow is expected to bond fairly well to the wet and warm surface, creating a new interface. We expect most avalanche activity to occur at or above this layer unless there is enough rain to break down the crust and get to drier snow below. That doesn’t seem likely in most areas, with crust thickness recently measured as much as 7 inches by NWAC forecasters. 

After warm temperatures and a few atmospheric rivers to start the season, the snowpack should be well suited to handle additional liquid input. Unfortunately, this storm will likely only exasperate our early-season coverage and travel hazards. Gushing creeks, exposed boulders and logs, holes, and variable surfaces have littered the landscape and provided challenges over the past week for backcountry travelers.

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