Avalanche forecast

West Slopes South

Northwest Avalanche Center
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Avalanche danger

Sat
Alpine
2 · Moderate
Treeline
2 · Moderate
Below
1 · Low
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Highlights

 Avalanche danger will increase to moderate throughout the day, as the storm will start as rain at most elevations before transitioning to snow. You could trigger an avalanche in wind-drifted snow deposits, so steer around heavier drifts when they start growing over 6 inches deep on steep slopes. Mt Rainier is forecasted to get more snow than other areas in the zone, so danger may be higher in that location. 

Avalanche problems

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    1–2

    Avalanche danger will probably start on low in the morning but expect the danger to rise to moderate as rain transitions to snow and new snow depths increase. During your outing, focus on new snow and wind activity, as you can expect conditions to change.

    Moderate to strong winds will redistribute snow, and drifts will grow. You may find these drifts in gullies, around rocky outcroppings, or along ridgelines.  Identify features that may be wind-rippled, or possibly smooth.  Identify hollow-sounding or firmer-feeling snow. These indicate wind-affected snow, which you can expect to be more reactive.  Search for other obvious signs of instability like long, shooting cracks from your feet or sled.  Avoid slopes steeper than 30° when drifts are around 6" or deeper.

    An illustration of early-season wind loading.

Avalanche Discussion

It's time to transition back to thinking about winter snowpacks and avalanches for Friday. The storm will start warm before cooling off, which is when most of the precipitation is forecasted to arrive. Some areas in the zone may only receive 2-4", while other areas, specifically Rainier, may get closer to 6". Avalanche danger may be higher than forecasted at Rainier. 

Old snow surfaces may be smooth and firm, and new wind slabs could slide easily on the smooth surfaces.  Observers also reported finding weak surface hoar crystals Wednesday afternoon. These crystals may remain preserved, which could lead to more reactive slabs.

One observer in the Crystal backcountry on Wednesday said their biggest takeaway was how much snow base was lost in the last week. They said the snow that was present was mainly a supportable crust. An observer who went touring at Paradise, up to 8600ft, echoed similar conditions with a supportable crust as well.  We did get snow at upper elevations on Tuesday, so pockets of dry snow could exist in some areas beneath the new snow layer. Once snow starts falling, remember that early season obstacles and a variable old snow surface will be thinly hidden under the new snow layer. Chunky avalanche debris, rocks, trees, and open creeks are all suspect, even more so once the snow starts falling. 

If you make it into the backcountry please send us an observation. Also keep in mind that conditions will be very different on Friday from many of the days we've had so far this year. 

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