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The coldest February in 30 years wants to go out with a bang!  A Winter Storm WATCH is up for much of the FOX12 viewing area, including north Oregon Coast, I-5 corridor, Gorge, Cascades, and north-central Oregon. 

Why?

For the next two-three days, a boundary will be setup across the state of Oregon between cold/dry arctic air flowing south out of Canada (the chilly colors on the map), and TONS of moisture streaming in from the Pacific to the south. 

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Wherever the moisture rides over the cold air, heavy snow will likely be the result.  TWO separate systems travel along that boundary; one tonight and early Sunday, then another one late Sunday night and Monday.  Most snowfall tends to fall close to and north of the red line, within about 150 miles or so (highlighted).

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ALL numerical weather prediction models (THE MODELS) are showing this setup and have been since at least Wednesday.  As always the exact positioning is critical to whether it snows at YOUR house or not.  If the whole zone is south of you, most likely you just stay chilly and mainly dry through the period (Seattle).  If it shifts north of you (maybe Eugene or Roseburg?), then no snow for you!

West of the Cascades, the first system coming through tonight and Sunday morning is a bit too far south to produce snow in most of Northwest Oregon, plus we don't have an atmosphere quite cold enough either.  So snow level hovers around 1,000'-1,500' through Sunday afternoon here.

The 2nd system for Sunday night/Monday is why we have a Winter Storm Watch up west of the Cascades.  That one tracks a bit farther north, sends far more moisture overhead, and pulls in a cold east wind through the Gorge as it approaches.  Take a look at the WRF-GFS forecast for 7am Monday morning.  Low pressure passing over Willamette Pass headed east and cold air pulled down from the north.  This setup is perfect for producing a snowstorm many areas west of the Cascades (and north-central Oregon)

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If I were to look only at this model for Sunday night and Monday? I'd say no snow up at Longview and on the north coastline, just a Trace to 3" in the metro area, but MANY inches Salem southward to Roseburg.  The GFS model is similar.  

How about my favorite ECMWF?  It (along with the GEM model) buries the Willamette Valley in a major snowstorm by midday/PM Monday.  Many inches of snow from Portland to Eugene, a bullseye directly over Salem on that one.  GEM has even bigger totals as it brings the low from Florence right up to Salem.  By the way, the last 6 runs of that Euro have pushed a foot of snow into some location west of the Cascades.  It has been as far north as Olympia and as far south as Roseburg.  That's some great model consistency showing that someone is going to get nailed westside.  The morning ECMWF shows the precipitation from late Sunday through late Monday.  Wow, that's juicy (and white) south of the metro area.  You could get a foot of snow out of that much precip in the southern Willamette Valley, and only flurries at Longview and Astoria (with this model run).  This could be a historic February snowstorm somewhere in the Willamette Valley.

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WHAT DO I THINK IS GOING TO HAPPEN? 

We still have three more model runs before this event, so plenty of time to figure it out

  • SOME OF US west of the Cascades between Longview and Roseburg are likely going to get buried by a beautiful, heavy, coat of wet snow between late Sunday night and sunset Monday; extra amazing that it's happening on February 25th.  VERY late in the season!
  • I don't have a good feel yet for exactly where that's going to happen, but it's time to assume your life could get messed up by weather at least Monday morning, maybe for the following 24 hours.
  • SOME OF US will get hosed by little or no snow, depending on where the low tracks
  • We're still two days away, but the NWS is thinking 2-8" is the possible range right now in the metro area.  It could be below or above that number for the reasons mentioned above.  Seems like a good starting number though.  Just like the last event, we'll narrow it down as we get closer.
  • The Columbia River Gorge and north-central Oregon have the best chance at getting buried by two snow events, the weaker one late tonight and Sunday, then bigger Sunday night and Monday.  I can see 12-24" falling out there.

IMPORTANT POINT

It's late February folks!  Even if your town west of the Cascades gets 10" of snow Monday morning, we're not going to be in a snowy & frozen hell for the next week.  A few sunbreaks and snow starts melting off streets.  You are not going to be trapped in your home for several days.  Leave that kale alone... (west of the Cascades).

I'll post again midday tomorrow as the drama continues to unfold...

Chief Meteorologist Mark Nelsen

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