The Snow Forecast Update

The Snow Forecast Update

 Light snow has begun to fall across the area.    Earlier at present, circulate from the  Fraser River Valley and Strait of Georgia moved southward into the northern Olympics, and being compelled to rise, dropped snow round Sequim and north Olympic foothills (see image alongside US 101)

And the marketed first low stress system is now heading in the direction of Oregon (see forecast place at Four PM), sending a defend of precipitation over northern Oregon and southern Washington

The Snow Forecast Update

The climate radar picture round 1 PM reveals the sunshine precipitation related to this method.  Snow is now noticed from SeaTac Airport and to the south,  lighter to the north.  Flurries to the north.

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The newest WSDOT cams round Olympia are downright winter-like.
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Now that we’re shut in, I can present you up-to-date excessive decision forecasts.  The newest run of the NOAA/NWS HRRR mannequin exhibiting collected snowfall is proven under.
First, by 10 PM tonight.  Light snow over most of western WA…however solely .1 to 1 inch.  More (as a lot as 2-Four inches round Olympia and to the south).

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The complete by 5 AM.  Shows extra in the identical spots.  But there’s a essential subject right here…much less snow west of the Cascades from Tacoma northward…with the snow deficiency extending to the Sound.  This is because of sturdy easterly circulate (from the east) sinking on the terrain.  Thus, native mayors can sleep nicely tonight.
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Let me present you the wind forecast for 10 PM tonight with a dashed oval indicating the easterly winds. Click to enlarge.  It might be blustery from North Bed to Enumclaw.
The Snow Forecast Update
So that is stage one of many occasion.
Now stage two is the threatening and tough half.  This isn’t your typical massive snow occasion and Puget Sound is correct on the sting for a number of causes.
Another low will strategy the Washington coast on Saturday.  Which means moisture extending farther north.
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The snow totals from this morning European Center mannequin is spectacular.   But you’ll discover the pesky Cascade “snow shadow” as a result of drying easterly circulate.  Seattle finally ends up with 5-6 inches of snowfall…maybe half of that in depth.  But MUCH extra west of the Sound and over the south Sound, the place some locations may get a foot of snow.  
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The predominant U.S. mannequin the GFS, has refined variations, with much more snow normally, significantly round Puget Sound.  Much much less north of Everett.
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Is there uncertainty for the snowfall over central Puget Sound?  You wager there may be.  Subtle variations within the place of the northern extent of the moisture, the placement of the low, and the diploma of downslope circulate off the Cascades may actually change issues.
To reveal this, right here is the ensemble of many forecasts for SeaTac for snow accumulation over time.  The forecast by Four PM Saturday (00z/14) vary from 1 inch to 20 inches!  The larger decision run (blue line) is about eight inches.  And I hate to say it….there may be one other snow occasion lurking on Monday for most of the ensemble members.
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I’ll weblog about this extra tomorrow and can do my common Friday morning podcast, which I’ll dedicate to the snow occasion.
The flurries outdoors are fairly proper now.    

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