Another Cold Blast is Coming to the Northwest

 Winter has not finished with us.  Another shot of snow is heading for the mountains.  And some lucky folks in the lowlands may see some snowflakes!

Another cold Arctic Blast is coming our way on Sunday.

As discussed in earlier blogs, there has been a major ridge of high pressure over the eastern Pacific (see upper-level 500 hPa pressure/height map for about 18,000 ft ASL at 1 PM today, below).  

Such ridges are quite frequent during La Nina years like this one.   Troughs of lower pressure can move southward down the eastern flanks of such ridges....and you can see one over southern California right now.  It is raining now around LA.


But on Sunday morning, another trough will move around the high...a strong trough...and one that will be in the right position to draw cold air into the region....with the most frigid stuff east of the Cascade crest (see image below)


Cold air will move in later on Sunday and Monday.  

To prepare you for the chill, here is the sea level pressure map (solid lines) and low-level temperatures (colors) for Tuesday at 7 AM.  

 VERY cold air will move southward east of the Rockies (brown and dark purple colors) and eastern Washington will get modified Arctic air (purple).   But even western Oregon and Washington will get a piece of the cold action (blue colors).  Cold enough to snow anywhere over the region by Monday.  But we will not have much precipitation by that time.

  Another shot of snow is heading for the mountains Another Cold Blast is Coming to the Northwest

But the trough will bring precipitation and snow to the mountains on Sunday...little doubt about that.

Here is the snow total forecast by the European Center model for the 24-h ending 4 PM Sunday.  Over a foot in the Cascades and some flurries over the lowlands away from the water.   Skiers will be smiling.


For the next 24-h, the snow will follow the trough southward (see 24-h snowfall amounts ending 4 PM Monday).  Light snow in eastern WA, but more will fall over the Oregon Cascades and eastern Oregon.

  Another shot of snow is heading for the mountains Another Cold Blast is Coming to the Northwest

We are still far enough out for the forecast to shift a bit, but colder air and some wintry weather will arrive on Sunday and Monday.

And did I mention the winds?  

Strong, frigid, northeasterly flow will push out of the Fraser River valley, across Whatcom County, over the San Juans, and then out the Strait (see the wind forecast below
4 AM Monday).  You got to feel sorry for those Whatcom country folks...they have really experienced a lot of weather.  Strong easterly flow will build over the Cascade crest as well.

  Another shot of snow is heading for the mountains Another Cold Blast is Coming to the Northwest

Skiers will be happy with the snow, but Monday will bring fairly extreme wind chills over the Cascade crest. So be prepared if you go up there.

It will be nice to have some active weather again after the boring last few weeks.  

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