Cold Showers This Weekend; Maybe Some Snowflakes Too

9:30pm Tuesday…

Today was a spectacular early spring day with temperatures reaching the lower 60s just about everywhere east of the Coast Range

Todays Observed Highs OrWa 2017

This is due a weak and “splitting” jet stream.  Most of the action is sliding by to our north

Mark Jet Stream

Now that inversion season is over, we don’t get significant fog stuck in the valleys either.  This same setup with weak onshore flow might have left us with all-day long fog or low clouds in December/January.

Models are in very good agreement that the mild ridging over us will move farther offshore as a new ridge develops over the Gulf of Alaska this weekend.  By Saturday it looks like this…

Mark Jet Stream2

This is a classic setup for a snow “close-call” in the lowlands.  A cold upper-level trough digs south out of western Canada, and then cold north or northeast wind at the surface follows as the upper-low moves south of us.   If it was winter (Thanksgiving to late February) I’d be thinking we have a decent chance of getting sticking snow out of this, but in mid-March everything has to be EXACTLY RIGHT (or wrong) to get sticking snow near/at sea-level.

Right now it appears a surface low will “spin up” along the Washington coastline Friday, sending rain inland along with an increasing southerly breeze.  That means cold rain Friday with high temps 45-50 degrees.

Then on Saturday models generally agree that surface low is either right over us or shifting slow south offshore.  That potentially allows colder arctic air to slip south into the Pacific Northwest.  That would be on a north or easterly wind (through the Gorge).  The regularly awful (with cold weather) GFS model thinks the airmass will be so cold it stays in the 20s in the central/eastern Gorge all day Saturday.  That’s not going to happen.  More likely 10-15 degrees warmer than that as ECMWF and GEM models show. Our 7 day forecast numbers here:

Data Driven Forecast Highs Next 7 Day Meteogram

Precipitation intensity Saturday plus how much cold air (if any) arrives will determine our snow chances.  If we get cold easterly flow before precipitation runs out, then we could easily see snow in the air just about anywhere later Saturday or Saturday night.  During the daytime Saturday we’ll be up around 42-48 degrees.  That’s a good 10 degrees below average for mid-March.  It seems prudent to put those “mixed showers” in the forecast for Saturday so we did.  I should have a much better idea by Thursday, two days ahead of time.

By the way, we’ve only seen measurable snow in March (in Portland) 5 times in the past 50 years!  We saw 0.5″ last year and in 2012.  That March 22, 2012 event is the latest on record at the airport/NWS office.  Those records go back 80 years.

Portland Snow Latest 22

There was one snowfall in the old downtown record books on April 1, 1935.

Portland Snow Latest 2

 

All models forecast that cold upper-level trough to move south quickly Sunday.  That puts us back into lots of sunshine, a cold east wind, and likely dry later Sunday and Monday.  Then as high pressure gets closer temperatures jump back into the 50s, if not Monday then Tuesday.

That’s the real story; our unusually dry February/March will continue.  The ECMWF and GEM models both show only about 1/2″ rain in the next 10 days!  Just the ECMWF is shown here

ecmwf-deterministic-oregon-total_precip_inch-4705600

Chief Meteorologist Mark Nelsen

18 Responses to Cold Showers This Weekend; Maybe Some Snowflakes Too

  1. Roland Derksen says:

    Ahhh… I just love that “cold Canadian air”! 🙂

  2. rmlounsbury says:

    Well, the GFS hasn’t flinched for a few runs now… A few tenths of an inch of precip available once temps have dropped to near or below freezing.

    I’m still assuming that the GFS is still too aggressive with how cold and how quickly the air arrives. It always is and if we make that assumption it is safe to say we just get rain/snow mix before it dries out and the cold air actually arrives.

    2020 has been about as weird as anyone can imagine.

  3. Diana F. says:

    It’s amazing how minutely important the weather becomes when you get a dog requiring 2 hours per day of walking lol…..thanks, Mark! I’ve had Sasha now for 4 months and only twice have I cussed you out, and twice I had to go back home after getting a block away, because my clothes were way too hot, or way too cold. A veritable Goldilocks syndrome! Not bad Mr. Nelsen, not bad at all! Thanks again it’s a huge help…

  4. Evan -- Cedar Mill says:

    The GFS is back on drugs!! 🤣🤣

  5. Andy says:

    I dusted off some of my weather records for March snow here in the Albany area.On March 21st 2012 snow started falling and it didn’t stop until early morning of the 22nd the low bottomed out at 29 deg and 6 inches of snow and much more around the hills. We have had some smaller events in March…however 2012 stands out in the Albany and Corvallis area for one of the more memorable late snows.

  6. Scott Reeves says:

    Weather Channel has 1-3 inches of snow Saturday morning and they’re usually right

  7. Ziggy says:

    This will have all the geeks glued to the windows, hoping for some chunky rain. It is a nothing event just like the winter. I can’t wait to hear all the crying on Monday morning 😁

    • Peter Christenson says:

      Zigster, I for one will shed no tears. I may gloat, however, if the grass gets white. BTW, if any of you wonder why the Europeans are so much better at medium range forecasting than “we” are, read the chapter on ECMWF in the recent book “The Weather Machine.”

      • JohnD says:

        Z is apparently a joyless person—whose only apparent life pleasure is propagating his (or hers) big fat downer.
        Had to put up with this all winter long on Mark’s blog.
        No doubt next year too after—yet again—a new name is created.
        Really compassion is the only valid response for such types.
        Whatever.
        I and a friend are layering up for Dog Mtn. Sat.
        Teens-wind-snow as we ascend.
        Yeow Baby! Bring it! No crowds on Dog Sat. Just a few crazies like me enjoying the weather!

  8. Roland Derksen says:

    It reminds me somewhat of March 2002 here-( with snowfalls in the third week of the month, just before the official start of spring)

  9. Grizzly Bear says:

    Looks like winter isn’t over yet, here is the National Weather Service forecast for Kamiah, ID

    ~ “Saturday Night
    A 30 percent chance of snow before 11pm. Mostly cloudy, with a low around 19.” ~

  10. rmlounsbury says:

    If you reaaalllyyy want snow just take the 06Z GFS Op at face value and you’ll get a couple inches to the valley overnight before we run out of moisture. Wouldn’t that be something?

    If nothing else this weekend will be entertaining.

  11. Paul D says:

    Not gonna happen. Quit teasing us with the flakes!

  12. Thanks, Mark for the update.

    Potentially the best pattern of the entire Winter occurs in Mid-March. Seems legit. The GFS is routinely overly aggressive with cold air and pressure rises into Eastern Washington. Why are we still using it for model guidance? I have to wonder. The Euro, GEM, for Operational models would be wiser. Then the EPS, CMCE, and GEFS or a blend of them. I wonder if we really see enough cold air. A mix at times, wet slushy stuff at times down to 500′, but 750-1000′ sticking snow levels. That’s my guess. I’ll look forward to the gusty east winds I guess, but even I, yes, the Gradient Keeper himself, well, I’m done with Winter. That was a good amount of commas for those keeping score. 6 in fact. Not bad. I’m awaiting 70 degree weather. Who’s with me? C’MON!!!! Think Cold and SNOW!!!!

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