A Tough Thursday Forecast For Metro Area

Tomorrow’s forecast is a tough one for the Portland Metro Area.  So let’s focus on what we already know.

  • The coastline should be REALLY warm, by that I mean well into the 60s in some spots.  Same thing in the Coast Range and Cascades.  Even the Cascade foothills will be warm; basically any spot above 1,500′ should be springlike.  Today there were some 60 degree temps in the Cascades…more of the same tomorrow.
  • Most areas along the I-5 corridor from Longview to Eugene will see another cloudy, cool, and foggy day.  High temps will struggle to get into the lower 40s.
  • Part or all of the Portland Metro area will clear out as a drier east wind pours out of the Columbia River Gorge.  Exactly which parts get the sun are a big challenge

Strong high pressure if firmly in control of our weather along the West Coast right now.  Temperatures have surged everywhere above about 1,500.  Take a look at our tower temps on top of the West Hills this afternoon.

towertemps

38 at the base of the tower and mid 60s at the top!  That’s a very low inversion for one, and very sharp.  You can see the view this afternoon up in the 60 degree air:

Camera-LiveBugAnd the view from space at 4pm:

VIS1PDX

Within that cold layer (that most of us are living in right now), the moisture has condensed into cloud cover and fog.  That doesn’t change through at least Saturday for most lower elevation sites.

But one significant change occurs overnight that should allow a good chunk of the metro area to break free of the clouds and fog tomorrow.    A “Gap Wind” develops at the west end of the Columbia River Gorge.  Pressure gradients, which were westerly today, switch to easterly overnight as high pressure builds in quickly east of the mountains.  Mesoscale models show about 5 millibars easterly gradient from The Dalles to PDX by sunrise tomorrow.  That amount of wind should be enough to clear at least the central/east side of the metro area out by midday, possibly enough to clear areas west of the West Hills too.  Clark County is a tougher call.  It’s possible areas north of the Columbia River won’t be able to shake the fog.  Here’s the WRF-GFS wind forecast for 10am tomorrow morning:

cgw_wssfc.27.0000

You can see the swath of northeast wind exiting the Gorge south of the river and heading out towards Happy Valley and Milwaukie.  That’s very common.    In fact tomorrow MIGHT look just like December 26th from space.  Sorry to bring back that image again, but a weaker gradient produced this:

MarkSat_Tease

A tough forecast!  My gut feeling is that 5-6 millibars easterly gradient should be enough to clear out just about the entire metro area by late afternoon.  The National Weather Service thinks the gradient will be too weak to bust us out; they have a gloomy forecast for tomorrow, like today.  We’ll see how the forecast turns out.  May the best man/organization win!

Further ahead…not much to talk about still with the ridge hanging on.  Here are the 12z GFS and ECMWF ensemble plots showing temp at 4,000′ or so over the next 16 days:

tseries_850t_000-384_Portland

tseries_850t_000-360_Portland

I’ll take the -20 member of the 2nd chart please for $200!

No rain in sight, unless we get a few sprinkles next Tuesday-Wednesday with a weak upper trough passing through the ridge.  Dry pattern continues at least through the weekend of the 25th/26th

Chief Meteorologist Mark Nelsen

17 Responses to A Tough Thursday Forecast For Metro Area

  1. WEATHERDAN says:

    Becoming mostly sunny in Salem even as I write. Looks like some colder weather at the end of the month but still dry. Who knows Salem might have less the 20 inches of rain this year if this drought continues until years end. Last week the NBC news said the PDO was to blame for what some are calling the RRR or ridiculously resilient ridge. Peace.

  2. It was great hiking above the inversion today! Mid 50s up high, mid 40s just above the inversion, and mid 30s within.

    Great views of what should be a very rare treat in the gorge with fog!.

    https://www.facebook.com/US.NationalWeatherService.Portland.gov?ref=br_tf

  3. I’m thinking we’ll get another taste of winter the first week of February. Cold but dry. 2013 was super dry. If September would have been near normal our precip total for the year would have been well south of 20 inches in Salem. September was our wettest month by far. Thats messed up. Maybe I’ll head up to Mary’s Peak this weekend. 77f today, I would not be surprised to see 80f+ tomorrow or Friday.

  4. RobWaltemate says:

    What is this? Are we headed for a large drought? Is the ocean to blame? Something is different.

  5. dharmabum says:

    Like they now say in the Valley, “If you don’t like the weather, wait a month, it might change!”

  6. W7ENK says:

    The East wind is pretty much the only sure bet when it comes to “interesting” weather in Milwaukie. It’ll be nice to dry out my yard and firepit, maybe a BBQ and the first fire of the season will be in order on Friday evening?

    Mayhaps it would be a good time for my annual ceremonious burning of the Christmas tree…

    • boydo3 N Albany says:

      I used to burn my dried out tree on Earth Day but my wife told me it was totally inappropriate. I don’t know why….

    • W7ENK says:

      lol

      There’s never an inappropriate time to burn… things… :mrgreen:

      Here’s last year’s burning. Pardon the language…

    • karlbonner1982 says:

      Why not save the tree burning for Imbolc?

    • David B. says:

      Imagine a pile of dozens of Christmas trees, all tinder dry, at least 20 feet high and more wide, on Ocean Beach in San Francisco being lit afire. It happens:

  7. Sifton says:

    “If you really need to get in touch with me tomorrow I’ll be at The Sunny Hole!!”

  8. PDX Weather Nut says:

    Not good. We’ll need a February like last September (except much colder) just to get back within shouting range of normal snow pack.

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