A Beautiful Start to October

6pm Tuesday

It’s only the 3rd of October, but we’ve already seen more sunny days than ALL OF LAST OCTOBER.  Today is considered a “clear” day and last year we didn’t have a single clear day.  Remember October 2016?  The rainy season began a month early last year.  Lots of clouds…

And of course it was a big soaker as the jet stream ramped up early.  Last October was the 2nd wettest on record in Portland

In a typical October here, the first half (or more) of the month is reasonable; occasional weak weather systems mix with sunny/dry periods.  But last year the rainy pattern began in earnest immediately.  My neighbor told me it was the last straw…he sold his house and moved to the Desert Southwest this past summer.  He should have stayed one more year because the first 10 days of this month still look fantastic.  That’s due to high pressure in the upper-atmosphere wanting to linger nearby or just to our west.  You see the current IR satellite image with the stable “high over low” pattern along the West Coast.  That means the jet stream is going well north, then swinging south around the high and then low. This pattern also gives us a nice & warm offshore flow regime at the surface.


That gave us the warm temperatures in the lower 70s this afternoon.  Expect a few degrees warming the next 3 days.  Now Saturday and Sunday (sorry about the weekend timing) the high breaks down with a strong WNW jet stream just to our north.  That pattern will bring in a very thick marine layer plus lifting.  TranslationExpect a very gray and cool day Saturday with a good chance of drizzle or light showers.  That will linger in the mountains through SundayResultThis weekend will NOT be warm & sunny.

But then high pressure develops right over us again for a quick return to offshore flow and sunshine next Monday.  This shows up nicely in the ECMWF relative humidity cross-section.  I’ve circled the weekend.  Thick saturated airmass up to Timberline Lodge or so = gray days.

The 2nd period of warm and mainly sunny weather may last a good chunk of the 2nd week of October.  Yes, it’s possible most of the first half of October will dry and pleasant!

The ECMWF ensemble 24-hr precipitation chart shows that 2nd dry period, then quite a bit of “noise” from the 13th onward.  That’s because the basic pattern appears to change after the first two weeks of the month.  The ECMWF/GEM/GFS models all show upper-level troughing (low pressure) developing in the Eastern Pacific for the 3rd week of October

And here is the corresponding weekly precipitation anomaly (drier than normal is brownish) for NEXT WEEK

Then the 3rd week of the month…looks like wetter westerly flow may come back after this two-week period of mainly dry weather.

By the way, we will be close to the frost point in only the coldest outlying areas west of the Cascades tonight.  I think 99% of us westside will remain frost-free for at least the next week though, and that’s not unusual.  Most areas west of the Cascades don’t get a first frost until the 2nd half of the month or even early November.

Enjoy the sunshine!

Chief Meteorologist Mark Nelsen

28 Responses to A Beautiful Start to October

  1. WEATHERDAN says:

    The morning sun touches the dew. The dew kisses the grass. Well what a beautiful afternoon it is today. 63 after a low of 39. Nice to see the Autumn colors changing the leaves. I sure do love poetry though. Peace.

  2. Lee Wilson says:

    Brrrr…had to run heaters last night lol.

  3. Joshua Downtown PDX says:

    The urban heat island has been crazy this week. The temps when I leave my house just before 6:00 have been between 49.5 and 51 the last 3 days. PDX made it to 42 yesterday. It has been 12-15 degrees warmer here than the coolest spots in the metro area.

    • I used to live just west of downtown Portland some years ago, and when riding my bicycle home at night via downtown was often impressed by how much warmer it got right after I crossed the river. All those tall buildings have vertical surfaces that tend to radiate back and forth to each other instead of out to space, and it really makes a difference.

      If you want to experience the opposite effect, try visiting the mouth of Balch Canyon (aka Macleay Park) some evening. I lived there for a couple of years and my evenings were as much as 17°F cooler than the automated ODOT Fremont Bridge weather station.

      41°F overnight here. Many areas in my region have seen thirties already but the nearby salt water is delaying that inevitability for me (at least for now).

    • Joshua Downtown PDX says:

      Interesting to know about Macleay Park. Thanks. Time to find a place near there. Ha.

  4. W7ENK says:

    Bright sunshine, blue skies, wispy high clouds, comfortable daytime temps, dry leaves swirling and skittering across the ground in the breeze, chilly nights, sometimes with a touch of fog… The weather this week has been glorious!

  5. Nahtalkin says:

    32 degrees here this morning first heavy frost of the season, all the roofs and yards white with frost.

  6. Jake-(Gresham near Nadaka Nature Park) says:

    Fairly upset this week. Glad to see the weather will be really nice. Have to cut down a plum tree my great grand father planted. Carpenter ants got to it. Last Winter was too much. Peeved.

  7. Lee Wilson says:

    ELEVATION 1722.0 ft.

    Congratulations on 2 cities getting their first freeze!

  8. Lee Wilson says:

    KOROREG061 Oregon,OR
    45.8 ,-123.3 ELEV:650 FEET
    29 degrees F!
    The done got thier first freeze!

  9. ocpaul says:

    38.7 at 300′ in Oregon City.

  10. Lee Wilson says:

    Hey Marc, were 300 dollars in credit to the PUD. because of the Awesome summer we had.

    Which meant we Didn’t have a PUD bill to pay this month.

    were working on Upgrading our battery bank so we can run everything we have off solar.

    I hear in some areas, Weatherman use solar and wind energies to power weather labs.

    and heck our Space station in orbit uses solar to power heaters, Co2 Scrubbers and the like…So we are going to challenge our selves this winter to keep our PUD under 30 kw-hrs no matter what.

    seeing how we can’t get our Dryer off the grid..Yet…

  11. Lee Wilson says:

    We are at 36 this morning.
    and I got a bad feeling about this winter.
    How Many of you remember this from 10 or was it 15 years ago?

    Yes, I have been keeping records of our winters 🙂
    and it is rare photo’s like theses that serve as a reminder, we can have some very bad winters.,

    • Lee Wilson says:

      I had used the T-Mobile “Wing” for those photos

    • Jake-(Gresham near Nadaka Nature Park) says:

      Oh I don’t think we have to look that far back. My bones still recall last Winter well!

    • No, the bad winters are the disappointing ones where it doesn’t measurably snow at all in the lowlands.

    • Lee Wilson says:

      Not sure what you get no mewrable snow fall….especially when we had to make up school due to snow and ice….and we had a lot of snow last year.

    • Roland Derksen says:

      I didn’t think winter 2007-08 was all that bad where I was either. A little more snow and cooler than normal perhaps, but the winter after that (2008-09) had a lot more snow and freezing temperatures.

  12. MasterNate says:

    I hope they get that Radar fixed before the real fall weather arrives.

  13. Paul D says:

    Really enjoying this weather! Easy to rake the leaves when it’s dry 🙂

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