September: Record Hot 1st Half but October Weather Next Week

10am Friday

I just checked the numbers and sure enough, you just survived the hottest start to September on record here in Portland…

First2Weeks

But the payback next week is going to be rough, we’re going straight from July weather to October in just a couple of days.  Those first two weeks of the month blew away any other early September period on record.  The average high was 85 degrees!  Plus we set 5 record warm lows and had the warmest nights ever recorded in Portland in the month of September.  You can see the entire West has been hot, but it’s balanced out by a chilly eastern USA.  This month is a “perfectly normal” month when averaged across the country

conus_mtd_t2avg_anom_2017

And of course this follows the hottest August on record all along the West Coast.

divisionaltavgrank-201708-201708

Now we’re about to see the most dramatic change we can possibly get this time of year.  Remember we’ve had a hot upper-level ridge along the West Coast most of the time since late July.  But beginning Sunday that ridge develops way offshore, in the Gulf of Alaska. Look at the 500 millibar height deviation for midweek.  If it was winter that could give us an arctic outbreak with cold/snow likely:

anomaly_nextThursday

Of course it’s not winter, but this means we’ll go from record warm to near record chilly!  The best part about this pattern change?

I EXPECT FIRE SEASON TO AN EARLY END NEXT WEEK ALL ACROSS THE REGION.  The Eagle Creek Fire is going to be out a week from now if our models are correct.  Take a look at the ECMWF rainfall and temperature forecast for the Portland area for the next 10 days

ecmwf_nextweek

We still expect rain to arrive Sunday afternoon (light rain at first) and then a big soaking Monday and Tuesday as cold showers/thundershowers/hail showers arrive.  Also look at those chilly temps!  High temperatures only in the 60s, maybe even a couple of days where we spend most of our day in the 50s!  That’s a huge change.  Now remember this is just one run of one model, but they are all showing the same thing.  Here is a peek at the ECMWF ensembles; 51 members of the same model showing 24 hour rainfall

ecmwf_24hrqpf

The first half of next week is wet, with far smaller accumulations in the rain bucket beyond next Thursday.

But there’s more!  Just about all the big fires are burning in the Cascades and look at how much rain could fall Sunday through next Thursday…first the ECMWF:

ecmwf_7dayrain

Widespread 2-5″ rain totals on the west slopes and crest of the mountains.  No fire will survive that deluge…excellent news!  Note the valley gets around an inch or so.  Then the GFS model, which has some terrain issues so don’t read too much into all that rain in the metro area:

gfs_7dayrain

Same idea, 2-5″ (or more!) in the mountains and around an inch in the driest part of the valleys.

To summarize…

  1. A VERY DRAMATIC CHANGE FROM “JULY” TO “OCTOBER” ARRIVES SUNDAY
  2. PREPARE FOR ANYTHING OUTSIDE TO GET SOAKED FOR SEVERAL DAYS, FINISH UP ANY OUTDOOR PROJECTS BY SATURDAY EVENING
  3. YOU CAN TURN OFF YOUR GARDEN/YARD WATERING FOR AT LEAST ONE WEEK
  4. FOREST FIRES WILL LIKELY BE EXTINGUISHED OR JUST BE SMOLDERING ONE WEEK FROM NOW

 

Enjoy these next two days, although light easterly wind means fire smoke will be moving around the area as seen in this AM pic from Andrew Mork:

sunrise

Sunday’s rain should put an end to our smokiest summer in memory!

Chief Meteorologist Mark Nelsen

 

25 Responses to September: Record Hot 1st Half but October Weather Next Week

  1. 0.14″ today. Radar indicates it’s mostly over. Not a gully washer by any measure, but that smoke is gone (and probably for good, as the forecast is on the damp side this week).

  2. J Patrick Moore says:

    My wife is sending me to change our furnce fileter as well. Good to see that much green on the radar image.

    • Joshua Downtown PDX says:

      Huge bust in the Portland metro area so far. Good that the gorge got what appears to be some steady moderate rain though. Thankfully, we have a few more days to get some good precipitation before we warm up and dry out.

    • W7ENK says:

      Huge bust? It wasn’t even supposed to rain very much on Sunday anyway, the bulk of the rain comes overnight tonight and all day Tuesday. That’s been the forecast for a week now…

  3. ocpaul says:

    Put a lot of the garden to rest today. Cut down the sunflowers, Pulled the tomatoes that don’t stand a chance. (It was a great tomato summer!) One more week of dry 80’s would have been perfect for the cannabis to finish. Had to build a hoop house over the plants. I hope they finish this week, without mold. So close!
    On to fall and winter. Hoping for the coldest, wettest, snowiest
    ‘on record’.
    Hate to think what all of this rain will mean for the stability of the gorge. Could be a tough Harvest Fest in H.R..

  4. Rain is here at last. Currently 61 after a high of 65. Forecast is for highs in the upper 50s for the next few days for me.

  5. Jason Hougak says:

    Fire and smoke to rain and slides in the Gorge. Trail work in the Gorge could take years to complete, especially up Eagle Creek.

    • Nahtalkin says:

      no kidding, thanks for that important information, you’re a help to us all kid. keep up the good work, and god bless

  6. W7ENK says:

    Woke up this morning to the strong smell of smoke coming in my window, so strong in fact that in my fuzzy-headed half asleep incoherent haze, I momentarily thought it was the smell of my yard on fire. Brown sky and red/orange sun all day, visibility has been down below 2-3 miles.

    And now it’s snowing ash again. 😦

  7. Roland Derksen says:

    Mark, thanks for the top 10 list of your warmest mean temperatures for Portland in the first 2 weeks of September. I compared it with my data and found the top 4 for my location were in the same order. I was a bit surprised September 1989 or 1990 weren’t included, but other than that it was much the same.

  8. Jason Hougak says:

    Winter Storm Warning for Yellowstone, Tetons and Rockies of Montana

  9. Nahtalkin says:

    Almost time to get my fall camping gear out again, now that the “glamper’s” and “touristia’s” have finally moved on to their next “experience” and the first fall rains have come and lifted the campfire restrictions. Now I can have the peaceful forest to myself in all of “her” beauty & grandeur (of course there will be a fair amount of detritus to pick up and dispose of properly but that is a fair price to pay for unspoiled solitude).

  10. W7ENK says:

    RAIN WATCH
    NATIONAL WEATHER SERVICE PORTLAND OR
    614 AM PDT SAT SEP 16 2017

    https://inws.ncep.noaa.gov/a/a.php?i=16005516

  11. Jack says:

    Significant smoke in Camas, Washington this evening. Strong smell, markedly reduced visibility.

  12. Katherine says:

    There is some concern for flooding and landslide potential to those areas affected by fire in the gorge. especially in areas with moderate to heavy fire damage. Can you speak to that?

  13. Jason Hougak says:

    Arrivederci

  14. Paul D says:

    Won’t be rough for me. Bring it on!

  15. Roland Derksen says:

    It’s going to be quite a change, but looking back a year ago, I received 1.20 inches on Sept.17th, so in a way it’s just a repeat,

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