Unusually Warm and Sunny Start to October

8pm Sunday…

Now that we’ve seen a nice soaking across most of the region, it’s time for some classic early fall weather. Cool nights and mornings plus briefly (very warm) afternoons. Fall in the Pacific Northwest is typically like this; rainy periods alternate with bright sunshine. The key messages…

  1. It’ll be all dry through at least next Saturday/Sunday
  2. Temperatures reach 80 degrees or warmer Monday through Friday
  3. A gusty east wind blowing out of the Gorge will arrive in the metro area tomorrow, then come and go through Friday.
  4. Fire smoke is unlikely to return in any significant fashion in the lowlands. But high-level smoke from California likely arrives Wednesday. Expect much hazier conditions Wednesday-Friday

Today was about as normal as it gets…we hit 51 last night and 75 today in the city. 1 and 3 degrees above the 30 year average. Strong high pressure is now in place overhead. Here’s the view for Tuesday…

The typical fall jet stream is diverted far to the north and then plunges south into the Great Lakes region. We go much above normal and they turn very chilly. It still looks similar NEXT Sunday, October 4th, although the ridge has “flattened” a bit. That could lead to onshore flow and areas of fog/clouds. We’ll see how that plays out.

Regardless, rain is not in the cards through at least next Sunday. Actually the GFS model ensembles (newly upgraded last week!) show the ridge popping up a bit again early-mid NEXT week. Here’s Wednesday the 7th (click for a better view). Warm colors indicate a positive (warm) upper-level height anomaly.

The ECMWF and Canadian models look the same. So confidence is relatively high that we have a dry (or mainly dry) 8-10 days ahead.

How warm? 850mb temps over Salem sit between 20-23 for the next six afternoons! This would be a major heat wave in summertime. But this time of year a “heat wave” is 80-90 degrees. We appear to have good offshore flow the next two days, then it backs off a bit Wednesday. A bit stronger again Thursday, weakening Friday. At no time do we have a strong east wind event. More of a typical “gusts 40-55 mph in the Gorge and breezes over the mountains” setup. That begins tomorrow. I’m going with these numbers…only Tuesday and Wednesday would be close to record highs.

If you don’t like warm/hot weather, at least this time of year long nights mean we’re back in the 60s soon after sunset. Lots of 40s/50s for overnight lows of course.

I just check past Portland weather stats to see how uncommon 5 days in the 80s is this time of year. Not unheard of, but somewhat unusual. So how many days have we made it to 80 AFTER this date? This will be the most since 2014-2015.

But you have to go all the way back to my first year in TV…1993 to find another early fall with this many 80 degree days. Definitely unusual. In 1987 we saw 8 days at/above 80 this late in the season, and 1991 was similar.

Everyone keeps asking me about smoke…will it come back? I think that’s a yes/no question.

  1. Little or no smoke was visible on the perfectly clear GOES-17 satellite image today. There’s no reason to believe any of our local fires will suddenly start raging out of control or even put up a big plume of smoke again. That’s due to wet forest, no strong wind forecast, and some good fire lines.
  2. But, communities close to those fires may be smelling smoke regularly again or we could even get a slight haze down here in the lowlands. That should be about it.
  3. MORE NOTICEABLE…As the upper-level high shifts slightly east of us late Tuesday, a southerly flow opens up overhead. This means Wednesday-Friday could see a lot of milky/hazy sky overhead with filtered sunshine. Hopefully that wouldn’t make it all the way down to the surface.

Here’s the GEOS-5 modelling that shows smoke about to arrive Tuesday evening. You can see the center of the upper-level high around La Pine at that time.

By the way, check out this 20 year span of Portland metro area PM2.5 pollution. Except for last year, our late summers have turned smokier; you aren’t crazy in thinking that’s the case. The poor air quality you regularly see in late fall and early winter is due to inversions; common due to weak sun angle and long nights. Data is from EPA

35 Responses to Unusually Warm and Sunny Start to October

  1. W7ENK says:

    The sky is orange and the Sun is red again. Let’s hope the smoke stays off the surface, but it looks like it’s already trying to filter down. Visibility of the West Hills from here is clearly dropping into a thickening haze…

  2. Roland Derksen says:

    The smoke is back- it was noticeable yesterday with the red sunrise and sunset. It’s not as thick- thank goodness, but until we get a major change in the weather, it looks like it’ll stick around again.

  3. Grizzly Bear says:

    Love this time of year, we are entering the seasons of uncertainty, it’s anybody’s guess what kind of weather we will see in the next 5 months. The crystal balls are starting to cloud up.

    • Jake in Gresham says:

      I know right, especially since the La Nina probability is up from 75% to 80%. It is anyone’s guess and the opinions are why I’m here too. I hope we get more arctic air, lowland snow even if it stops at the foothills because if it’s all rain and not much with cold arctic air often enough? There’s some big mudslides occurring from all this charred Cascade foothills. My buddy likes hunting out East of Estacada. He said it is unrecognizable and the forest service is really freaking out about repairing roads and stabilizing the hillsides there as best they can before the Fall.

      • Ken in Wood Village says:

        Hey Jake, it’s been awhile since we talked!! One thing I have been noticing is the Jet Stream. I think that is going to be a big factor for this season. If you look at the models, you can see the Jet Stream has is very active and fairly strong. With the Jet Stream this way, storms should be able to race across the Pacific into the PNW more but also, some of the Low’s will tape into this strong Jet to possibly create a windstorm.

        We’ll see how things go this fall/winter season 🙂

        • Jake in Gresham says:

          Oh it’s always the factor in my book and whatsup! I think it’s going to keep us busy mainly because I know from past early Fall seasons that the La Nina will at least carry through Fall if I see a strong Jetstream. What I really care about is Winter activity. I think this will be a good Winter but it is my hunch based on us kind of being due for a snowstorm.

        • Ken in Wood Village says:

          I’m doing good. My mom on the other hand isn’t. I was told back on Sept. 18th that she has from 6 months to a year to live. Her kidneys are not doing well and she has become to weak to do dialysis so it’s not looking good. Sorry for putting a downer on the blog.

          Gong to what you wrote. Yes, I believe this winter season could be interesting. Not only do I believe your right about a snowstorm but with the Jetstream and the possibility of wind, maybe we could see a blizzard too.

          I think this Fall/Winter season could be very active and interesting. It’s just a matter of waiting and seeing how this seasons play out.

        • Jake in Gresham says:

          Hey good to hear you are well and that is rough. Disease seems to be the theme for 2020. I don’t know what climate change will bring to us next.

          For sure, I have high hope for an active Winter but that is my guess if I were to make one. And I could only wish on a blizzard. I know some here have been comparing the La Nina projection and Jestream strength to 2007/08 Winter season where as you well know we had blizzard-like conditions occur. Time will tell!

  4. ocpaul says:

    No certainty we’ll get the goods this year, but, the 9-10 ENSO is calling a 80% probability of a La Nina Fall/Winter. Fingers crossed.

    • Ken in Wood Village says:

      Thank you for the link. The models look good for a La Nina this Fall/Winter.

      I’ve been watching the Euro and GFS models and I’ve been noticing the models are pumping out some very strong storms in the Pacific. If we were to assume the models are correct, around the 8th we could start getting into a active weather pattern.

      With that being said, I’m thinking there is a good chance we also could see a major windstorm this Fall/Winter season. One reason why I believe we could see a windstorm is how strong these lows are showing up in the models. All we need is one to form just right and move just right off the Coast to cause the PNW to have a major weather event.

      This is just my opinion. I also feel it in my gut we will have a major windstorm. 🙂

      • Andy says:

        I agree with you on a stormy fall and possibly an active winter. Some weather experts are saying we could have an active fall here in the NW. The Farmers Almanac is pretty much the opposite… though I have little faith in it for the NW.

  5. Joshua Lake Oswego says:

    Looks like this will either be the warmest or second warmest September ever. That’s with a week or so of smoke keeping our high temps up to 30 degrees cooler than they otherwise would have been.

    Without data to back it up, I will go out on a limb and say that this will be the warmest ever first 10 days of October too.

    Looks like a pattern change MIGHT actually happen at the end of next week. Let’s hope the RRR stays away until next July.

  6. runrain says:

    There are swarms of stink bugs flying around this afternoon. Anyone else noticing this?

  7. Roland Derksen says:

    There’s a chance- although a slim one, that I’ll see an 80F temperature here in the next few days. It’s really rare at this time for my location up here in coastal BC. The last time I recorded that temperature in October was back in 1980.

  8. Joshua Lake Oswego says:

    So much for the long nights this time of year equaling quick cooling after sunset. Still 64.5 degrees here at 4:30am. It was 72 when I went to bed at 10pm.

    • Andy says:

      Cooled off much faster here in Albany, My weather station showed 48 deg for the overnight low. I think the urban heat blanket from Portland and surounding cities have created localized heating at night. Would be interesting to see how the growth of Portland metro area has changed temperatures over the last 25 years.

      • Joshua Lake Oswego says:

        I think it was because of the east wind. We ultimately dropped to 57.7 and the humidity increased quite a bit after I checked at 4:30am. Wind must have calmed down a good amount a bit before sunrise.

    • runrain says:

      I sat out on the deck at 6am this morning drinking my coffee is shorts and a tshirt. My thermometer said 68 deg.

  9. tim says:

    Does anyone know if the gfs operational runs were upgraded last week with the ensemble also?, if so whould it be on tropical tidbits? thanks.

    • Joshua Lake Oswego says:

      The operational was upgraded last year (FV3). I believe there is another upgrade proposed for next year. As you said, the GEFS was recently upgraded. The HRRR will be upgraded in November. A lot more ECMWF/EPS data/charts will be available for free in a week or so.

  10. W7ENK says:

    Anyone else notice the interesting little recurrence of poorer air quality on the same day every year, almost right in the middle of the graph?

    I’m willing to bet that’s the 4th of July…

    • lurkingsince’14 says:

      It’s a very nice visualization – the wildfires certainly pop out but I’m surprised by just how often the fall/winter stays in the moderate to unhealthy zone. Would be curious to see how that compares with other parts of the state 🧐

      • Phil says:

        Yes, wouldn’t it be better air quality in the winter with consistant rain and stormy weather scurrying out stagnant air? I can see having bad air under a strong inversion but usually the winters have crisp clear skies on a clear winter day. At least over here in Beaverton. Maybe it has to some do with some degree people burning wood in fire places to heat homes?

  11. Ken in Wood Village says:

    I’m seeing something way out on the 8th of October. I know it’s way out there and most likely won’t happen but it’s interesting to see. Both the Euro and GFS model are showing what is left over from what I think could be a hurricane (it shows the low/hurricane at 954mb SW of Baja California on the 3rd) then it moves up and merging with a low from the West around the 8th. If that happened, we could probably see a lot of rain and maybe wind.

    Like I said, that’s a long ways off and probably won’t happen but it’s something to keep an eye on the next few days.

  12. Roland Derksen says:

    Great to see the sun again- I know, the rain was needed, but I had over 4 inches in 3 days here. That’s more than normal for September.

  13. Mike says:

    Thank You Mark for always taking the time to forecast with yearly comparisons. It’s so interesting with everything the way you put it in perspective.

  14. Kyle says:

    Wouldn’t it be nice if Mark or somebody had an archived multi-day day forecast as far as their records go?

  15. Grizzly Bear says:

    Great weather ahead, maybe “Gov Kate” should throw a Vortex 2 to get all the bad boys and girls out of Portland. “Make love not war”…. 50 years later !!!

  16. JohnD says:

    Let’s enjoy it (nice weather) while we have it! Good heavens, amid everything else that is going on! I guess it remains to be seen if there is a “Weather Conference” this year (at least other than virtual); but some of the astute are already noting the potential for a significantly different year vs. the last couple—evolving especially by prime time (e.g. late Dec.)
    Who know? But fun to speculate. What we do—right?!

  17. tim says:

    No, not another 2014/15 fall/winter that was awlful, i guess i won’t hold my breath for la nina after all, dam.

    • Tanis Leach says:

      Its only late September, normally La Nina patterns don’t take full shape until November or December from what I’ve noticed.

  18. Joshua Lake Oswego says:

    Looks like another 6 month summer.

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