Rain ahead, but October starts warm & dry

Well this is exciting…we’re going to see some widespread (light) rain for much of the region tomorrow.

It’s been very dry; in the past 3 months Portland has only picked up about 1/4″ of rain! That’s very stressful for our native vegetation, even with that huge soaking all through the spring months. And this September has been something else…warmest on record in Portland and Salem, and one of the warmest in other areas.


Right now September in Portland is running about like an average July 10-20 years ago! High 81, low 58.


So what’s ahead? Light showers both tomorrow and early Thursday, then we’re heading back to unusually warm and dry weather for the first few days of October. A weakening front is approaching the coast. Technically it’s an “occluded” front, but for TV purposes I left it as a cold front. One surge of rain arrives around sunrise, then the surface low with it’s attendant showers arrives tomorrow evening and night. There should be a brief dry period DURING THE DAYTIME tomorrow.


That surface low dies and is replaced by building high pressure late Thursday and on into the weekend. What about rain? Just perusing many different models gives somewhere between .10″ and .50″ for the metro area


Areas NOT showing color means less than .10″ rain forecast. Here’s the 18z ECMWF model’s precipitation forecast


You can see many areas east of the Cascades will just get a few showers. The Cedar Creek Fire in the central Cascades should get a soaking once again. Smoke from that fire drifted into the Willamette Valley today; I could smell it a couple of times while running errands.

We’re headed back to dry weather Friday through at least early next week, and even later NEXT week doesn’t look very wet. That’s because upper-level heights will remain higher than normal the next 8-12 days. Take a look at the 500 millibar anomaly for days 2 to 12 from the ECMWF model ensembles. Above normal heights through October’s first week (or longer).


GFS model ensembles are quite similar


Clearly the “wet season” isn’t going to arrive in the next 1-2 weeks. You can expect a very warm first weekend of October, then drier than normal through much (or all?) of that first week of the month.

Enjoy the showers, and a warm/dry weekend. I’ll be off on vacation through Sunday the 9th; hopefully we don’t get any surprises while I’m gone this time. Time for a 25th anniversary trip with my wife!

Chief Meteorologist Mark Nelsen

169 Responses to Rain ahead, but October starts warm & dry

  1. Roland Derksen says:

    So far the prediction for rain next weekend is still holding here- but it’s still far away. If the rain does come, the best scenario is a light steady rainfall, nothing intense.

  2. tim says:

    18z looks good but it’s the 18z it’s never right why even have it.

  3. runrain says:

    This late warm weather feels like a baseball game that goes extra extra innings, like it doesn’t belong to the regular game. It shouldn’t feel like the middle of summer right now, but it does. Very out of sync feeling when I walk outside.

  4. West Linn 200 says:

    God I hope the Euro is right. These fires that are still burning need to die already. And the trees are so parched. We need this!

    • Joshua Lake Oswego says:

      We REALLY need a good soaking. Same story with the 12z suite… GFS and GEM are terrible if you want rain in the next 300 hours. GFS ensembles are better than the operational, but drier for our part of the world overall compared to previous runs. The Euro still looks strong.

  5. Joshua Lake Oswego says:

    00z GFS and GEM are dogsh*t. I genuinely hope the Euro finally caves (it will eventually) and puts us out of our misery.

    • tim says:

      Not a drop on the 00z even for Seattle that’s impressive but not unherd of, in 1895 Seattle only had 0.02 that October so maybe we’re due if we’re gonna break records for dryness then let’s beat the 1895 record.

    • The GFS and GEM are sorry models right now. They can’t even stick to a solution before showing a different one every 6 hours. They are going to cave to the ECMWF if not meeting up somewhere in the middle. Maybe a little cooling and a little precip, but nothing Earth shattering.

    • Zach says:

      Not sure why you would bet on the GFS being right here. Its an outlier from both the EPS & GEFS in how dry it has been. The GEM is a joke, and there is no good reason to look at it anyway.

    • Well you’re gonna be waiting another day for the Euro to cave. Cuz it just continued with the same solution for the 3rd day in a row. Consistency has to count for something.

      • Joshua Lake Oswego says:

        The Euro and EPS are still solid. The 6z GFS operational is a joke. Zero rain through the whole run. The GEFS is better, but nothing too great. The GEM operational was horrible, but the ensembles were quite a bit better.

        Seems weird that both the GFS and GEM operational are off on their own compared to other ensemble members. Not just one run either. They are either on to something or completely out to lunch. I lean towards whatever the driest and warmest solution is based on the past 4 months.

  6. tim says:

    18z has 949mb low off our coast on the 27th crazy 18z.

    • Joshua Lake Oswego says:

      Unfortunately, the RRR won’t get the heck out of the way and let it swoop on in. All in all, better than the 12z, but it’s always 10+ days out.

  7. tim says:

    Mark must not have anything to say about this unusually dry/warm record breaking October maybe when things pick up he’ll post.

  8. Roland Derksen says:

    Normally, in an extended streak of dry days in October, I’d be seeing fog up here, but other than some very light misty stuff over park grounds, it’s been absent. I’m thinking there are 2 reasons: 1. The ground has been so dry from no precipitation that there is little moisture for fog to form. 2. Overnight temperatures have been consistently above normal. Warm nights mean less condensation. So, until we get a good rainfall, I don’t think fog will make much of a showing.

  9. tim says:

    00z has a couple of systems coming through then more ridgeing at the end nothing unusual for late October.

    • Joshua Lake Oswego says:

      The GFS is not trending in a good direction. The 6z is crap too. Euro and GEM still on board.

      • Joshua Lake Oswego says:

        Game over. The 12z GFS and GEM are a mess. What an epic rug pull.

        • tim says:

          A new trend to dryer?, it’s up to the euro now cliff mass might be eating his words if the euro follows the gem and gfs.

        • Zach says:

          GEFS mean is actually trending wetter.

        • The GEM and GFS are all over the place including its ensemble members, while the ECMWF has remained nearly the same over the last 2-3 days. Can’t pay much attention to individual op runs as much as the ensemble mean. Op runs do wild swings when a pattern change is about to happen like this.

        • Joshua Lake Oswego says:

          The GEFS is wetter than the 6z, but much drier than yesterday’s runs. The 12z Euro still looks solid. I still have a bad feeling about this. I very much hope I’m wrong.

        • The change is at 7 days out and ECMWF still hasn’t budged while the GFS looks unstable. It’s not a secret that the GFS spots pattern changes better between days 11-16. Inside 11 days the GFS starts dropping the ball.

  10. tim says:

    Back too reality on the 00z light mist and mild temps going into winter.

    • Joshua Lake Oswego says:

      Dude, as pessimistic as I usually am lately with anything but ridging, there is a very, very good chance we will be entering a pronounced period of pattern change by next weekend.

      It will be wet and it will be cooler than normal. Don’t forget that normal is low 60s for highs and mid 40s for lows by next weekend. It’s going to feel like fall pretty abruptly.

      • Zach says:

        Agreed. The model agreement is almost unanimous for much cooler weather.

        • tim says:

          Perhaps but models have been in full agreement for past events but only to fall apart at the seam,well see.

        • tim says:

          The Gem ensembles says not so fast buddy.

        • Joshua Lake Oswego says:

          GEM ensembles still show a pattern change next weekend, but not as cold or wet as the GFS or Euro. But… who cares? It’s the GEM.

      • West Linn 200 says:

        Not so sure about the “wet” part of that equation just yet. I’ll stick with my rule of each day out represents an accumulated 10% chance of something happening. 10 days = 10% chance, 9 days = 20% chance, and so on. We’re still too far from it and the quantity of rain predicted keeps going down as we approach closer. We’ve been burned by this too many times

  11. tim says:

    Gfs 18z is bullish again but the 18z is always on the extreme side of things which always makes it a outliar unfortunately.

  12. tim says:

    Seatac is one inch above normal from January to current date interesting how nature likes to balance it selfout that explains the dry weather.

  13. Opie says:

    Big picture…
    this April – June was the wettest on record for that time frame at PDX. Now, after 4 months of record dry, we’re nearly back to average for calendar year precipitation (still slightly above).

    Definitely a year of seasonal extremes!

  14. runrain says:

    Temps in the 80’s this week. In a little over two months the days start getting longer. ‘Nuff said.

  15. Joshua Lake Oswego says:

    Looks like PDX just missed out on a low below 50. There hasn’t been one since May 22nd!!!

  16. tim says:

    Well cliff mass thinks there’s a big pattern change coming on his latest blog but cliff has the tendency to jump the gun too soon,well see.

    • tim says:

      Why did cliff say winter will start on October 21 this year if models are right we’re just gonna have our typical rain and cool temps for late October at best,odd.

    • Roland Derksen says:

      I think there will be a big pattern change, though I’m not sold on the date exactly. In any case, if there is, I’m worried about the effect a sudden big rainfall could have on the trees and forests. A lot of rain after a dry spell can cause damage. An AR especially.

  17. Joshua Lake Oswego says:

    00z GFS looking sexy by day 10.

  18. tim says:

    The Weather is so dead Mark isn’t even posting this week or is he?.

    • Paul D says:

      He’s back in town, but why bother.

    • Joshua Lake Oswego says:

      My $.02… I’m sure he will post soon about the ongoing record-shattering warmth and persistent dryness. He will have to mention the apparent likelihood of at least a temporary pattern change in about 10 days.

  19. Roland Derksen says:

    No rain here yesterday either. Just some clouds and breezy conditions in the evening. I’m not giving up on rain here this month yet- but as the day progress it appears we may have a chance to beat October 2002 for driest ever October.

  20. tim says:

    Well I happened Seattle ended it’s October drought with OO.1 of rain at seatac this morning the rivers are flooding in my backyard..

  21. Joshua Lake Oswego says:

    The Euro, GFS, and GEM ensembles all show a pattern change to troughing emerging in 10 days. The 12z GFS operational was an outlier.

    • tim says:

      Well I don’t think we’re gonna get any thing more than run of the mill systems and that’s being generous.

    • tim says:

      The euro and gem ensembles are in agreement but the gfs isn’t as bullish.

    • Bethany250ft says:

      The 06z GFS was showing a massive snow dump in the cascades, over 80″ in some places! Obviously unlikely but it was fun to look at

    • Timenators says:

      I’m with Joshua on the pattern change. I still believe in the infamous “fall” to “winter” light switch occurring in the Portland area every year. Can’t recall a year(rare) where it didn’t do that. I say we place some $$ on it with Tim, ha!

  22. tim says:

    Record highs again for Seattle and Portland Saturday if current forecast holds and if no inversion occurs.

  23. West Linn 200 says:

    GFS has been bullish on pattern change since the 18z yesterday hmm. Not just wet, but colder too with freezing temps over many states. It’s still 11-12 days out, but it’s interesting to see nevertheless.

  24. tim says:

    I’m sure Mark will post tomorrow today’s a holiday.

  25. tim says:

    18z gfs is looking decent for rain but it’s the 18z, I don’t think it’s gonna be a like a light switch from bone dry to extreme wet. Dryer then normal is more likely through the end of the year.

    • Tim, it’s not out of the ordinary for the switch to flip like that from summer dry to Autumn rains. It’s like this because we live 100 miles from the Pacific Ocean. We went from pretty wet to pretty dry in June so why not the other way around in October?

  26. tim says:

    00z is wet at the end but again models been breaking down the ridge too soon this fall for some reason.

  27. Oliver says:

    I’ve been listening to some different stuff on YouTube from different forecasters. It seems from what I gathered that the mjo and water temps of the Pacific ocean play a part in where our ridges and troughs set up. It seems that over the last 15-20 years the ridge has been setting up more over us, whether it be winter, spring, summer, or fall. The question is why is the ridge so persistently over us and not a few hundred miles east or west of us. If we can figure that out we may not have to waist so much time model riding

  28. Oliver says:

    Our models are broken and useless. I always wanted to be a meteorologist from the time I was 10. I loved active weather and studying weather patterns. I’m sure glad I never went into the field at least here in the Pacific Northwest. It’s totally a different place than the early 90’s. I don’t feel like the rules apply anymore making forecasting or even understanding it so frustrating.

    • Michael says:

      I think this same scenario is developing in many parts of the globe, hopefully causing our attention to go back on faith and prayer, a very good thing.

      • Peter Christenson says:

        Do you mean go back TO (rather than ‘on’)? In any case, I won’t do that.

        • Michael Gelien says:

          If these times are the beginning of the prophetic times, ‘coming on like birth pains’, gives us a chance to begin trusting Him.

  29. Oliver says:

    Anymore when is see the models trying to break down the ridge and give us more normal weather they are basically just tired of the same old pattern we’ve been in and are saying ” come on! In the past we would swing the other direction in such a warm dry pattern, it’s bound to happen again. It’s just totally different times we are living in with no indication whatsoever that we will ever go back to the good old days

  30. Oliver says:

    I really don’t think we can put our trust in any analog, or el nino or la Nina, or pdo, or pna, or solar cycle or any other index anymore. They COULD have a bering but there is so much going on that we don’t understand or know about that really make believing the models more than 3 days or more out useless. They playbook is being rewritten as we speak

  31. Paul D says:

    The new normal is here.

  32. tim says:

    18z gfs is more fall like but that Pacific ridge isn’t too far away either.

  33. No doubt. says:

    Guys seriously would it be possible to have an entire fall and winter this warm and dry?? That would be devastating for next year fire season.

  34. tim says:

    Both 2014 and 2015 Octobers we’re record warm months which we’re followed by warmer than normal winters this October so far is record warm does that mean this winter will be warmer than normal too?, Maybe.

  35. Garron Slocum near Hillsboro airport says:

    Again another record-breaking month back to back to back? That would be a game changer we have 3 months in a row of bone dry record-breaking Heat! Today looks like we’re going to overachieve again on the temperatures and hit 90? Hashtag middle of october?

    • Joshua Lake Oswego says:

      Yea. Hottest week ever in July, hottest month ever in August, hottest September ever, hottest October ever and most anomalously hot month ever. Longest 70 plus high streak ever, longest 50 plus low streak ever (active), 40 straight days above average, 72 out of last 77 days above normal (active). Driest astronomical summer ever, driest 4 months ever looking possible, longest streak without at least .15” in a day ever (active).

      The good news is that it literally cannot be worse.

  36. Patrick says:

    When does Mark post again? Where the hell are you? I miss your updates.

    • West Linn 200 says:

      Vacation until today. Read the last paragraph in his blog post, he’s celebrating the 25th anniversary with his wife. He’ll be back soon, so hang on.

  37. Roland Derksen says:

    A chance of precipitation here on Monday- but it’s declined to 40%. Some winds with it should help clear the air.

  38. Patrick says:

    88 here in Hillsboro, must be a record.

%d bloggers like this: