A Late Summer This Year

We’ve only got 2 more days to go this month and it looks like August will end up right around average.  That’s due to cooler than average temps the first part of the month, then a very warm 2nd half of the month.  Now this workweek appears to be quite chilly with marine air dominating west of the Cascades.

That cooling is just in time since all the lightning late last week started dozens (maybe hundreds) of fires across central and north central Oregon.  The latest (the Dollar Lake fire) flared up the last couple of days and is now burning southwest of Laurance Lake and a few miles north of the summit of Mt. Hood.  A huge plume of smoke was towering over the Upper Hood River Valley all day today.  I see temperatures at the 5,000′ elevation have plummeted into the 40’s this evening up there as a cooler airmass moves in.  It’ll be here through Thursday, and maybe Friday, so firefighters have plenty of time to get caught up.  And I don’t see any lightning pattern either.

Starting this weekend, we appear to be headed into a very warm early Fall pattern with easterly surface flow at times and a dry airmass.  This is one of my favorite weather patterns of the year.  It’s not uncommon to have a crisp low around 45-50 and a high of 90; a huge daily range due to the dry air and long nights with a warm airmass overhead 24 hours a day.  We went somewhat conservative with our 7 Day forecast due to models uncertainty about placement of a thermal trough.  For example one run of the GFS showed a strong thermal trough west of the Cascades for quite a few days beginning Saturday.  But the ECMWF showed weak onshore flow, or at least a loss of offshore flow, Sunday-Monday.  That can make a huge difference in high temperatures.  You need easterly flow at the surface to get hot after the 1st of September.

Chief Meteorologist Mark Nelsen

46 Responses to A Late Summer This Year

  1. bgb41 says:

    8/30/2011 Oregon (All) Temperature Summary

    High:96 at ALKALI FLAT(2495 ft)
    Low: 65 at CW4650 Pendleton(1152 ft) & Blalock(280 ft)

    High:50 at MUD RIDGE(3800 ft) & HEBOWX Mt. Hebo(3160 ft) & WANDERER’S PEAK(4350 ft)
    Low: 27 at DESCHUTES PORTAB (5100 ft )

    Largest Diurnal Change: 52 degrees
    DESCHUTES PORTAB (79/27 ) (5100 ft )

    Heaviest Rainfall:
    0.08″ at WANDERER’S PEAK(4350ft)
    0.05″ at TIDEWATER(2035ft)

  2. pappoose in scappoose says:

    Hahaah! Great minds think alike eh Mark? Tuned in to your broadcast and felt like I was still at the computer watching the fires from space!

  3. Tyler in Battle Ground says:

    66 for the high in Battle Ground today, even cooler than forecast! Tomorrow has the potential to be the same!

    If it’d clear up tonight we’d probably drop into the mid 40’s.

  4. boringlarry says:

    …Hey y’all…hows it going?..as i gear up for the last human tsunami of the year…anyone feels like any fall visiting, I’ll be up at Clear lake from mid sept. thru early october, then up at the old ripplebrook ranger station for the winter, so I’ll be able to report conditions in the upper clackamas area thru march, at least, with internet access…yay!!!!!!!…talk to all my friends soon….

  5. PaulB/Eugene says:

    Headed to Dallas TX for UO/LSU game…should still be toasty down there..then off to Cabo San Lucas Sunday…there is an outside chance I could experience some sort of tropical cyclone there..probably a weak tropical storm…..more likely diarrhea.

  6. pappoose in scappoose says:

    Tropical update, sure hope the date is correct:

  7. Garron says:

    I remember the start of my senior year,September of1988, took marching band for an” easy “elective credit. We had a performance at a Labor Day thing in downtown Portland at Civic Stadium, on Sept, 5th,so we had a final rehearsal march the Friday before. I got stuck carrying the bass drum, and had to practice for 3 hours the day it was 104! Long story short, there are no easy A’s!!!!

  8. pappoose in scappoose says:

    Lots of blue skies at this moment in the land of gravelly plains.
    Guess I’m one of the few with this kind of activity.

    National Weather Service Portland or
    825 am PDT Tuesday Aug 30 2011

    Short term…satellite pictures show marine clouds covering much of
    the forecast area this morning…with sle sounding indicating the
    depth of marine air around 5500 feet deep.


  9. pappoose in scappoose says:

    Here are the local forecasts off the 7-day posts:

    KATU 86 87 90
    KOIN 86 90 89
    KGW 85 88 90
    KPTV 84 90 88

  10. Runrain says:

    I remember Oct. 1979. The first week of that month we saw a few days of 85-90 weather. What I’d REALLY like is a first week of November that has a couple days pushing 70. Then, after a cold and snowy late Nov – early Feb we push 70 towards the end of Feb. Thats all I ask. Not much!

    • Nichole says:

      I like your thinking, that sounds just fine to me.
      We can only hope.

    • Karl Bonner says:

      Well, at least flirt with 65 in late February…it would take a REAL fluke to ever hit 70 without some kind of south/southwest wind.

  11. I love warm September days, with nice cool nights. Come on 110 degrees a week later than we’ve ever hit 100!……

    • Ryan (Walnut Grove) says:

      Even with cool September nights if we hit 100+ during the day we will remain uncomfortably warm at night.

  12. Chuck on Mt Scott says:

    A late summer it will be. I was telling my son that I want to take up skiing again this winter. We have been camping up on Mt Hood and it has given me the bug to go enjoy the snow once again. Thus, Snow will not start falling until well into December 🙂 Earlier this year, I told him I wanted to take him camping more. Well, Summer got a late start, so why shouldn’t winter start late too? This is not scientific and is more of a Murphy’s Law type forecasting.

  13. Timmy_Supercell (Klamath Falls @ 4200') says:

    Not heat related, but I wanted to bring up something about the F3 Vancouver tornado…. April 5th, 1972 = KPDX had a high of 61F with a dew point of 48F (thats not incredibly moist) and aside from the actual tornado, I heard there was quite the thunderstorm outbreak with lots of fairly strong winds and some large hail too.

    And the convection was I believe that of a ‘textbook’ kind of event we’d see on a hot/sticky June afternoon with a great deal of instability (by PNW standards anyhow). Reports indicated a single cellular supercell storm rushed to the northeast (tornado producer) followed by a line of severe convection behind the supercell.

    The only things I haven’t found out about this day (yet), are how much instability was present, and what kind of shear amounts were we dealing with? Those two parameters must have been in great quantity to be able to allow this event to unfold like it did, under only 60+ degrees on an April afternoon. And April alone is just not a month that we see anything close to this, it would normally take until at least late May to early July before we start to see more organized convection. And I am also really interested in seeing some sort of 500mb map on this low pressure system that produced the F3 tornado.

  14. Karl Bonner says:

    If Portland gets a hot east wind this weekend and next week, I wonder what The Dalles temps would be like *relative to those in Portland* ? A couple days ago the ECMWF called for much cooler 850mb temps east of the Cascades than west for Saturday and Sunday, which would have felt more like early fall than late summer had it come to pass. I suppose it could still re-materialize, but the ECMWF no longer shows any signs of a wannabe cP airmass east of the Cascades this weekend. When the trough exits, everybody warms back up nicely.

  15. bgb41 says:

    Tonight will mark the 11th consecutive night of above average lows at PDX.

  16. joe3986 says:

    hey with the possiable heat wave will the leaves still change with the longer nights does the heat affect it at all

  17. Thanks for the update, Mark.

    Heat wave? It all depends on how amplified the ridge is and where the axis position is….

    Prediction: One of the next 4 runs of the GFS/EURO will show a 99 on model output guidance or the extracted data.

    • Boydo3 N. Albany 500' says:

      Great time to be at the coast! Offshore wind with curling blue waves begging for a surfer. And then…damn that water is frigging cold!

    • Ryan (Walnut Grove) says:

      GFS is backing off a little bit on the overall heat… Cools things down a little bit after the weekend. It does keep the toasty temps in the extended though.

      Considering some of the swings on the GFS going from mild to blow torch to a more moderate solution I’d stick with EURO guidance.

  18. bgb41 says:

    Lets not forget September 1974. It could happen again.

    • Mark Nelsen says:

      Yes…never forget…

    • chiefWright says:

      And for those of us who have lost most of our brain cells, could those of you who haven’t remind us of September 1974?

    • pappoose in scappoose says:

      Hahaah! I’m on that train as well chiefWright.

    • Runrain says:

      All I remember about that time period was playing in the marching band at Oregon State and attending games in raw, cold, rainy weather with about 10,000 fans in the stands. That was more like Oct or Nov, ’74, but shows how quickly things can turn around.

    • boringlarry says:

      I turned 21 that year, and most memories are unsuitable for a family blog :)…

  19. bgb41 says:

    8/29/2011 Oregon (All) Temperature Summary

    High:96 at Nelson(2560 ft)
    Low: 69 at HERMISTON(550 ft) & Blalock(280 ft) & Rufus(185 ft)

    High:55 at SOUTH FORK BULL(2630 ft) & NORTH FORK(3120 ft)
    Low: 28 at DESCHUTES PORTAB (5100 ft )

    Largest Diurnal Change: 58 degrees
    DESCHUTES PORTAB (86/28 ) (5100 ft )

    Heaviest Rainfall:
    0.30″ at BLUE MOUNTAIN SP(5900ft)

    • Garron says:

      58 degrees,that’s quite a range! We should get some large swings in temps next weekend, not to mention the tower temps and cascade foothills might stay above 70 degrees at night with strong easterly outflow. Seems like the first REAL east wind activity of the summer!

  20. Mike near Clackamas Town Center says:

    I’m betting the Euro 00Z will show the same thing the GFS did earlier and that was a possible historic heat wave for next week.

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