Warm Summer Nights & Improving Weekend Outlook

I’ve heard a few complaints this summer.  Not about the hot days (there haven’t been many), but the warm and humid nights.  A good reason for this…3 times we’ve seen a humid air mass overhead and/or light showers in the area for several days at a time.  It happened just before the 4th of July, a couple of weeks ago, and now it’s happening again this evening.  Dewpoints are way up in the 60s again.   Tonight and two weeks ago we have been in a pattern with moist flow coming up from the south on the back side of an offshore trough of low pressure.  It’s sitting just close enough to give us moisture, but not close enough to give us a big marine push with the cooler air.

Take a look at the 60 degree or warmer nights over the past 8 years:

Mark_Nights_VeryWarm

We will end up quite close to June-August of 2009.  Of course that summer saw tons of hot days, but not much of the humid weather.  Brian Schmit put together this chart showing that this August will end up #2 for 60 degree nights here in Portland since 1981.

60degreenights_brian_schmit

The urban heat island effect is more dramatic the last few decades due to the growth of the Portland Metro Area, but it seems to me we’ve had more of these “humid nights” the 2nd decade of my career compared to the first.  I can’t believe that this fall I will have been doing television here in Portland for 20 years!  Add on 2 years of non-television forecasting before that and I’m becoming an old man…22 years in meteorology.

Thursday could be a real interesting day.  Lots of tropical moisture, good lifting as the upper-low offshore kicks out, and some afternoon sunbreaks.  I think we’ll see thunderstorms around that could be real juicy.  00z WRF-GFS and our RPM are both showing that.  They are also showing some “training” of shower bands later tonight and early in the morning over our area.  That’s when a line of showers moves parallel to the upper-flow, allowing one shower after another to move over the same area.  With such a juicy atmosphere overhead, SOMEONE IS GOING TO GET SOAKED.  Not sure exactly where that will be.  We’ll know within 12 hours.

Beyond tomorrow, the big story is the 2nd upper-level low’s movement this weekend.  Once again models have slowed things down.  Plus now they are showing some offshore flow for Saturday = hot for the last day of August.  Labor Day Weekend is looking better and better!

Chief Meteorologist Mark Nelsen

119 Responses to Warm Summer Nights & Improving Weekend Outlook

  1. schmit44 says:

    SEPTEMBER 2013 WEATHER FREQUENCY CONTEST — Entries close at midnight tonight
    http://www.directpaintsaleswa.com/SEPT2013/add.php

  2. pappoose in scappoose says:

    Mark Nelsen says the air might bubble up tonight, with flashes of light and rumbles of thunder!!! (probably after midnight)

  3. BoringOregon says:

    Going to be a great week of mild weather. With a chance of, Thunder storms on Thursday. And then after that nice and warm weather for the weekend ohhh time to go, camping !!!!

    • BoringOregon says:

      Wow, nocturnal thunderstorms for tonight did not see that one coming whats the chance for are area tonight?

  4. runrain says:

    Amnesiatic strays tonight?

  5. Jeff Raetz says:

    http://classic.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KORPORTL110

    ———————————————————————————————
    Averages\Extremes for the month of August 2013

    ———————————————————————————————
    Average temperature = 69.2°F (Warmest average temperature for the month of August)
    Average humidity = 69%
    Average dewpoint = 57.8°F
    Average barometer = 29.947 in.
    Average windspeed = 0.7 mph
    Average gustspeed = 1.9 mph (Lowest average gustspeed for the month of August)
    Average direction = 307° ( NW)
    Rainfall for month = 0.559 in. (Average is 0.32”)
    Rainfall for year = 16.366 in. (Year average at this time is 23.85”)
    Maximum rain per minute = 0.020 in on day 29 at time 05:46
    Maximum temperature = 90.8°F on day 06 at time 16:58 (Lowest Max temp for the month of August)
    Minimum temperature = 51.6°F on day 20 at time 06:38
    Maximum humidity = 97% on day 29 at time 09:27
    Minimum humidity = 21% on day 06 at time 15:23
    Maximum dewpoint = 67.4°F on day 29 at time 11:05
    Minimum dewpoint = 43.5°F on day 06 at time 15:22
    Maximum pressure = 30.12 in. on day 02 at time 09:52
    Minimum pressure = 29.75 in. on day 27 at time 19:16
    Maximum windspeed = 11.5 mph from 180°( S ) on day 29 at time 16:10
    Maximum gust speed = 18.4 mph from 180°( S ) on day 29 at time 16:10
    Maximum heat index = 89.8°F on day 31 at time 17:26

    Avg daily max temp :81.9°F
    Avg daily min temp :58.7°F
    Total windrun = 551.3miles (Lowest windrun of the month of August)

    Record low wind chill temperature = 51.6 on day 20 at time 06:32
    Record daily rain = .32” on day 29
    Record rain in 1 hour = 0.11” on day 29 at time 06:04
    Warmest day (6am to 6pm) = 75.9 on day 05
    Coldest night (6pm to 6am) = 58.8 on day 01
    Coldest day (6am to 6pm) = 61.2 on day 01
    Warmest night (6pm to 6am) = 72.0 on day 22

    ———————————–
    Daily rain totals
    ———————————–
    00.03 in. on day 22
    00.03 in. on day 23
    00.10 in. on day 25
    00.05 in. on day 26
    00.03 in. on day 28
    00.32 in. on day 29

    *Records since October 2008*

  6. pappoose in scappoose says:

    I’m all in for a South-southeasterly flow!

    229 PM PDT MON SEP 2 2013

    BY WEDNESDAY NIGHT THE UPPER LOW BEGINS TO MOVE ONSHORE SO EXPECT INCREASING CLOUDS AND SHOWERS. THE CENTER OF THE LOW MAKES LANDFALL NEAR THE CENTRAL OREGON COAST…ALLOWING UPPER LEVEL FLOW TO TURN MORE SOUTH-SOUTHEASTERLY.
    THAT COMBINED WITH LIFTED INDEX VALUES NEAR -2 MAKES A PROMISING ENVIRONMENT FOR MORE WIDESPREAD THUNDERSTORMS LATE THURSDAY MORNING AND AFTERNOON. /27

  7. schmit44 says:

    9/1/2013 Oregon (All) Temperature Summary

    Warmest:
    High:98 at WARM SPRINGS BAS(1563 ft) & Rye Valley(I-84(2230 ft) & John Day River B(305 ft) & DW0462 Umatilla(390 ft) & JOHN DAY RIVER A(1742 ft)
    Low: 72 at JUNIPR(359 ft)

    Coldest:
    High:64 at Port Orford(0 ft)
    Low: 31 at KIRK (4519 ft )

    Largest Diurnal Change: 52 degrees
    CABIN LAKE (90/38 ) (4560 ft )
    KLAMATH NWR (87/35) (4531 ft)
    Sand Creek (US 9 (84/32) (4525 ft)

  8. MasterNate says:

    Possible record sea ice extent for South pole region. North pole ice on par for last 5 year average. Good reading.

    http://nsidc.org/arcticseaicenews/

  9. schmit44 says:

    8/31/2013 Oregon (All) Temperature Summary

    Warmest:
    High:98 at CRN SITE AT JOHN(2214 ft) & MERLIN SEED ORCH(1144 ft) & UNION(2708 ft) & CW8140 Spray(1772 ft)
    Low: 69 at Rye Valley(I-84(2230 ft)

    Coldest:
    High:56 at YACHTS Yachats(82 ft)
    Low: 32 at KIRK (4519 ft )

    Largest Diurnal Change: 56 degrees
    FOSTER FLAT (93/37 ) (5000 ft )

  10. ocpaul says:

    Because I SO despise the current hot/muggy weather, I grasp at straws for a ‘better’ forecast. So, that takes me to Accuweather.
    Oct. 14 has a high of 56 and a low of 39, with rain (we haven’t hit 56 for an over-night low for a loooong time). Gotta dream big.

  11. pappoose in scappoose says:

    I really like it when the models agree this way!

    NATIONAL WEATHER SERVICE PORTLAND OR
    810 PM PDT SAT AUG 31 2013

    THE MODELS ALL INDICATE THE LOW IS FORECAST TO
    MOVE ONSHORE AND THROUGH THE AREA IN THE THURSDAY THROUGH SATURDAY TIME FRAME. THIS COULD BE THE BEST TIME FOR SHOWERS OVER THE GREATEST PART OF THE AREA…ESPECIALLY THURSDAY AND FRIDAY. DEPENDING ON THE TRACK OF THE LOW AND THE ASSOCIATED UPPER LEVEL COLD POOL…WE COULD SEE SOME THUNDERSTORMS ACROSS OUR FORECAST AREA.

    • pappoose in scappoose says:

      I really like nocturnal convection!

      909 AM PDT SUN SEP 1 2013

      THE MODELS THEN SHOW A SHORT WAVE ROTATING AROUND THE OFFSHORE LOW AND NORTHWARD THROUGH NORTHWEST OREGON AND SOUTHWEST WASHINGTON MONDAY NIGHT AND TUESDAY MORNING. THIS MAY GIVE US AN INCREASE IN SHOWERS…AND POSSIBLY SOME NOCTURNAL CONVECTION LATE MONDAY NIGHT AND TUESDAY MORNING. THIS IS ESPECIALLY POSSIBLE OVER THE SOUTH WASHINGTON AND NORTH OREGON CASCADES…BUT MAY POSSIBLY WRAP BACK TO THE WEST SOME IN THE NORTHERN VALLEYS AS IT SPREADS NORTH THROUGH WESTERN WASHINGTON.

    • Hal in Aims says:

      I’ll believe it when I see it….

    • Timmy_Supercell (Klamath Falls @ 4200') says:

      omg nocturnal strays!!!

    • haha I’ll believe it when I see it also. I never believe any thunderstorm chances for us anymore.

    • pappoose in scappoose says:

      Bring on the Strays!

      829 PM PDT SUN SEP 1 2013

      THE GFS AND ECMWF ARE NOW IN FAIRLY GOOD
      AGREEMENT TRACKING THE LOW CENTER ONSHORE AND NEARLY OVERHEAD ACROSS NORTHWEST OREGON LATE THURSDAY EVENING INTO FRIDAY. THIS SYSTEM WILL BRING RAIN CHANCES ACROSS THE FORECAST AREA THROUGH FRIDAY. THUNDERSTORMS WILL BE POSSIBLE FOR MUCH OF THE AREA WITH BEST CHANCES
      ON WEDNESDAY NIGHT AND THROUGH THURSDAY NIGHT AS THE UPPER LEVEL LOW AND ASSOCIATED COLD POOL MOVE THROUGH THE REGION.

    • pappoose in scappoose says:

      So you’re telling me there’s a chance…

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