Hottest Day of 2015, But Big Cooldown On The Models

Today was the hottest of the year here in Portland; we hit 97 degrees


All of the metro area was in the upper 90s, with McMinnville (and possibly Salem) hitting 100 degrees.

If you hate the heat, you’ll want to stay hidden in a cave or underground bunker for a few more days.  I don’t see any significant drop in temperatures until after Monday


But notice the last bullet point on the graphic!  Over the past two days models have been giving us major hints that something is going to change as we head into mid-July.

The hot weather has been caused by persistent upper-level high pressure over the Western USA.  There is a slightly change for the middle of next week when the ridge splits into an offshore part and the rest retreats farther east of us.  That should give us more marine influence and a better chance of high temps dropping down into the 80s.

Beyond that, there is a common theme across all models today showing an upper-level trough developing near the West Coast in the middle of the month.  Take a look at the ensemble average 500 millibar heights for 16 days from now.  From the GFS, the GEM, & ECMWF.




They all look quite similar don’t they?  The show the ridge weakening and shoving much farther west out over the mid-Pacific.

This should lead to normal to below average temperatures.  Wow, that will be the first time we’ve seen that in about 5 weeks.

Here is the 12z ECMWF ensemble chart showing pretty good ensemble agreement on the cool down.  850mb temps come down right to average NEXT weekend (not this coming weekend) and stay there.


Last night’s monthly run of the ECMWF was similar, showing warm to hot first week, then big change during week 2:



We sure haven’t seen a below average deviation like that on the monthly run for quite a while.  Here is week 3 and week 4:



It’s interesting that any sort of significant ridging is totally absent anywhere on the map in late July and early August.  Taking a closer look at maps from WeatherBell it looks a bit different.  Apparently WSI’s contouring is a bit more coarse.  Heights are indeed above average during both of these weekly periods; just not dramatically so.  My gut feeling based on the info above is that we’ll have a below-normal period in mid July, then return back to normal conditions the latter part of the month.  Regardless, it’s also interesting that in the coming 1-2 weeks we’ll see temperatures go DOWNHILL instead of UP.  The old saying “summer doesn’t begin until after the 4th of July” is going to be wrong this year!

Chief Meteorologist Mark Nelsen

26 Responses to Hottest Day of 2015, But Big Cooldown On The Models

  1. Right now, that cool down feels a long way off- I’m worried about Sunday. Still, it’s nice to know…

  2. Paul D says:

    The 7-day forecast has a “75” next Friday and it says “cool”. HAHAHA! That’s hilarious!!! Cool is when you have to put on a light coat.

  3. WEATHERDAN says:

    97 at 3:00 PM. Next weekend looks to be down to mid to upper 80,s. But still sunny. Sounds real nice. Have a wonderful Independence Day. Peace.

    • chris s says:

      Mid to upper 80’s????? Dan what are you looking at ??? I mean i realize you have a warm bias, but geez show me where you are getting those numbers after looking at the euro past few days, and 12z run from gfs? It looks below avg over the weekend into early next week, not 10 degrees above. At least say that what your wishing for instead of saying it like its predicted by the models to be that warm.

    • Boring Oregon says:

      I think he lives in Redmond if I’ve heard right.

    • Mark Nelsen says:

      Salem. It’s be far cooler than mid-upper 80s in Salem next weekend!

    • Boring Oregon says:

      Mark, if you know where WEATHERDAN lives…do you know where i live?lol

  4. WEATHERDAN says:

    91 at 1:00 PM. Headed for 100 again today. That would be the third day in the past week. Last Friday, yesterday, and possibly today. And Sunday looks to be up around 100 again. Maybe in a week or so we get a run of 4 or 5 days only in the 80,s. That sounds pretty good. I don’t see it more dramatic than that but it would still be a significant cool off. Still how many times last Winter did those super reliable models show a cold spell 7-10 days out. And how many times did it actually happen? Cooler yes, but a real cool spell with any precipitation is unlikely. More likely we will see 3-5 days of 82-87 and lows of 53-58. I don’t see any extreme heat on the horizon either. Maybe after the cool down we see a few days of 86-91 with lows of 56-61. After that who knows. However I do feel that sooner or later the high heat returns. Probably by the 25th of July. We shall see. Peace.

  5. schmit44 says:

    Deadline to enter July 3rd…..which is today

    • Joshua says:

      Can you please delete my entry with >80 days at 31? That was an error. Thanks!

  6. schmit44 says:

    JUNE 2015 CONTEST RESULTS: Karl S Bonner has become a forecasting guru crushing the competition for the contest. Here are the final standings. Jeffrey Kadell finishes 2nd place. These two gentlemen are truly talented forecasters. Congrats guys!

  7. Jason Hougak says:

    Is this a sign that the winter death ridge may be packing out this winter? The mountain needs a break it’s taking a toll on the glaciers.

    • Farmer Ted says:

      Remember Mountains and the Earth could care less, it’s us people that should be worried.

  8. schmit44 says:

    7/2/2015 Oregon (All) Temperature Summary

    High:109 at Celilo, East of( 225 ft)
    Low: 78 at Rye Valley(I-84(2230 ft) & ALKALI FLAT(2495 ft)

    High:55 at Newport(30 ft)
    Low: 44 at Meacham (3724 ft )

    Largest Diurnal Change: 51 degrees
    CW5507 Camp Sher (103/52 ) (3020 ft )

  9. Paul D says:

    Below normal!!! Bring it on!!!!

  10. David B. says:

    Excellent news by me. If I wanted lots of hot weather, I wouldn’t have moved to this part of the country.

    And it won’t invalidate the long-term forecast of a warmer than normal summer, either. Late June and early July have been so extraordinarily warmer than normal that a long run of normal or even slightly cooler than normal temperatures probably won’t stop this summer from being warmer than normal overall.

    Bring it on!

    • David B. says:

      Also, next weekend is when I’m going to be doing volunteer botanical survey work in Okanogan County. East of the mountains is not the place to be during a warm spell, so nice to hear temps should be near normal by then.

  11. paulbeugene says:

    Cooler yes…but dry. Active fire season seems inevitable.
    I don’t see highs dropping into the 70s in Eugene but nighttime temps will get back into the low 50s. Can’t wait .

  12. JohnD says:

    It has been great riding the hot/historic current weather pattern of late. Also very interesting envisioning the dramatic changes ahead–as Mark presents. Who knows how this might further evolve as the seasons progress!? ALSO thanks, once again Mark, for your dedication AND forthcoming candor. We–as weather buffs all–are simply extremely fortunate “to have you”!

  13. I’ve already started my Christmas shopping.

  14. Boydo3 N. Albany says:

    Winter’s coming..

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