May Heat Ahead…Forecast Numbers Going Up

6pm Thursday

Today was sure a nice day after 7 days of rain showers.  Other than a sprinkle or two late this afternoon, we saw partly cloudy skies and much warmer temps.  This is about as normal as it gets in the latter half of May

High pressure is strengthening over the Pacific Northwest as the cold upper-level trough has moved off to the east.  In general high pressure will dominate our weather for the next week.  Temperatures climb tomorrow with very weak onshore flow and a warmer atmosphere overhead.

Saturday will be cooler with even a chance of a shower or drizzle through midday.  That’s because a weak system rides through the building high pressure, allowing a surge of cool marine air inland.  That marine layer will be quite thick Saturday…up to about 4,000′ or so.  When it does that the possibility for a shower or drizzle exists.  The ECMWF is sure seeing this, although less than .10″ in any lowland location

Sunday through Tuesday a big upper-level ridge builds with 500 millibar heights above 585 dm.  That is a summertime ridge and air overhead will be warm like summer.

Models are in excellent agreement that 850 millibar temperatures (the temperature around 5,000′ elevation) will rise to around +15 (celsius) Sunday, +19 Monday, and +20-21 on Tuesday.  That’s just plain hot overhead.  On Monday and Tuesday easterly flow at that elevation lowers pressure west of the Cascades.  It appears all day Monday through early Tuesday what we call a “thermal trough” will be located quite close to the coastline.  A thermal trough is a very warm area of low pressure that forms in the lee of the Cascades/Coast Ranges.  In this case, with it getting out along the coastline, temperatures should skyrocket at the beaches just like in the valleys.  Most likely that happens on Monday; that IS the one day that should be a scorcher on the beaches…80-90 is possible out there.

Here in the metro area, if we combine May sunshine, offshore wind flow (both Monday & Tuesday), and those 850mb temps?  We get a high temperature somewhere between 92-98 based on past setups in May just like this.  Highest temps are likely on Tuesday assuming no onshore flow begins.  As a result I raised 7 Day forecast high temps a could degrees again today.

TO SUMMARIZE

  • NO RAIN THE NEXT 7 DAYS, UNLESS WE GET A SPRINKLE OR DRIZZLE SATURDAY AM
  • COMFORTABLE TEMPERATURES THROUGH SUNDAY
  • MONDAY & TUESDAY WILL BE HOT DAYS, ESPECIALLY FOR MAY.  92-98 IN THE METRO AREA
  • IT APPEARS THIS WILL BE OUR WARMEST MAY WEATHER IN 9 YEARS
  • EXPECT DRY HEAT THIS TIME WITH THE DRY NORTH & EASTERLY WIND
  • SUNDAY & MONDAY AT THE COAST?  75-90 DEGREES, WARMEST MONDAY

 

So when might it rain again?  Some ensemble members of some models imply a weak upper-level low could bring showers/clouds Thursday and beyond next week.  That said, more members are remaining dry through Memorial Day Weekend than wet.  Only 5 of the 21 GEFS ensemble members give PDX .10″ or more rainfall by the end of that holiday weekend.  Each of the horizontal lines below represents 1 of those 21 members.  Time goes from now on the left to the 3rd of June on the right.

The ECMWF ensembles are similar…11 of 51 members produce .10″  rain in the next 10 days.   Only 4 have .50″ or more.

Basically we MIGHT get a few showers as we head toward/into Memorial Day weekend, but as of now there’s no reason to believe a long spell of cold and showery weather is coming back before the end of the month.  There’s also no sign that hot weather continues beyond Tuesday.

Chief Meteorologist Mark Nelsen

19 Responses to May Heat Ahead…Forecast Numbers Going Up

  1. Gene says:

    The good news is, after a cool Wednesday, it looks like temperatures rebound nicely over the weekend and into next week.
    It’s hard to complain about great weather like this!

  2. JERAT416 says:

    Looks like we may just have one hot day.

    • Paul D says:

      YES!!! Forecast numbers are dropping! More 70’s, less 90’s, please and thank you!

  3. Roland Derksen says:

    Absolutely wonderful day here; mainly clear skies, gentle SW breeze, and 70F temperature. Doesn’t get any better than this in May!

  4. ocpaul says:

    Time to get the plants out of the grow tent, and into the garden!

  5. Roland Derksen says:

    It’s going to be great this weekend here. Could see the temperature rise to the mid-80’s by Monday (Victoria Day). I don’t mind that at all!

  6. …there’s going to be some serious snowmelt going on…rivers are going to be high and COLD!!! …

  7. W7ENK says:

    This is why I survive Winter!! 😀

    Looks like e19 has a little bit of an attitude…

  8. Gene says:

    Thanks for the sunny update, Mark. Looking forward to this stretch of warm/hot weather, as are most of the people I know. Good to feel the warm sun on our bodies again.

  9. Phil in Beaverton says:

    I thought we got some mid-to upper 90 degree days last year towards the end of May?

  10. Paul D says:

    One 90 degree day is one too many.

    • Joshua Downtown PDX says:

      Yes, sir. It is. I have a feeling us cool weather lovers are going to hate this summer. We have had quite a run though.

    • Paul D says:

      Don’t talk like that! We’re due for a 2011 repeat. This is just a speed bump.

    • Joshua Downtown PDX says:

      I will try to be cautiously optimistic. It seems like it’s hard to get through summer lately without a few scorching heat waves and never ending mid to upper 80s crap.

    • Paul D says:

      Wednesday’s forecast is now below 80 – we’re going in the right direction on that day!

  11. Lee Wilson says:

    Perfect and in time for our maters and pumpkins we got growing…as well as cucumbers and some other things…

    Well now we can really test our Solar finally..

    Probably use it to run a few things like the Air-conditioning Unit in the bedroom along with our fridge and water cooler…

    This will be Interesting.

    • Lee Wilson says:

      And a fan..and…our bread machine..
      Did you know you can bake chicken or other meats in a bread machine? Lao heat up stews too.

      Oh.we can make icream using Solar…Oooooooo…..yum……real icecream…….yum…

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