It’s Portland’s Driest Spring So Far, Plus Summerlike Temps

9:30pm Thursday…

It’s been nice waking up to sunshine every one of the past five days. And we’ll do it for at least another five, but now it’s getting a bit…weird. It’s been nice, but we don’t live in Sacramento. Most of our viewers live in western Oregon and Washington.

Take a look at those temperatures the past few days. We’ve gone from a high of 53 Saturday to 76 today in Portland…the warmest day of the year.

VERY DRY SPRING

We’ve only seen .09″ rain so far this month and now we’ve reached the midpoint of meteorological spring. March-April-May is spring in the northern hemisphere (officially defined by NOAA). Take a look at the numbers…in the past 7 weeks we’ve seen less than 2″ rain in Portland.

Assuming it doesn’t rain by Sunday (it won’t), this will be the driest March 1st – April 18th on record at PDX. Those numbers go back to 1940. I checked Salem, Astoria, & Olympia. Similar extremely dry numbers.

Last year was a bit dry, our 5th driest April. Luckily last year we had a wetter May and very wet June to make up for it.

I remember the flooded sports fields back in 2017 & 2018. Each year is different, but this spring (so far) is exceptionally dry.

The NWS has a Red Flag Warning out for much of western Oregon, also quite rare for April

WHAT’S AHEAD?

A strong ridge of high pressure in the upper atmosphere is centered in British Columbia with a cool low just to our southeast. It’s been a chilly mid-week from Boise over to western Colorado, snow in spots

That warm ridge slides down right over us by Saturday…warmer atmosphere overhead

Then it weakens a bit by Monday, but at the same time another pocket of cool air is sliding down just to our east

The result will be offshore (easterly) flow and warming temps tomorrow & Saturday. 850 millibar temps to around +12 to +13 imply we could get as high as 84, but we’re going slightly conservative with a high of 82 Saturday. That would be enough to break a record for the day

Then onshore flow arrives on the coast Saturday afternoon and tries to push a bit inland Sunday. I don’t think that will drop our temperature more than a degree or two Sunday. The result is a very summerlike 3 days ahead. Then as the cool air drops in to our east Monday, that’s high pressure which renews the easterly flow across the region. A cooler airmass Monday, but offshore flow returns quite strong. Looks like more sunshine for Monday and Tuesday. This all adds up to five more days of sunshine.

When does the rain return? Each operational model is different, but they all suggest a pattern change later next week. The ECMWF ensemble forecast suggests not much rain Wednesday/Thursday, but by Friday and into that last full weekend of April we could be back to a more typical wet/showery weather pattern

We can’t do anything about the lack of rain, so enjoy the sunshine while we have it. And there’s no reason to panic thinking that we’re going to have a “terrible fire season”…remember last June we had soaking rains the first part of the month.

Chief Meteorologist Mark Nelsen

25 Responses to It’s Portland’s Driest Spring So Far, Plus Summerlike Temps

  1. Jason Hougak says:

    So bizarre having such dry mild conditions and still have no leaves on the Alder and Bigleaf Maple up here in the Cascade Foothills. Very strange indeed…
    I’m praying for a soaker of a summer, we need it!

  2. Tanis Leach says:

    The following isn’t to say any month is going to be wet, or dry, but to say our dry streak shouldn’t last the entire spring/summer if history is a guide:

    2 water years in a row under 30 inches of rainfall has never happened in Portland’s history. I chose 30 inches since its a nice round number, and it has a 12.5% frequency in the data (1/8 years). 2 years in a row would be 1/64 chance or about 1.5% chance. You can take that as we’re due for it, or things will change. I’m not saying either will happen, just the history.

    However, based on the atmospheric patterns thus far, and seemingly likely patterns into the summer, it could happen. Then again, we are pacing for 31.5 inches for the water year right now so it can still be drier than average and we could hit 30″+. Also, 2018-2020 water years were the first time 3 years in a row were under 32 inches (25% frequency, which also equates to a 1/64 chance).

    Lastly, IF next winter is La Nina (I’m not saying it will be, I just looked at it), the 2nd La Nina tends to be drier than (or within an inch to) the first, but also colder (or within 0.25°F to) the first. Exceptions:

    50-51 (warmer and wetter than 49-50)
    55-56 (wetter than 54-55)
    74-75 (warmer than 73-74)
    17-18 (warmer than 16-17)

    No trend on snow though. These trends aren’t as clear if the ENSO state is different the following winter.

  3. Winter Enthusiast says:

    Got HARRP…

  4. tim says:

    00z is showing a week of “light rain” late April then ridgeing afterwards, bottom line our long hot/dry summer is here so forget the rain until next fall.

  5. 5OClockCharlie says:

    I’m still not optimistic about that low next weekend. Models have really been struggling with it, particularly the Euro. Every run is significantly different than the last. There’s another low directly behind it that’s looking much better though, so perhaps we’ll not be going into May without some measurable rain. One can only hope at this point. I was outside doing much needed housework all day in the heat and it was brutal! Hard to believe I was nagging about frost only a week ago. Plants are finally in the ground but now I’m having to make sure they don’t dry out. Can’t win 😕

  6. tim says:

    It’s good to know if u want long blazing hot dry summers u don’t have to move to Arizona anymore and that’s exactly what we’re gonna have this year and it already started.

  7. Roland Derksen says:

    I realize it’s been very dry this spring- especially in April. Might make a record dry April for me too- I have to go back to April 2004 for that. However, it doesn’t mean June is going to be wetter(or drier) than average. We ‘ll just have to wait how it develops.

  8. Anomynous says:

    “We can’t do anything about the lack of sunshine, so enjoy the rain while we have it.”

    Next time on sentences you would never see Mark type on this blog if you reversed the words sun and rain.

  9. Roland Derksen says:

    73F the high for me yesterday:I have to admit it’s earlier than I predicted by about 2 weeks- and today i expect 75, with probably the highest temperature on Saturday at 77F. Not a record though- I recall April 18th, 2016 with an amazing 85F. I don’t expect 80’s up here in BC in April. They happen very rarely to us.That 2016 reading was the first for me since 1976!

  10. Joshua Lake Oswego says:

    Called the red flag warning.

    High pressure is always stronger than initially forecasted and always lasts longer. Case in point… look at Mark’s post from Sunday. Every one of those temperatures forecasted for the upcoming week will be exceeded. And now we’re looking at 70 or above for most or all of next week.

    Our next CHANCE of any rain is not until next Sunday. Mark’s post is too optimistic in mentioning that we could be starting a typical onshore wet/showery pattern by next Friday. Not happening. As we know with the Euro ensembles for rain, it’s not how much you subtract from the long-term forecast, it’s how much you divide by.

    • 5OClockCharlie says:

      I agree, the wet/showery is optimistic. Yesterday the Euro was showing a big soaker for next weekend. Now? Less than .04in over the next 10 days.

      Personally I think ensembles are great, but only half the story. I have to look at the temps and high/low pressure systems on the map of the entire northern hemisphere to get a better idea of where things could land. The positioning and speed of those two systems out in the eastern pacific for example keeps rapidly changing, which will dramatically alter the forecast depending on its final position and the high pressure it’s going up against. That’s what makes me less optimistic about rain.

    • Zach says:

      I think the major takeaway is that all the signals point to a wetter pattern starting next weekend.

      https://www.cpc.ncep.noaa.gov/products/predictions/814day/

  11. tim says:

    What are the odds of having another wet June this year?, I don’t think we should count on it brace for a dry spring and summer.

  12. Anonymous says:

    1000 percent

  13. Paul D says:

    Spring please.Summer needs to wait its turn.

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