July 1st: One Day Heat Wave Ahead!

The next 48 hours should be fun as we see an abrupt switch to strong offshore flow (rare in July) tonight through Tuesday afternoon, pushing high temps into the mid-upper 90s in the valleys.  Then just as quickly we get a surge of wind off the chilly Pacific Tuesday evening through Wednesday, so high temps will drop 14-18 degrees in one day.  Further cooling Thursday means highs in the mid 70s.  So I think everyone can find something they like in the next 3 days.

The Details

  • We’re forecasting 97 for a high at PDX Tuesday, at least a 10 degree jump from today.  That is the warmest we saw last summer too.
  • That will be the warmest so far this season, we hit 91 back on May 14th, the first 90 of the year.
  • It will not be a record because there was a heat wave during this time in 1942 and we hit 105 on July 1st!
  • No high humidity…we’ll see dry east wind, our typical hot weather pattern.
  • Gusty east wind develops at the west end of the Gorge and over the Cascade foothills by sunrise, then it’ll surface in some areas in the lowlands
  • The Oregon Coast should be very warm, especially north of Pacific City, but light west wind after the noon hour should cap Lincoln City and Newport’s high temps below 80.
  • There is only one very warm and sunny day coming at the coastline…that’s tomorrow.

BMAC Summer Highs 10 years


June has not seen any temperature extremes, in fact until today (June 30th) we didn’t even get above 81!  A bit weird considering the month was average temperature-wise.  One would think at some point we would have seen an 85 or 90 but no.

Tomorrow’s forecast high temperature has been steadily creeping upward the past few days, partly due to confidence in a sharp thermal trough setting up west of the Cascades, but also due to 850mb temps warming in successive model runs.  The 12z suite of models (NAM, GFS, ECMWF) are all showing +22 to +23 deg. C over Salem tomorrow afternoon.  Looking at my chart of past cases with easterly flow at that temperature, we should see a high between 96-100 degrees, so my 97 might be slightly low.  Everything appears perfectly aligned for maximum heating tomorrow, including a drop off of the wind at max temperature time around 4-6pm.  There is even a chance we hit 100 tomorrow afternoon at PDX.

Since the upper-level trough is shifting east rather quickly later tomorrow and Wednesday, the center of warmest weather will shift quickly east of the Cascades tomorrow night and Wednesday.  That means a pretty decent onshore flow will immediately follow tomorrow’s offshore flow.  And that equals a quick cooldown.

The rest of our 7 day forecast has ridging to the east and upper-level trough to the west, with us in the middle.  That pattern will bring us the morning clouds and afternoon sun routine.  Here is a glance at the 12z ECMWF 850mb ensemble chart:


Note the huge spike tomorrow followed by cooler temps through the 5th, then a bit warmer than average next week.  The GFS disagrees


showing temps near average through the 8th, and the operational run is the chilliest of all the members.  So (normal operating procedure) I ignored the GFS.

Chief Meteorologist Mark Nelsen



22 Responses to July 1st: One Day Heat Wave Ahead!

  1. Dave in SW PDX says:

    There’s a classic example of cirrus uncinus (“mare’s tails”) clouds in the sky this afternoon, a fine display.

  2. WEATHERDAN says:

    84 at 11:00 AM in Salem this morning should reach between 98-101 today. 85-90 on Wednesday with some marine air. Low 80,s on Thursday and Friday with some low clouds. Portland will see more than Salem so they may only see mid to upper 70,s. Then Salem should rebound to the mid 80,s over the weekend. Happy 4th one and all. Peace.

  3. Garron near Washington Square says:

    As of 10 AM temp. readings, Portland is + 10 degrees from this time yesterday,
    Hillsboro is + 16!

  4. pappoose in scappoose says:

    Hot weather tip.
    Eat ice cream cones quickly to avoid a sticky mess,
    or better yet, order ice cream in a dish. Hahaah!


  5. David B. says:

    Forecast high of 83 today up this way. Just about right for me… warm enough to make it really feel like summer, not warm enough to induce any real discomfort. Sea breezes for the win!

  6. W7ENK says:

    I woke up to the epitome of humid this morning…

    60 degrees and foggy in Nõmme, just outside of Tallinn. Blechhhh!! Very unusual for this time of year, but we have had a lot of rain, so…

    Now it’s been raining for most of the day, and the temperature has hovered between 55 and 57.

    Reminds me of home.

    I’m hoping that the weather will be dry for the song festival this weekend.

  7. Garron near Washington Square says:


    Larch Mtn Washington dropping dewpoints, gusty east winds, and temps in the 70’s at 3 am…PS, is the Crown Point wind sensor still on the fritz? Just wondering as it was showing North winds currently.

  8. schmit44 says:

    6/30/2014 Oregon (All) Temperature Summary

    High:100 at DW5789 Eagle Poi(1463 ft) & EW3335 Jacksonvi(1390 ft)
    Low: 65 at RED MOUND(1753 ft)

    High:57 at Timberline Lodge(7001 ft) & CW7477 Lostine(7002 ft) & HOWARD Mt Howard(8150 ft) & ANEROID LAKE #2(7300 ft)
    Low: 28 at CRANE PRAIRIE (5500 ft )

    Largest Diurnal Change: 56 degrees
    Chemult (US 97 M (89/33 ) (4750 ft )

  9. alohabb says:

    Just got back from Turtle Bay in Oahu….so this is just right!!

  10. Paul D says:

    Tuesday will be a great day to stay inside after about 11am. Glad the heat wave is only one day.

  11. oldwxwatcher says:

    It did get above 85° (86.7°, to be exact) at my home in E Portland today but it was accompanied by a 60° dewpoint. Ugh!

  12. JERAT416 says:

    Summer is here! Other than those few death ridge lovers, a one day heatwave is enough for most of us. Power bills have been low due to not any heat this month and very little AC. Despite the rain recently, June has been quite pleasant. Be careful if you’re going in local mountain rivers, they will be cold and the sudden shock can be dangerous. Enjoy the hot day!

  13. Karl Bonner says:

    Strong offshore flow is rare in July??? That’s a rather unusual statement to make. Don’t most July heat waves involve offshore flow?

    Or is it the abruptness of the switch to offshore flow that’s rare this early in the summer?

    • Mark Nelsen says:

      Yes, sometimes we only get 1 or 2 instances of a thermal trough with several millibars easterly gradient in July or August. In fact I’d say it’s rare to have more than 3 episodes in one month.

    • Karl Bonner says:

      Well it’s kind of misleading if MOST of our big heat waves involve offshore flow, to call it “rare.”

  14. One day heat wave is just right.

  15. One day is just right.

%d bloggers like this: