7pm Wednesday

We’re just three weeks into summer but our first heat wave of the season is closing in on us.  So far this year we’ve been as warm as 91 (May 22nd, just before Memorial Day), but June has seen very “average” temps and rainfall.

What’s going on?  We have a strong upper-level ridge developing offshore, that’s a large area of warmer than normal air.  It will move right over the West Coast Friday through Sunday, then weaken and head south Monday and beyond.

Jet Stream Forecast 2017


Headlines Spring Summer

Heat waves are FAR easier to forecast than any other extreme weather in our area.  In fact I can’t remember screwing up a heat wave forecast in the past 20 years.  Sure maybe a 100 degree day became a 90 degree day because of high clouds, but in general we’re talking sunny skies and it’s just a matter of “HOW HOT IS IT GOING TO BE?”.

Well this time the answer is “pretty darn hot!”.  The all-time record June temperature at PDX is 102 degrees, set 11 years ago.

Models are in good agreement that 850 millibar temps over Salem (the temp in Celsius at 5,000′) will peak around 20 Friday, 23-24 Saturday, and 22-25 Sunday.  With neutral to slight offshore flow Friday turning to relatively strong offshore flow Saturday and Sunday, temperatures are going to skyrocket.

How hot?  Looking back at the 2006 heat wave, 850mb temps peaked out around +24 to +25 and we ended up with two 100+ days (101 and 102).  My “magic” chart for June says with offshore flow there’s no reason we can’t hit 100 (or higher) with the forecast temps, especially off the ECMWF model on Sunday; it’s the warmer model that day.  To summarize, afternoon temperatures both Saturday and Sunday will be somewhere in the 97-102 degree range in the Portland metro area.

Will it be humid with this heat wave?  The short answer is NO…good news.

How much wind? I think Saturday and Sunday will be breezy, especially Saturday afternoon and early Sunday.  That’ll mainly be a northerly wind in the western valleys.  In the Gorge it’ll be breezy Saturday and then windy the first part of Sunday with that easterly wind.  Most likely no westerly wind in the Gorge for windsurfers and kiteboarders until Monday.

90s at the Coast?  I think that’s unlikely this time around unless we get the east wind out over the beaches.  Mostly likely 70s to 80 Friday, 80s Saturday, and then 60-80 Sunday as c chilly southwest wind kicks in first on the central coast and then works its way north.  Saturday should be the warmest day on the Oregon and SW Washington coastline.

Get your air conditioners and pool ready!

By the way, there is no substantial rain in sight, at least through the end of June.  Check out the ECMWF model’s ensemble of rain accumulation forecasts:


Each horizontal line up above represents one member of the ensemble.  Green indicates .10″ rain accumulation.  Notice only 8 of 51 members produce a tenth of an inch of rain over us through the 6th of July.  That gives some confidence to the idea that we MAY have already entered the very dry season.  If so, vegetation is going to be drying out quickly with the warm temps.

Chief Meteorologist Mark Nelsen

19 Responses to 1ST HEAT WAVE OF 2017 THIS WEEKEND

  1. J Patrick Moore says:

    Not sure why the NWS heat advisory and warning include mention of high humidity. Even if you sent all the fireboarts in Portland and all the fire trucks in the region into the gorge to spray water into the air, it would still be a dry wind coming down the gorge.

  2. Paul D says:

    I’m hoping for the biggest forecast bust of Mark’s career, but I know it won’t happen because he’s really good at getting the heat wave forecasts right 😦

  3. runrain says:

    Heading to Austin next week for our family reunion. Yuk! Not the reunion, but the fact it’s Texas in the summer. How does anyone tolerate living there? Fortunately, most of our activities will be inside.

  4. W7ENK says:

    In all honesty, I wouldn’t really consider heat waves as “extreme weather,” per se. Not for around here, anyway. Maybe if said heat wave included a string of 100°+ days (a la July 2009 or August 2016) or if it lasted for an inordinate number of days (June/July 2015), but a three or four day stretch with temperatures reaching into the 90s is by no means “extreme.” Certainly far more reliable around here than both thunderstorms and snow, as we can go an entire year without either, sometimes (a lot of times) longer. In fact, I’d be more apt to consider the lack of an appreciable heat wave in any given Summer to be the extreme for Portland.

  5. Roland Derksen says:

    Another beautiful day here in Vancouver,BC. Not warm yet- that should kick in Friday, and perhaps we’ll see it near 90F this weekend.

  6. JERAT416 says:

    Hotter than I prefer but I’m not gonna complain after a very wet, cool few months until mid May. This isn’t unusual and nature’s AC will eventually kick in after. Stay cool and hydrated, and if you go to the beach , pack your patience. Good luck finding a place to park haha

    • Paul D says:

      The beach looks nice over the weekend, but there’s too many people that want to enjoy it, so I don’t even try.

      Plenty of room for me in my air conditioned house and guaranteed parking 🙂

  7. John says:

    You know summer started yesterday, right? Not three weeks ago?

    • Mark Nelsen says:

      For meteorologists, summer is June/July/August in the Northern Hemisphere (the 3 warmest months for most of us). Astronomically it starts when the sun is at it’s highest point in the sky, which was just two days ago.

    • W7ENK says:

      And realistically, we all know Summer generally doesn’t start until July 5th.

      • JERAT416 says:

        Makes sense but September is much more likely to be dry and warm than June. Less heat waves due to lower sun angle but definitely more consistent. June can be a roller coaster with a few cool days with showers and mid 60’s, or a heat wave like what’s coming up. September is also one of my favorite months due to cool nights and warm days, campfire weather! My observation is that the hottest weather is usually mid July through mid August. I remember this discussion we had a while back about what “summer” is. My definition would be July through mid September.

  8. Paul D says:

    Way too hot. Gonna be an indoors weekend.

    • Jake-(Gresham near Nadaka Nature Park) says:

      Agreed. Just got back from a family wedding in Sacramento in time for this. It was 97 – 105 there every single day… Time for slushies.

      I hope Tuesday we get some thunderstorms if we’re going to suffer this so early on!

    • I actually enjoy warm spells now that I’m living someplace with significantly cooler summers than Portland. I remember them being trying and unpleasant when I lived in PDX, however.

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