Heat Wave #2 Later This Week

August 14, 2016

11pm Sunday…

It has been a hot and sometimes sweaty 4 days!   Check out the PDX numbers:



At McMinnville, Troutdale, and pretty much all of the Willamette Valley it has been 4 days at/above 90.  Whew…time for a cooldown.  Sure enough, we are finally getting drier air/lower dewpoints along with a weak marine push this evening.  That should drop the valley temperatures a good 8-10 degrees tomorrow keeping high temperatures below 90.

The bad news is that we have another heat wave on the way later this week.  This one is a little different because it’s brought on by a bit more of a “fall pattern”.  A cool shot of air drops into Montana; that’s high pressure to our east Thursday and Friday.  Then we get easterly wind over the Cascades and through the Gorge.  Not a strong wind like mid-fall but enough to push our temperatures way up.  Right now it looks to me that we’ll see high temps in the 95-100 degree range both Thursday/Friday.

So much for a “cool” summer (which wasn’t cool anyway); it appears August is going to end up very warm.  As of now we’ve seen 8 days at/above 90 in Portland, and we have at least 3-4 more.


Chief Meteorologist Mark Nelsen


Warmest Stretch Of Summer Ahead

August 10, 2016

6pm Wednesday…

This summer has sure been different.  A perception I keep hearing is that it’s been a “cool and cloudy summer”.  The cloudy part might be partly right, but it definitely has not been cool here in Western Oregon and Washington.  June was above normal and July was near or 1-2 degrees below normal:

I think what sticks out this year is a lack of very hot days; and I don’t think any of us are complaining!  That said, it IS a bit strange to go from early June to early August and only see 2 days above 90 degrees.  Note the 5 warmest days so far:


How does this summer compare to the well-known “green tomato” summers?  Not even close.

July average high temperatures at PDX and rain:

1954   72.6  1.24″
1955   72.2    .89″
1983   75.2  2.68″
1993   72.8  2.41″
2011   76.9    .96″  <– Not really a green tomato year but close
2016   79.1    .66″  <– Rainfall exactly normal

Yeah, this past July was definitely not “wet” or “cool” west of the Cascades…just NORMAL.  And it’s obvious why 1983 and 1993 stick in our minds…cool and very wet!  I wasn’t around for 1954-55 but those must have felt about the same.

Where do we go from here?  Models say we’re headed for the longest/warmest period of the summer between now and the third week of August.

Check out the 850mb ensemble chart from the ECMWF.  The thick line is the average temperature this time of year over Salem (in celsius).  Note that just about all of the next two weeks the forecast temps are ABOVE that line:


There is a huge amount of spread after about day #8, but most of those 51 ensemble members are above average.  The actual forecast highs for Portland look like this:


That’s the most consistent warm to hot weather we’ve seen so far this summer.  And considering we’re moving through mid-August, that’s likely to end up the warmest as well.  Once we get to late August temperatures typically are cooling off a bit.

The GEFS ensembles are similar:


so confidence is high that a prolonged spell of warm to hot weather is on the way.  No rain in sight either of course.

By the way, the all-time high temperature at PDX was set on this date 35 years ago.  During the big 1981 heatwave we hit 107 not once but twice!  That was a huge scorcher.  As I recall I was 12 years old and watching a Planet of the Apes marathon right here on Portland TV from the cool family room in the basement.  It may have been on KPTV as well!  Full circle right?


We’ve actually hit that 107 mark THREE times…one day in July 1965 as well.

Chief Meteorologist Mark Nelsen



Cool Next Few Days, Then Warmer, Then Cooler

August 5, 2016

11pm Friday…

Quite a bit cooler out there this evening, I see it’s already down to 60 here at the FOX12 Studios.  A major marine push means some low clouds Saturday morning, but I think we’ll see tons of midday/afternoon sunshine.

Sunday through Tuesday a weak upper-level low drifts across Washington giving us June-like (or is it September-like?) weather for a few days.  Due to this we might see showers on the coast Sunday, especially up north:


Enjoy the cooler weather because the heat is on again late next week.  There is good model agreement on a warm-up Wednesday-Friday next week.  Ensemble model numbers from both GFS and ECMWF show 90 is likely again in P-Town for a day or two.  There is pretty good agreement not only on the warm-up but a rapid cooldown again around the 15th.  Check out the GFS ensembles…this shows temperature at around 5,000′ over Portland for the next 16 days:


Quite a roller-coaster look isn’t it?  At least no one can complain that we’ve been stuck in just one pattern this summer!  The ECMWF ensembles are similar, so my 12 Day Trend graphic looked like this tonight:


I use this most nights at 10:45pm to give a general look beyond the 7 Day forecast.

Enjoy your weekend!

Chief Meteorologist Mark Nelsen

Warmest Day of the Week

August 4, 2016

9am Thursday…

Today looks like a hot one.  I think most of the metro area will end up between 88-92 degrees.  For the first time in a few weeks we have very light EASTERLY flow over the Cascades and through the Gorge; that’s when air is flowing from land toward the sea.  I see the pressure gradient is about 0.5 millibar from Portland to The Dalles.  You can see the (light) easterly flow on the Troutdale profiler nicely this morning.


Current time is on the left side of the image, 48 hours back in time is on the right side.  Two things show up; note the easterly flow from about 1,200′ up to at least 5,000′.  But what really sticks out is the dramatic warming overhead since yesterday morning.  At 3,000′ yesterday it was around 50 degrees at 7am.  Yet at 7am today it was in the low-mid 60s at the same elevation.  Combine that with the offshore flow and we’ll see quite a jump in the temps today.  At least 8-10 degrees.  So I think it’s quite likely we hit 90 at PDX, maybe a few notches warmer in a spot or two.

Cooler weather returns Friday and beyond.  In fact the ECMWF says below normal temps Saturday through at least next Tuesday as another upper-level trough moves down into the Pacific Northwest.  You can see the below average 850mb temps (temp in celsius at 5,000′) through the 9th…pretty good agreement on that on the ensemble chart here:


Check out that trough on Monday morning.  500vty_f108_bg_NA  This says SHOWERS to me just looking at the pattern only.  Yet it is early August (not June or September) so models want to keep most/all of the showers north of the Columbia River in the lowlands and in the northern half of Oregon in the mountains.  Take a look at the ECMWF rain total ending Tuesday:


The GFS is slightly wetter with 0.10″ extending down into the Northern Willamette Valley.


The rain showing up south and east of the highlighted area is thunderstorm action east of the mountains not directly related to the cool showers coming in with the trough.  For those of you planning on camping in the northern Oregon Cascades or Washington (me) Sunday-Tuesday, it appears to be another cool and possibly showery early August period.

Chief Meteorologist Mark Nelsen

Not As Sunny This July

July 26, 2016

11pm Tuesday…

A few people have complained about the “cool” July so far.  It sure hasn’t been “cool”, but about average temperature-wise.  Portland, Salem, & Eugene are running within 1 degree of their average temps for July.  The coastline has been a bit warmer than normal.  Eastern Oregon has been a bit below normal but the next 5 days in the 90s and then 80s should bring you folks closer to normal.

I think what most of us are noticing is the increased cloud cover and lack of extreme heat.

Cloud cover:


Notice we’ve seen a typical number of mostly cloudy days.  But then note the lack of mostly or totally sunny days:

MarkCloudy Clear Days July

Yes, we’ve had tons of partly cloudy days, but have been missing the real sunny days that we typically get.

Now the heat:



We haven’t had a 90 degree temperature this month.  In fact we haven’t hit 90 since the first week of June, only tallying up 3 so far this summer.  I assume we’ll hit 90 both Thursday and Friday so that will bring us up to 5.  Beyond that it appears unlikely we’ll have another 90 through the first week of August; tonight’s 12 Day Trend was based heavily on the ECMWF & its ensembles…ignoring the trough the GFS keeps trying to bring through next Tuesday:


So much for my thinking that we’d see 12-18 90+ days this year!  That said, the bulk of the summer outlook I put out on May 23rd is okay:


There is one other topic this change of weather the past 7 weeks brings up.  During the past two summers there were some proclaiming that this is the “new normal” and summers are going to be a blazing hot hell (or something like that) from here on out.  No, that’s not how it works.  In a gradually warming climate we will still have ups and downs.  We might have a few cooler summers, then the next period of hot summers could be even hotter.  Who knows, but in general temperatures should continue to warm over the long term…we’re talking over many decades.  Our cooler periods should become less frequent and hotter periods more frequent.

Chief Meteorologist Mark Nelsen

Mellow Midsummer Weather

July 24, 2016

9pm Sunday…

I’m back from vacation and working hard in the weather center this evening.  Well, the weather is slow so I’ve spent more time on normal/mundane “office tasks”.  Such as: catching up on emails, doing schedules, planning software upgrades etc…and I even vacuumed out the dirty area behind the green wall that’s been bothering me for months.  I think I had empty boxes and junk  thrown back there from almost two years ago.  As a result I’ve kept quite busy considering it’s almost the slowest time of the year weather-wise.  I think only September and early October are more boring for us.


  1. Cooler the next two days, but temperatures just come back down to about normal
  2. A 3 day period of very warm to hot weather Wednesday-Friday
  3. This will be the first hot weather since early June.  That’s if you define 90+ as “hot weather”
  4. 95+ is unlikely, and no records will be broken
  5. Back to typical clouds/sun mix with highs 75-85 the first week of August


Speaking of slow weather, we are in the warmest few weeks of the year and our 7 day forecast takes us through the last day of July now (next Sunday).  So far this month has been a notch cooler than average here in Portland and right at normal in Salem and Eugene.  The Oregon coast has been warmer than normal; not sure why unless it’s the lack of strong northerly wind compared to some other summers?  You can see in general the farther north you go along the West Coast the cooler it has been compared to normal:


Compared to California which has been normal to slightly above.  Nothing too dramatic west of the Cascades/Sierra anywhere along the coastline.  Yet east of the Cascades the cool July sticks out in Oregon, Washington, & Idaho.  I would guess no one is complaining in those typically hot areas.

Today’s 88 in Portland was the 2nd warmest of the month.  Seems strange to say we haven’t hit 90 in Portland this month…and it’s the 24th of July.

Even more strange, we’ve gone through 7 weeks in the middle of summer in Portland without hitting 90 degrees!  That’s a huge contrast to the past 3 Julys.  More like 2012 which was not exceptionally cool by any means but 90+ held off until early August.  Clearly something “switched” after the first week of June this year as mentioned in a previous posting.  We went from a crazy warm spring again to just about normal now for the past 7 weeks.

Looking ahead, we have a weak marine push tonight and then a bit more tomorrow night.  The result is a few more patches of morning clouds and slightly cooler temps each day.  Then Wednesday through Friday we get 3 days of very warm to hot temperatures.  Right now I’m going with 88-92-95.  Hardly record-breaking hot weather (records 100-107) in this upcoming period) but the warmest we’ve seen since early June.  The reason is weak and “flat” upper-level ridging developing along the West Coast.

Take a look at the 500mb pattern for Friday morning, the peak of the warming overhead:


You can see an upper-level disturbance dropping out of Alaska and it’s headed right into the Pacific Northwest next weekend.  Thus a very quick cooldown next Saturday/Sunday…could even bring a spot of drizzle inland next Sunday AM.  This is in stark contrast to what models were showing 2-4 days ago.  At that time models were giving us a big heat wave with temperatures well above 100 degrees.  This graphic tells the story, although it does use the typically inferior GFS model:


Let me explain.  Each HORIZONTAL line is one run of the GFS.  The latest is on the bottom.  These are 850mb temperatures, which means temperatures in celsius around 5,000′ elevation.  Go UP the chart to go back in time for the forecast for any particular date which is VERTICAL.  Focus on the circled areas; next Friday-Sunday.  See that 72 hours ago up to 48 hours ago the GFS was giving us +25 to even a +28 temperature.  That’s up in the 103-107 range with any sort of offshore flow.  I’m sure some of your automated apps showed 100+ weather during that period.  Since 48 hours ago models have continued to gradually back off on temperatures AND cut off the end of the heat wave.  So we no longer really have a heatwave forecast.  It’ll be plenty hot late week, but nothing unusual for late July.  I think most of us would agree that’s a good thing!

Looking farther ahead, we return to average temperatures for the first week of August.  Other than the drizzle possibility, no rain is in sight.  Keep watering!

Chief Meteorologist Mark Nelsen

Vacation Time

July 14, 2016


Cue the Mark vacation jokes in 3…2…1…

I’ll be off on vacation for a wedding and a little trip up to B.C. mountain biking, plus painting my house through next week.  I’ll miss 6 work days and be back on Sunday the 24th.  Likely no posts during that time.

It’s the best & warmest weather of the year in the Pacific Northwest (mid-July to mid-August) so get outside and enjoy it!

Chief Meteorologist Mark Nelsen



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