Cooler Thursday, Then A Hot Weekend!

July 15, 2015

9pm Wednesday…

That was a windy bike ride that I just took between shows!  Obviously not a stormy-type of wind, but gusts 25-30 mph coming in from the northwest.  Quite a chill in the air (for July) too.  We are getting a strong push of cool marine air as an upper-level disturbance passes by.  The breezes and cool temps are refreshing after an 83 degree day here in Portland.

The result will be most noticeable tomorrow morning in the form of low clouds in the northwest part of Oregon and southwest Washington.  These “northwesterly pushes” don’t tend to have the extensive thick low cloud cover in the mornings that southwest pushes do, so temperatures won’t be dramatically cooler tomorrow, just down about 5 degrees.  You can see our RPM model forecast of cloud cover…


After that it’s on to sunshine again in the afternoon.

I’ve upped forecast temperatures for this weekend a few more notches today.  It’s looking pretty obvious that our current onshore flow will go flat or even slightly offshore.  850mb temps jump from +9 tomorrow morning to +20 (celsius) Saturday afternoon.  It’s going to get hot!  According to my July “magic chart”, that should get us to at least 90.  Easterly wind flow situations have been as warm as 98 in these conditions.  We should be closer to 90 than 98 both Saturday and Sunday.  Either way we’re likely going to add two more 90 degree days to our summer total.


That’ll make 18, just 7 away from breaking the all-time record.  If we have typical summer weather through early September, there’s a chance we’ll break that record of 24 days set in 2009

It looks unlikely that we’ll hit 90 after that for at least a week.  Take a look at the ECMWF ensemble chart


you see the big rise this weekend and then a big fall as an upper-level trough tries to set up over us later next week.

It is interesting to note one week ago it appeared we would have a cool a showery weekend; now that weekend will be in the 90s.  In this case it was because models were too far west with the trough dropping over us.  Instead of coming over us, it’s dropping into the Intermountain region Friday and Saturday.

Enjoy the cooler temps tomorrow!

Chief Meteorologist Mark Nelsen

The Historic Heat Wave Is Finally Over

July 10, 2015

9am Friday…

For the first time in over two weeks a thick layer of cool marine air has flooded the western valleys of Oregon and Washington…the big heat wave is over!

Just as weird though, it appears temperatures will be consistently cooler than normal with a few chances for showers as we head through the next two weeks.  This is at the time where that is considered most unlikely in our “weather year”.  Typically the 2nd half of July is the most dependable time of the year for sunshine and totally dry weather.  It’s as if we’re doing things out of order with July in June and now June weather coming up for the next two weeks.

Let’s recap:

  • You just endured a bizarre period of (very early) heat here in Portland.
  • The past 15 days were all above 87 degrees.
  • 12 of the 15 were above 90!
  • As mentioned in the previous posting, this is unprecedented in Portland’s history, especially so early in season.
  • We topped out at 97 in Portland and over 100 a few times at Salem/Eugene
  • Hermiston just wrapped up 13 consecutive days at/above 100 degrees!  A gusty west wind is blowing there this morning, so cooling is arriving for you folks.  Note today’s high on the graphic is only as of 9am.


By the way, the June numbers are out from NCDC.  No surprise, the warmest June we’ve ever seen in our area.  The record warmest in a large part of the West (deep red color)


Take a look at the time series of just the lower elevations of Western Oregon; each June for the past 100 years or so.


Amazing that not only is it the warmest on record, but it totally blew away any previous warm Junes.  Looking at this I think it’s fair to say that it’ll likely be a long time before we see a June like that again!  Too bad for my garden, but better for those of you without air conditioning.

Knowing that it’s unlikely we’d see such a warm period again this summer to warm the mountain lakes, the family and I just camped two nights in the Cascades.

First, the bad news.  Clear Lake (the one near Timothy Lake) is drying up quickly.  It’s used for irrigation in the Maupin/Tygh Valley area and it’s headed down quickly.  The water was freakishly warm…my above-ground pool was 80 degrees when I left Tuesday and the lake was at least that warm.  But my kids could also walk most of the way across.  Here’s a pic from the dam:


Now the good news…we then spent one night at Lost Lake (near Mt. Hood).  Wow…it was incredible.  Of course it was full since it’s not a reservoir, crystal clear, deep blue color, and the water was in the 75-78 degree range at least 2-3 feet down.  That was a fun two days of water play with the kids!  The only thing I don’t like about Lost Lake is the campsites are so far from the lake (most of them).  I remember when I was a kid they were closer.

The marine layer is about 4,000′ thick today, so even the mountains have cooled off.  Enjoy the June-ly weather over the next week.

Chief Meteorologist Mark Nelsen

Vacation Time

July 6, 2015

I’ll be off through Sunday the 12th, so no posts during that time.

The Great 2015 Northwest Heat Wave; A Historic Weather Event

July 5, 2015

We are suffering through the longest heat wave we’ve seen in at least 75 years west of the Cascades.  Does it live up to the title billing of THE GREAT 2015 NORTHWEST HEAT WAVE?  I feel that’s definitely a YES in the lower elevations of SW Washington and NW Oregon.  Likely it’s the same in many other locations as well.

I had a lot of free time this evening since it’s a Sunday and we only have one show at 10pm.  So I took an hour and looked over past records for the Portland area.

Where the heat wave stands right now

  • Today is our 7th consecutive 90 degree day in Portland (all-time record is 10 days from 2009)
  • Today is the 5th consecutive day at/above 95 degrees! (not a record, we’ve seen 5 100 degree days in the past!)
  • 10 out of the last 11 days have been at/above 90 degrees
  • Today is the 14th day this summer above 90 degrees (we’ve passed our yearly “allotment” on July 5th)

* Note I’m calling this a heat wave (singular) because of the duration.  We only ended up with one day down at 85 degrees.  Looking back I’m quite confident we’ll look at it as one long event.

Our 7 Day forecast looks like this right now:

7 Day

Note that we PROBABLY have 4 more days in the 90s before the well-advertised cooldown at the end of the week.

Assuming we stay above 90 degrees as forecast, by Thursday evening it should look like this:

11 consecutive 90 degree days (A NEW ALL-TIME RECORD)

14 of 15 days reached 90 degrees or hotter (Unprecedented in Portland history)

18 – 90 degree days for the season…ALREADY BY JULY 9TH!


I have looked all the way back to 1940 in airport weather records (official observations) and can not find a similar duration of hot days; or anything close to it!  Now add the fact that warm overnight lows have been breaking records right and left (6 tied or broken so far).  This is a truly historic hot weather event for our area.  Not the hottest heat wave we’ve seen, but the longest.

Remember our “greatest heat wave” in 1981?  Yes, 4 days at/above 100 culminating in a 107 twice!  Or the July 1941 heat wave when we were above 100 for 4 days!  Even in those events, cooler weather (60s-80) preceded it or followed soon after.  This time it’s just been one long continuous warm spell.

There are two heat waves that attempt to come close to this one…

JULY 1985:  10 days 85+, but no more than 3 consecutive days above 90 at a time.  22 consecutive days;  only 2 were below 85!

AUGUST 8-22, 1967:  8 days 90+, 15 days 85+.  But all nights were 60 degrees or cooler…much more comfortable

By the way, you may be thinking of some other heat waves.  Wondering if I missed your favorite?  Here are 2 others that were quite impressive.

JULY 2009:  10 days 90+, then quickly down to 60s/70s for highs!

AUGUST 1992:  A hot month, 10 days 85+, but cool just before and after

AUGUST 1972: A hot 10 days, 7 days 90+, but cool just before and after like 1992

Have you noticed one thing has been missing?  No 100 degree days (in Portland).  In fact we haven’t been above 97 which is very strange for such a long period of hot weather.  This is the 2nd summer (so far) in which we are not seeing sharp thermal low pressure troughs develop west of the Cascades; sending a hot east wind down into the valleys.  That’s when we go above 100 degrees.  Those are often followed by a dramatic cool down as well.  Interesting that we’ve had upper-level highs consistently over us for a hot atmosphere both years, but very little amplitude to the flow to give us brief offshore flow.  We’ve been doing much of this heat with weak-moderate onshore flow.

So you’re sick of the hot weather and wanting a cooldown right?  I think most of us are. We definitely have one for next weekend, but it remains to be seen if it’s just a brief cooldown and hot weather returns the 2nd half of the month.

Chief Meteorologist Mark Nelsen

At Least It’s a Dry Heat

July 3, 2015


I’ve noticed the past few days have been very hot in the afternoon hours as the sun pounds down on me between car-work-store etc…

Yet in the mornings and evenings it’s not so bad…part of the reason is that we’ve had nice low dewpoints (moisture in the air).  They’ve been well down into the 50s most of the time.  That’s our classic “dry heat” here in the Pacific Northwest.  None of that sweaty stuff we had last weekend.

Due to the dry air, the Heat Index (a “feels like” temperature measurement) has been quite low over our area.  Compare that to some notoriously sweaty areas:


Key West (Florida) was 8 degrees cooler than Salem today, yet the heat index value was 10 degrees hotter!  I can attest to the heavy and sweaty feel to the air down there; that’s where I spent a few days early in June on vacation.  One bonus down there is that there’s usually some sort of easterly breeze.

There was a fire today near Mt. Adams and Oca Hoeflein’s Mt. Adams camera captured the smoke plume nicely.

Notice how it died down around sunset.  It’s possible the fire ran into the burned out area from 2012.  All through  September 2012 the Cascade Fire burned out much of the south/west sides of the mountain, eventually reaching 19,000 acres:


When a fire moves into a recently burned area there isn’t much left to burn!  Just grasses and small brush.

You may remember another large fire, the Cold Springs Fire, which burned about 8,000 acres on the SE side of the mountain in 2008.

Fireworks weather looks great tomorrow, temperatures in the 70s to around 80 right as most fireworks begin at 10pm.  Have a fun and safe holiday!

Chief Meteorologist Mark Nelsen

Hottest Day of 2015, But Big Cooldown On The Models

July 2, 2015

Today was the hottest of the year here in Portland; we hit 97 degrees


All of the metro area was in the upper 90s, with McMinnville (and possibly Salem) hitting 100 degrees.

If you hate the heat, you’ll want to stay hidden in a cave or underground bunker for a few more days.  I don’t see any significant drop in temperatures until after Monday


But notice the last bullet point on the graphic!  Over the past two days models have been giving us major hints that something is going to change as we head into mid-July.

The hot weather has been caused by persistent upper-level high pressure over the Western USA.  There is a slightly change for the middle of next week when the ridge splits into an offshore part and the rest retreats farther east of us.  That should give us more marine influence and a better chance of high temps dropping down into the 80s.

Beyond that, there is a common theme across all models today showing an upper-level trough developing near the West Coast in the middle of the month.  Take a look at the ensemble average 500 millibar heights for 16 days from now.  From the GFS, the GEM, & ECMWF.




They all look quite similar don’t they?  The show the ridge weakening and shoving much farther west out over the mid-Pacific.

This should lead to normal to below average temperatures.  Wow, that will be the first time we’ve seen that in about 5 weeks.

Here is the 12z ECMWF ensemble chart showing pretty good ensemble agreement on the cool down.  850mb temps come down right to average NEXT weekend (not this coming weekend) and stay there.


Last night’s monthly run of the ECMWF was similar, showing warm to hot first week, then big change during week 2:



We sure haven’t seen a below average deviation like that on the monthly run for quite a while.  Here is week 3 and week 4:



It’s interesting that any sort of significant ridging is totally absent anywhere on the map in late July and early August.  Taking a closer look at maps from WeatherBell it looks a bit different.  Apparently WSI’s contouring is a bit more coarse.  Heights are indeed above average during both of these weekly periods; just not dramatically so.  My gut feeling based on the info above is that we’ll have a below-normal period in mid July, then return back to normal conditions the latter part of the month.  Regardless, it’s also interesting that in the coming 1-2 weeks we’ll see temperatures go DOWNHILL instead of UP.  The old saying “summer doesn’t begin until after the 4th of July” is going to be wrong this year!

Chief Meteorologist Mark Nelsen

Dang, It’s Hot Today!

July 1, 2015

We are in the mid 90s at 6pm…wow, what a scorcher today!  We have hit 95 in Portland, tying the hottest temperature so far this year (last Friday).  It’s possible there has been a “between-hour” high temp of 96; we’ll find out when the climate report comes out around 7:30pm.  Check out the near-100 degree temps in the valley.


As of today we’ve hit the 90 degree mark 10 times already this summer.


Add in a few more over the next 4-5 days and we will have already had our normal yearly “allotment” of 90 degree days! The crazy warm weather continues…