Hottest Weekend of Summer? Could Be!

June 22, 2017

10pm Thursday

Our heat wave is still on for this weekend.  And it’s going to be a scorcher.  This is what we are forecasting as of Thursday evening here at FOX12:

Sunday will likely be the warmest day, that’s based on models showing a weak marine push just beginning to head into the Willamette Valley late afternoon Sunday.  In these cases of a “southwesterly push” of the cool air, the Portland metro area is typically the last to see cooling, or technically I suppose it’s the last area west of the Cascades to see the end of the hot temps.  I wouldn’t be surprised if Portland reaches 102 Sunday but Eugene only gets up to 95 for example.  Both Saturday and Sunday we’ll see perfect “offshore” windflow with a hot airmass overhead combining with easterly wind through the Gorge and down off the Cascades.  This pattern is just about as “perfect” as it gets for a heat wave west of the Cascades if you want maximum heating.  We don’t have many weekends with both days around 100 degrees, even in July or August so it’s always possible this weekend WILL be the hottest of summer.  But we won’t really know until late August of course.

So I think it’s pretty obvious we have a scorcher coming up, but what about the coastline?  The next two days will be cloudless with warming temperatures.  Saturday is the “scorcher” along the coastline since light offshore wind could push high temperatures (especially up north) up around 90 degrees.    Then a southerly wind reversal, which means a push of cooler air scoots north along the coastline, drops temperatures into the 60s or lower 70s Sunday.  A bank of fog/clouds will likely move north too.

A few questions you might have?  I’ve heard a few about humidity and nighttime temperatures.  Don’t worry about humidity, it’ll be dry.  Nighttime temperatures will be warming, but nothing too unusual due to the low humidity.

And the biggie…isn’t this unusual this early in June?  Yes, two highs right around 100 ARE unusual this early in the season, but it happens sometimes.  Back in 2006 we had a 101 followed by 102 in late June.  Summer temperatures ARE gradually increasing west of the Cascades, check out the change during my lifetime, or at least the part of my life that I would remember:

This is a graph showing average June through August temperatures for ALL stations in the Willamette Valley climate zone.  A few are in cities, but most are in rural areas, so this isn’t just a case of urban heating.  If you’re my age (around 50) and have lived here your whole life then you’ve probably noticed the same thing.  The last 4 summers have been quite warm with 2015 our warmest on record.  Assuming this warming trend continues, earlier heat will become more normal in our lifetimes.  Better get an air-conditioner!

Chief Meteorologist Mark Nelsen



June 21, 2017

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

A Week of Summer Temps Ahead

June 18, 2017

11pm Sunday

Apparently I picked the right week and a half to take off this June.  I had randomly picked this time about 9 months ago to take a trip with the family.  The high temps in the 60s and low 70s started the day I left (the 8th), and ended with high temps around 80 in the metro area today a few hours after I arrived back in town.

The sunshine was perfect today for Father’s Day and it appears we’ll see more pleasant summer weather through at least next Sunday.  Models are in good agreement with the first hot western USA ridge of the summer holding on all week just to our south.  This keeps wet weather systems away; all we have to worry about is the strength of onshore flow.  Eastern Oregon will be very hot tomorrow closer to that upper-level ridge

Meanwhile west of the Cascades I think it’s unlikely we get over 90 tomorrow, that’s in spite of 850mb temps around +18 or +19 in the morning.  Don’t think it’ll be a totally comfortable day…with leftover moisture from sprinkles yesterday plus high temps around 90 expect a bit of a “sweaty feel” compared to normal hot days around here.

Enjoy the warm sunshine this week!

Chief Meteorologist Mark Nelsen

Summer Vacation Time

June 10, 2017

The kids are out of school so it’s time for a trip.  I’ll be off all of next week, back at work Sunday the 18th.

No posts during that time

Chief Meteorologist Mark Nelsen

Rose Festival Weather

June 7, 2017

11pm Wednesday

Whew!  Two parades down and one to go.  FOX12 is the Rose Festival station so we broadcast all three parades.  That means everyone around here is VERY interested in the weather this coming Saturday.  Showers are an easy forecast because we’ll have an upper-level low almost directly overhead.  The airmass will be unstable so we’ll see a classic spring-like mix of showers/sunbreaks/downpours/thunder.

I think “bring umbrella, it could be wet” pretty much covers it.  The past statistics are sure interesting:

This time of year (as you probably know) is the transition between spring and summer, which gives us widely varying conditions from year to year.  This time of year you’ve got a little over a 1/3 chance of getting measurable rain on any one day.  I remember the 93 degree parade day…that was a scorcher about 14 years ago.  I don’t remember the 1/2″ rain in 1982.  And we can’t forget the street sweeping and dust masks needed for the 1980 parade…just days after an eruption of Mt. St. Helens.

We haven’t had a real soaker since 2007, most “wet” years we just tend to get a few light showers.


Chief Meteorologist Mark Nelsen


Spring 2017 Wrap-Up: Wet, but Normal Temps

June 6, 2017

7pm Tuesday

We are 6 days into summer, at least from a meteorologist’s viewpoint.  June through August are the 3 warmest months across most of the northern hemisphere and we’re just 2-3 weeks away from decreasing daylight.


So after all the wailing about a “cool and wet spring” how did it turn out?  Take a look at temps:

MarkSpring WrapUp

March and April were cool, but then May ended up as our first warm month since November.  So in the end there was nothing abnormal about our temperatures…very close to average, in fact the most “average” since 2008.


MarkSpring WrapUp2

Yeah, we know…very wet to start, then suddenly the faucet turned off the 2nd half of May.  So it ended up being the 5th wettest on record at PDX and the wettest spring in 5 years.

Those last two weeks of May were sure memorable…a taste of summer we haven’t seen during that same period in quite a few years.  I always find it remarkable how the “faucet” can just suddenly shut off in the Pacific Northwest.  We go from consistent showers and chilly weather and then suddenly no rain for 3 weeks?  Can’t there be a middle ground?

Looking ahead I see one more very warm day tomorrow, then a classic “Rose Festival Low” moves down over the Pacific Northwest Thursday through Sunday.  Check out the huge drop in temperatures on the ECMWF ensemble chart.  This shows temperature around 5,000′ in celsius for the next two weeks.


The screaming message here is that we’re headed into a cooler than normal period for at least a week beginning Thursday.  There are strong hints that we return to normal or even go a bit above by late NEXT week.

We haven’t seen real rain in Portland for about 3 weeks.  The last time we’ve seen more than .01″ was May 17th!  It’s time.  So how much will see?  It’s pretty clear that most of the rain Thursday and beyond will be in the first 3 days (Thursday-Saturday).  Check out the ECMWF model ensemble showing 24 hour rain totals:


Each of the 51 ensemble members are on the upper chart and the lower chart shows the average of all the ensembles.  Pretty clear that the wettest period is early on as I just mentioned, but now there are hints of some additional rain trying to show up that following weekend (17th/18th).  It’s something to keep an eye on.

Enjoy the last summery day Wednesday and make sure you have all your dry weather activities done by Wednesday evening.

Chief Meteorologist Mark Nelsen

Great Blog Post On The Paris Accords

June 5, 2017

7pm Monday…

Last week President Trump decided that the USA would pull out of the nearly world-wide agreement to limit carbon dioxide emissions signed by President Obama in 2015.  Of course the media went nuts with the story, but what does it REALLY mean?  I was thinking of posting about it, but then Professor Cliff Mass up at the UW wrote an EXCELLENT article detailing some facts (and some opinion) on what just happened and what he thinks should happen going forward.  He did a far better job than I ever could!  Here’s a quote:

“…First, the reality check.   Some politicians,  the media, and others have claimed that the loss of the Paris Accord is nearly the end of the world.  In truth, the Paris Accord was a voluntary agreement, with little teeth, and inadequate to do the heavy lifting that is necessary to deal with increasing greenhouse gases.  The voluntary national reductions would have only a minor impact on rising temperature, perhaps reducing the warming by a few degrees fifty years from now.”

and another quote referring to the political wasteland that the Climate Change discussion has become:

“Both the left and the right have used global warming as political tools and as litmus tests of “right thinking.”    Both sides need to stop doing this.  It wasn’t long ago (2008) that Senator McCain, the Republican presidential candidate, talked about the need to deal with global warming.  More recently the Republican party made skepticism about global warming an official tenet of their belief system.   Democrats and “progressives” have taken a similar tack, making  global warming action a central principle of their belief system.  And they have made the serious mistake of connecting climate change to their political goals (such as equity, racism, labor practices) and have participated in exaggerating current climate impacts in order to push folks  to “do the right thing.”

It was such a great read that I insist you read it yourself here:


Enjoy and discuss…Chief Meteorologist Mark Nelsen