Thick Smoke = Cooler Today, Back to Hot Tuesday

August 20, 2018

10pm Monday

Fire smoke had no problem moving down into northern Oregon last night and this morning.  In fact it was so thick (shadows barely visible at midday) that we were COOLER instead of WARMER today.  Lower 80s were the rule in the western valleys of Oregon and SW Washington

Todays Observed Highs OrWa 2017

What about tomorrow?  I think temperatures will soar quite a bit higher for two reasons.

  1. We had weak onshore flow today, but pressure gradients are switching now and we’re headed into one day of gusty offshore easterly wind tomorrow.  That alone would raise our temps 5 degrees or more.
  2. There are strong hints from the HRRR smoke modeling that smoke will thin significantly tomorrow afternoon.  That’s due to the strong easterlies bringing clear air from Montana westward all the way to the Cascades and beyond.  Check out the current smoke forecast for right now; widespread thick smoke across all of Oregon and Washington.  Much cleaner air just across the border in Canada.


Then the view at 5pm tomorrow after almost 24 hours of easterly flow


Look at that punch of cleaner air moving through much of Eastern Washington and right down into NW Oregon.  NASA’S GEOS-5 model shows a similar situation with smoke thinning the next 24 hours.

So the current air quality readings might improve quite a bit in the metro area and Gorge tomorrow afternoon.  At this moment it’s just as bad as we saw during last week’s smoky period

AirQuality Western Oregon

Looking ahead, it’s very obvious we have a sharp turn towards fall-like weather beginning Thursday.  It’s not that we’re suddenly going to turn rainy with highs in the 60s, but there’s no sign of a return to 90s or even 80s through the end of August (just 10 days away).

Check out the ECMWF ensemble chart for 850mb temps for the next two weeks.  Very good agreement that we’re headed into a much cooler period.  The green line is the average temperature at that elevation around 5,000′.  Notice most of the time Thursday and beyond the forecast temp is below that line.  Red is the average of all the ensemble members.  If this is the case, we’re done with the endless warm-hot days of summer and headed into a early fall pattern.

tseries_850t_000-360_Portland (1)

Unfortunately at this point I don’t see a good chance for a big soaking…the ECMWF average rainfall for this entire period is less than 1/2″ of rain.  Still, this weather will put a damper on fire behavior…baby steps toward the approaching wet season.

As for temps, you can see the stark change from Wednesday into Thursday as onshore flow kicks in and temps lower


I’ll be off the next few days, but back at work Sunday.  Things should look quite a bit different by then.

Chief Meteorologist Mark Nelsen

Hot & Smoky Ahead; Then “Fall” Arrives

August 19, 2018

8am Sunday

I’ve ignored weather maps during my weekend, but this morning I see three highlights while perusing weather maps with my coffee.


The first is that we’ve got another brief period of hot weather coming, although once again the heat won’t be too extreme.  We don’t get long heat waves in late August and this will be no different.  Highs reach right around 90-95 or so Monday-Wednesday.  Today should be fine.  Just a bit warmer than yesterday with highs in the mid-upper 80s.  You’ll notice a little more fire smoke than yesterday, and in parts of the metro area the air quality has gone downhill again.  We’ve got weak onshore flow today, keeping those temperatures in check.  Notice the easterly flow on the cross section forecast for Tuesday.   The colored areas are relative humidity above 70%, see how the marine layer disappears Monday PM and Tuesday AM.  “21/12” on the chart refers to 5am Tuesday.  “20/12” is 5am Monday.

But later Monday and all day Tuesday we get an offshore/easterly flow coming down out of Eastern Washington, through the Gorge, over the Cascades, and into NW Oregon.  That helps things heat up Monday and Tuesday, but brings a problem back…


Yuck!  I just checked the HRRR smoke modeling and it shows smoke from all those fires in northern Washington pouring back down over us just like it did last week.  The loop is here:  Here’s the image for right now.


and then the image for tomorrow morning around 8am…you see the northeast flow has brought the smoke right down over us again.


The smoke will be with us Monday-Wednesday (3 days), then a HUGE change is showing up on all models the latter half of the week…looks like FALL!


Yes, I know it’s not technically fall but it’s the biggest change we’ve seen since late spring.  All through July/August we’ve had a semi-permanent ridge of high pressure either over us, just to the east, or just to the west/northwest.  Here’s the ECMWF ensemble average of upper-level heights for Wednesday; warmer colors are above average heights and blue are below average


and then one week from now, Sunday the 26th


A cool upper-level trough over Western Canada and the Pacific Northwest.  This screams “end of summer weather” for at least 4-5 days starting Thursday.  A thick marine layer Thursday and beyond means you’ll need to get used to lots of morning (or all day) clouds and spots of morning drizzle at times.  High temps will drop at least down into the mid 70s.  This late in the season a thick marine layer with AM drizzle can keep us in the upper 60s too.  Here’s the ECMWF ensemble meteogram for Portland; quite a change eh?


Looks pretty comfortable!  It’s not like we’re entering a cool & wet period, but the chance for showers definitely goes up at times beyond Thursday, or maybe it’s better to phrase it as “guaranteed dry weather goes away for a few days.  Notice temps do rise slightly beyond Sunday, back to normal which is in the upper 70s the last few days of August.

I’ll be back at work today (I work Sunday-Thursday), forecasting on the 5, 8, 9, 10, & 11pm shows…I shouldn’t be hard to find!

Chief Meteorologist Mark Nelsen

Clean Air Returns & Thunderstorms Tonight Eastside

August 16, 2018

9:40pm Thursday

Today has been refreshing…brief morning clouds and then cooler temps.  We hit 83 in Portland this afternoon; down from 89 yesterday and 90s on Monday and Tuesday.

High Temp Last 13 Days

Most noticeable is the cleaner airmass over us.  Everyone in the metro area is breathing GOOD air quality this evening


You probably noticed there is still high-level smoke overhead, evidenced by the yellowish sunshine.  Even that goes away Friday as upper-level winds turn westerly for a few days.

We are getting another push of marine air this evening and models show low clouds coming up mainly the Columbia River for a gray start in much of Cowlitz, Clark, and Multnomah counties Friday.  After that you can expect a very BLUE sky overhead since that smoke should be gone.

As expected, thunderstorms have fired up across central and eastern Oregon this evening.  Take a look at the 100+ cloud/ground strikes in the past half hour

KPTV 2017 Default Earth

Many of these are producing very little rain so obviously this is a huge concern for fire starts.  Hopefully new fires remain small.  I saw what appears to be a new fire producing a large smoke plume just southwest of Summer Lake earlier this afternoon on GOES-16 imagery.

What’s ahead?  Typical late August weather…a little heat, but cooler periods as well.  It’s pretty obvious we have passed the worst of summer.  That is normal for us.  Nights are getting longer; giving us cooler nights.  In fact even the middle of the metro area should drop into the mid 50s tonight and tomorrow night.  Nice.

There should be one more brief hot period Sunday-Tuesday, then cooling again later next week.  Notice the good agreement on the ECMWF ensemble chart; a peak around Monday/Tuesday, then quite a dip later next week before more warming.


Down here at ground level that translates to high temps back into the 90s early in the week and then back down around 80 (or below) a week from now.  This is what the same ECMWF model thinks Portland will look like over the next 10+ days


Rain?  Unlikely we’ll see anything other than sprinkles out of marine clouds the next 10 days.  Only 6 out of 51 ensemble members bring .10″ or more to Portland in the next 2 weeks.


Chief Meteorologist Mark Nelsen

Thick Fire Smoke Is Back; But It Keeps The Heat Away

August 14, 2018

9:30am Tuesday

It’s back! For the first time since last summer’s Eagle Creek Fire,  the Portland metro area is basking in thick low-level fire smoke. This type of smoke with lowered visibility is what SW Oregon has been dealing with for a month!  Here’s a pic from Andrew Mork


Air quality is in the UNHEALTHY category across the Portland metro area and Columbia River Gorge this morning.


Up until this point we’ve only seen smoke high overhead. Easterly wind has brought smoke from Eastern Washington down into our area. It should clean out quite a bit tomorrow with a switch back to westerly wind. Air quality sensors from Oregon DEQ show UNHEALTHY air over us right now due to those smoke particles. Notice it only extends into the metro area with cleaner air down in the Willamette Valley.

The easterly flow this morning is the strongest we have seen since June.  Wind has been gusting up around 40 mph the past few hours at Crown Point in the western Gorge and Corbett was just about the warmest place in the metro area last night…only briefly dipping into the upper 60s due to mixing from the wind.

The wind goes back to westerly at low levels tomorrow which should clear us out quite a bit, but we’ll still be left with all the high level smoke as we’ve seen the past few days.  Fires are burning north of us in Canada, northern Washington, and to our south in SW Oregon.  It’s hard to get out of the smoke until flow goes westerly at all levels; we’ll likely not get totally out of it until Friday west of the Cascades.  Note the HRRR experimental smoke model forecast for Wednesday afternoon has the entire Pacific Northwest bathed in a smoke layer of some sort.  Click the image for a loop


The one HUGE benefit is that the smoke layer is going to keep temperatures well below what we would typically see with this airmass.  We have easterly offshore flow plus an 850mb temp of +20 on the morning sounding at Salem.  Models are forecasting +22 by this afternoon.  Under blue skies I would forecast a high of 100 this afternoon.  I think 90-93 is more likely due to the smoke…hot, but nothing crazy hot.

Chief Meteorologist Mark Nelsen

91 in Portland Monday

August 13, 2018

11pm Monday

Even with the thick fire smoke overhead we managed to make it over 90 in Portland once again as we head into a 3 day period of hot weather.  That makes today our 27th day reaching 90 this year.  It appears we’re going to break a record this year…likely early next week.

90 Degree Days Summer Heat

Assuming the smoke is at least as thick tomorrow, we should stay in the low-mid 90s once again.  IF we had typical clear blue sky I would forecast 100 degrees for Tuesday.  We have light easterly flow through the Gorge and over the Cascades plus 850mb temps should peak out around +22 by afternoon.  Luckily that smoke coming from fires in British Columbia, Northern Washington, & SW Oregon will keep temps lower.

There’s one other bit of good news, our average temperature begins to fall off tomorrow as we move into the final weeks of summer.

Heat of Summer Hot Temps

EVENTUALLY, it will turn cooler after this blazing hot summer of 2018!

Chief Meteorologist Mark Nelsen

A Rare Showery Saturday In August

August 9, 2018

1pm Thursday

Just a quick post about showers for Saturday.  I know there are lots of outdoor events, weddings, reunions, or camping in my case, this time of year, but at least this will settle the dust.

YES, most of us north of Salem and Newport (along the coastline) will see at least SOME rain during the daytime Saturday.

NO, this is not the beginning of a cool & showery weather pattern.  Hot August weather returns after the weekend.  Enjoy the showers and cool temps!  Highs will likely only make to around 70 or so that day.

The colored areas on these model forecasts (RPM & ECMWF) are where they expect at least .10″ of rain.



Showers could fall anytime between sunrise and 5pm or so Saturday north of Salem. South of there just a sprinkle or two. There could actually be some hefty showers (think spring downpours) NORTH of Longview and Astoria. And yes, I’ll be out there in the weather with everyone else…camping at Silver Falls SP.

There will be no rain south of Eugene along I-5, Mt. Jefferson in the Cascades, in the Gorge east of Cascade Locks, or anywhere else east of the Cascades.  Unless we get a rumble of thunder out of the heftier showers in SW Washington this isn’t a thunderstorm pattern either.

We go right back into hot weather the early part of next week; here’s the ECMWF forecast for the next 10 days.


Ignore the 100 late next week…that’s an “outlier” as we call it.  The model ensembles do not show extremely hot weather later next week.  But Monday/Tuesday WILL be hot.

Chief Meteorologist Mark Nelsen


Hot Weather Through Thursday, Then Cooling

August 6, 2018

11pm Monday

Today we hit 92 in Portland, our 22nd day this year at/above 90 degrees.

90 Degree Days Summer Heat

We are two days into our early August heat wave; I expect three more hot days this week.

Mark Hot Heatwave So Far

Will we hit 100 degrees?  I think it’s unlikely since fire smoke will continue to stream north through the rest of the heat wave.  Today you could see the “dim sun” outside giving the ground a yellowish look.  It sure reminds me of late last summer!  That, even with 850mb temps up around +23 Wednesday & Thursday should keep us just under 100.  But it’ll be close.

There is excellent agreement that an upper-level trough will move overhead late Friday and Saturday, pushing in a 5,000′ thick layer of cool marine air along with a much cooler atmosphere higher up.  That drops us into the 80s Friday and maybe 70s on Saturday.

By the way, as of this moment (through August 6th) we are enduring the 2nd hottest summer on record in Portland.  That’s right behind 2015 and just ahead of 2009.  Of course we still have 3 weeks left in meteorological summer so we’ll see how things turn out in the end.  Regardless, any hopes of a reasonably “cool” or average summer have been dashed by now!

MarkSummer So Far

Notice Salem, which has a much longer period of record, is running at 3rd hottest.  Other cities aren’t even in the top 5.  Seems like this is likely due to a growing urban heat island on top of our warming climate.  Cities are warming more quickly than rural areas or smaller towns.

Try to stay cool the next few days!

Chief Meteorologist Mark Nelsen