Vacation Time

August 13, 2019


I’m on vacation the rest of this week, through Saturday.  No posts until I get back to work Sunday.  Looks a bit September-ish on those weather maps.


Record Rain In Portland Saturday Evening

August 10, 2019

11pm Saturday…

Just a quick post to let you know we set a rain record in Portland today.  Between 4:30-6:00pm a line of heavy showers formed right over a line from Sauvie Island down to Parkrose.  Portland Airport, the official observation location for Portland, happened to be right under the downpour.  And it REALLY rained hard!  0.67″ in one hour from 5pm-6pm.  Just by chance, that number also happens to be the 30-year average August monthly rainfall.  So yes, we saw our typical August rainfall in just one hour…at PDX

Rain Record PDX_AC

Now that was at PDX.  At the same time, little to no rain fell just a couple miles south in Alameda and the Lloyd District!

Rain Metro Plot MANUAL

That’s how heavy summer “convective” showers operate.  Little areas of big downpours milling about, dumping big loads of rain on some neighborhoods but leaving others dry.  There were two Portland HYDRA sites (Portland Bureau of Environmental Services) that recorded over 1.50″ of rain at the same time.  You see the Portland Airport Post Office location recorded over 2″ of rain.  I’m a little skeptical of that one only because we didn’t hear of any flooding issues at the airport itself.  When we had 1″ rain in one hour about 10 years ago I remember there was water all over the place around the terminal.  Regardless, the graphic above shows the wide variety of totals, sometimes even just a couple miles apart (Newberg).

Showers are FINALLY dying down this evening and Sunday should be dry…unless we somehow get a morning sprinkle out of the low clouds.

By the way, today is one of three times we’ve hit our all-time high in Portland.  107 on this date in 1981.  But no heat waves in sight the next 7+ days.

Mark PDX Record Hottest Days Ever 100

Enjoy your Sunday!

Chief Meteorologist Mark Nelsen

Thunderstorms Across Much of Oregon This Evening & Tonight

August 9, 2019

5:00pm Friday…

We are in a “perfect” setup for thunderstorms across the region the next 12-18 hours.   Just take a look at the latest GOES-WEST satellite image, thunderstorms popping up all across SW, Central, & far Eastern Oregon.  Notice only the northern section of the state is seeing significant sunshine.  There was one small thunderstorm that moved through the metro area around noon, from Tualatin up to Helvetia.  Otherwise it’s been quiet up here.

satellite image

The geostationary lightning mapper shows widespread lightning at this moment.  That’s a new feature of the GOES-R satellite series.


All week long an upper-level low has been sitting offshore not doing much, but it’s on the move now.  Here’s what it looks like up around 18,000′.  Sitting off the northern California coastline.  Wind follows those lines which means the flow overhead is now coming at us (west of the Cascades) from the southeast.  Assuming atmospheric dynamics are good, there’s no reason thunderstorms can’t drift from Central Oregon over the Cascades and then down into the lower elevations westside…that includes the metro area.


This setup IS the pattern in which we get our good “summer” thunderstorms in Portland.  That doesn’t mean everytime this pattern sets up we get an event, but it’s a good sign.

By midday Saturday the low has moved into Southern Oregon, the vast majority of showers Saturday will be over and east of the Cascades because of this movement.


By Sunday morning it’s moving into Idaho and we’re back to boring westerly flow.

500 sunam

Right now there is a Severe Thunderstorm Watch from Lane county northeast into Eastern Oregon.  In fact at this moment several severe storms are ongoing in Central Oregon.


Models disagree whether we get a bunch of storms moving north WEST of the Cascades this evening, but since the pattern is nearly perfect I’m inclined to believe the HRRR model is doing well.  It shows thunderstorms moving north through the Willamette Valley and Southwest Washington and looks like this at 2am.  It wants to keep most action close to the Cascades.



  • My gut feeling is that ANYONE from the Coast Range to Idaho could see an overnight thunderstorm.  Best chance near/over the Cascades.
  • Severe thunderstorms (producing wind gusts 58mph or higher and 1″+ hail) are unlikely north of Eugene in the valleys.
  • This COULD be the one night each summer when we get a lightning display…maybe.
  • Saturday doesn’t look very wet west of the mountains, in fact the Coast may just stay dry!

I’ll be heading into work for the 8/9pm shows on FOX12PLUS, and 10/11pm shows on FOX12.   Right now I’m nursing a twisted ankle from a midday run.  Ouch!


But I should be able to hobble into work the next couple of hours.  Don’t want to miss any thunderstorm fun…I only need one foot to stand up right?

Chief Meteorologist Mark Nelsen




A Record Warm Night In Portland’s “Urban Heat Island”

August 5, 2019

6pm Monday…

Do you remember WAY BACK in time the common saying that “you don’t need air conditioning in Portland“?  By “back in time” I mean at least 20 years ago, and really back in the 70s/80s and earlier. And that saying applied to any area west of the Cascades too.

I think those days are long gone and won’t be coming back for any of us alive right now.


For one, our slowly warming climate (globally and in the Pacific Northwest) means warmer nights in general as each decade passes.  But a larger influence in the urban areas is the steadily growing “heat island” we are creating, especially around Portland.  More on that just ahead.

Last night we broke a “record warm low” record at the airport where it only dropped to 65 degrees.  20 years ago that would have been a real big deal.  Today no one even mentioned it to me here at work, just another “warm night”.

Mark Portland Record Warm Night

We’ve seen a large number of 60 degree or warmer nights in Portland this year.  Here are the numbers compared to recent years; note each count is up to August 5th only.  Apples to apples comparison…

60 Degree Nights Portland

That’s rough sleeping weather if you don’t have air conditioning!  Most of the night was spent in the 70s.  I talked to someone over at PGE maybe 10 years ago and he mentioned only about 30% of customers had air conditioning in the early-mid 90s, but something like 70% do now.  Part of the reason is due to people moving here from hot climates that expect AC.  The other part is due to the rising popularity of heat pumps (I have one).  They heat in winter and then function as an air conditioner in summer.

Now check out other low temps across the metro area last night:

PDX Observed Low Today

Notice all the areas down into the 50s.  Those are generally locations not surrounded by miles of concrete and buildings.

That warm central part of the urban area is called an “urban heat island” and it has been growing over the decades.   In the 1960s the Portland metro area contained around 1 million of us.  Now that number is about 2.5 million!  That’s a lot of new homes/businesses, highways, asphalt and concrete…

Take a look at number of nights above 60 in Portland over the decades.  The 15 year average has gone from around 8 back in the 1950s to 33 now!


That’s quite a rise.  So then I checked Salem airport which has seen a slower urban growth during these decades.  Not quite the same; a far less dramatic rise, until just the past few summers.  Average goes from maybe 4 a year to 13.  Keep in mind that both of these graphs only show the nights this year SO FAR.  That won’t be the final number on the far right side.


I also checked a few non-urban locations west of the Cascades with a long record.  Many of them have seen a SLOW increase in warm nights.  Portland Headworks, around 700′ between Sandy and Corbett has seen a gradual rise from around 1-2 60 degree nights to around 8 now.  That surprised me.  There ARE more warm nights in summertime even in rural areas west of the Cascades.

Coastal lows are rising as well.  Since Astoria almost never stays above 60 degrees I lowered the criteria to 55 degrees.  There were about 30 lows that warm in the 70s, but that has risen to around 45 the past 15 years.

But the warming doesn’t cover areas east of the Cascades.  Pendleton sees FEWER 60 degree nights than it did before 1950.  Baker City is similar.  Interesting eh?

A Quick Summary

  • Summers are warming in the Pacific Northwest, and that season has been changing more west of the Cascades than any other season.
  • Summer nights are gradually warming for all of us west of the Cascades
  • Summer nights are rapidly warming in urban areas (mainly Portland Metro)
  • Summer nights have seen little/no change east of the Cascades at night.  Just open your windows at night and you should be good!

Chief Meteorologist Mark Nelsen

94 in Portland Sunday; 3rd Hottest of Summer So Far

August 4, 2019

9:30pm Sunday…

Today was a scorcher, officially 94 at PDX

Todays Observed Highs OrWa 2017

That 94 is the warmest since the early June heat

Hottest Days This Year

For the geeks out there, the afternoon sounding over Salem showed an 850mb temp of +17.2; it’s amazing we made it into the low-mid 90s.  According to my chart from 1999-2009, even the warmest east wind events at +17 have not been able to produce a high temp higher than 90 in Portland in August.  Today was day #7 at/above 90 degrees in Portland, a little more than halfway to our typical 13 day allotment each summer

90 Degree Days Summer Heat

Very little changes the next two days, in fact models warm those 850mb temps another 1-3 degrees.  Marine layer along coastline remains very thin so there won’t be much inland push. The result should be two more days in the lower 90s in the metro area.  Overnight lows remain very warm in the Portland “urban heat island”.  The majority of each night will be spent in the 70s with just some mid-upper 60s after 3am.  Outlying areas will be warmer than normal, but at least down into the upper 50s or 60 degrees.

We are right on the edge of the usual summertime western USA hot upper-level ridge.  And once again there is a “hot” upper-level ridge across southern Alaska as well.  Here’s the ECMWF ensemble forecast of 500mb heights plus anomaly (in color) for Monday:


Notice there is a weak upper-level low offshore, by Thursday the low has deepened and is moving toward the West Coast.


The result is a much deeper marine layer Thursday, maybe even some spots of drizzle and high temps back into the 70s.  As that low moves overhead Saturday (next image) a few showers may show up, similar to what we just saw Friday.  PDX picked up .04″ that day.


If you have a wedding or outdoor event Saturday, don’t freak out yet.  It might just be scattered AM showers, but too far out to see exactly what’s going to happen.  Regardless, the ridge seems to bounce back and Sunday-Monday sunshine and normal temperatures return.

Chief Meteorologist Mark Nelsen


Nice Summer Weather Ahead as August Arrives

July 28, 2019

7pm Sunday…

Today has been another fantastic summer day; wall to wall sunshine with high temps reaching the mid 80s west of the Cascades.

Todays Observed Highs OrWa 2017

8 of the past 9 days we’ve reached 80 degrees or higher and we haven’t gone above 92 degrees.  Many of us would say this is summer perfection in the Pacific Northwest.

High Temp Last 13 Days

July has been running just slightly warmer than average west of the Cascades.  But statistically it’ll just be considered a “normal” July temperature-wise.  Some parts of Oregon are running slightly cool for the month, but again no big departure from average.  Basically kind of a “Meh” sort of July.  My garden seems to like it and the pool is getting good use so no complaints from me.  It’s a nice break from the excessive heat the past 4-5 summers.  By the way, we still haven’t seen 3 or more consecutive days above 90.  Other than those two days 97-98 degrees in early June, we just haven’t seen any sort of extended hot period.  The tally for this summer so far stands at 5 days at/above 90 degrees.

90 Degree Days Summer Heat

My gut feeling is we will end up close to average for the year, or even a bit below.   We’ve seen LOTS of 80 degree days, far more than the very cool summers of 2011, 2010, 1993 & 1983.  That probably explains the happy garden; no extremely hot weather but lots of warm nights plus warm days

80 Degree Days SO FAR

There is still no sign of a pattern change.  That’s either a change to cooler/showery weather or a change to more ridging with hot weather.

I expect a bit more weak onshore flow Monday/Tuesday for some areas of AM clouds + cooler PM temps.  Then weaker onshore flow Wednesday/Thursday = warming temps again.  Probably mid-upper 80s those days.  After a weak system passes close by on the way to B.C. on Friday some upper-level ridging briefly tries to assert itself along the West Coast again.  So the first weekend of August looks similar to what we just saw today; plenty of sunshine and temperatures likely into the 80s.

I’ve got some time off later this week so probably no new post until Sunday the 4th.

Enjoy your week!

Chief Meteorologist Mark Nelsen




Last Work Week of July Ends Hot

July 25, 2019

6pm Thursday…

Today was a hot one west of the Cascades.  We hit 91 degrees in Portland

Todays Observed Highs OrWa 2017

You see the entire Willamette Valley made it into the lower 90s.  Today was the 4th day this summer with temps above 90 degrees

90 Degree Days Summer Heat

That’s FAR better than last year.  It was a crazy hot July, & summer.  Half the month baked under 90+ weather.  At this time last year we were in a 9 day stretch with temps at/above 90 degrees!

Heat Wave July 2018

This month is running right around average; highs a little below normal, lows a bit above normal.

What’s ahead?  One more 90 degree day is likely tomorrow, then a good push of marine air = lots of clouds through at least noon Saturday.  Then the marine layer thins Sunday morning for a warmer/sunnier day.   At FOX12 we now have access to high-resolution ECMWF model data at 1 hour increments.  That’s for the first 3.5 days.  Very useful for upcoming snow/cold forecasting since we’ll be receiving midday and overnight runs (6z/18z) as well.  In this case it shows that thick marine layer Saturday morning…

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So something for everyone in the next week!  Well, not if you like rain.  I don’t see any decent chance for rain; but that’s normal this time of year.  The ECMWF ensemble 24 hour precip forecast for the next two weeks


We appear to be somewhat locked into a “just right” weather pattern for at least the next 10 days.  A hot ridge of high pressure remains somewhere just to our east, and upper-level lows go by to the north or remain well offshore.  This keeps us from turning crazy hot (no heat waves), but a cool/showery pattern isn’t in sight either as those lows stay away from most of the Pacific Northwest.


Normal summer weather continues until further notice.  Daytime highs somewhere between 75 and 90 into at least the first few days of August.  So get off your computer/phone and get outside!

Chief Meteorologist Mark Nelsen