Yep, it was cold! Coldest September day in at least 71 years in Portland

September 29, 2019

8:00pm Sunday…

No, you aren’t crazy; today felt like Thanksgiving Day outside.  Cloudy, rain showers at times, a breezy and chilly east wind blowing out of the Gorge etc…

Todays Observed Highs OrWa 2017

Officially it appears Portland only hit 52 degrees at the airport.  That’s ties the all-time coldest September day.  It hit 52 on September 26th 1948 as well.  That’s an average high for the 3rd week of November around here.  For the first time a cold east wind was blowing through the Gorge too, gusts up around 35-40 mph.  This is due to a modified arctic airmass that has spilled south out of Canada.  Compare this to the coldest day each of the past few Septembers

September Coldest Day

We were probably complaining about those lower 60s too…

By the way, there is still an observing site in downtown Portland and the preliminary high there was only 49.  If that holds, that means it may have been the coldest September day in Portland in 145 years!  That said, the downtown temperatures records are a bit sketchier, sometimes on top of very tall buildings and they’ve been moved around quite a bit.   Regardless a high temp around 50 shows how rare it is to see an airmass this cold so early in the season.

Of course it’s been snowing in the mountains since Friday night and a LOT has fallen above 5,000′.  These are estimates, based on pics, ski area reports, and NW Avalanche Center telemetry.  There is

Snow Mt Hood Totals

The next 7 days look uneventful…lots of sunshine and a couple cold mornings ahead.  A few outlying areas could see light frost tomorrow or Tuesday morning.  Just in case, bring in anything that shouldn’t freeze tonight.  No, not pipes/hoses etc…just plants.  We’re talking just a bit of frost touching the plants, not a freeze.

Forecast Tonight Metro

Alright, so the #1 question I keep getting is:


I think the short answer is NO.  What happens in September or October typically doesn’t have any positive correlation to the following winter that I’m aware of.   I’ve never noticed a weather pattern in these months that repeats through the following winter season.  But just for fun, let’s see.

Because this cold/snow event is so early in the fall season, there aren’t many winters to compare this one too.  For example, late September or very early October snow has only been recorded 4 autumn seasons at Government Camp.  3″-1984, 2″-1972, 2″-1971, and then October 4, 2009 when 3″ fell. Then let’s take 1948 as the other year we only hit 52 in Portland in September.  There were 3 very chilly days in late September that year.  So that gives us 5 years with very early season snow at Government Camp and/or very cold lowland temps.

What happened the following winters?

Winter 1948-49 

23″ snow in Portland that year, mainly January and February.  Extremely cold January 1949.  Nov, Dec, & Feb brought big snow to mountains.  466″ total for winter at Santiam Pass.  A very active winter with lots of lowland snow and extremely cold January

Winter 1971-72

Good snow year in Cascades, in fact 3rd snowiest winter at Government Camp.  But that wasn’t reflected down in Portland, 5″ snow for winter season.  An active winter with big mountain snow but nothing too unusual in lowlands.

Winter 1972-73

Extremely cold arctic blast early-mid December, 6″ snow fell in Portland that month, but little/no snow rest of winter.  A relatively dry winter with no real good Cascade snow until later in December (slow ski season start).  Crazy cold early, then a typical winter otherwise.

Winter 1984-85

Big October snow in Cascades and good ski season start.  Then NO snow with a massive ridge overhead all of January.  I remember that one.  Fog or east wind all month (depending on where you lived).  Then tons of February snow in mountains and even some lowland snow that month.  It was a relatively active winter, but with a weird “stoppage” in January.  8″ total in PDX.

Winter 2009-10

Other than a December freeze, a classic mild El Nino winter.  Only one 3 hour snow event (the December 29, 2009 commute debacle) in Portland.  This was the 2010 Whistler Olympics when it was very mild and they didn’t have enough snow at some of the venues.  Cascades didn’t have a very good snow year.  Only 9″ fell at Hood River all winter in the Gorge.  A mild & “boring” winter much of the time.

I suppose one could argue that in each of these “early cold” years at least SOME snow fell in Portland the following winter.  Maybe that’s because this big ridge offshore and cold trough dropping through Canada tends to repeat in the following months?  That’s a possibility.   As mentioned in previous posts, the current pattern is what gave us the record cold/snowy February this year.

One more thought…we’ve now seen three consecutive winters with 6″ or more snowfall at PDX.  The last time we’ve seen FOUR is way back in the mid 1950s.  We’ll see if it happens this year


Chief Meteorologist Mark Nelsen



Thunderstorms Pop Up Over Central & East Metro

September 29, 2019

4:25pm Saturday…

Today has been uneventful in the lowlands…until a line of thunderstorms formed over the southern Washington Cascades and dropped down into east Clark County.  These storms have slid south across the Columbia River and into East Portland, along and east of I-205.  Notice how nice it is Downtown right now, but dark skies and thunder to the right


Radar shows the heaviest action is over NE Portland & Parkrose right now, headed directly toward southeast Portland & Milwaukie.  It’s plenty cold for lots of hail too.

web_metroradar (1)

I see Clark Public Utilities has over 20,000 customers out…that’s a lot of lightning-related outages.

Showers have been powered by the very cold air overhead and relatively “warm” air down here at the ground.  A 60 degree high when it’s around freezing up at Timberline is an unstable atmosphere.  By the way, it appears Timberline has picked up 7-8″ of new snow so far.

So keep an eye to the sky the next 2 hours, storms are moving from north to south.  Showers and thunderstorms will die down as sunset approaches.

Chief Meteorologist Mark Nelsen

First Snow In Cascades This Weekend, Plus Cool Showers in Lowlands

September 26, 2019

7pm Thursday…

Get ready for a real taste of October weather this weekend!  Luckily that does NOT mean a ton of rain.  Let’s just say it’ll feel a bit more “refreshing”.


  • Nothing dramatic is expected (weather-wise) below 4,000′ over the next few days
  • Cooler showers arrive Friday afternoon in NW Oregon and SW Washington.  Then expect light showers off/on Saturday.  Sunday might be dry west of the Cascades.  There will be plenty of sunshine between showers the next few days, not gloomy at all.
  • Coastal weather looks great!  Not many showers Saturday OR Sunday.
  • Temperatures drop well below normal for late September, but frost is unlikely for 90% of us west of the Cascades
  • Light snow is possible down to around 4,000′ or maybe a bit below both Saturday and Sunday mornings.  Trace-2″ at Government Camp, but possibly 6-10″ up at Timberline Lodge by Sunday afternoon when things dry out
  • Passes should remain clear, although a brief morning dusting or icy spot is possible both Saturday and Sunday mornings.

This weather pattern has been forecast quite well by our weather models.  For the past week they’ve been showing a cold pool of air dropping south through western North America.  Sure enough, this evening a cold “upper-level trough” is right over Juneau, AK


By Friday afternoon it is right over Washington, this IS our “arctic outbreak” pattern in winter.


Then by Saturday afternoon it’s over NE Oregon.  A large upper-level ridge has developed in the eastern Pacific and cold northerly flow extends from the Yukon down to California!


We get a surge of showers ahead of it Friday afternoon and evening, then the majority of shower action Saturday evening and beyond moves south and east of us.  At the same time high pressure at the surface turns our wind flow “offshore” late Saturday.  That gives us an easterly wind Sunday and Monday, drying things out with plenty of clearing.

The WRF-GFS (from UW) cross section over Portland shows the big cool down in the airmass overhead.  Time goes from right to left, starting with this morning and ending on the left side with Sunday afternoon.    I’ve drawn the zero degree line (celsius) in blue.  The 850 horizontal line is around 4,000′.  You see it goes from around 50 degrees (F) at that elevation today to about 32 degrees late tomorrow night.  It remains within 5-10 degrees of that freezing mark through at least Monday morning.


That means it’s reasonable to say anything above that 4,000′ elevation will fall as snow beginning sometime after sunset Friday.  Models are showing plenty of mountain precipitation tomorrow night through Sunday morning.  I see the 18z ECMWF is giving the higher parts of Mt. Hood 6-10″+.  That seems reasonable.  Same thing in the central Cascades of Oregon and at least 2-6″ in higher parts of Eastern Oregon too.


Our RPM model thinks there will be spots over 10″ up around Timberline and higher.  Seems reasonable and goes with the Euro forecast

RPM Snow Accumulation Mt Hood Zoom In

There are even hints that at least a dusting could fall down to Sisters, Bend, and Redmond by Sunday morning with a cold northerly wind blowing moisture “upslope” into that area.  This is a classic hallmark of an “arctic blast” in that area.  Northerly flow moves uphill from the Columbia River into Central Oregon, clouds form, and snow is squeezed out when the air rises.  We don’t get many situations with flow from that direction but it’ll probably happen over the weekend.

The big snow/cold event will be to our north and east.  Look at all the Winter Storm Watches and Warnings across Washington, Idaho, & Montana.  Some spots in the Rockies could see 3-4 feet of snow!  Very early, even for that area.

Winter Weather Advisory 2017

So how “cold” will we get in the lowlands west of the Cascades?  For most of us Sunday will probably be the coolest day.  Even with abundant sunshine we’ll barely make it to 60…maybe only upper 50s

Forecast Max Temperature NWS NDFD Grids

If you’re a gardener like me you might be worried about frost.  I think that’s unlikely for most of us west of the Cascades.  Maybe either Monday or Tuesday morning around Tillamook, Vernonia, Banks, Battle Ground.  Just the very coldest outlying areas.  The rest of us remain above 35 degrees.  Your warm weather veggies won’t like it, but it’ll sure give them the hint the “end is near” for this growing season.

Forecast Min Temperature NWS NDFD Grids

What you’ll notice most Saturday through early next week will be the refreshing air and bright sunshine and of course much cooler mornings.

Enjoy your weekend!  Chief Meteorologist Mark Nelsen


September Ends Cool; Some Mountain Snow Too

September 23, 2019

9:30pm Monday…

With a week to go, September is running near average temperature-wise.  That comes from a very warm start followed by the last 9 days of cool temps.  Across other parts of Oregon it’s a bit below average.


Looking ahead, it’s clear September will end very cool this weekend and early next week.  In fact it’ll be about the coolest it can get this time of year.

Right now the very weak late September jet stream is just to our north, sending plenty of clouds and a few sprinkles.  That general setup continues through Thursday.

Mark Jet Stream

There won’t be any weather systems nearby Wednesday so that should be a spectacular day like we saw this past Saturday.  But Friday through the weekend that strong ridge of high pressure offshore pushes west and north.  That forces a cold dip in the upper atmosphere south over the western USA.  This IS the same setup that sends cold arctic air down into the Pacific Northwest during the winter.

Mark Jet Stream3

But of course it’s late September so snow won’t fall down to sea-level, or anywhere close.

For the weather geeks, 850mb temperature is forecast by both ECMWF and GFS to fall to at least +1, and possibly as low as -2 over Portland/Salem.  The coldest on record over Salem anytime before October 7th is between -2 and -3.  So it doesn’t get much colder than this in late September.  What does that mean?  It means snow COULD fall as low as Government Camp (3,500′).  Of course that means precipitation has to show up.  The earliest fall snowfall at Government Camp was September 23rd, 1984 when 3″ fell.

ECMWF Snow Level From 850mb Temps LONG TERM

This setup is typically not a big rain/snow producer; because the air is coming down from dry land up north, not from the Pacific Ocean.  Take a look at three rain forecasts for Friday through next Monday.  Generally not much rain in the lowlands

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This general pattern is likely to stick around for awhile.  Both 6-10 day and 8-14 day outlooks from CPC show the same “western trough/eastern ridge” pattern continuing through the first week of October.


Mark CPC 6-14 Day Outlook wKML

Mark CPC 6-14 Day Outlook2 wKML

Chief Meteorologist Mark Nelsen

An Early & Wet Fall Continues; Even Cooler Temps On The Way

September 19, 2019

7pm Thursday…

It was dry today!  No rain in Portland today, what a nice break after so many downpours the past week.   Don’t get used to the dry weather, it’ll be wet again after midnight, plus Sunday should be a soaker too.  Maybe more important, all our models are showing even cooler conditions to wrap up the last 10 days of September.

Summer “ended” on September 6th this year in our area; that was the end of reliably  warm & dry weather.  There’s no sign of anything above 75 in the next week either and our very wet September will continue…

The updated September numbers so far for Portland.

Rain PDX Last 10 Days

A rain total above 3″ in September has only occurred a few times the past 30 years.  In 2013, 2010, & 1996.

Take a look at some other spots around the region, some hefty totals in the Coast and Cascade Ranges

Rain Totals Metro Area

The entire region has been wet too.  The precipitation anomaly for the past 10 days


What’s ahead?

Real quiet tonight through Saturday, but a strong onshore flow and a dying weather system gives us light showers tonight through the morning commute Friday.  Saturday still looks great, at least compared to what we’ve seen lately.  Partly cloudy with temps making it into the lower 70s; at least a little more reasonable for late September.

Sunday = a soaker as an upper-level trough moves overhead accompanied by a cold front.  The entire first part of the day should be wet, then it’s on to showers the 2nd half.   Monday should be reasonable as showers end, but cool with 850mb temps only around +5.  Even with some sunshine the best we’ll do is mid-upper 60s.

Weather geeks will recognize the weather pattern the rest of next week; a classic arctic blast setup for wintertime Wednesday through Saturday.   Look at the ECMWF ensemble 500 millibar height chart for next Tuesday.  A strong ridge attempting to build over and just west of the West Coast.  Heights go up to around 580 or so which is typically warm fall weather.  Yet there is plenty of fast westerly flow overhead which keeps us from getting very warm with lots of cloud cover and maybe even showers making it as far south as northern Oregon.


But see what happens by Thursday a week from now?  The ridge is retrograding (moving farther to the west) and building over Alaska.  That forces a cold airmass to move south through Western Canada.  You can see a cold upper-level trough dropping south around Juneau.  At this point it’s showery over us (although not stormy) and snow levels are heading down toward the Cascade Passes for the first time this fall season.


Then two days later…Saturday the 28th.  This is the pattern we had in February with cold (cool in September) Canadian air pouring south into the western USA.  A strong ridge is…wait for it…parked right over Alaska and the eastern Pacific.   Hmmm, just like February and parts of this past summer.  Interesting.  This pattern is not very wet and could give us partly cloudy skies with daytime highs in 60s and lows in the 40s.


I’ve only shown you the ECMWF ensemble maps, but the Canadian and GFS are very similar.  September will likely end cool.  The previous run of the ECMWF showed this similar “dipole” of a chilly western USA and warm east continuing into at least the first few days of October (through the next two weeks).  Surface temp anomaly from September 29th through October 6th…


The effect is clear; the 15 day ensemble low/high temps for Portland are almost all well below average for late September and early October



  • We are done with “summer weather” and even any significant warm & dry spells.  At least through the end of this month.  We can have spells of warm & dry weather in October, but that comes with nights in the 40s and highs in 70s; definitely not “summer-like”.
  • It won’t be quite as wet the next 7-10 days, but we could easily see another inch of rain or more in the next week
  • A first frost is likely many areas east of the Cascades within the next 10 days, and possibly a few of the coldest areas in Western Oregon and Southwest Washington.
  • Timberline Lodge at 6,000′ will likely see its first snow of the season about a week from now.  Snow may get down close to the Cascade Passes (briefly) too.

Chief Meteorologist Mark Nelsen

A Wet September, And More Rain On The Way

September 15, 2019

11:30pm Sunday…

A busy day with 5 shows this evening, but I’ve been watching lightning offshore from our Seaside and Lincoln City cams.  That’s been fun.

What a soaker today with around one inch of rain in parts of the metro area as a slow moving system moved overhead.  It was one of Portland’s wettest days this year.

In the first half of the month we’ve picked up our typical September rain AND it’s been the wettest first half of September in 23 years!

Rain Record PDX

There were quite a few spots that picked up more than 1″ of rain.

Rain Metro Today Databound.png

Cool and unstable air is moving over the very “warm” ocean water offshore this evening.  Did you know it’s 65-66 degree water just offshore?  That’s much warmer than normal.  These temps in Celsius of course.


The “Blob” covers a huge part of the Eastern Pacific this fall.  Just above all areas are running much warmer than average.  But that’s a story for another day…


So if you live at the coastline, expect thunderstorms at times tonight, but they should die as they move inland.  Then from midday tomorrow through afternoon, the inland heating with sunbreaks should give us thunderstorms with the associated downpours and possibly hail.  That will be for anywhere west of the Cascades including the Portland Metro Area.

Lots more rain to come with an organized frontal system Tuesday.  More on that tomorrow as we plow through a wet September.

Summer seems a long way back now…

Chief Meteorologist Mark Nelsen

Summer 2019 Wrap; A Surprisingly Warm Summer

September 11, 2019

7pm Wednesday…

It feels like autumn outside and there’s no sign of a long warm & dry spell ahead.  Fall is here which has worked out just about right this year.

Officially fall arrives weather-wise on September 1st according to NOAA & the National Weather Service.  Traditionally of course we think of it starting with the Autumnal Equinox late next week.  Regardless, as meteorologists we consider summer to be June-July-August so let’s take a look back at Summer 2019.   The numbers might surprise you.

First, let’s get this out of the way…


That includes both urban and rural areas.  Even now I’ve seen people claim this was a “cool summer” or a “terrible summer” on social media.  That’s a ridiculous claim and not supported by facts.


In many areas west of the Cascades, this summer was WARMER than any summer before 1958.  A better way to state this?  In the 1930s-50s this would have been considered one of the the warmest summers on record!  That shows how our summer climate has warmed over time.    First image includes lowlands west of the Cascades between the Coast Range and Cascades.  Second image is coastal areas.  Data from NCEI.




Even though west of the Cascades it was in the top 1/3 of “warm summers”, this summer was COOLER than the past six.  The coolest since 2012.  That also tells you how crazy hot the past few summers have been.  This is likely the reason many of you think it was a “cool summer”.  But definitely not.  In fact check out the 80 degree days in Portland; a bit above average so far

80 Degree Days Yearly


Warm nights were the rule this summer.  Of course in the urban areas it’s hard to chart long-term climate trends for low temps since cities turn warmer as they grow.  I covered that in a post earlier this summer.  But even in rural areas there were plenty of warm nights.  Part of it was due to cloud cover, some likely due to the return of a warm “blob” of water in the Eastern Pacific, and some due to a warm airmass in general.  Here are the PDX numbers, of course heavily influenced by the urban heat island

60 Degree Nights Portland


It SEEMS like we had more partly cloudy or cloudy days right?  Especially in early-mid July.  I think that may be where the feeling of a “slow start to summer” began.  That said, if we take all of June through August, we saw FEWER totally cloudy days than average.  And a normal number of clear days.   Anecdotally I would say that’s true.  Many of our marine pushes off the Pacific Ocean were weak this entire warm season.  Fewer thick morning cloud cover days but maybe more partly cloudy days in the afternoons?  Just a guess.

Mark Cloudy Days Summer


No heatwaves!  This was a strange one.  We had two very hot days in early June, then two more at the end of August.  Otherwise no extended periods of hot weather.  Many times from late June onward the models tried to push a hot upper-level ridge in over us.  But it only happened twice. It was continuously mild to warm but no long stretches of 90+ days.  In fact as of today we’ve seen just 11 days at/above 90 degrees.  That’s FAR less than recent years.  That’s also a little below the 13-14 day average.

90 Degree Days Summer Heat


Remember those dramatic predictions of “another smoky summer ahead” by some in media and elsewhere?  I remember thinking at the time that it all depends on what happens DURING the summer, not leading up to summer (a dry late spring).  Sure enough, we had occasional cooldowns and even some showers here and there to keep things in check.  It shows you how important the heatwaves are (plus lightning) in getting the big fires started and growing.  As of right now, this fire season is pretty much dead.  Fuel moisture on the western side of the Mt. Hood National Forecast is at a record high for this time of year too.  So far, less than 200,000 acres have burned in Oregon and Washington; the lowest number since at least 2010.  I have a feeling that isn’t going to change much over the next three weeks.

Fire NW Summer Stats

Chief Meteorologist Mark Nelsen