Goodbye to 80 Degree Days

September 28, 2017

6pm Thursday

Today we hit 86 in Portland, the 2nd consecutive day we’ve reached well into the 80s

As expected the onshore flow…well, flowed onshore quickly this afternoon at the beaches.  Check out mid-afternoon temps vs. highs yesterday (in red) on the Oregon Coast

Today was the 79th day at/above 80 this warm season in Portland.  That’s the 3rd greatest number of 80 degree days we’ve seen (chart doesn’t count today)

As I’ve mentioned regularly, our summers have been warming somewhat dramatically the past 30-40 years.

Portland averages about 15 more days above 80 than back in the mid-20th century.  That’s great if you live in the foothills or mountains in the summer, but not so great if you live down in one of our cities near sea-level (inland).    I’m bringing up the “80 degree chat” because I think it’s unlikely we hit 80 again this season.  Of course it’s POSSIBLE we hit 80 for the next 3 weeks, but unlikely

Models are showing a normal to below normal temperature weather pattern for the next week or two.  The upper-level pattern is not very wet, with ridging in the Gulf of Alaska.  But we remain on the cool side of that ridge.  Note the Tuesday, then NEXT Saturday GEFS (GFS ensembles) chart:

Then the ECMWF showing a weaker ridge, but same general pattern in its week 2 ensemble.  This is the average of all 7-14 day maps

A few thoughts on the next 10+ days based on this:

  1. With weak systems coming over the ridge and even some split-flow at times, this will be a real pain forecasting showery periods
  2. But the next two weeks won’t feature a stormy & wet pattern in the Pacific Northwest, in fact most likely it’ll be a little drier than normal
  3. Cooler and drier air coming down from the north should give us sunny days at times (middle of next week)
  4. Drier air also means much cooler nights.  Those typical chilly October nights are on the way by next Tuesday…way down into the 40s in urban Portland and 30s outlying areas
  5. Hitting 80 in Portland again appears unlikely, although if the ridge edges closer with offshore flow it COULD happen again.

Showers arrive tomorrow midday and expect more light showers Saturday & Sunday.  ECMWF says less than 1/2″ rain the next 3 days, then we go dry after Monday.  That’s good, I can avoid watering the garden once again…


Chief Meteorologist Mark Nelsen

Warm East Wind Returns, Without The Fire Smoke

September 26, 2017

7:30pm Tuesday

Today was a spectacular early Fall day with high temps right around 80 in the metro area

It was the warmest day in about a week and a half

Tomorrow will be much warmer since we’ll go from a northerly flow today to a pure easterly wind flow

This means a big jump in temps, not only here in the valleys but also along the coastline.  Models are forecasting a 3-4 millibar pressure gradient across the Cascades which should give us gusts 35-45 mph in the western Gorge.  That east wind at the beaches (for just one day!) should push temperatures up into the 78-88 degree range

A wind switch back to west or southwest Thursday drops temperatures 15-20 degrees that day.

Here in the metro area temperatures should rise a solid 4-6 degrees tomorrow plus another degree or two Thursday.  Of course that puts us in the mid-upper 80s.  I think it’s unlikely we hit 90 at PDX; it’s more likely that at least one of the official metro area stations hits 90 one of those days.  It’s always a tough call at the end of the warm season due to lingering overnight inversions.  Regardless, it’s going to be quite warm for a few hours each of the next two afternoons.

As for fire smoke, I took a close look at the high-res GOES-16 visible imagery and couldn’t find any smoke being put out by any fire in our region.  That said, the view is from 23,000 miles out in space and most likely there are smoldering spots with each fire.  This morning I smelled fire smoke at my home but skies/air remained clear otherwise.   As a result I think we’ll at least smell a bit of smoke in parts of the metro area tomorrow, but that should be it.  No dense haze or smoke this time around.

Enjoy the warm & sunny weather because it’s pretty obvious we’re headed into another cool & wet pattern.  Friday and Saturday sure don’t look like soakers, but a wetter southwesterly flow Sunday and Monday should give us quite a soaking.  Here’s the ECMWF rain forecast through next Monday afternoon:

Notice in this pattern (southwest flow) more rain can make it over the Cascades.  You might finally get your first fall soaking in central Oregon if you get lucky! Looking farther ahead here is the 2 week outlook from the ECMWF model, showing 24 hour rain totals.  Time is from left to right.   Left is now, right is two weeks from now.    Top half of the graphic consists of 51 horizontal lines…each one representing one of the ensemble member 24hr rainfall forecasts.  You can see just about all of them start off with rain later Friday, then a 2nd peak in rain next Monday, and a 3rd sometime later next week.  Big picture is that there is no obvious dry period after Thursday, but there may be some sort of break the middle of next week.

Chief Meteorologist Mark Nelsen





Mainly Or All Dry Next 7 Days

September 24, 2017

6:45pm Sunday

It has been a beautiful fall Sunday with temperatures reaching the low-mid 70s across the metro area.  Quite a change from exactly one week ago!  Remember that’s when the first rain was arriving.  You may also remember models were forecasting up to 2″ or so rain in the valleys and 3-8″ in the Cascades, followed by sunshine.  That’s exactly what happened:

Portland has now seen more than its typical allotment of September rain.  Typically September is our 3rd driest month (after July & August).  But this year we had a very dry start to summer with just over an inch of rain both in May and June.  So this was a much-needed soaking.  Notice the final rain totals in the mountains show a “season-ending” event for fire season in most of the Cascades…well before the typical time we’d see that happen.  I just checked the morning fire briefing and every single fire is showing minimal fire behavior.

Of course with a dry week ahead I’m sure some fires will produce some smoke, but the woods don’t dry out easily the last week of September so it appears unlikely any fire will suddenly start charging the lines again.  Good news!

The extra September rain has cemented this “water year” as the 3rd wettest in Portland’s history.  This follows those crazy wet back to back years of 1995-1997.  Water year is how we measure rainy seasons in the West.  On this side of the Rockies most precipitation falls during the cool season, which means it is dropped into two different “yearly buckets”.  So by starting each “year” on October 1st, all the rain/snow from one season gets put into “one bucket”.  Then looking back we can easily compare rainy seasons.  In this case we are wrapping up our 3rd wettest rainy season on record!


Looking ahead, the general plan for this next week is a building upper-level ridge over us, then it gets flattened next weekend.  We get a somewhat strong “thermal trough” west of the Cascades late Tuesday through early Thursday.  That means gusty east wind through the Gorge and over the Cascades, maybe out over the Coast Range too.  This will be the first time since early in the summer that easterly wind will bring blue (instead of smoky) skies.  Enjoy the warmup…a +17 degree (C) temperature at 5,000′ combined with offshore flow should push us well into the mid 80s for the last time this season.  Then onshore flow and much cooler temps return Friday and into next weekend.

As the ridge builds tonight and tomorrow, a weak system dies as it squeaks by the ridge; Monday will see lots of clouds and maybe even measurable rain in spots north of Portland.  So tomorrow may be a relatively gloomy fall day before the bright sun returns Tuesday.

For you gardeners, of course you don’t need to water right now (soil is wet) and you can probably get by all this week without watering.  That’s because soil is slow to dry out in late September with the weak sun angle.  But pots/containers will definitely need a soaking by midweek.

The next real soaking, or wet fall storm, will likely show up at some point early/mid next week.  Using the ECMWF ensemble forecast system, you see the ridging still overhead next weekend:

But by the following Wednesday (10 days out) troughing with the associated showers & cool weather is back

Then at the 2 week point, ALL 3 MODELS (GFS, ECMWF, GEM) show a wet pattern with upper-level troughing filling the far eastern Pacific and Pacific Northwest.  This is a wet mid-fall pattern

The message here is: USE THIS WEEK TO WRAP UP OUTDOOR PROJECTS, NEXT WEEK MAY TURN QUITE WET ONCE AGAIN.  Now a bit more rain is fine, but let’s hope we don’t have a ridiculous October like last year.  The entire month was a washout.  28 out of 31 days saw measurable rainfall.  It was so bad that my (ex) neighbor told me that was the final straw to get him to move.  Now he’s in Las Vegas…that’s quite a change!

Chief Meteorologist Mark Nelsen


A Busier Day: Tornado, Funnel Cloud, & Cat 5 Hurricane

September 19, 2017

10pm Tuesday…

I thought yesterday was busy, but today was just plain crazy.  Back in the old days (20 years ago) I might have appeared on 1-3 TV newcasts per day, maybe with a radio hit or two as well.

Today I was in 6 newscasts, plus regularly tweeting, facebooking, & keeping up on other internet activities.  It can get crazy!

So today we had our 2nd Oregon tornado of the year (first was in central Oregon earlier in the year).  This one was east of Lacomb, which is well east of Lebanon.  Way out in rural Linn County.  It was a classic westside “barn-buster”;  No deaths, injuries, or damage to homes.  Just 4 barns damaged along with some trees.  An EF-0 is the weakest tornado one can get.  Thanks to the Portland NWS for all the hard work doing their storm survey.  Here are the results:


Here’s how it compares to some other recent tornadoes in our area

Tornado Categories

We received two different videos of funnel clouds both there and near Molalla.  So an exciting day.  I saw nothing on radar that showed much wind shear or rotation with the Lebanon storm.  Part of the reason (other than it was such a weak event) is that Lebanon is a long way from the Portland radar.  The lowest elevation radar beam is up around 9,000′ or even a little higher by the time it’s over Lebanon; that means it’s quite easy to miss rotation in the lower parts of the cloud.

Tornado Why We Cant See Eugene

Our very wet week continues, take a look at rain totals so far (since Sunday PM) in the Cascades…apparently models were right on showing 5-8″ in spots in the North Oregon Cascades

Mark Rain Cascades East Metro Today

Mark Rain Cascades East Metro Today2

And the rain has made it all the way down into south Cascades…very good.

Expect one more soaker tonight and then showers should taper off a little Wednesday afternoon.  Thursday will just be a light shower day.

By the way, it’s beautiful but deadly and dangerous…Category 5 Hurricane Maria is directly over the west end of St. Croix in the U.S. Virgin Islands right now.


Wow, imagine a 175 mph wind.  Remember those gusts we feel up at Vista House in winter are maybe 100-120 at most.  Think what that storm is doing to the island right now.  It’s headed for Puerto Rico Wednesday.

Chief Meteorologist Mark Nelsen

A Busy Weather Day: Thunderstorms & A Waterspout

September 18, 2017


As expected, thunderstorms and hail showers are moving across the western part of Oregon & SW Washington too.  That’s due to a chilly airmass overhead but we still have relatively warm temperatures down here where we all live.  That means lots of rising motion in the atmosphere = thunderstorms.

Note the 1st fall snow up in the Cascades…Timberline Lodge this morning:


One thunderstorm produced a waterspout just offshore of Happy Camp (between Netarts Bay & Oceanside).  IF that would have moved onshore, it would be a tornado.  Remember Manzanita last October?


Of course many of you are seeing thunder and hail right now as a cluster of action moves over the Portland Metro area.  This will continue through the afternoon, of course interspersed with sunbreaks too.  Classic spring, or fall, weather.  Enjoy the change and by the way, enjoy the fresh air!  Particulates in our air this morning were so few and far between they could barely be measure…all of 8 on the AQI:


Stay safe this afternoon while driving through downpours, we’re out of practice with our rainy driving skills…


That’s the 12:40pm radar image here in the metro area, looks like Sherwood and Newberg getting the action, but the cells will continue moving to the east/northeast.

Chief Meteorologist Mark Nelsen

The Rain Is Back!

September 17, 2017

11pm Sunday

The rain is back this evening, although we’ve had less than 1/10th of an inch in the city.  Much more has fallen since mid-afternoon out over the Cascades, including the western portion of the Eagle Creek Fire:

There is lots more rain to come, as I’ve been mentioning for the past week.  Our RPM model is estimating 1-2″ by late Wednesday in the western valleys and 3-5″ over the Cascade crest and down into the western foothills.

Even the dry north-central part of Oregon will get enough to settle the dust.  This may be our wettest week since March; for sure the wettest since May.

Enjoy all your indoor pursuits the next few days!

Chief Meteorologist Mark Nelsen

September: Record Hot 1st Half but October Weather Next Week

September 15, 2017

10am Friday

I just checked the numbers and sure enough, you just survived the hottest start to September on record here in Portland…


But the payback next week is going to be rough, we’re going straight from July weather to October in just a couple of days.  Those first two weeks of the month blew away any other early September period on record.  The average high was 85 degrees!  Plus we set 5 record warm lows and had the warmest nights ever recorded in Portland in the month of September.  You can see the entire West has been hot, but it’s balanced out by a chilly eastern USA.  This month is a “perfectly normal” month when averaged across the country


And of course this follows the hottest August on record all along the West Coast.


Now we’re about to see the most dramatic change we can possibly get this time of year.  Remember we’ve had a hot upper-level ridge along the West Coast most of the time since late July.  But beginning Sunday that ridge develops way offshore, in the Gulf of Alaska. Look at the 500 millibar height deviation for midweek.  If it was winter that could give us an arctic outbreak with cold/snow likely:


Of course it’s not winter, but this means we’ll go from record warm to near record chilly!  The best part about this pattern change?

I EXPECT FIRE SEASON TO AN EARLY END NEXT WEEK ALL ACROSS THE REGION.  The Eagle Creek Fire is going to be out a week from now if our models are correct.  Take a look at the ECMWF rainfall and temperature forecast for the Portland area for the next 10 days


We still expect rain to arrive Sunday afternoon (light rain at first) and then a big soaking Monday and Tuesday as cold showers/thundershowers/hail showers arrive.  Also look at those chilly temps!  High temperatures only in the 60s, maybe even a couple of days where we spend most of our day in the 50s!  That’s a huge change.  Now remember this is just one run of one model, but they are all showing the same thing.  Here is a peek at the ECMWF ensembles; 51 members of the same model showing 24 hour rainfall


The first half of next week is wet, with far smaller accumulations in the rain bucket beyond next Thursday.

But there’s more!  Just about all the big fires are burning in the Cascades and look at how much rain could fall Sunday through next Thursday…first the ECMWF:


Widespread 2-5″ rain totals on the west slopes and crest of the mountains.  No fire will survive that deluge…excellent news!  Note the valley gets around an inch or so.  Then the GFS model, which has some terrain issues so don’t read too much into all that rain in the metro area:


Same idea, 2-5″ (or more!) in the mountains and around an inch in the driest part of the valleys.

To summarize…



Enjoy these next two days, although light easterly wind means fire smoke will be moving around the area as seen in this AM pic from Andrew Mork:


Sunday’s rain should put an end to our smokiest summer in memory!

Chief Meteorologist Mark Nelsen