April “Heat Wave” Doesn’t Disappoint; Showery Weekend Ahead

April 26, 2018

9:30pm Thursday

Okay, I’ll admit it.   Today was weird…hazy and on the edge of “hot”.  I had the AC cranking in the car, on April 26th!  The haze was likely due to controlled burns in Central Oregon.  We warmed another two degrees in Portland today, reaching within 4 degrees of the all-time April high temperature (90).

Mark PDX Record High Hot

We’ve only seen a few instances of 3 consecutive 80 degree days in the month of April and this was one of them.  We broke records the last two days, then tied the record today

Mark Hot Heatwave So Far

The most interesting aspect today from a meteorological standpoint was the surge of southwest wind into the central/south Willamette Valley and up the Columbia River to Kelso/Longview.  Check out high temps today:

Todays Observed Highs OrWa 2017

The metro area sticks out doesn’t it?  I think this is the only time I’ve seen mid 80s in the metro area and only 60s in the south Valley, with both locations under sunshine most of the day.

This evening the cool air is pouring inland and temps are falling like the proverbial “rock” in Portland

2017 Current Temps PDX Metro Area Earth Scene

Nice natural air conditioning don’t you think?

I have been tracking a few thunderstorms the past few hours moving out ahead of the upper-level low offshore.  Earlier a few strikes were detected in Linn County, and I see a thunderstorm just east of Florence at this hour.  Most likely this action will continue through the overnight hours, but I doubt it’ll make it all the way up into NW Oregon.

The forecast for tomorrow through the weekend is easy…cool, cloudy, with showers at times.  That’s because the upper-level low will be tracking across Oregon from tomorrow through Sunday afternoon.  It’ll be strange to turn on the heat again after the past few days!

Chief Meteorologist Mark Nelsen

Another Record Breaker…Slightly Warmer Tomorrow

April 25, 2018

9pm Wednesday

It sure felt like July today!  Here in Portland we started in the 50s and ended well into the 80s; a typical mid-summer day.  Except that it’s the 25th of April.  The result was several more record high temperatures, mainly in the metro area:

Record Highs Cities

And we did that with extremely weak offshore flow.  Even in the Gorge the wind died down to a slight breeze plus downslope wind off the Cascades disappeared.   So it’s quite impressive from a meteorological standpoint we were able to make it into the mid 80s. Models absolutely nailed the atmosphere overhead.  850mb temps at Salem were 16.6 degrees on this afternoon’s balloon sounding.

Todays Observed Highs OrWa 2017

Check out the coastline…what a change!  Newport was 30 degrees colder today…that’s always a tough forecast right along the cold ocean/warm land interface (the beaches).  Notice the onshore flow didn’t make it up to Hoquiam; still well into the 70s there.


A very interesting setup with the thermal trough (warmest air) sitting from about Kelso to just east of Salem and Eugene.  That means west of that line onshore flow kicks in during the afternoon = cooler.  But from Kelso/Longview to the Portland metro area we get a light easterly flow once again as high pressure briefly strengthens east of the Cascades.  Result?  All models are adding 2-4 degrees to our highs tomorrow.  85-86 is likely throughout the Portland metro area.  You can see the bubble of warmer temperatures from Portland north on the GFS and the cooler temps to our south.  This is the 5pm Thursday forecast:


South of the metro area it should be the same or cooler.  I bet Eugene only reaches 70-75 tomorrow afternoon.

Regardless, expect a major push of cool ocean air tomorrow evening even in the metro area.  By Friday morning the marine layer is 5,000′ thick from the Cascade crest to the coastline.  We’re not going to see any sunshine Friday!

Two more thoughts on Friday’s weather:

  1. A band of rain pushes north midday and into the afternoon across the state.  Most likely the last commute of the week will feature steady rain and temps in the low/mid 50s in Portland…the earlier sunshine and 80s will be a memory less than 48 hours from now.
  2. The thick marine layer will push through the Gorge on a huge westerly wind.  Gusts 40-50 mph are likely from Hood River to The Dalles and out into the desert areas farther east.  Windsurfers prepare…

Chief Meteorologist Mark Nelsen



A Very Warm Night, Then A Record High Today

April 24, 2018

9:00pm Tuesday

Today sure felt like summer didn’t it?  The strong “offshore” easterly wind didn’t let up for many of us last night; some of us in the metro area and most coastal cities didn’t even get down to their typical high temp!

Mark Coast Warm Lows

Here in Portland we dropped to 53 degrees, not quite a record warm low, but close.  Then the easterly wind pushed temperatures above 80 degrees for most of Western Oregon and parts of Southwest Washington this afternoon.

Todays Observed Highs OrWa 2017

The 88 at Roseburg was the highest observed temperature in Oregon today.  Two cities set records for the day: Portland and Astoria.

Record Highs Cities

Obviously the “scorcher” is a bit tongue-in-cheek, but these temps are far above normal for the last week of April.

I expect 3 changes (minor) for Wednesday:

A) Wind turns onshore (southwesterly) along most of the coastline = MUCH cooler.  Likely 60 around Newport to low-mid 70s up at Astoria

B) Warmer atmosphere overhead everywhere east of the Coast Range.  850mb temps at Salem were +14C from the balloon this afternoon.  That’s exactly what models showed.  They all say +16 tomorrow afternoon.  That would give us about 3 degrees warming.

C) East wind backs off.  It’s already happened the past 6 hours, but pressure gradients east to west over the Cascades will be weaker tomorrow.  We still get offshore flow, but with far less mixing, afternoon temperatures should rise a few degrees.

Combining the last two I figure we get about 5 degrees of warming in the metro area tomorrow, specifically the areas that were a little “cool” due to the wind today.

Thursday is real interesting because the east wind comes back a bit stronger, then goes almost calm late in the day as a major marine push begins to push into the central/southern Willamette Valley.  Thursday may be one of those days where we make it to 85 in Portland, Salem is 78, and Eugene only hits 70.

We have a HUGE change coming up Thursday night and Friday as we get a “double whammy”.  A major marine push (solid marine layer 5,000’+ thick west of the Cascades) plus a band of rain moving north through Western Oregon.  It’s likely we stay in the 50s Friday.

So we’ll likely go from summer-like warmth in the 80s Thursday to 50s and wet/gray all day Friday.  Pretty drastic for our climate, but I’ve seen it happen before.  Plan to have all your dry weather projects done by Thursday evening!

Chief Meteorologist Mark Nelsen



Four Days of “Summer” Ahead

April 22, 2018

7pm Sunday

What a nice run of weather the past 5 days…we’ve been in the 60s since Wednesday.  Several of those days have been warmer than forecast too!  I could do this for another week or so.

High Temp Last 13 Days

Instead we have a big jump in temperatures coming the next few days.  It’s going to feel like June & July Monday through Thursday this week.

What’s going on?  An unusually warm airmass will settle over us plus easterly flow develops at the same time.  Easterly wind in the warm season is a warming wind.  That’s because it’s keeping any cooling from the ocean away plus when it comes down the west slopes of the Cascades it warms heading downhill.   Take a look at the surface pressure forecast for 11am Monday from the WRF-GFS


You can see lower pressure (a thermal trough) centered right over western Oregon and then down into northern California.  High pressure has nosed into eastern OR/WA = easterly flow.  Then check out Tuesday 11am; the thermal trough is nicely established right on the Oregon Coast.  Gusty east or northeast wind will be blowing through the Gorge/Cascades/Coast Range at that time.  Anytime April through September, this is the warmest possible weather pattern for us.  80s in April, 100+ in mid-summer.


By Wednesday at 11am the airmass has reached its warmest, but the trough has moved generally into the interior of western OR/WA.  Likely not so warm on the central coast of Oregon this day:


How warm?  Models are all in excellent agreement that the 850mb temperature over Salem will reach around 11 tomorrow, 15 Tuesday, and 17 Wednesday PM.  Past situations like this push Portland’s high temperature into the 83-88 degree range; so I bumped up our 7-Day Forecast to 84-86-84 starting Tuesday.  I looked closely at April 2016, 2012, & 2004.  The ECMWF morning run had a secondary little push of easterly wind returning Thursday, but I’ve discounted that a bit for now.

In this pattern, as long as easterly wind makes it to the coastline, there’s no reason you can’t see the same temperature out there as here in the valleys.  As a result, high temperatures well into the 80s are likely at the beaches Tuesday, and possibly on the north coastline Wednesday too.

It’s interesting to note the past 7 years we’ve seen our first 80 degree temperature a bit “ahead of schedule”.

Mark First 80 Degree Day Heatwave

Most of us probably remember those two very chilly springs in 2010-2011.  Those two years we didn’t hit 80 until early June.

Alright, it’s dinnertime so I’m headed out.  Enjoy the warm weather because models are also in good agreement that at least some showers (and maybe thunderstorms) are coming at some point Friday or Friday night.  Almost all EPS (ECMWF) ensemble members show decent 24 hour precipitation totals by 5pm Saturday.  Maybe not a lot, but enough to ruin your freshly stained deck!  Get dry weather activities done by Thursday.



Chief Meteorologist Mark Nelsen

June Weather Next 7 Days: 80 Degrees For Some!

April 19, 2018

11pm Thursday

Today was incredible wasn’t it?  It sure is true that stretches of gloomy/cool weather make us appreciate the sunshine.  I worked a half day today which meant about 5 hours in the sunshine.

Todays Observed Highs OrWa 2017

I think I burned my face just a bit.  That is very possible from now through early September; the highest sun angle of the year is only 2 months away.  I think most people are surprised the sun is just as strong as late August.  In fact the sun angle is the same today as it was during the solar eclipse last year.

Mark Sunburn Season SpringSummer

Just a quick note to let you know we are in a pretty stable “early summer” weather pattern for the next week.  The weak late April jet stream has shifted a bit to the north and seems to stay up there for the next week.  One weak system moves by to our north Friday night, but after that time the atmosphere warms up quite a bit.

The result is a switch of cool & wet to warm and dry.  A typical high temperature in June is the mid 70s and that’s where we are headed much of next work week.

Headlines Spring Summer

Could we hit 80 degrees?  Yes, I think that’s likely if current model runs hold.  As of now they are all showing a perfect setup for 80+ weather.

A) A classic “thermal trough” or low pressure west of the Cascades or along the Coast Monday-Wednesday.  That gives us easterly wind through the Gorge and over the Cascades.  A “downsloping” wind warms us nicely in this warm half of the year

B) Mostly sunny skies Monday-Wednesday

C) 850mb temps are forecast in the +12 to +15 range over Salem.  That’s the temperature in celsius around 5,000′ elevation.  It doesn’t get too much warmer than that in April; +18 is the highest from 1992-2009.

Past setups with these 3 ingredients in late April have pushed Portland metro high temps up to 80-85 degrees.  Get ready for summer weather for a few days.

A week from now you’ll need to water your potted plants, although there’s still plenty of ground moisture so you can skip watering the lawn/garden.

Enjoy the weekend!

Chief Meteorologist Mark Nelsen

A “Normal” Spring So Far; But Much Drier & Warmer Ahead

April 17, 2018

5pm Tuesday

I’ve heard some whining the past few days, people wondering when we’ll get out of this “cold & wet spring”.  Would it surprise you to know that isn’t really true this year?

It’s been pretty close to normal! Take a look at the numbers.  First, much of the USA has been colder than average this month:


Notice the Pacific Northwest is a bit cooler than average, but that’s nothing compared to the cold month so far east of the Rockies!

Here in Portland, as of the 15th of the month, temperatures were right at average.  March was one degree below average.

Mark Spring So Far 1

So yes, it has been slightly cooler than average.  But these numbers are exactly like 2017 so far…interesting eh?  It’s no colder than last year, but the previous 3 (2014-2016) springs were warmer than normal up to this point.  Apparently this spring (so far) the pendulum has gone back to cool.

How about rain?  That’s an easy one…it’s been a wet April so far.  We had exceeded our typical monthly rainfall by the 15th.  Yet March was DRIER than normal.

Mark Spring So Far 2

So if we take the 45 day period (spring so far), rainfall this season has only been slightly above normal.  I think the perception of a “cold and wet spring” only comes from the past two weeks; quite a bit of gray and consistently wet weather.

What about a changing climate?  I just gave a talk last week and included these two graphics.  They show 100 years of spring temperatures and rainfall in Oregon climate zone 2.  That’s the lowlands of NW Oregon where many of us live.

They show springs over the past 100 years have been trending WETTER although you see some decadal trends in there too:


Are springs getting colder?  Definitely not.


The trend is WARMER, although you see some interesting trends…cooling springs late 1930s through late 1950s.  After warming, cooling again early 1990s to around 2011.

Looking ahead, I see a somewhat dramatic change ahead.  The jet stream will be lifting north and the few upper-level troughs that move by will be weaker/milder than recent events.  We’re going from cool March-like showers to a much slower May-like weather pattern.   Our lawns/gardens/fields will finally get a chance to dry out.  Check out the ECMWF ensemble precipitation forecast for the next two weeks:


The lower part of the graph shows accumulated precip from the operational model (blue) and the 51 member ensemble average (green).  Note the operational model gives us less than .10″ in the next two weeks!  That would be extremely unusual in April, but possible.  More likely is the ensemble average showing dry days late this week, a shower or two early Saturday, then a few more dry days.

How about temps?  MUCH BETTER.  Not excessively warm, but well above average this 2nd half of the month.  I’m quite confident we’ll see widespread low-mid 70s next Monday/Tuesday, but maybe no higher.


A major weather pattern change is underway

  1. It’s going to feel like May much of the next 10+ days
  2. Many days will be dry in the next two weeks.

Chief Meteorologist Mark Nelsen

Rainy & Windy Sunday Night Ahead

April 15, 2018

9:00pm Sunday

Surprise…it’s still raining!  What a gloomy April Sunday don’t you think?  We’ve picked up about a third of an inch of rain here in Portland, but more than 1/2″ fell once again in Salem.  Yesterday over 2″ fell in parts of western Washington.  Yes, April has been much wetter than average.  We’re halfway through the month; check out those monthly totals so far!

That Portland total is the 4th wettest first half of April on record.  We’ve seen rain on 12 of 15 days this month:

But the weather pattern will become far more “reasonable” this week.  By that I mean we’ll be drying out quite a bit…after Tuesday.

Tonight we have a deepening surface low pressure center traveling straight north through NW Oregon and a 2nd low moving north through Eastern Washington and northern Idaho.  Here’s the 8pm position of the low:

By 2am note the lowering pressures over Washington, both western and eastern sides of the state.  Quite a southerly gradient through the Willamette Valley!

Then by 8am the weaker low has been absorbed by the 989mb center in southern British Columbia.   This is a windy pattern for the Pacific Northwest so you can expect a windy day Monday after tonight’s gusty wind.

We’ve already seen gusts in the 30-40 mph range in parts of the Willamette Valley and south metro this past hour.  I see a 35 mph gust suddenly just arrived at I-205/Division ODOT sensor and a 39 mph gust at Aurora.  We have 12-18 hours of wet & windy weather on tap.

Here’s the good news!  In the past 3 days models seem to be keying in on a change…actually 2 changes for the next 10+ days:

  1. The upper-level troughs moving along the westerly flow appear to get weaker/milder and don’t dig as far south
  2. Upper-level heights rise as the weakening spring jet stream pushes farther north more often.

The result is a significantly drier and somewhat warmer weather pattern.  It appears we’re going from mid-March cold troughs to more of a May-type pattern.  Take a look at the ECMWF ensemble precipitation forecast:

You can see almost all ensemble members are dry from Wednesday through early next week, minus the shower chance Saturday morning as a trough passes by to the north.  This is the driest chart we’ve seen in many weeks, maybe since early February.  Notice temperatures rise quite a bit too, this is from the 18z GFS:

To wrap it up…AFTER Tuesday I see a much milder/nice mid-spring weather pattern ahead.  Not totally dry, but our gardens/lawns/fields will get a chance to dry out.

Chief Meteorologist Mark Nelsen