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

A Good Night To Migrate! Birds On Radar Tonight

April 9, 2018

10:30pm Monday

It happens each spring; the huge nocturnal (night) migration of ducks, geese, swallows and all those other birds from warmer regions on our planet to northern/cooler areas.  Think about this; there are probably birds flying right over your home tonight that will end up spending the warm season in the Yukon or even near the Arctic Ocean!  Oh, and they may have spent the winter in Mexico or Costa Rica too.  That part doesn’t sound too bad does it?


Because birds are large compared to precipitation (rain/hail/snow) they show up quite well on radar and it doesn’t take that many to trigger an “echo” on the radar screen.  Of course you might be wondering like me why we don’t see birds on the radar screen all through the warm season?  We usually don’t because those birds don’t have any reason to move high up into radar range (more than a thousand feet or so).  But when migrating they go high to avoid low-level wind fields, instability, and denser surface air.  Tonight is a great night for them since there is a solid south/southeast wind ahead of the approaching cold front.

They are quite visible on the “VAD” wind display.  That’s the wind profile the past couple of hours from the Portland radar.  The radar is located up around the 2,000′ elevation just west of Scappoose.


Time goes from left to right.  Look at how the targets rise quickly in elevation right after sunset.  Note it says 50 knots!  That’s likely the 20-30 kt southerly wind plus the motion of the birds.   It’s also fascinating that the highest echoes (birds) gradually increase in altitude…those guys are working hard to get up to their “cruising altitude”.  Ducks have been known to fly up around 30-50 mph even under calm conditions.  They can cover 800 miles in one night if they really want to.

This is what it looks like on the “regular” radar screen as the birds take off, from an earlier blog post.   Note they don’t like to fly over water.  The Ocean Shores radar on the Washington coastline shows almost all “bird action” tonight is over land.


One final note, the dual-pol radar is pretty good at detecting the type of “target” we are seeing in the sky.  Note the current display shows almost all “BI”.  That means BIOLOGICAL.  It could be insects, but not in this case.


By the way, there is a movie called WINGED MIGRATION (a documentary) produced about 10 years ago using hand-raised birds. They follow the birds (usually geese) while flying and migrating using some sort of very light aircraft. Or, actually I suppose the birds follow the aircraft since they imprinted on humans at hatching.  That means they think humans are part of their family. Now, believe me, this is no “party movie”, actually it’s REALLY slow, but great visuals for little kids to watch. Filming was done all over the planet. Here’s a clip for a little evening relaxation:


Chief Meteorologist Mark Nelsen


A Blustery April Day; Wind Dying Down

April 7, 2018

5pm Saturday

I was out and about for 4 hours this afternoon attending that groundbreaking and then doing errands.  The wind was a little…well…underwhelming.  Gusty wind at times, calm other times…seemed just a little winder than an average blustery April day.  I just saw a Twitter post from another media outlet saying a “strong wind storm” is on tap for tonight…but that’s definitely not the case.

The 35-50 mph gusts we forecast DID end up materializing, but it was another relatively weak wind event in our area and nothing like last year’s April storm.   Portland barely hit 40, and only a few thousand PGE customers lost power at one time from tree limbs or trees that fell here and there.  Not a “non-event”, but not a windstorm in the valleys either.

Peak gusts so far look like this, plus or minus 1 mph since the FAA is having some sort of rounding issue going from knots > mph recently:

Portland 40
Hillsboro 41
Troutdale 40
Scappoose 33
Vancouver 35
Aurora 45
McMinnville 47
Salem 45

Astoria 53
Pacific City 58
Newport Bridge 63
Cape Foulweather (very exposed) 72

Models show wind gradually decreasing this evening/overnight.  We’ll lose the warm daytime mixing too which means we just have a breezy night ahead.

Gusts will be mainly in the 25-35 mph range through the night, more like 20-35 mph by sunrise Sunday.

Expect lots more rain tonight…it’ll be a soaker!


Chief Meteorologist Mark Nelsen

Saturday Morning Update: Windy 24 Hours Ahead

April 7, 2018

8am Saturday

The gusty south wind has arrived across the region as a deep surface low is passing by to the west.  It was a beautiful satellite loop the past 12 hours as the storm wrapped up offshore; especially considering we’re a week into April!  Here’s the latest image:

The yellow spot is the location of the low pressure center.  Notice it’s just now making it across the important 130West longitude?  Unless the low is far deeper, here in the interior valleys we generally don’t get big windstorms with storms this far offshore.   With this image I’ve added the expected movement of the low (in blue) and then a more typical windstorm track for the inland valleys.

The low will gradually weaken and very slowly move toward the central/south part of Vancouver Island the next 24 hours.  This will give us a prolonged period of gusty south wind…all the way through the first half of Sunday!  See the current location from the NAM-MM5 model:

and at 5am Sunday…that’s still a “south wind gusts 30-45 mph” setup in the valleys there:

To summarize:

  1. Coastal wind (so far) appears to be significantly weaker than expected once again (it happened with last April’s storm).  I see a 72 at Cape Foulweather, but lots of 45-60 mph gusts otherwise.  Windy, but nothing too crazy out there.
  2. Inland wind gusts will ramp up with daytime mixing.  Pressure gradient will line up better with the north/south valleys the next 12 hours.
  3. Peak gusts still likely in the 35-50 mph for most of us in the valleys.  That could happen anytime between now and early Sunday morning.  Not a big windstorm by any means, but plenty of power outages and a few trees down.


If you have any outdoor activities, they can still go on since showers will come and go, but expect a blustery & wet spring day.  If you are an organizer of an outdoor event I sure wouldn’t cancel it.

I’ll be at the Crown Point Country Historical Society groundbreaking event in Corbett at 11am…looks windy.  At least the ground will be soft for plunging those shovels into the ground!

Chief Meteorologist Mark Nelsen