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  • Posted

9pm Monday, July 26th

It’s vacation season in the Pacific Northwest; the best weather of the year! So, I’ll be joining many of you travelling across the region the next week and a half. Heading out for camping in parts of southern Oregon. No posts during that time, unless something serious pops up (major fire close to us, huge earthquake, volcanic eruption, tsunami, etc.…). I’ll be back at work Sunday August 8th.

The end of July is quickly approaching, and it’s been a warm month! No record-breaking heat, or heatwaves, but consistently warmer than normal. It appears we’ll end up with at least the 5th warmest July on record, likely #3 or #4.

The western 1/3 of the USA has been sizzling so far this month, following the warmest June on record for some.

We’ve been “lucky” west of the Cascades, picking up just enough cooling onshore flow to keep us near/below 90 degrees most of the month. Portland has seen (12) 90-degree days so far this year

Yet, just slightly farther removed from that ocean air, both Salem and Eugene have seen over 20 days at/above 90!

Looking ahead, we have a heat wave on the way Wednesday-Saturday. This is what we’re thinking this evening for Portland:

No record highs since they are generally 100+ this time of year. But four 90+ days to wrap up July.

Why is it turning hot again?

Strong high pressure bringing heat over the Rockies is far enough east to keep our temps reasonable again tomorrow. That “594” contour centered over Colorado is the center of the upper-high.

But you see it snuggles up a bit closer to us Friday and Saturday. Here’s midday Saturday; the ridge of high pressure has amplified, and southerly flow is in charge across the West Coast. This MAY bring thunderstorms north into the Cascades and Eastern Oregon. There are even a few GFS and ECMWF ensemble members sending a disturbance north with showers/thunderstorms WEST of the Cascades this weekend. But not enough to put it in the forecast. Just be aware that this weekend is not “guaranteed” dry. Keep an eye on the forecast.

This pattern doesn’t produce a hot easterly wind over the Portland area (ridge is too far east), which should keep us below 100 degrees…but just barely! Then Sunday and beyond the ridge weakens; we’re back to reasonably warm temperatures for the first few days of August. This is Tuesday (August 3rd)

By the way, we are at day #41 without rain in Portland. The last MEASURABLE rain was June 15th. There WAS a trace at PDX on July 1st. Assuming we don’t get rain in the next 12 days (possible), we’ll be up in the “top 5” range for dry spells.

But for now, we’re a long way from that 71 dry day record

A few more notes:

1. I don’t expect high humidity during the upcoming heat wave UNLESS we get some showers or thundershowers Saturday/Sunday.

2. Overnight temperatures will be turning very warm, mid-upper 60s. This isn’t as extreme as the historic heatwave back in June, but it’s still worth checking in on elderly friends/relatives.

3. Southerly flow = overhead fire smoke from California fires. Expect increasing haze and yellow/orange sun after Wednesday. Low-level smoke is UNLIKELY west of the Cascades since wind will be coming from the northwest and west.

Stay safe during your summer vacation travels!

Chief Meteorologist Mark Nelsen

  • Updated

Tuesday, August 3rd, 4:05 A.M. 

Good morning!

It's another mild start this morning with most of the metro starting off in the 60s. Look for areas of smoke and haze this morning, then mostly sunny to hazy this afternoon with a high of 92.

Some patchy clouds tomorrow morning, then mostly sunny, high 93. Increasing clouds by Thursday afternoon, increasing clouds, high 84.

Showers possible Friday, otherwise mostly cloudy and much cooler, high 74. Partly cloudy on Saturday, high 76. Areas of morning clouds, then sunny on Sunday, high 79. Mostly sunny on Monday, high 83.

  • Posted

9:30pm Sunday…

I’ve been on vacation the past 9 days, a bit of bike riding down in the Moab (Utah) area with my son. Sorry, not many pictures because I was having fun. Actually I was home part of that time as well; but I’m back at work this evening. Calling it “work” is a bit of a stretch meteorologically since we are in a VERY stable weather pattern for at least the next 7 days.


First, the record cold this morning. We’ve seen LOTS of late season frost the past month, because we’ve seen much drier than normal weather. Keep in mind we’ve seen less than 2″ of rain in six weeks in Portland! Drier air = less cloud cover = colder nights. Basically west of the Cascades we’ve been in more of a “continental climate” than usual. Right now dewpoints are down in the 20s in the metro area. Sometimes we don’t see them get that low all April long. Our spring in Portland (so far) is similar to a typical spring you would experience east of the Cascades. Wide temperature range; nights running cooler than average, but daytime slightly warmer. Last night we saw widespread cold readings. Look at the Portland metro lows:

Lots of upper 20s, even a few mid 20s…pretty cold for mid April! Portland airport dropped to 32 degrees, the first time we’ve seen frost beyond April 10th since 1982.

Quite an impressive reading considering the metro area is much larger than 40 years ago, more of an urban “heat island” now. Plus our climate has warmed a bit in general. We don’t see many record lows in Portland the last couple of decades. Record lows were also set in several other locations west of the Cascades

My peach tree is blooming and still LOOKS okay. Maybe it needed to be under 27 degrees to do significant damage, we will see within the next couple of weeks.

Tonight won’t be quite as chilly as the airmass has warmed a bit. Sure, some frost for outlying areas, but everyone should be at least 2-3 degrees warmer than last night.


When I came in and looked at the maps/models today, it became obvious we are in for almost continuous sunshine for the next week for much of Oregon and SW Washington. That includes the coastline.

In the upper atmosphere, a ridge of high pressure and its sinking airmass is developing just to our west and north, keeping weather systems away. But a cold pool of air (upper-level trough) is coming down the back side of that out of Canada. By Tuesday it is centered over the Idaho/Nevada/Utah area.

It’s far enough south and east of us to keep cloud cover away. But we get a relatively strong northeast flow overhead. That’s offshore flow. Even though the air starts cool, this pattern under strong April sunshine will push our temperatures above normal. By Thursday the setup is strong high pressure to the north with a low south. This can be (and will be) a very stable weather pattern. It’s called a “Rex Block”.

Then between Thursday and Saturday the warm ridge expands south and east over us as the low moves away. A warming atmosphere means high temperatures climb from just above average to MUCH above normal. We’re headed from the lower 60s tomorrow to mid-upper 70s Saturday west of the Cascades. After tonight the widespread frosts west of the Cascades should disappear as well.

Meanwhile offshore wind flow appears to continue all week, although it may weaken briefly Wednesday/Thursday. Check out the WRF-GFS cross-section over Portland; Wednesday afternoon (right side) through Sunday afternoon (left side). Yellow line is around mountain pass elevation.

Offshore flow almost the entire time, plus a warming atmosphere. No cloud cover (maybe a few thin high clouds). It doesn’t get any better than this anytime April through June!

At this point we don’t appear to be setting up for record high temperatures…all in the 80s mid-April and beyond. But we’ll go from a perfectly average 60, to around 70 by Wednesday/Thursday, to upper 70s Saturday and possibly Sunday. For the weather geeks, 850mb temps need to make it to at least +10 over Salem this time of year to hit 80 in Portland with perfect conditions. That COULD happen Saturday, we will see. Regardless, this 7 Day forecast is something else for mid April!

When will it end? ECMWF ensemble precipitation forecasts imply the ridge breaks down somewhat next week, so it’s safe to assume showers will appear at some point after NEXT Monday

That’s it for now, enjoy the sunshine!

Chief Meteorologist Mark Nelsen

  • Posted

Now that we’ve seen a nice soaking across most of the region, it’s time for some classic early fall weather. Cool nights and mornings plus briefly (very warm) afternoons. Fall in the Pacific Northwest is typically like this; rainy periods alternate with bright sunshine. The key messages…

  1. Expect dry conditions through at least next Saturday/Sunday
  2. Temperatures reach 80 degrees or warmer Monday through Friday
  3. A gusty east wind blowing out of the Gorge will arrive in the metro area tomorrow, then come and go through Friday.
  4. Fire smoke is unlikely to return in any significant fashion in the lowlands. But high-level smoke from California likely arrives Wednesday. Expect much hazier conditions Wednesday-Friday

Today was about as normal as it gets…we hit 51 last night and 75 today in the city. 1 and 3 degrees above the 30 year average. Strong high pressure is now in place overhead. Here’s the view for Tuesday…

The typical fall jet stream is diverted far to the north and then plunges south into the Great Lakes region. We go much above normal and they turn very chilly. It still looks similar NEXT Sunday, October 4th, although the ridge has “flattened” a bit. That could lead to onshore flow and areas of fog/clouds. We’ll see how that plays out.

Regardless, rain is not in the cards through at least next Sunday. Actually the GFS model ensembles (newly upgraded last week!) show the ridge popping up a bit again early-mid NEXT week. Here’s Wednesday the 7th (click for a better view). Warm colors indicate a positive (warm) upper-level height anomaly.

The ECMWF and Canadian models look the same. So confidence is relatively high that we have a dry (or mainly dry) 8-10 days ahead.

How warm? 850mb temps over Salem sit between 20-23 for the next six afternoons! This would be a major heat wave in summertime. But this time of year a “heat wave” is 80-90 degrees. We appear to have good offshore flow the next two days, then it backs off a bit Wednesday. A bit stronger again Thursday, weakening Friday. At no time do we have a strong east wind event. More of a typical “gusts 40-55 mph in the Gorge and breezes over the mountains” setup. That begins tomorrow. I’m going with these numbers…only Tuesday and Wednesday would be close to record highs.

If you don’t like warm/hot weather, at least this time of year long nights mean we’re back in the 60s soon after sunset. Lots of 40s/50s for overnight lows of course.

I just check past Portland weather stats to see how uncommon 5 days in the 80s is this time of year. Not unheard of, but somewhat unusual. So how many days have we made it to 80 AFTER this date? This will be the most since 2014-2015.

But you have to go all the way back to my first year in TV…1993 to find another early fall with this many 80 degree days. Definitely unusual. In 1987 we saw 8 days at/above 80 this late in the season, and 1991 was similar.

Everyone keeps asking me about smoke…will it come back? I think that’s a yes/no question.

  1. Little or no smoke was visible on the perfectly clear GOES-17 satellite image today. There’s no reason to believe any of our local fires will suddenly start raging out of control or even put up a big plume of smoke again. That’s due to wet forest, no strong wind forecast, and some good fire lines.
  2. But, communities close to those fires may be smelling smoke regularly again or we could even get a slight haze down here in the lowlands. That should be about it.
  3. MORE NOTICEABLE…As the upper-level high shifts slightly east of us late Tuesday, a southerly flow opens up overhead. This means Wednesday-Friday could see a lot of milky/hazy sky overhead with filtered sunshine. Hopefully that wouldn’t make it all the way down to the surface.

Here’s the GEOS-5 modelling that shows smoke about to arrive Tuesday evening. You can see the center of the upper-level high around La Pine at that time.

By the way, check out this 20 year span of Portland metro area PM2.5 pollution. Except for last year, our late summers have turned smokier; you aren’t crazy in thinking that’s the case. The poor air quality you regularly see in late fall and early winter is due to inversions; common due to weak sun angle and long nights. Data is from EPA

  • Posted

It has begun…complaints about cool summer weather. I often get complaints this time of year, some people expecting that we should have Sacramento style heat in Portland. To be fair, the past two days have been especially cloudy and cool. Today was the 2nd day in Portland without seeing a 70 degree temperature; our typical high this time of year is 78-79 degrees!

We’re now approaching two weeks of below average temps. The average high temperature for this first week of July is the coldest since 2000! My little butternut squash and cucumber plants are struggling…just a few inches high. Too little sun and most days only in the 60s up in the hills. At least we haven’t seen much rain the past 2+ weeks; it’s very clear our dry season has arrived.

So, the big question…



The short answer; it’s unlikely this same cool weather pattern continues the next 9 weeks to Labor Day. But there is no sign of hot weather in the next 7-10 days either.

First, we are overdue for an average or cool summer west of the Cascades. I’m not saying that’s about to happen, but the past six years have featured an unprecedented string of warm to hot summers in the Portland metro area. 2016 wasn’t crazy warm and neither was last year. In fact much of the warmth last year was due to excessively warm nights; a consequence of warmer than normal ocean water offshore.

My point in bringing this up is that, at some point, we should expect to get a cool summer.

The weather pattern the past two weeks has featured a setup like this in the upper-atmosphere; weak “troughing” or a dip in the westerly flow over the Pacific Northwest. High pressure (and warmer air) has been suppressed to the south and east regularly. Notice most of the country is very warm to hot! We are all alone in the cool weather out here

A warm/hot July weather setup looks more like this; the westerly flow pushed farther north into Canada. That takes much of the cloud cover and showers north as well = sunnier and warmer weather west of the Cascades

Looking ahead, that upper-level trough backs off a bit the rest of this week. The result is more sunshine and warmer days. By Saturday that hot upper-level ridge is much closer to us. At this point it appears this should finally be a setup for a sunny Saturday and temperatures in the 80s.

But by Monday another system is passing by to the north, once again bringing a surge of cool marine air inland Sunday and maybe even a shower. A continuing issue the past couple of weeks is models only catching onto these cold troughs about a week ahead of time. A week ago it appeared we’d be heading into a very warm summer pattern this coming weekend. Instead that is being delayed once again by this system Sunday/Monday

Looking farther ahead, we should warm again a week from now as high pressure builds just offshore. This is the GFS model for next Wednesday the 15th

The morning ECMWF model’s forecast for high temps in Portland shows this trend as well.

Warming through this Saturday, then cooler, then warming again a week from now. You can add about 5 degrees to most of these to get a Portland high temperature. In general this is a bit warmer than what we’ve seen the past two weeks. It would imply the next 10 days will be near average for mid-July.

No model shows a wet weather pattern ahead, just a few drips here and there. ECMWF says less than .20″ in the Willamette Valley through the next two weeks. As mentioned earlier, the dry season is here:

It’s summer and vacation time, so I’ll be off until Sunday. Enjoy the warmer late-week temps!

Chief Meteorologist Mark Nelsen

  • Posted

It’s been a very “normal” Memorial Day Weekend. Cool and cloudy Saturday, then warm and sunny Sunday. Of course a weak weather system lingering overhead the first half of today left us damp through noon or so. We expected that. We eventually warmed into the upper 60s in the Willamette Valley.

Memorial Day High Temps

Portland ended up with .07″ rainfall, about what models were showing last night at this time. A mix of sun, clouds, & showers are perfectly normal for this “beginning of summer” weekend. Take a look at Memorial Day Weekend weather the past 10 years (click for a better view)

PDX Stats for each Memorial Day Weekend

What’s Ahead?

We are in flat “westerly flow” right now. That means a weak late May jet stream is overhead. That’s why a wet weather system is lingering so close this evening.

But that warm upper-level high pressure to our south pushes north and east the rest of this week. By Thursday/Friday it’s centered right over Nevada

A heat wave is coming for California this week. Excessive heat warnings are up for the Central Valley. Highs reach upper 90s to upper 100s tomorrow through Thursday!

Scorching heat next few days in California

How warm for us this week? Tomorrow we’ll be back into the 70s; lots of clouds leftover from today will keep temps under control. But then weak offshore flow Wednesday/Thursday plus 100% sunshine warms us dramatically. 850mb temps reach +14-16 Wednesday, then +17-19 Thursday-Friday. With good offshore flow, there’s no reason we couldn’t hit 90 in Portland both Thursday and Friday. But I see “flat” upper-level ridging, plus most models are not showing a sharp thermal trough. So I’ll go a bit more conservative with the highs. 85-90 is a good forecast for those days. Anything over 87 would be the warmest day so far this spring in Portland. Enjoy another taste of summer, but without the record heat. By the way, record highs at PDX for Wednesday-Friday are 95-100-90.

I’ll be watching Saturday closely since a “cutoff” upper-level low is forecast to swing north along the West Coast. Sometimes this can give us a good soaking and/or thunderstorms as it passes by. That southeasterly upper-level flow just ahead of the low (shown) is great for steering some thunderstorms west of the Cascades.

Models are in very good agreement that we move into a wetter/cooler pattern again after Saturday. Check out the ECMWF ensemble rain forecast. Each line on this chart (upper part) represents one of the 51 ensemble members from this morning’s run. Great agreement that we’re dry through at least Saturday morning. Then every member shows showers later Saturday through sometime Sunday. Get your deck staining done this week and wrapped up Friday. Or early Saturday would be a good time to put out some warm weather veggie transplants; they will get watered over the weekend.

That’s it for now…enjoy the warm weather this week!

Chief Meteorologist Mark Nelsen

  • Posted

May has arrived after the 4th driest April on record in Portland.  Less than 1″ of rain through the entire month!  That’s mid-summer dry.  Some areas west of the Cascades had a bit more…around 1.00 to 1.50″.  Still a dry month.  Warmer than average as well.

What’s ahead?

May in Portland Stats

May is typically the month where we turn the corner, leaving behind the really chilly spring weather.  We also tend to see some “very warm” weather at some point during the month.  In fact each of the past 8 years we’ve hit at least 85 at some point during the month.

May Warmest Temp

Most interesting is that the 89 last year occurred on May 10th.  That would be this coming weekend.  It appears we’ll be very close to that number again this Saturday.

We have our first warm season “heat wave” pattern setting up Thursday through Sunday.  The weather setup for these events is always similar.  Strong upper-level high pressure builds along the West Coast.  Then the sinking/drying of the airmass leads to surface high pressure east of the Cascades.  At the same time easterly wind around 5,000′ develops across the region.  That produces a “lee side trough” in western Oregon & SW Washington.  We also call that a “thermal trough”; an area of low pressure that develops on the “back side” of the Cascades due to the easterly flow.  That leads to a surface easterly wind as well since pressures are lower west of the Cascades.  This all adds up to the warmest possible weather for us anytime between April and September.  In the case of late this week, the atmosphere overhead won’t be crazy warm, so no 90s.   But we’ll be close.

You can see the progression of events on the Canadian model.  Strong surface high pressure building just north of us Wednesday afternoon.


Quick clearing that afternoon after some morning showers…ignore the colors.  Then by Thursday afternoon the “thermal trough” is getting established west of the Cascades, although it’s more of an northeast wind instead of straight easterly at the surface.


Friday is the big warm up, a very sharp trough is sitting right along the coastline.  Strong easterly wind through the Gorge and down the west slopes of the Cascade/Coast ranges


This is the one day the beaches may hit the low-mid 80s, especially north of Lincoln City to the Long Beach peninsula.

7 Day North Coast

The thermal trough is still west of the Cascades by late Saturday afternoon, but easterly wind goes calm.  This is typically the warmest day of the episode in the metro area; early east wind going calm or very light westerly late in the day.


By this time flow is back to onshore along the coast and maybe into the southern Willamette Valley too.  Could be a few degrees cooler from Salem south

How warm could we get Friday and Saturday?   It is possible we make it to 90 degrees. otherwise it’ll be close.

Models are in very good agreement laying down +15 to +17 (celsius) 850mb temperature both afternoons over Salem.  Based on past cases in early-mid May with offshore flow and 100% sunshine, PDX should see a high temp between 86 and 91!  Last year a +16 produced that 89 degree day on the 10th.  So our temperature forecast of 84 & 86 those two days might actually be a bit low.

Data Driven Forecast Highs Next 7 Day Meteogram

Regardless, we have several days of summer weather coming up Thursday through Mother’s Day.  Get your BBQs and kiddie pools ready…

Since it’s been so dry you should be watering everything starting this week, including your lawns.  Dry easterly wind really dries out potted plants quickly.  That’s too bad since it’ll be the third consecutive year we’ve seen very dry weather start early in the season.

Chief Meteorologist Mark Nelsen

  • Posted

After a very cool two weeks, the Pacific Northwest has “turned the corner” and now we’re seeing more typical April weather.  In fact temperatures will be near or above normal for at least the next week.  Plus, we’re headed for our first 70 degree day of 2020 tomorrow!  This is the typical time of year we see our first 70 degrees.

First 70 Degree Day Heatwave

Over the past 30 days most of the western USA has been experiencing below average temperatures.  Only the yellow/orange colors on this map represent warmer than average weather:

anomimage (1)

Precipitation has been below normal as well…in this case the colors yellow/orange on the map below represent drier than typical conditions over the past month:


High pressure is building offshore and upper-level maps show that ridge cozying up to the West Coast the next two days.  Right now:




But then the ridge weakens a bit and shifts a little farther west again.  This is Easter Sunday.  Much of the nation east of the Rockies will see some cold Easter Egg hunts.


For us?  The strong ridging just west of us the next week means little or no rain.  That’s the easiest part of the forecast.  Then it’s a matter of how warm we get the next two days and how much cloud cover Friday/Saturday as a weak disturbance moves by.

First the warm weather.  Today we’ve seen relatively strong “onshore flow”, that’s air flowing from ocean inland.  But models show 2-3 millibars of easterly flow through the Gorge and over the Cascades by midday tomorrow.   Easterly wind from late March to mid-October is a “warm” wind.  That’s warm relative to normal.  Not like that cold east wind from Halloween to St. Patrick’s Day.   The WRF-GFS model from UW shows this at 2pm:


Tomorrow we add in 850 millibar temperatures (temp at 4,000′ or so) of +10-12 deg. celsius; quite a bit warmer than the +4 we saw today.  Then add all-day sunshine both tomorrow and Thursday.  Taking a look at my warm season “magic chart” for April, historically we have seen high temps at PDX between 72-80 degrees with this same setup.  In 2009, we hit 78 at PDX on April 6th with similar conditions. Those 80 degree highs on my chart were likely later in the month.  So, our forecast of 72 tomorrow and 74 Thursday seems good.  It’s quite possible we hit 70 tomorrow and 76 Thursday instead.  Or 73/73.

You get the idea…it’s going to feel like May for the next two days!

Onshore flow returns Friday with morning clouds, then more of that cool onshore flow might even give us a sprinkle or drizzle Saturday.    This is our only chance for rain in the next 6 days.

As cold air surges south out of Canada Saturday night and Sunday, we get another round of offshore flow.  Although the airmass will be cooler, this means Easter Sunday may just be sunny with temperatures in the lower 60s for your egg hunts.


We are still doing some serious “social distancing” here at KPTV/KPDX like many of you.  In the past 10 days two of our meteorologists have “left” the office.  Both Brian MacMillan and Jeff Forgeron are broadcasting from home.  That’s not because they/we have any virus issues, but to move us farther apart.  Fewer people in one space = good.



It’s amazing; with today’s technology we are able to perform just about all tasks from home that we can do at work.  20 years ago this wouldn’t have been possible.

The rest of us are still working here.  I have to admit I don’t mind working alone in this environment at all.  I go most of the work day without getting physically close to coworkers as mentioned in a previous post.

Stay healthy this week and enjoy the sunshine!

Chief Meteorologist Mark Nelsen