Early Cold Snap Delivers; But Back to Mild & Dry

October 26, 2020

8pm Monday…

It’s a beautiful October evening! A nice view of sunset from several of our weather cameras

Everything turned out just about as expected late last week through this morning. A chilly Canadian airmass dropped down into the Western USA right on schedule. Gusty northeast wind arrived in the metro area Saturday afternoon, clearing out the cloud cover and leftover morning sprinkles. Spokane ended up with the snowiest October on record. Around a half foot in that area. Temperatures hardly rose Saturday as the colder air moved in.

Then Sunday (yesterday) we saw a very chilly and windy day. Peak wind gust at PDX was 39 mph yesterday. Highs stayed in the upper 40s in Portland; one of the colder October days we’ve seen in the last few decades

Skies remained clear last night, dewpoints were down in the teens, and east wind backed off. That gave us just perfect “radiational cooling” conditions. Portland (airport) officially dropped to 29 degrees this morning. That was the earliest 29 in many years, although we’ve hit 30 earlier in the month in some years. Check out the rest of the metro area…

Some records were set too, the coldest October 26th in Portland, Hillsboro, & Eugene.

You might be wondering how cold it can get in October? The all-time October records…

I’ve hardly mentioned the eastern half of the state…brrrr!

Ignore Hermiston, there are a bunch of missing observations during the night. A warming airmass today, along with low relative humidity, allowed afternoon temps to climb rapidly. Redmond went from 9 this morning to 57 this afternoon!

What’s ahead?

Mild and mainly dry weather. Notice the ECMWF monthly run last night shows upper-level heights well above average this week

Then next week looks similar, possibly slightly wetter. That’s a warm pattern across much of the USA for the first week of November

A mild westerly flow, aided by a continuing “warm” eastern Pacific tells me we’re headed back into warmer than normal conditions for at least the next 10 days

With the main jet stream shunted north of us we can expect drier than normal conditions to continue. Just one weak system Friday afternoon/evening and that should be it for October rain. Another very dry month

Looking farther ahead, the ECMWF ensemble average paints drier than normal weather through the first week of November.

The monthly run of the GEFS is similar…very dry well into November. The new/improved GFS ensembles (in September) are now run 5 weeks into the future, once per day. But remember accuracy goes downhill after 10-14 days. You get the idea…dry. We’ll see.

To summarize:

  1. There’s no sign of a rainy/wet pattern in the next 7-10 days. We’ll be much drier than average.
  2. Significant snow at the Cascade ski resorts is unlikely over the next week or so.
  3. Have some outdoor projects you STILL haven’t finished? You’ve been given a reprieve! Lots of good/dry outdoor weather ahead in what is typically the beginning of the rainy season

Chief Meteorologist Mark Nelsen

Cool Weekend Ahead, Lots of Wind Too!

October 22, 2020

6pm Thursday…

So far this week has turned out about as expected. I made these points on Sunday (bold is what happened)

  1. Temperatures finally cool down to, and then below normal for late October this week. That’s going to be quite a change! In fact by next weekend it’ll be jacket/sweater weather (WE HAVE COOLED AND THIS WEEKEND LOOKS COLDER)
  2. First snow is likely in the Cascade Passes either Wednesday (less likely) or Friday night (more likely) (SNOW IN THE AIR YESTERDAY; AN INCH OR TWO STILL POSSIBLE LATE FRIDAY NIGHT)
  3. First frost is likely in outlying areas Thursday and/or Friday mornings (JUST HAPPENED THIS MORNING!)
  4. I don’t see a rainy weather pattern for the next 7-9 days, just some showers at times (ONLY .01″ SO FAR THIS WEEK, & ONLY A FEW LIGHT SHOWERS EXPECTED THE NEXT 7 DAYS)
  5. There is a small chance some lower elevations in the Gorge and eastern Oregon get a very rare October snow dusting late this week. (MOST OF THIS WON’T HAPPEN, MODELS BACKED OFF ON COLD A BIT AND MOISTURE TOO)

Today was the coolest day so far this fall…only 57 degrees in Portland. Not exactly a “chilly” day, but we get used to all the warm weather so far this month

Of course what was most noticeable was the morning chill and frosty areas. About 1/2 of the metro area saw a first frost today

Here in Portland we had an early frost last year, but most years we don’t see it until sometime in November

Right now a warm-ish area of upper-level high pressure is centered south and west of us. A cool upper-level trough moved through yesterday (remember a few showers?); that’s why we’ve turned cooler.

But look up to the north right where British Columbia, Yukon, & NW Territories meet. A pocket of cooler air is about to surge south. By midday Saturday it is swinging through the northern Rockies and Intermountain region

That’s chilly air for this early in the season. Ahead of it a Pacific frontal system brings us light showers tomorrow. Then cold air pours in behind during the day on Saturday. By that time most of the moisture for producing snow to lower elevations east of the Cascades is gone. That’s why I don’t expect any significant snow in the Oregon Cascades or most of Eastern Oregon. Notice the ECMWF snow forecast is quite “dry”.

You’ll need to be in the Blue or Wallowa mountains to get more than 1-2″ snow this weekend. Even there models have really backed off, because that upper-level system is shunted a bit farther east. By Monday, the warmer upper-level ridge is popping back up over us…lots more dry weather ahead!

What we WILL get over the weekend will be an increasingly strong easterly wind. This will be the strongest event since the Labor Day East Wind Storm. Models are consistently showing a 16-20 millibar gradient from Spokane down to North Bend (OR) by Sunday morning. The WRF-GFS tends to overplay the low level cold, but you get the idea. Lots of isobars = a very windy day Sunday for ALL areas west of the Cascades, not just near the Gorge. Here’s the WRF forecast for 5am Sunday…brrr! It may be tough to get above 50 degrees Sunday. Combine that with wind and it’ll feel more like late November or early December; for one day

The cross-section gives 50-55 knot wind (circled) Saturday night through early Sunday between 2000′-4,000′ over the Portland area. That’s not ridiculously strong like what we experienced Labor Day evening. But it’s strong enough to give us gusts 35-45 mph Saturday night through Sunday. Even though dewpoints will be plunging Saturday night, all that wind will keep us well above freezing. Sunday night should be a different story as the wind dies down. Very dry air, calming wind, low humidity…much of the urban area away from the Gorge will see a killing frost (down to 30 or so).

Much of next week will be dry. The ECMWF 15 day ensemble run from this morning…each horizontal line is one ensemble member. Time goes from now on left side to 15 days out on the right side. Highlighted is next work week.

So, much like last year it appears we’ll be seeing a slow start to the rainy season. Maybe a dry Halloween? We’ll see, that’s still 9 days out.

Enjoy the sunshine! After tomorrow’s showers…

Chief Meteorologist Mark Nelsen

Winter 2020-21; What’s Ahead?

October 21, 2020

11pm Tuesday…

About this time each fall people start asking me “What this winter will be like?” or “I’ve heard it’s going to be a bad winter!“.  Actually sometimes they start asking in August!  For the record, I’ve NEVER had a person say “I’ve heard it’s going to be an easy winter“.  Apparently most of us are quite cynical and expect the worst.  Since it’s 2020, I suppose this year everyone gets a pass.

I don’t put out a “winter forecast”.  That’s because the few forecasts I see are often (not always!) wrong and seasonal/climate forecasting has a long way to go before we say we can “forecast” a winter.  So we’ll just call it “my thoughts” for the upcoming winter since we can at least glean a few ideas by looking over some weather tidbits.  I’ve been doing this for quite a few years and it seems to work.

For those of you with a short attention span, just three points:

  1. Plan on an “active” winter this year.  The last two winters were quite “boring” for the weather professionals. Which means they were “easy winters” for regular folks. I think we’ll see more changeable weather this winter; I expect to be quite a bit busier here at KPTV. A better chance for windstorms, flooding, and lowland snow.  And I doubt we’ll be locked into weather patterns for weeks/months at a time as we’ve seen the past two winters.
  2. Expect at least once we’ll see some snow or freezing rain in the metro area and lowlands west of the Cascades.  I would be surprised if we get through this entire winter without measurable snow in Portland. I’d peg the chance of “sleddable” snow at about 70% some point between November 10th and March 1st. No, we have no idea when that could happen. Any forecaster that claims so is making it up or click-baiting you…#FakeWeather.  
  3. Expect a good snow year in the Cascades. Good for both water next summer and skiing during the winter.  Go ahead and plan on a normal ski season with the usual variable ski conditions from week to week. I’d give this about a 70% chance of happening too. It is possible to get a low snow year during a La Nina winter. In fact the last one gave us terrible ski conditions through January! Then February/March were incredible.


Two winters back…2018-2019  Up until around February 3rd 2019, we had experienced the most boring winter I can remember in my 28 winters forecasting in the metro area.  Long periods of weak weather systems, almost no real “storms”, and mild temperatures.  This was typical for a weak “El Nino” winter.  That means the tropical Pacific Ocean was a bit warmer than average.  Things were progressing according to plan…but then all hell broke loose around February 5th.  Cold northerly flow became a common weather theme for much of the following five weeks!  Several snowstorms moved through the region, affecting different parts of the FOX12 viewing area at different times.  Who can forget the “Kale Fiasco” when some metro-area stores ran out of kale & other groceries?  A good learning time for local forecasters…

Last winter…2019-2020  So boring…this was our 2nd consecutive “El Nino” winter. There was a real lack of Pacific storms; it was as if the jet stream just didn’t want to perform last winter.

So much of the past two winter seasons have involved a lack of storminess and drier than average weather. About time for some action don’t you think?


It appears we have a weak to moderate “La Nina Winter” on the way.  That can give us a few hints, definitely not a forecast, but what direction our winter might be “weighted” toward.  I’ve spent some time looking at past La Nina episodes and what happened here in the Pacific Northwest.  I based all my graphics/research on a weak/moderate event.   Right now the Oceanic Nino Index (or ONI) is on the edge of WEAK to MODERATE La Nina category.  

Model consensus says we’ll likely be in a WEAK-MODERATE category during this upcoming winter.  Here’s the latest plume of ocean/atmosphere models. Anything below the “-0.5” is weak La Nina, below “-1.0” is a moderate event. Strong would be “-1.5”.

Typically in these winters there are 3 effects observed to varying degrees:

  1. The north Pacific jet stream tends to be more “wavy” which means there is more of a north & south component to the jet instead of travelling straight west to east
  2. There is increased tendency for blocking somewhere in the east Pacific
  3. As a result there is sometimes more interaction of the cold Canadian air to the east and Pacific moisture with the jet stream weakening dramatically at times too.

Likely effects this winter based on a moderate La Nina event:

1.  Rainfall

I think it’s unlikely that we’ll have a drought winter; but far more likely precipitation will be above average.  La Nina winters in the Pacific Northwest are dominated by a strong jet bringing frequent disturbances across the region, interspersed with sudden ridging or northerly flow.   Then it’s back to the westerly flow.  For this reason they tend to be wet.  It’s likely the #1 most noticeable event in these winters.

1a.  Flooding

This goes with the rainfall.  For obvious reasons we tend to have more flooding events in La Nina winters due to the wetter weather. Keep in mind we haven’t seen a major regional flood in 24 years. That was 1996. Previous big flood was 1964. I wouldn’t say we are “overdue”, but one of these winters it’s going to happen again.

2.  Mountain Snow

Lots of precipitation and cool weather systems = plenty of mountain snow.  This is probably the #2 most likely event.  7 out of the last 10 La Nina winters have brought above normal snow to ALL elevations in the Cascades.  Note that there CAN be a bad year; it just happened during the last La Nina in 2017-18. Ouch! Check out the mid January snowpack during the last event…

3.  Foothill Snow

This happened in several of the past La Nina winters…significant snow to lower elevations (1,000′-2000′).  This MAY happen again if we get a succession of cold and wet systems coming in from the west and northwest.  Of course these are the same systems that give forecasters headaches because then snow it quite close to the Valley floor multiple times during the season.  News people get really excited about it too.

4.  Wind Storm

We are overdue for a regionwide major windstorm here in the Pacific Northwest.  The last BIG one was December 1995.  That’s 25 years ago!  14 years before that we had the major November 1981 storm.  It’s interesting that all those La Ninas from 1950 to the mid 70s had a wind gust of 60+ mph at PDX each time!  Not as frequent since that time though.

5.  Portland Snow/Ice

This one is tough.  Anyone who says a La Nina winter means lots of snow in Portland is mistaken.  Average snowfall in weak-moderate La Ninas DOES go up a bit, but not a dramatic increase.  Two La Ninas in the last 20 years have produced a major snowfall here in Portland…December 2008 and January 2017.  I should point out that the “cool/wet” La Nina winters sometimes produce little freezing rain because we don’t get as many inversion episodes to our east, which means less east wind in the Gorge.  We need that for a good ice storm either in the Gorge OR in Portland.


The elephant in the living room I suppose is the fact that our winters are gradually warming, and snow in Portland is more rare than it used to be when we look back more than 50+ years.  Take a look at total snow each decade since the airport observations started about 1940. Divide by 10 to get average per winter.

And downtown records that go back to the late 1800s.  The low spot in the 80s is missing some data…it should be a bit higher…

We have always been in a marginal snow climate, but now warming temps are cutting off even more of the winter snow.  Every few winters we get 1 good snowstorm. We all remember that event and that pops up the long-term average.  It is interesting that the last 3 decades seem to have leveled out a bit at around 4″ per winter at both downtown and PDX locations.


  1. Warm Blob In Eastern Pacific The sea surface is much warmer than normal in the eastern Pacific once again this fall. Some would consider it another “warm blob” offshore. I can’t find a La Nina in the past 40 years that started with such a warm ocean offshore in October. Local meteorologist Charlie Phillips has a great writeup about this in his blog: http://charlie.weathertogether.net/2020/10/18/blob-the-third/

It’s possible the relatively shallow layer of warm water gets “mixed out” as fall/winter storms arrive, we will see.

2. Pacific Decadal Oscillation (PDO) This is directly related to the sea surface temps. Typically during a La Nina we get a negative or “cool phase” of the PDO at the same time. That is not the case this time, or at least ocean temperature anomaly doesn’t seem to match the current “cool phase”. Strange, although sometimes it happens. You can read up on the PDO here: https://www.climate.gov/news-features/blogs/enso/going-out-ice-cream-first-date-pacific-decadal-oscillation

This gives the general picture

3. Anthropogenic Global Warming (Climate Change) A warming globe doesn’t necessarily mean we don’t get cold air outbreaks or snow. It can also mean the usual circulations get disrupted. For example it seems to me we just aren’t getting as much storminess over the eastern Pacific the last 2-3 years. That’s just anecdotal of course. But has something shifted the past 20 years? We don’t know, although 30 years from now, we might look back and notice something did change during this period. There is still a LOT we don’t know about climate.

That wraps it up…as always we’ll see how the winter turns out…my money (again) is on “wet”, “good Cascade snow”, and at least one “snow/ice event” in the lowlands. Maybe several, but hopefully I won’t be spending too much time at the hotel right near the TV station…

Chief Meteorologist Mark Nelsen

A Record Warm Fall For Some; But Much Colder Temps Ahead

October 18, 2020

10pm Sunday…

Today was very mild with just a few showers, continuing a “dull weather” theme we’ve seen lately. Temperatures are running well above normal this month, partly due to warm nights. We’ve only seen one cooler than normal day so far this month (last Thursday). We’re running over 4 degrees above average for October, but of course we still have 13 days to go. Check out central and eastern Oregon!

If we combine the warm September with this month so far, the numbers are record or near-record breaking warm. Meteorologically fall began on September 1st (arrived about 10 days later for us in the middle of the cool/smoky period). Right now Portland is running 2nd warmest on record, just like Astoria to the west and Olympia up north. It’s the warmest fall on record (so far) at Redmond

But the main weather message for the upcoming week is…COOLER. We’ll finally see some cooler than average weather after tomorrow and maybe close to record cool next weekend.

Right now we are in a mild westerly flow coming over the top of an upper-level ridge offshore. It looks like this up around 18,000ft.

But several weak weather disturbances gradually “carve out” a cool upper-level trough Tuesday-Thursday. Looks different by Wednesday doesn’t it?

For the first time this season we’ll see cold air drop south out of Canada. Snow will fall down around 3,000′ in this setup, possibly bringing the first snow of the season to Government Camp and surrounding ski areas. Except there isn’t much moisture available. Maybe a dusting to an inch up at Govy later Wednesday through early Thursday, but it sure looks wintry north and east of us doesn’t it? Lots of cold air in southern Canada and into the USA Rockies

As dry and cooler air filters south Thursday & Friday, expect much cooler nights for all of us. First (and overdue) frosts are likely everywhere except in the cities west of the Cascades and along the coastline. High temps fall into the mid 50s even with some sunshine.

The most interesting event showing up on models occurs Friday evening through Saturday morning. Both the GFS & ECMWF models show some variation of our typical wintertime “snow storm setup” in Portland and the Gorge. That’s when a surface low pressure system comes down the coastline, pulls cold/dry air air out of the Gorge, and throws moisture over the top of that. Of course it’s extremely early for this setup and everything would have to be perfect for snow to fall to sea level in this pattern. The very reasonable ECMWF looks like this late Friday night

Low pressure is moving onto the Oregon coastline. A gusty east wind is pulling cold air down through Eastern Washington and through the Gorge. Yes, the ECMWF is producing snow in the eastern Gorge and down into Central Oregon.

Snow has fallen as early as October 26th in Hood River (5″ in 1919), and the 29th in Madras. The GFS model has been unrealistically cold plus wet the past few runs, so I discounted it. But this evening’s run is looking a bit more like the Euro (more reasonable). I’ll be keeping an eye on it all week, but in summary

  1. Temperatures finally cool down to, and then below normal for late October this week. That’s going to be quite a change! In fact by next weekend it’ll be jacket/sweater weather
  2. First snow is likely in the Cascade Passes either Wednesday (less likely) or Friday night (more likely)
  3. First frost is likely in outlying areas Thursday and/or Friday mornings
  4. I don’t see a rainy weather pattern for the next 7-9 days, just some showers at times
  5. There is a small chance some lower elevations in the Gorge and eastern Oregon get a very rare October snow dusting late this week.

Chief Meteorologist Mark Nelsen

Quiet Mid-October Weather

October 13, 2020

9pm Tuesday…

Weather is a bit slow this evening…

We’ve seen some weather action the past few days with three Pacific frontal systems moving across the region. That first one Friday night and Saturday morning was sure a soaker; up to an inch in parts of the metro area. Our October rain total is slowly starting to add up

Western slopes of the Cascades have picked up 7-9″ of rain the past month…that has pretty much finished off the fires up there!

Last October was very dry, but we’re tracking a bit wetter this year so far

After a very warm start (and warm September!), we’ve cooled back to normal

What’s ahead? Typical October weather…lots of clouds and some showers at times.

A large upper-level ridge is building just west of us. It’ll be the main factor in our weather over the next week. It looks about like this right now

By Friday…

The forecast is very tricky Saturday through the middle of next week. That’s due to the ridge wanting to move just slightly farther west and “flatten” a bit. That leaves the door open to weak systems moving by to the north. Basically we may get clipped by several waves of clouds and light rain showers. You can see one moving by Sunday

The morning ECMWF model (pictured here) really flattened the ridge and carved out a cool upper-level trough. This would be a setup to bring light snow down below 5,000′ in the Cascades. But other models and even some ensemble members of this model keep a stronger ridge closer to us. We’ll see. I think the main point is that we’re probably not headed into a warm and sunny 7-10 days, but also no sign of stormy weather either. Just a typical mix of clouds, showers, and occasional sunny days. The ECMWF ensembles show temps cooling a bit more the next 10+ days; that would be normal for late October

Speaking of cooler temps, La Nina is now into the MODERATE category in the equatorial Pacific. Forecasters are confident this will be the case for upcoming Winter 2020-21. I’m working on the general winter outlook and should have it finished up next week. I’m feeling very confident we should see quite a bit more action than last winter. Remember how boring it was? Almost no storms and no lowland snow until mid-March! To whet your appetite a bit…take a look at the past 20 winters in Portland.

And farther back in time…seems like we have leveled off the past three decades a bit. Last winter finished off the 2010s decade; a new weather decade starts this winter. Snow measurements were taken at the NW corner of PDX up until 1996, then moved to Parkrose (near Sandy Blvd) for the past 24 years.

Last winter was very mild, some of my annuals from the previous summer made it through.

My banana bushes/tree, which most winters die down to the ground, made it to the 2nd story roofline by late August!

In fact last winter EVERY SINGLE DAY made it to at least 40 degrees for a high. It’s been 18 years since we’ve seen a winter without a 30-something degree day.

Chief Meteorologist Mark Nelsen

September’s Historic Fires, Smoke and Wind Storm

October 11, 2020

Saturday October 10th, 2020

It’s been a over a month since a series of massive (mainly forest) fires broke out across western Oregon. It was an event not seen in Oregon for at least 100 years, possibly farther back into the late 1800s. For historical purposes I want to make sure all the information/graphs/charts I’ve gathered will be in one place. This is nothing groundbreaking or “new”, but a summary of the event for future reference. It’s a LONG read, but that’s the point.

First, my heart goes out to all of you that lost family members, friends, & neighbors in the fires. As far as I’m aware, we have not seen a loss of life this great in Oregon from forest/range fires since the Bandon Fire of 1936. As of early October, the official death count is 10.

The loss of homes is staggering and beyond anything experienced in Oregon for at least the past 80 years. I remember when the Canyon Creek Fire in 2015 burned 43 homes just south of John Day; I couldn’t believe that many homes could be lost in one fire. But in September 2020, Oregon lost almost 100 times that number! The latest estimate is slightly over 4,000 homes destroyed; over half of those were in the Phoenix/Talent area just south of Medford during the Almeda Fire.

How much of Oregon burned? Just under 1 million acres west of and over the Cascades…most of that in a week starting Labor Day (Sept. 7th).

A summary of the fires (click for a better view)


A historic easterly wind event (storm) showed up at the worst possible time; early September before fall rains had arrived. The same setup anytime between late September all the way through June likely wouldn’t have produced any sort of significant fires.

We’ve always known that September CAN produce big fires west of the Cascades in NW Oregon and SW Washington, but it had been a long time since we’ve seen a huge fire during this period. For years we’ve looked back to the 1933 Tillamook Burn as an example, although this one started in August. This was the view from (I assume) the west metro area; fields look like Hillsboro or North Plains area.

Of course just three years ago, Labor Day 2017, a dry east wind helped burn 50,000 acres. That was the Eagle Creek Fire which spread along 35 miles west, then east through the Columbia River Gorge.

This year we did not see any late summer or early fall rain by Labor Day. Take a look at Summer 2020 ERC (Energy Release Component) of some weather stations on the west side of the Cascades. It reached a record high just after Labor Day (black line). Red is the highest on record for any date in the warm season.

Next image is a measure of “1000 hour fuel” for those same stations. That’s how dry 3-8″ dead branches/logs are on any one day. Notice most of the summer (which was very quiet for wildland firefighters) fuels were a bit slower to dry out than normal (gray line). Until the last week of August…the red line is lowest fuel moisture on record for any date during the summer. Just a few days with light rain showers at the end of August would have made a significant difference. This weather setup that arrived Labor Day came at the worst possible time; fuels over and west of the Cascades were ready to burn and burn quickly. Fire conditions were extreme.

A hot upper-level ridge was centered over and just offshore the Pacific Northwest over Labor Day weekend. During the last few days of August it appeared this ridge would sit directly overhead, possibly pushing Western Oregon up to around 100 during the holiday weekend. But as the weekend approached, models started forecasting a fast moving upper-level trough diving down the east side of the ridge. That would be an early fall pattern with cool air diving into the Rockies and eastward. As the weekend arrived it became obvious this would be an unusually cool shot of air; Denver was looking forward to snow. And models showed a very strong push of northeasterly flow for Labor Day all across the Pacific Northwest. This was pretty much a warm season version of an “arctic front”. Here’s the ECMWF forecast for Sunday afternoon (the 6th). Hot ridge over and west of us. We had already hit 95 on Thursday in Portland, then onshore flow cooled us Saturday into the 70s. On this day we were back up to around 90 in the metro area.

The forecast for Labor Day evening shows the trough dipping down to the east; hot ridge over and west of us is ready to move back in overhead.

Down around 5,000′, the 850mb anomaly chart for Monday afternoon shows an extreme setup for us. Over NE Oregon, temperatures are running about 18 degrees BELOW normal as the “cold” air plunges south. At the same time temperatures over southwest Oregon are forecast to be 23 degrees ABOVE normal. An incredible contrast!

This leads to a tremendous pressure gradient between the cool high pressure to our east and lower pressure to the southwest. Models were forecasting up to 23 millibars from Eastern Washington down to SW Oregon. Take a look at the “cross-section” of wind speed forecast over Portland. I’ve highlighted the important part. This was from the Sunday morning WRF-GFS model run (UW-Seattle). Note the abrupt change forecast around 5pm Labor Day; strong and deep easterly flow suddenly arrives from 7,000′ all the way down to sea level.

I’ve never seen 70 kts forecast by this model, even with strong easterly events in the winter. It was obvious this was going to be a historic wind event (or storm). And in this setup EVERYONE west of the Cascades gets the wind, it’s not like a typical Gorge easterly wind episode. When I saw this Sunday I knew we were headed for something big, especially in the foothills. That’s due to the wind rolling down the west slopes of the Cascades. I figured gusts down at the surface in the valleys would be around 35-45 mph, but they went higher than that in a few spots.

The SPC (Storm Prediction Center) nailed the extremely critical fire weather forecast. Due to high winds and very low relative humidity; remember this started as cool/dry Canadian air.

By midday Labor Day things were looking ominous to our northeast. Numerous fires were started by downed power lines across Eastern Washington (orange areas) and blowing dust (brown streaks) could be seen spreading south toward Oregon in this satellite image.

Then right on schedule, around 4-6pm, strong wind suddenly arrived with a bang. When we get these “downslope” easterly windstorms that sometimes happens; a very quick start. Often the central part of the metro area gets the strongest wind; from just east of the Interstate Bridge east over PDX to the I-205 bridge. Peak gusts over the next 24 hours show that was the case again this time. 52 mph gust at PDX was the strongest easterly wind gust on record in the month of September.

There aren’t many observations in the Cascades, but wind was extreme in those locations. Note the 66mph gust at Horse Creek RAWS, I rarely see real strong gusts there. This was right between the Riverside and Beachie Creek fires. Check out the coastal gusts! I’ve never seen such strong easterly gusts there at ANY time of the year.

LocationPeak GustNotes
Timberline Ski Area (7,700′)106 mph12 hrs w/peak gusts 90+
Hoodoo Ski Area (5,700′)98 mph
Mt. Hebo (Coast Range)92 mph
Horse Creek RAWS (3,400′)66 mph10 mi. NE Silver Falls SP
Lincoln City (tower in city)62 mphMany hrs. missing obs.
Tillamook 52 mphWind blew hard all night
Astoria 51 mphODOT
Newport Airport45 mph

The strong wind coming from an unusual direction plus fully leafed out trees led to thousands of power outages. PGE was up to 80,000 customers out at one point. But they did cut power to the Hwy 26 corridor from Sandy to Government Camp around 6pm Labor Day; a very good move since no significant fires started in that area.

Dewpoints, a measure of moisture in the air, dropped to mid-winter values. PDX went as low as 20, Tillamook to 18! By Tuesday afternoon relative humidity was in the high single digits and teens as the easterly wind blew; we were in southern California fire conditions Tuesday & Wednesday, the 8th and 9th

Of course we were all hoping we could get through 2-3 days of extreme fire weather with no new fire starts. But Monday night GOES fire detection showed massive growth of the Beachie Creek and Lionshead fires. Later we learned numerous downed power lines in the Santiam Canyon started fires that merged into Beachie Creek Fire. Along with the Big Hollow fire in Skamania County they show up as black areas. Also the Holiday Farm fire started and blew up along the Mckenzie River; presumably also due to downed lines. This is just before sunrise Tuesday morning. Notice the Riverside Fire SE of Estacada was still very small at this point.

Sunrise revealed a startling sight from space; massive plumes spreading westward off those fires; along with streamers of dust blowing of the volcanic peaks due to 100 mph gusts up there. I saw this and knew it was going to be bad since we had two more days of dry easterly wind.

The easterly wind blew all day Tuesday, most of Wednesday, and then retreated back into the Gorge early Thursday. Satellite image midday Wednesday

Wednesday was the day fire plumes spread a bit more to the north; during the afternoon thick smoke moved over the metro area. This reminded me of pics from Yakima the day Mt. St. Helens erupted in 1980. Keep in mind there are no clouds here…only smoke. 86 degrees, a dry east wind, and a thick layer of orange/gray smoke moving in.

Thursday was the “transition day” from low dewpoints and gusty wind back into normal (weak) onshore flow and higher humidity. Just in time because Thursday was the day Molalla was evacuated; fire officials say another day of easterly wind may have burned Estacada, Colton, and Molalla. You can see the smoke spreading eastward across the region that day

Fire intensity diminished rapidly Friday and beyond. The vast majority of acreage burned was Monday night through Thursday.

How rare was this easterly wind event/storm?

Quite rare. Definitely a historic event. Professor Cliff Mass did some research and found this was the strongest 2 day easterly wind event during fire season since at least 1950. That’s July-September over NW Oregon. A similar strong event occurred September 16-18th, 1971. That one was quite a bit cooler with high temps near/under 80 degrees. Relative humidity values were not as extreme. Portland had seen 3″ of rain from mid-August to mid-September. Forests were damp; totally different situation 50 years ago.

Were these fires historic?

You bet! I did some research and it’s a bit disturbing. In the past 100 years, we’ve seen 11 “mega-fires” over and west of the Cascades. 3 in the 1930s, one in the 1940s, then 52 years with none! 2 more in 2002/2017. So 5 OF 11 MEGA-FIRES OVER/WEST OF THE CASCADES IN THE PAST 100 YEARS BURNED IN SEPTEMBER 2020

1933 Tillamook Burn 240,000

1936 Bandon Fire 287,000

1945 3rd Tillamook Burn 173,000

1939 2nd Tillamook Burn 217,000

2002 Biscuit 500,000

2017 Chetco Bar 191,125

2020 Riverside 138,000

2020 Beachie Creek 193,000

2020 Lionshead 199,000

2020 Holiday Farm 173,000

2020 Archie Creek 133,000

Why did it happen? Climate Change? Mismanaged Forests? Utility Companies?

It’s a loaded question; my personal opinion is that it was a combination of factors. I’m sure many studies are on the way…

  1. The number one factor is what I’ve already outlined. The most dangerous fire weather pattern showed up at exactly the wrong time. And it happened to be an “extra-extreme” version of that pattern (wind/humidity). Everything lined up just right this year in a very bad way. Even if our climate wasn’t warming, at least some of these fires would have exploded out of control.
  2. No, they weren’t “climate fires”, that’s silly. But our warming climate likely played a part. But how much? 10-20% responsible? 50%? No one knows right now. Summers (especially July-September) have been warming/drying for several decades. I’m not a forester, but it’s safe to assume trees are more stressed & drier than they used to be.
  3. Fires have been suppressed for many decades, but we know fires were a natural part of Cascade forests in the past. Pioneers that arrived in the late 1800s probably experienced late summer fire smoke almost every year. Forests west of the Cascades were/are going to burn at some point; either this way or with controlled burns.
  4. What part did downed powerlines play? I’m sure we’ll be hearing more about this in the future.


As the fires slowed down (Friday the 11th), we were left with light wind and thick smoke throughout the region. It looked like this that first day (Thursday the 10th)

Downtown Portland in the smoke

For most of the next week the Portland metro area experienced the worst air quality seen in modern times. It lasted about 8 days here, but 10-11 days from Salem south since that part of the valley was immediately downwind of the first fire blowups. AQI numbers were regularly in the 300-500 range for most of us. I saw a few 600-700 numbers as well; just unreal. Many of us stayed indoors for most of that week. The numbers from September 8th-14th in Portland. One more reason to refer to this event as historic.

We had a terrible time getting out of the smoke because the weather pattern was just stagnant; nothing unusual for early fall. No strong onshore OR offshore flow to blow the smoke one way or the other. It took a weather system moving through the 17th-18th to finally clear us out.

A few bits of info that still blow my mind; I’ll never forget these

  1. Easterly wind pushed the Echo Mountain Complex from Otis just about to the beaches. Almost 300 homes burned just miles from the 55 degree ocean. Parts of Lincoln City, on the cool coastline, was under Level 3 evacuation orders.
  2. Labor Day morning, just hours before those 50-100 mph gusts hit the higher elevations of Mt. Hood, a small fire popped up within Mt. Hood Meadows ski resort. If it wouldn’t have been doused within those first few hours by multiple water drops, I think we could have seen another mega-fire come racing around the south side of the mountain. Probably right through Government Camp and on down to Rhododendron/Welches. Incredibly lucky! Video here: https://youtu.be/In53N_6ixzg
  3. The explosive fire growth the first two days was incredible. The Riverside Fire grew from nothing to 110,000 acres in just 1.5 days!
  4. A dewpoint around 20, with a temperature around 90 in Portland…amazing.

That’s about it. One last image showing the burn scars seen from space in early October once skies cleared and fires were pretty much out. You can clearly see the five big fire footprints on the landscape.

Chief Meteorologist Mark Nelsen

Dry First Week of October

October 1, 2020

9pm Thursday…

October is already here; the month in Portland where we see the largest temperature swing. Today’s average high is 70, by Halloween a typical day is only in the 50s! We don’t see such a dramatic change (up or down) in any other month. We DO live in a climate dominated most of the time by the mild Pacific Ocean. West of the Cascades that keeps our winters warmer than at a similar latitude elsewhere. But summers are cooler than similar latitudes. We’re sure not Denver with those wild daily swings in temps!

Today is the 2nd day of fire smoke streaming overhead from all those California fires. Luckily it has been the more typical “hazy/milky” sunshine without terrible air quality at the surface. This evening most areas are in the GOOD-MODERATE category.

Air quality will likely remain in this general range through Saturday. I see little or no air movement. On Sunday a push of northwest wind should clean things out not only at the lower elevations, but overhead as well.

Because of morning low clouds and fog in the valleys west of the Cascades we were a bit cooler today. 3 days in the 80s wrapped up September; then today we stayed in the 70s…still well above average for October 1st. But check out the heat at the higher elevations! Redmond’s high of 91 was the warmest October day in 19 years!

September ended up well above normal west of the Cascades, especially in urban areas due to the warm nights. Portland ended up 3rd warmest on record. Without the early month smoke, it probably would have been our warmest September on record

What’s ahead? Well last year we had a very dry October, but that was following a series of wet Octobers

The big message for this October is that the first week will be dry.

A ridge of high pressure is over the West Coast right now. Very warm airmass covers the whole region. This is the ECMWF ensemble forecast of 500 millibar heights. Color is the anomaly; MUCH warmer than normal tomorrow overhead. Technically the anomaly shown is much higher than average heights. But the effect is the same.

Next Tuesday isn’t much different is it?

Ah, but a change late next week. Here’s Friday the 9th. An upper-level trough and below normal heights over us. In October that means clouds and rain.

The ECMWF ensemble precipitation forecast chart shows the majority of ensembles are giving us rain at some point late next week. You’ll definitely want to click for a closer view. Each horizontal line on the upper part of the chart represents ONE of the ensemble members. They all want to produce some significant rain NEXT WEEKEND, the 10th/11th.

To summarize, we’ve got about one more week of dry weather. But there are strong hints that we’ll get soaked somewhere beyond next Thursday. Plan accordingly!

Chief Meteorologist Mark Nelsen