• Updated

It’s been an exciting 24 hours!

Thunderstorms showed up as expected last night, most of them west of I-5 until early morning. Then 2-5am a large cluster of storms moved from near Lebanon up into the metro area. I wasn’t watching closely, in fact I was asleep Midnight-9am except for an hour around 4am. That’s because way out on the eastside I only saw lots of flashing, some occasional distant rumbling, and a sad 0.20″ total rain! That’s okay since the May 30th event was spectacular way out here. For the central metro area down to Salem it was an epic nocturnal lightning event; and well predicted by models! It was nice to see both summertime events west of the Cascades forecast well.

Some of you witnessed the heaviest rain of your life! Or at least the heaviest in a few years. Some spots saw more than 1″ in an hour, or even 30 minutes. That’s serious tropical moisture. Check out the official totals:

As always with thunderstorms we’ve seen a HUGE variation in rainfall depending on location. Ignore Kelso, something is wrong with that rain gauge. The massive downpours missed some of the official stations. For example, when that cluster of storms started moving north around 1:30am, it just nailed the Stayton/Sublimity areas. Here’s an account from Denny, about 6 miles east of Sublimity… “Last night between 1:30am and 2am I had 1.6″ of rain (mostly in 20 minutes) and 2+ inches of 3/4″ hail with continuous lighting causing a mudslide from a tree farm across the road into my driveway and pasture. Two foot deep in places, what a mess…” This is a pic he sent us, notice all the hail still lying around at least 6 hours later.

Just looking at totals over 1.00″… mid Willamette Valley (click for a better view)

Then the metro area…just totals at 1.00″ or higher

And late this afternoon/evening some flooding rain up in Kelso/Longview area. Lots of flooding on streets and hearing that first floor of hospital was at least partially flooded.

Clearly this marks our turn to fall weather; the long summer dry spell that began around June 20th has ended. The long period of “dependable dry” is over. We ended up with less than 1.50″ rain in the past three months. Looking ahead, I see a few showers tomorrow and then again around Wednesday PM or Thursday next week. There’s no sign of a long dry spell ahead; time to start paying attention to the rain forecast again.

And how about that smoke??? It’s gone! A southwesterly push of clean marine air came into the metro area between 3-4pm; suddenly the air quality went from poor to excellent. Even the Gorge has cleared out. The only spots left with bad air are in Central Oregon. Our 8 day “smoke storm” has ended. It was 10-11 days from Salem south since you folks had 2-3 days of smoke from the Cascade fires while Portland metro area stayed relatively clear. Current readings from www.purpleair.com

All those beautiful green circles…Portland is at 18! That’s even better than most summer days. Another site I use is http://aqicn.org/city/usa/oregon/portland/ In general we stay with good air quality from here on out, that’s unless wind direction turns south or southeasterly again. That would bring smoke north from California, SW Oregon, or Cascade wildfires. But our own fires in the Cascades will be knocked down a bit due to cool weather, high humidity, and some rain from this point forward. Not out, but more of a “creeping fire” instead of torching quickly across the landscape.

That’s it for now, enjoy your smoke and “weather-free” weekend. I’ll be back at work Sunday afternoon and take a look ahead into the last week or so of September. October is right around the corner…

Chief Meteorologist Mark Nelsen

  • Updated

4pm Thursday...

I've been off work the last three days and will be through Saturday. But I want to update you on two important changes ahead. Tonight looks especially interesting.

First, I see almost nothing has changed with regard to smoke. We are in an unprecedented (at least for the past 40 years or so) smoke event over the region. This is the 8th consecutive day with VERY UNHEALTHY to HAZARDOUS air quality in the Portland metro area. I never saw that growing up here and sure haven't in my career that started in 1991. We've been receiving a "double-whammy" of: light wind at sea level keeping surface conditions smoky, plus tons of high level smoke streaming north from Oregon and California. They have conspired to keep temperatures well below what they should be in the current weather pattern. The effect is that this fire/smoke event brought our "summer to an end" on the 10th this year, when under normal circumstances it would have continued through today. We don't have any sort of spell of "summer weather" in sight. Fall is here weather-wise starting tomorrow.

My wife is tired of me saying "if it wasn't for the smoke we'd be sunny and in the low 80s again today". That would be the case today of course. If we didn't have fires burning, this could have been a record warm first half of September. But you see starting a week ago the dense smoke kept us a solid 10-20 degrees cooler than we would have been otherwise.

Air quality numbers at 3pm:

Yesterday evening was interesting down in the south Willamette Valley. That's because a weak westerly push of marine air briefly dropped Eugene and Albany down into the GOOD to MODERATE category. But then a light northerly wind today has allowed the pollution to slosh back into the southern valley.

THUNDERSTORMS TONIGHT

This is the biggie. We haven't seen this setup since the end of May; a nice nocturnal lightning event is on the way.

  • Anytime after 8pm then on through sunrise tomorrow, ANY of us west of and in the Cascades (including coastline) could see quite a light show.
  • In fact the Portland NWS has the recently burned areas under a Flash Flood Watch since any heavy rain on dry/burned soil will cause all sorts of trouble. Landslides, rock fall, trees drop, etc...

The Storm Prediction Center even has us under a MARGINAL to SLIGHT risk of severe thunderstorms. A severe thunderstorm in this case would be a damaging wind gust over 58mph or large hail. Yes, that could happen during the night. Rare, but I have seen it happen here. And no, no one knows why SPC still uses those categories. Does any normal person know the difference between MARGINAL, SLIGHT, & ENHANCED??? No.

What's the reason? It's the large upper-level low offshore that's been spinning in circles all week. Tonight it makes the big move. Right now, notice the southerly flow in the atmosphere. Imagine how many fires are upwind this afternoon, thus the continuing dense smoke overcast:

Then tomorrow midday, it's about to move right over Portland...

By Saturday midday it has moved to the east, and we have a west-northwest flow overhead. By this point all upper-level air will be coming in clean off the eastern Pacific!

There is a lot of moisture as this system moves in. HRRR says about 1.50" precipitable water west of the Cascades...that's juicy!

The way the low is moving in leads to tremendous lifting in the atmosphere the next 12 hours. Especially 8pm-2am. This IS the classic setup for thunderstorms west of the Cascades. Each model is slightly different with location and timing, but I think the NAM-NEST represents reality well. At 8pm storms are starting to pop just to our south.

But by 1am they are spreading north quickly

And by 6am it's obvious SOME of us will have seen downpours, others relatively light rain

It's important to not focus on specific spots; the point is that over and west of the Cascades we'll see some heavy rain from thunderstorms during the overnight hours. Some areas could see up to an inch of rain, others just a brief wetting.

Beyond sunrise tomorrow, we'll be into a more typical spring/fall showers & sunbreaks pattern. That continues the rest of Friday.

AIR QUALITY

  1. A westerly breeze and thunderstorms should clear out the densest fire smoke by sunrise and we'll just have a smoky smell/view instead of this hazardous stuff. That's an improvement.
  2. Then much cooler air overhead with the upper-level low will finally break the inversion we've been under for 8 days; that should help quite a bit. Lots of the surface smoke should easily mix out after sunrise.
  3. Continuing westerly flow in the upper atmosphere starting late tomorrow through next week should keep California and Oregon fire smoke moving east and away from us.

BY TOMORROW MORNING AIR QUALITY SHOULD BE NOTICEABLY BETTER, THEN BY SATURDAY AFTERNOON WE SHOULD BE BACK IN "FRESH AIR" AGAIN!

Enjoy the weather "show" tonight and hopefully we avoid any significant flooding issues in those burned areas. This will be our first measurable rain in about a month; which means roads will be slick at first too. Stay safe!

Chief Meteorologist Mark Nelsen

  • Updated

Sunday, September 20th, 4:30 P.M. 

Today was a classic early fall day; spots of fog and clouds led to a mainly sunny and warm afternoon.  Tomorrow should be similar, although maybe a notch cooler under partly cloudy skies.  Expect a few scattered spots of morning fog as well.

Tuesday a very weather weather system passes overhead early which could give us a few sprinkles, otherwise that should be a dry day too.

Wednesday through Friday we’ll be in a wet fall weather pattern.  A windy/rain system moves overhead later Wednesday, followed by the usual showers & sunbreaks Thursday and Friday.  Maybe even some thundershowers Thursday too.  Snow levels fall down to around 7,000’ or so in the Cascades and this rain will further dampen the smoldering fires in the Cascades.

Most forecast models are showing a return to some sunny/warm weather the last few days of September, and that begins next Sunday.

  • Updated

A very brief post to let you know…it still looks like this outside. View from Dayton at our Stoller Family Estate Cam

Air quality is still terrible at all inland locations at midday. Keep in mind any number above 300 is considered HAZARDOUS. There has been a slight improvement in just a few spots (Tualatin Valley & Longview) compared to yesterday.

BUT IT’S UNLIKELY WE SEE SIGNIFICANT IMPROVEMENT IN THE SMOKE SITUATION THROUGH TONIGHT

Why?

  1. The dense smoke layer is not part of the input for weather forecast models. Those models don’t know we’re staying chilly in the lowest elevations compared to how “we should be”. Typically we’d be in the lower 80s today under this weather pattern. In fact many areas way up in the mountains will be in 70s. But we’ve been stuck in the low-mid 60s; smoke is blocking a significant amount of solar radiation.
  2. Smoke modeling is BASED OFF THOSE NOW INACCURATE WEATHER FORECAST MODELS. For example the HRRR smoke modeling showed a surge of cleaner westerly wind coming inland last night. That was assuming we warmed up inland yesterday, that would give us the typical onshore flow in the evening. It didn’t happen and the smoke remained.
  3. These same weather forecast models keep trying to bring in a general southwesterly breeze this afternoon across the whole area. That would help “ventilate” some of the low level smoke up into the atmosphere. We have better conditions several thousand feet up with a breezy southwest wind. It’s just not happening down at ground level. But I have doubts that will really happen. Pressure gradients at 11am sure don’t show it’s about to happen.

I’ll be on the air for a bunch of this evening’s shows…starting at 4pm.

Cliff Mass has a much better write up about the current situation on his blog this morning. He’s a professor up at the UW, who I consider the “Godfather of PACNW Weather”. Actually he was my favorite when I was at UW back in 1991. I highly recommend reading his post today.

Chief Meteorologist Mark Nelsen

  • Posted

These are sure strange days…dense fire smoke is covering most of the western USA right now, especially along the West Coast. Take a look at the afternoon image from GOES-WEST. Click on any of these images for a better view

The smoke has moved so far offshore that it’s wrapped up into an upper-level low. A closer view shows smoke covers almost all of Oregon and Washington. I’ve circled a large plume pushing above the smoke layer over the Lionshead Fire, just east of Olallie Lake in the Cascades. Another plume is over the Brattain Fire just south of Paisley.

Of course we all know what it looks like down in the smoke layer. A sickly and cool yellow/orange world.

THIS IS THE WORST AIR QUALITY FOR THE LONGEST PERIOD OF TIME I’VE SEEN IN OUR AREA. This is our third day in the very unhealthy to hazardous category. Look at the numbers, most of us in the HAZARDOUS level. I’ve rarely seen a city go above 300; but Portland is around 500! The problem is not only smoke coming from those fires, but a weak push of cooler marine air has put us in a strong inversion. Temperatures in the 60s in the lowlands but 70s higher up. If we didn’t have the smoke we would have been in the lower 80s today.

When will it improve? Maybe slightly better tomorrow afternoon, but I think Monday should be much better with a strong push of westerly wind. Look at the HRRR smoke modeling for midday Sunday, this is a bit better than today

Then midday Monday…MUCH better

Smoke will still come and go next week since a system offshore will keep sending smoke out of California, but hopefully this long episode of dangerous smoke will end Monday

What about the fires? More good news today. No significant growth towards Molalla, Colton, Estacada, Silverton etc… in the past 2.5 days. Once the east wind disappeared the fires really slowed down. 700+ square miles burned with the 3 north Cascade fires. Today more of the area around Olallie Lake was burning as well as Trout Lake on the Warm Springs Reservation. It appears the Lionshead joined the (now in mop-up phase) P515 fire today too. So there is a 60 mile long corridor from Lyons to west of Warm Springs that has burned. That’s amazing.

Farther south, the Holiday Farm fire and Archie Creek fire continue to burn

Those fires will all burn until heavy rain and/or snow flies later in the fall.

To summarize:

  1. Fire fighting conditions continue to be good through the foreseeable future. No sign of hot/dry easterly wind for at least the next week
  2. All the Cascade foothill towns that are in Level 3 or partially burned shouldn’t see any additional burning. Hopefully lots of you get to go home in the next few days!
  3. Dense smoke should turn into more reasonable smoke in the lower elevations after tomorrow.
  4. The big fires in the Cascades will be burning for quite awhile. Luckily we’re not far from October when wetting rains usually end the fire threat

Chief Meteorologist Mark Nelsen

  • Posted

It's been another extremely busy day for fire crews over and west of the Cascades. These last two days have seen an unprecedented number of large fires west of the Cascade crest.

There is one bit of bad news, but much more good than bad weatherwise this evening.

First, evacuation zones have been expanded in Clackamas County; Level 3 (GO NOW) includes Marquam, Estacada, Colton, & Molalla. Even Oregon City, Canby, & Sandy are in a Level 2 (BE READY) zone now. You can find this map on the Clackamas County page Click for a better view...

DOES THIS MEAN THERE IS A WALL OF FLAMES AND QUICKLY ADVANCING WILDFIRES DOWN INTO THESE TOWNS?

ABSOLUTELY NOT AT THIS TIME! Authorities are being very careful and proactive. They are making sure people are not in danger in these towns. An "abundance of caution" might be the best phrasing here.

But there is very good news for evacuees weatherwise...the dry east wind is gone! The most dangerous "explosive fire growth" phase of this event has ended. As a state official said at a news conference earlier today, he felt today was the day "we're turning the corner". That's good news.

At this moment wind is either calm or almost calm everywhere west of the Cascades. I can't find a wind gust over 15 mph inland from the coastline! That includes the Cascade foothills as well. And that wind is coming from a westerly direction = more moisture from the Pacific Ocean. A fire sure won't be racing westward out of the mountains and down into the lowlands in these conditions. Check out relative humidity, way up from the teens and 20s yesterday at this time in the valleys.

The two coastal fires are now under the influence of a chilly & humid marine airmass. They are done making any advance towards the beach towns (Lincoln City).

Where do we head from here? A brief summary...

We now enter a more "normal" forest fire situation in the mountains and foothills. Each afternoon through Sunday a westerly breeze develops, but this will push those fires mainly eastward, farther into the mountains. So if a town hasn't burned yet, it seems very unlikely it will from this point forward. But fires WILL continue to grow; these are massive fires!

To summarize...in the lowlands of Northwest Oregon.

  1. There's no reason to believe any of the large fires will suddenly advance farther down into lower elevations (westward) and into more towns/cities.
  2. Thick smoke will be with us through Saturday, possibly Sunday as well. Air quality is hazardous in much of the metro area right now, and down into the Willamette Valley.

Now that things are settling down a bit we can take a look at the acreage...the numbers are stunning. Here are the "mega fires" burning in and along the west slopes of the Cascades. Click for a closer view on each one

The 900 square miles of public/private forestland burned hits relatively close to home. I grew up in this area and know how important timber is for these towns. My wife grew up in Sweet Home with relatives in Mill City, Gates, & Blue River. Remember that private timberlands support families and communities too, not just national forests. For some people their future income just burned up, along with a home and/or town.

That's it for now. I'll be on tonight at 10/11pm and the evening shows again tomorrow.

Chief Meteorologist Mark Nelsen

  • Posted

Can you believe that just over two days ago we were moving through a peaceful and sunny Labor Day Weekend? Things have changed…

Now, based on various reports/video/pics:

  • Firestorms have burned hundreds of western Cascade forests. Productive private timber lands have burned as well.
  • It is assumed hundreds of homes have burned. Large portions of several towns appear to have burned down. That would be Detroit, Mill City, Gates, Blue River, Talent, Phoenix, and possibly others. We know at least two people have died and it’s also assumed there are others that didn’t make it out of the firestorms late Monday night and Tuesday morning.
  • Medford and Diamond Lake Resort had close calls last night. Both appear to be safe for now. We will see about the Olallie Lake area.
  • Thousands have left their homes in many parts of western Oregon.

You may recall over the weekend we were warning a dangerous fire situation was on tap for late Monday through today. Check Sunday evening’s blog post. Sure, we get dry east wind and warm temperatures every fall, but this was forecast to be extra dry and extra windy. The wind wasn’t too extreme in the metro area as noted in yesterday’s post, but unusually strong gusts (for any time of year) hit the west slopes of the Coast and Cascade Ranges. Weather forecast models nailed that situation.

Satellite imagery today shows something I’ve never seen; almost all of western Oregon blanketed in thick smoke…not from California fires but our own. This is a GOES image that also includes fire detections (orange areas) as an “underlay”.

Fire crews have been totally overwhelmed in the region due to so many fire starts. Many fires have been relatively small (less than 100 acres), but the large fires continue to rage in the Cascades this evening. Here’s the 9pm fire detection, using the infrared channel. Black is a heat signature. Click on image for the current loop

The three big fires are quite close together now. Latest numbers are 112,000 acres for Riverside fire SE of Estacada/Colton. This one DID NOT EXIST 36 hours ago. The Santiam Fire (renamed from Beachie Creek Fire) is around 160,000 acres and has joined with the Lionshead fire as that one moved westward across the Cascade crest and down toward Detroit. Add in 90,000 acres there and you get a third of a million acres of timber burned…let that settle in.

I thought it was revealing what someone said this afternoon during a news conference. He was from from Detroit Fire District I think. He mentioned that late Monday night the high winds hit and suddenly fires were popping up everywhere due to power lines down. That tells me the extreme wind gusts really did surface in spots. Same thing with wind damage around Lincoln City where a gust to 62 mph was recorded…easterly of course. A 98 mph gust was recorded up at the top of Hoodoo Ski Area early Tuesday morning. Clearly this was an “off the charts” east wind event for September.

WHAT LED TO THESE MASSIVE FIRES? 3 SPECIFIC CAUSES

  1. Easterly wind was stronger than we typically see this early in the season = lots of powerlines down into dry trees/brush.
  2. It’s the driest airmass I’ve ever seen in September. Dewpoints in the 20s today and relative humidity below 10% at times west of the Cascades. That’s because it was an extra-early “arctic airmass”
  3. It was the worse possible timing for forests/grasslands. No fall rain yet, not even a weak frontal system. Fuels are the driest of the entire year. If the wind/dry air arrived in October with wet/moist forests the fires wouldn’t have blown up so much.

I’m sure there will be plenty of discussion about how much climate change (warmer/drier late summers), past forest practices (not enough harvesting), and power company maintenance (lines through forests instead of underground) played into this unprecedented event. It sure is interesting that the corridor where PGE cut the power has seen no fires (Sandy to Gov’t Camp). I’ll leave all that to others.

The good news is that onshore flow is about to return to the Oregon coastline, that should greatly reduce fire threat tomorrow for the coastline (only).

Inland, the easterly flow is weakening, although still about 5 millibars pressure difference across the Cascades. That easterly flow ends by late tomorrow. By Friday afternoon a normal (but weak) onshore flow arrives into the valleys and Cascade foothills. Humidity goes up, which slows fire growth a bit. So the explosive growth phase of these fires should end by Friday, but I don’t expect rain until early next week.

The massive plume of smoke stayed mainly south of the metro area yesterday and this morning. But you probably noticed it advanced overhead this afternoon & evening. At 6pm…

Smoke modeling shows the plumes will veer more northwest through tomorrow. There’s a good chance the metro area will be under a dense smoke layer tomorrow with temps around 80 instead of 95 we were thinking a few days ago (for tomorrow).

Thursday could be a real nasty day for air quality in Portland. Maybe as bad as early September 2017 when the Eagle Creek fire sent smoke/ash into the metro area.

That’s it for now, heading back to TV land for the 10/11pm newscasts. See you there.

Chief Meteorologist Mark Nelsen

  • Posted

It seems like the “morning after” here at home since we have blue sky and the wind is calmer. But I typically don’t complete a blog post via generator in summer!

Reality is pretty bad across western Oregon and southwest Washington this morning. Here’s a crazy satellite loop from GOES-WEST. The black areas are active fires burning (heat detected) before sunrise.

Then after sunrise you see the massive plumes of smoke spreading westward. The plumes coming off Mt. Hood and Mt. St. Helens are dust. Click for a loop

1) Multiple fires are burning now and spreading on extremely dry easterly wind

2) Beachie Creek and Lionshead fires have almost joined. A massive conflagration stretches almost all the way between the Warm Springs Reservation to west of Mill City. That’s 40-50 miles! Silver Falls State Park in danger now too. Lots of people had to drive through fire last night to get out of the North Santiam Canyon. Here’s the fire detection from space

3) New large fires east of Battle Ground and southeast of Estacada. These don’t have names yet as far as I’m aware…a developing situation for sure. A wider view of those detections.  Only red/orange are current detections.  Yellow is from earlier in the year or regular field burning

4) Another large fire burning down McKenzie River east of Springfield. 5) Many smaller fires prompting evacuations as well. Lots of highways and roads closed

6) PGE still has 70,000 customers out of powerEast wind isn’t quite as strong, but even 20 mph with relative humidities in the 5-15% range this afternoon is very bad.

Wind goes calm in some areas tonight and really dies down tomorrow afternoon for most of us.

Apparently vacation is over…my choice during this historic fire episode, and I’ll be on the air all evening. I’ll see you there.

Chief Meteorologist Mark Nelsen

  • Posted

It’s been a wild evening for some of us, very similar to the very strange ending to Labor Day Weekend 2017. That’s the night the Eagle Creek Fire sent ash into Portland and flames 15 miles through the Gorge.

This afternoon’s wind arrived exactly when models said it would (4-6pm) in the metro area and Cascade foothills. Here are the peak gusts so far; notice when we get a “downslope” wind event, the central part of the metro area around PDX tends to be windier than most other spots, including areas near the Gorge. The official peak gust at PDX so far is 52 mph! That was one of the highest gusts in the metro area. The other two (so far) are 60 mph on I-205 Glen Jackson Bridge and 59 mph at Corbett. Most other airport locations were in the 35-45 mph range. On the edge of “windstorm” strength for sure. It’s rare to see an easterly wind gust above 50 mph at PDX, the highest I’ve ever seen was a 60 with the February 1989 cold blast.

I’m hearing of lots of damage in the foothills. I had a gust to 49 mph at my home east of Corbett. I don’t live in an area that gets the usual strong Gorge wind. I’ve never seen a downslope east wind event like this produce a gust over 43 mph…in the past 16 years! In fact the highest gust I’ve ever seen anytime time of the year was a southerly gust to 60 mph during the December 2006 storm. This IS a historic wind event for the Cascade foothills. I see Multnomah County Sheriff had to get about a dozen vehicles down from the Larch Mountain area; they were trapped by trees across the roads. PGE did end up cutting off power to about 5,000 customers from Sandy to Government camp this evening and right now almost 100,000 are out of power in their entire service territory! That’s a lot for September, partly due to fully leafed trees and the unusual easterly direction

On the fire front things aren’t looking good. So far I haven’t seen a major fire flare up in the metro area or nearby foothills/mountains. But lots of smaller blazes. Here’s the latest fire detection from GOES-17. Note the Beachie Fire north of Detroit is on the move westward and must really be blowing up this evening. It appears to have moved a few miles. Then just east of there near Mt. Jefferson is the other big blob. That’s the Lionshead Fire. But notice a couple more spots, one each in both Clackamas and Lane counties. Click for a better view

There are evacuations along the McKenzie River right now east of Springfield. Apparently a large chunk of the town of Mansfield, WA burned in one of those fires up north today too. You can watch these fire detection loops (hit PLAY of course) here: https://col.st/LtOMo

So we’ll see how things go tonight and tomorrow. Many of us won’t be sleeping well knowing a fire could suddenly start up. The wind probably won’t get stronger, but it’ll continue off/on through the afternoon. At my home it’s died down quite a bit in the last hour. Daylight will reveal how many trees we’ve got down across the region, otherwise it’s unsafe to be driving around forested areas right now.

Chief Meteorologist Mark Nelsen

  • Posted

9pm Sunday…

I’m on vacation this week (at home for now), but we’ve got some serious fire weather ahead. First, while I’m standing in my kitchen about two hours ago, my wife’s phone gets an emergency alert. It came in with a blaring tone like a civil emergency or Amber Alert.

Other than the crisis of her phone having less than 50% charge, what does this mean? Power may be shut off in 24 hours? My phone didn’t receive this alert, but hers is probably pulling from a cell tower closer to Mt. Hood.

This is a first, I’ve never seen a situation where PGE has considered de-energizing power lines to avoid forest fires. Indeed, they have the “Hoodland Corridor” (east of Sandy to Welches to Government Camp) under this possibility

They are taking the proactive step after seeing what can happen with high winds, low humidity, and extremely dry vegetation. We’ve seen it in California the past couple of years. We get gusty easterly wind sometimes in September, nothing unusual, but this time is different. MODELS ARE FORECASTING A “HISTORICALLY STRONG” EASTERLY WIND EVENT BEGINNING MONDAY EVENING AND CONTINUING THROUGH TUESDAY

WIND HIGHLIGHTS

  • Nothing unusual through late afternoon Monday over and west of the Cascades. It’ll be a hot afternoon though, into the lower 90s in Portland.
  • Sometime around 5pm or so, a strong easterly wind will start coming over the Cascades, through the Gorge, and down into the lower elevations. Wind will be around through Wednesday.
  • DAMAGING WIND (gusts over 45-50 mph) should be confined to ridges in the Coast and Cascade Ranges, plus down into the Cascade foothill communities. That’s eastern Clark, Multnomah, Clackamas, Marion, & Linn counties. Wind gusts 40-60 mph are not a damaging wind in the western Columbia River Gorge.
  • I DO NOT EXPECT A “WIND STORM” IN PORTLAND, but gusts 35-45 mph are unusually strong for early September and some limbs will probably fall. Expect a few power outages Monday night and Tuesday.

THE BIG FIRE WEATHER PROBLEM

I’ve never seen a high wind setup (for the foothills and Cascades) this early in the “Fall east wind season”. This is unusually strong even for November/December, but this hasn’t happened when forests are still totally dry and humidity will be extremely low. This could be a once-in-a-quarter century type of event. I haven’t seen it in my 29 years forecasting here! The Storm Prediction Center has our area under an “extremely critical” fire threat; I don’t think I’ve seen that either

The problem?

  1. TERRIBLE TIMING: Forests are at the driest of the season…ready to burn. In fact a bit drier than average for early September. If this was May, we might be okay.
  2. DRY AIR: Relative humidity will plunge into the single digits to teens all across Oregon as dry air arrives Monday night. Almost unheard of west of the Cascades in September.
  3. STRONG WIND: Wind gusts 30-60 mph (depending on location) could whip any spark into a massive fire in a few hours in these conditions. Imagine if a Douglas fir branch drops onto a power line, bringing it down & starting a fire. 30-40 mph gusts could spread a fire many miles with downwind spotting. The Eagle Creek Fire on this date in 2017 spread 15 miles through the Gorge in one night! That COULD happen somewhere along the west slopes of the Cascades tomorrow night or Tuesday.
  4. HISTORIC SEPTEMBER FIRE TIME: The largest fires west of the Cascades have blown up under these conditions; Tillamook Burn in 1933, Yacolt Burn in 1902, Eagle Creek Fire in 2017 etc…

WHAT YOU CAN DO THE NEXT 2 DAYS

  • Stay out of the woods and travel only on graveled/paved roads. Never drive over grass once your vehicle warms up.
  • If you live in a rural/forest area DO NOT MOW or do anything outside that can create a spark during this time
  • No cigarettes, fireworks, or shooting practice (Pit Fire near Estacada started this way)
  • If you live in the foothills of the Cascades or western Gorge, be prepared to leave home quickly if needed and stay alert. I still have my camping trailer hooked up since we just got home. I decided to leave it that way until Tuesday night…just in case. It happened 3 years ago…

I won’t spend too much time on the technical details. We have a hot ridge of high pressure over the West Coast right now. Temps are running about 10 degrees above average and more like +15 coming up tomorrow. A 597 dm high is VERY hot. With offshore flow that could put us close to 100 degrees. But we had onshore flow today

The upper-air pattern becomes highly amplified (briefly) Monday night and Tuesday. An early season cold airmass digs south into the Rockies, doing a “drive-by” of the Pacific Northwest. This is 8pm Monday. That’s quite a setup, hot airmass along coastline and cool fall weather coming down through Idaho. This general pattern is perfectly normal in September/October, but this is an extreme version of that pattern

By Wednesday the hot upper high is back over us…other than fire weather the big story is a continuing hot/warm pattern through NEXT weekend.

To show the contrast between the “cold” airmass coming in to our east vs. the hot to the west. Take a look at 850mb map for tomorrow evening

About 35 degrees BELOW NORMAL at 5,000′ over Montana, yet 12 or so ABOVE NORMAL over the Oregon coastline. That’s a tremendous thermal gradient. So a dry cold front will push south and west across the Pacific Northwest tomorrow afternoon-night. You see the arrival in the WRF-GFS cross-section over Portland. Right around 00z tomorrow (5pm). 60-70kt wind speed around 3,000′ over Portland. That’s amazing; I’ve never seen that in September/October, and it’s very rare anytime in the cold season. So we’re in a bit of uncharted territory here. For example, how much of that strong wind will “mix down” into the valleys?

The same model shows the benign wind conditions at 2pm tomorrow. Northeast wind is just arriving at The Dalles and northeast Oregon. This is what we would call the “arctic front” if it was winter; the sudden wind switch to easterly. Note these are calculated wind gusts, not steady speed.

By 2am Tuesday (tomorrow night), high wind has arrived in the Cascades and gusty wind in most of the metro area as well. There could be some crazy strong wind gusts in the Cascades and western foothills. 50-65 mph possible there. Notice more reasonable wind in the metro area…gusts 25-45 mph; still strong for September.

Also note (in red) the 8-9 millibar easterly gradient across the Cascades; I’ve never seen that in September either. Right now there are two large fires burning in NW Oregon. One north of Detroit (Beachie), and one large one (Lionshead) just east of Mt. Jefferson. Imagine what could happen with either of these fires the next 48 hours. Not good..here’s the Beachie fire this afternoon from folks at Willamette National Forest

So, meteorologically we’re about to see something very rare for this time of year. IF we don’t get any large fires, it won’t go down in history as something that interesting for regular folks. But of course if we get one or more large fires, we’ll all remember!

Chief Meteorologist Mark Nelsen

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Mark Nelsen

Yes, for now (and probably for a long time into the future) I'm just copying the WordPress blog post into this KPTV-Friendly web site. Just keep commenting over on the old blog postings

Mark Nelsen

Mark Nelsen commented on Saturday Snow Update

Test. Anyone out there?