Mark Nelsen

Chief meteorologist

  • Updated

Yesterday was exciting with lots of lightning in the valley during the afternoon hours.  Then outflow wind from those storms plus a switch back to onshore flow gave us gusty evening wind in the metro area.  Overnight some hefty showers moved through too.  Here are the weekend rain totals:

Rain Totals Metro Area

I expect a little more rain west of the Cascades this week, but I think we’ll stay below a 1.50″ total going into the Memorial Day Weekend.  Maybe only an inch here in Portland.  This 10 day cool/wet period only has a few days left and we’ve been cheated a bit by lows going farther south into California than initially anticipated.  This is similar to a wintertime El Nino pattern.  Look how dry Seattle has been and then check out San Francisco and Santa Barbara!  May total so far…

Rain So Far This Month Or and Wa Earth Scene

Now those California numbers don’t look huge, but compared to normal they are “way out of whack” one could say.  Check how the numbers above compare to typical May rain through the 19th

Rain Totals West Coast Percent

So Sacramento has seen 6 times the average so far this month, that includes a record .83″ today with hail showers around too.

The general weather pattern is still on track this week; a chance for showers tomorrow and Tuesday, then warming/drying the 2nd half of the week.  Not TOTALLY dry, but west of the Cascades I don’t see many showers after Tuesday.  Models are hinting at thunderstorms developing over the Cascades Wednesday/Thursday; we’ll see if they head straight south along the mountains or come out over the valleys.  Regardless, temps will be warming the 2nd half of the week.  More on that tomorrow…

  • Updated

Tuesday, May 21st, 4:00 p.m.

It’s been a nice & (mainly) dry late May day in the metro area.  Temperatures will top out in the mid-upper 60s the next couple of hours.  A few showers have developed over the Cascades and are drifting out over the I-5 corridor.  So that means some of us could see a shower this evening; but many of us won’t. 

Tomorrow will be warmer and partly cloudy.  Temperatures rise into the 70s.  Then during the mid-late afternoon thunderstorms will pop up over the Cascades; stronger than today.  Some will drift down into the lowlands & metro area.  So beyond 3pm there is a chance for a shower or thunderstorm especially east metro area.    Thursday should be similar.

There is a better chance for showers Friday, then just a slight chance over the Memorial Day Weekend.  If we get showers this weekend it appears Sunday afternoon could see the best chance.  Regardless, in general it’ll be a partly cloudy and warm weekend.

  • Updated

Yesterday we saw vigorous showers move through the east metro area around this time, dumping up to 3/4″ of rain.  Today the heavy showers are east of the Cascades with lighter showers west of the mountains.  Models are shoving lots of moisture into far eastern Oregon tonight and Friday; NWS Pendleton has a flood watch out for that area

Mark Flooding California

The reason for all that rain is an upper level low moving into Northern California this evening.  I expect two more of these disturbances to take a similar track over the next week.  They show up nicely on the ECMWF model’s ensemble forecast.  First, Sunday morning you see that cold low in the same position as tonight’s low


Then a second low on Tuesday as the first low spread severe thunderstorms and tornadoes into the Great Plains…


Both of these are forecast to drop a little farther south than what models were showing earlier in the week.  That means most of the rain the next seven days heads into California and we see lighter showers across NW Oregon and SW Washington.

This setup of lows moving by just to the south is a forecast nightmare as well.  Little waves of showers spin north; each model run is slightly different on placement and timing.  It’s safe to say we’ll see light showers at times, but there could be large windows of dry weather some days in the next week.  Right now it appears the first 3/4 of Saturday will be dry and much of Sunday could be as well.

Check out the ECMWF rain forecast for California…FAR more than anything they typically see in late May

ECMWF Precipitation Accumulation

Now the big question…

How long will this cool/wet pattern continue?

There are strong hints that we’ll return to a drier/warmer pattern as we head toward/into the Memorial Day Weekend.  No, I’m not saying we have a sunny/hot/warm/dry holiday weekend on the way (for now).  And yes, it’s 9 days away, but we can see general weather patterns that far out.

For several days most long range model solutions are showing the cool upper-level troughing sinking farther south into the Desert Southwest and high pressure (ridging) developing once again just to our west.  Similar to what happened in late April and early May.  Notice the ensemble forecasts from the GEM, GFS, & ECMWF for Saturday the 25th all look the same

This would say mainly (or all) dry weather with average to above-average temps.  We’ll see how that plays out.

You can see the drastic change from week #1 to week #2 in last night’s 45 day ECMWF run.  This is surface temperature anomaly.  First from this coming Sunday to the Sunday of Memorial Day Weekend.   Look at that cold anomaly over Nevada/Utah, 15 degrees below average next week…Brrr!


Then the following week; cold moves farther east/south.  The west coast of North America from Oregon to Alaska would be very warm


So there you go.

Cool and showery this next week but not too much rain.

Enjoy your weekend!

  • Posted

The past 3+ weeks have been quite a ride.  We've only seen a few sprinkles in much of western Oregon and southwest Washington.  Soils are totally dry like what we'd typically see in late June or July.  All of us are watering (or should be) lawns, gardens, & crops well ahead of the usual time.  But the "outside living" has been spectacular with dependably dry weather as if we're in mid-summer.

This is the 2nd consecutive year we've seen a prolonged dry spell in late spring.  In fact this year is record dry.


Maybe more interesting is the lack of wet weather in May recently.  We haven't seen a wet May since 2013, although 2016 & 2017 were close to normal.


And of course we've seen quite a stretch of July weather in May.  The first 13 days this month have all been above average.  We didn't quite hit 90, but were very close with one record high on the 10th.

High Temp Last 13 Days

There has been lots of concern (including from me) that we're repeating the very early fire/dry season from last year and 2015.  But there is good news!

A pattern change means the next 10 days will be unusually wet across the region.  This is much different than the early dry seasons last year and 2015.

We've been very dry because upper-level high pressure has been just west of us in the Eastern Pacific or right over the Pacific Northwest since mid-April.  The 30 day anomaly shows those much-higher-than-average heights well


Now here's the forecast from the ECMWF ensemble run this morning.  Both the GFS and Canadian models are similar.  In three days (Thursday), a cool upper-level trough will run right into northern California.  Heights are below normal all along the West Coast.


Then a 2nd, even deeper low moves inland early next week


This means a stretch of much cooler weather plus widespread rain from southwest Canada all the way down into Southern California.   The showers/rain will come in waves and at this point I don't see any "atmospheric river" setting up over the Pacific Northwest.  Here's the ECMWF rain forecast for Oregon through Thursday the 23rd, just ahead of Memorial Day Weekend


The GFS model is similar for the next 10 days


I think it's safe to say at least 1.00" is likely in the western valleys, possibly over 2.00" in spots if we get convection (thunderstorms) at some point.  In the Coast and Cascade ranges a solid 2-4" is likely in the next 10 days.  Excellent news!  We can forget about fire issues through late May if this comes to fruition.  Notice they both show some rain east of the Cascades as well; good news for "dryland" grain farmers in central & north-central Oregon.

Does this mean all the rest of May will be wet and cool, including Memorial Day Weekend?  There's no reason to think that for now.  The ECMWF ensembles show at least weak ridging (or lack of cool/wet) arriving between 10-15 days from now.  That's over the long holiday weekend...


To wrap it up:

  1. By sunrise tomorrow (Tuesday) light rain arrives for many of us.
  2. Finish all dry weather projects this evening; bring in everything that shouldn't get wet.
  3. Waves of light rain/showers continue for the following 8-10 days.
  4. EVERY DAY WILL NOT BE A SOAKER.  At this point Friday and at least part of Saturday look dry.

  • Posted

Forecasting is quite simple the next seven days.  Strong high pressure is sitting just off the Pacific Northwest coastline.  That’s sinking & drying air, keeping weather systems away.

Jet Stream Forecast 2017

That’s why we hit mid 70s in the metro area today, matching our “warmest of spring so far” 76 degree high.

Tomorrow we lose onshore flow, plus a little warmer atmosphere overhead means we’ll likely see our first 80 degree day of the season.  This would be right about on schedule since the 2nd week of May IS the average first 80 degree date for PDX

Average First 70_80_90 Degree Days

We get some brief cooling Tuesday/Wednesday with onshore flow but that only brings us down to 10 degrees above average.  Thursday through Saturday that upper-level high nuzzles right up to the coastline, amplifying at the same time.

Jet Stream Forecast 2017_2

That means surface high pressure develops east of the Cascades and offshore (easterly) low level flow.   Offshore wind May through September can REALLY heat us up under sunny skies and that will be the case Thursday through Saturday.  Most models show onshore flow returning very late Saturday, or Sunday.

So how warm could we get?  Models are generally showing 850mb temps over Salem around 13 to 16 celsius Thursday, then 14 to 18 Friday and Saturday.  To hit 90 in May, past cases show (with offshore flow) we need to see at least a +15 or +16.  So 90 is definitely in the cards this time around.  I’m VERY confident we’re going to hit 85 later this week, far less confident we hit 91-92.

In the past 7 years we’ve seen at least 84 in the first half of May each year.  That said, we haven’t seen a 90 before May 11th for about 20 years.  There you go, lots of numbers.

Rain is a no-show the next week, which means ending Friday we will have seen only .02″ in three weeks!  That will be the driest April 20th-May 10th on record.  Let’s hope this isn’t a repeat of last year.  It would be nice to see a big soaking at some point between now and mid-June.


Starting midweek I’d say it’s time to begin watering everything you would typically water in summertime; lawns, gardens, very small shrubs/plants you just planted etc…  Trees are fine for quite awhile since we had heavy rain just a month ago.

Both the ECMWF & GFS show no rain for the next 8+ days. Click for a better view

That’s through next Monday.  There are still hints we turn wetter around the 14th-18th.  Both ensemble systems show at least some sort of soaking during that time.  That would be later NEXT week

So enjoy the sunshine this week, again, it’s going to feel like July with probably only one “morning clouds” day.  That’ll be Wednesday.

I’ll be off the rest of this week, back to work next Sunday. I’m turning 50 Monday (old!), and randomly chose a week in late April or early May to use up 4 vacation days.  Wow, I sure didn’t expect the weather to line up like this; I think it’s time to get the Nelsen pool up and running!  I’m way too cheap to use a heater so hopefully nature will take care of that Thursday and beyond.

  • Posted

Today was a typical “morning clouds then afternoon sun” day west of the Cascades.  We had a relatively strong push of marine air overnight.  That marine layer is thinning now which means less morning cloud cover Friday + more sunshine.  That equals warmer temps; although today’s 66 in Portland only came down to average for May 2nd

Todays Observed Highs OrWa 2017

We have a very nice early May weekend on the way.

Onshore flow weakens dramatically Saturday for a good 6-10 degree jump in temps with little/no morning cloud cover west of the Cascades.  That should push us into the mid 70s.  Expect similar weather Sunday, although several models are bringing a better push of morning clouds & cooler temps that day.  Regardless, a dry May weekend with plenty of sunshine plus temps above average = very nice!

But now things are getting strange again…

During the past two weeks we’ve seen little/no rain for most of us west of the Cascades.

1. That DOES sometimes happen in the springtime for a week or so, but dry spells to two weeks are unusual.

2. Now add in another week of dry weather on the way and that’s VERY unusual.  I just took a look at rain records here in Portland.  This is crazy.  Take the last two weeks of April, then add in these first 9 days of May (assuming little/no rain falls through next Thursday).

3. This year is the driest, followed by…last year!

Three of the five driest late April through early May periods have been in the past few years.  That’s 2019, 2018, & 2015.    We know what happened in those other two years…very warm/hot summers.

We have also seen 6 consecutive dry Mays in Oregon Climate Zone #2 (lower elevations west of Cascades).  That’s after the memorable chilly & wet springs 2010-2012


This does make me suspect (along with other evidence) that our warming/changing climate has a part in this.  Anecdotally, it seems we are seeing more episodes of upper-level ridging near/over the west coast of North America the past 5-6 years.  Remember last winter we (again) didn’t have any sort of typical stormy westerly flow.  The action (snow & cold) came from a big ridge to our west and cold northerly flow coming out of Canada.  Also it seems we are seeing higher “upper-level heights” in the warm season.  In this case everything would be pushed to the north; Portland’s warm season weather would become more like Roseburg.  Then Roseburg is more like Medford etc…  Again, this is anecdotal and based on what I’ve seen all these years forecasting in our area.

As Pete Ferryman said yesterday, maybe the old saying “summer begins on July 5th” will disappear in time.  We’ll see.

In the short term we have a very stable pattern offshore with an upper-level ridge over a cool upper-low approaching California


That ridge strengthens and snuggles right up to the Pacific Northwest through the middle of next week.  Notice ensemble averages of the ECMWF, GFS, & GEM models all show the same setup for NEXT WEDNESDAY.  At this point 850mb temps climb above +10 and offshore (easterly flow) may develop

If so, we’ll see our first 80s of the season the 2nd half of next week.  Here are the forecast numbers I’m using tonight:

Forecast Highs Next 7 Day Meteogram DCA

Our average high temperature now through May 9th is 65-67 degrees so this is well above average.  Not record-setting by any means since they are around 90 this time of year.

What about rain?  Both the GFS and ECMWF ensemble members say we might see some sort of cooler/showery pattern show up around the 13th/14th.  That’s still quite a way off.  Click for a better view

Enjoy the weekend!

  • Posted

I know I’m not supposed to editorialize, but I’ve been enjoying this real nice stretch of spring weather.  No real extremes and drier than normal.  What about you?  Take a look at the numbers.

1. This month has been a bit warmer than normal, but no huge departures from normal.  No “April heat waves”.  We haven’t hit 80, but lots of mild days/nights.  Two days at 70+ so far

Month Climate Temps Calendar

Most of the western USA has been warmer than normal this month as well


2. The “faucet” has just about shut off; we’ve seen very little rain in the last 10 days.  Not much is on the way for the next 7-10 days either. Unusual for late April, but not unheard of.

Rain PDX Last 10 Days

It’s interesting to see a huge gradient in monthly rainfall from dry western Washington down to a very wet central/southwest Oregon.  That’s due to the atmospheric river event that lead to flooding around the 6th-9th just to our south.  Gray/red colors are drier than average, green/blue wetter.  In fact blue is 180% of average or higher.


3. Refreshing and cool nights have returned.  After lots of warm nights the first part of April, we’ve cooled back to near/below normal with more clearing.  Last night was extra cold, with lots of frost in outlying areas behind the cold front that passed through early Saturday.  Never set out your tomatoes/peppers this early in our area.  Always wait until sometime in May unless you have them protected well and/or live right in the urban areas.

PDX Observed Low Today

What’s ahead?  More of the same for at least another week.  It’s interesting to note the cool/dry air coming down from the north plus upper-level ridging just offshore is quite similar to the cold pattern in February.   Havre, Great Falls, & Cut Bank Montana were near/below freezing with snow all day today along with a strong northerly wind.  Wind chills in the teens…rough life on the Great Plains!

Satellite Surface

The pattern may be similar, but it’s late April now and the sun is far stronger.  That’s why we are seeing colder nights, but daytime highs still made it above average.  You can see the effect at 3,700′.  Lots of bare areas have appeared on the lower slopes of Mt. Hood Ski Bowl at Government Camp.  Alpine Slide is scheduled to open Memorial Day.  Clearly this won’t be one of those years when the workers are shoveling it out in June!

Live Camera Skibowl Only 2017

Ridging breaks down later this week, but most of the next 10-15 days models are showing upper-level heights in the atmosphere overhead remaining above normal.  Briefly below normal about a week from now on the ECWMF


Then back to warmer (higher heights) again the first full week of May


Ensemble forecasts of total rain from both GFS & ECMWF give us around 1/2″ in the western valleys of Oregon & SW Washington through the next two weeks.  That’s well below average for early May

But as we’ve seen in early April (with the heavy rain), and February (with cold/snow), models sometimes have trouble seeing general pattern changes more than 10 days out.  So I feel comfortable saying we will be unusually dry for another week or so, but not comfortable telling you that will continue beyond May 8th or so.

Big picture…get your decks stained, lawns mowed, gardens cleaned up, and enjoy the dry spring weather!

Chief Meteorologist Mark Nelsen

  • Posted

We’ve seen quite a warm-up the past week.  We spent about two weeks in Portland with highs near/below average ending the middle of last week.  But since last Wednesday temperatures have “stepped up”.  Every day has been in the 60s and of course we hit 76 last Thursday.

High Temp Last 13 Days

After a very wet start to April, we’ve dried out quite a bit too.  The last 10 days we’ve seen very little rain, less than 1/2″ in Portland.

Rain PDX Last 10 Days

Of course it has been VERY wet across much of Oregon the past 30 days.  Some spots in Eastern Oregon have seen 2-3 times typical April rainfall!  So it’s about time we dry out a bit.

Tonight a weak cold front drags across southern Washington and northern Oregon.  Most rain/showers will be in Coast & Cascade ranges plus west slopes & foothills.  WRF-GFS shows just a few sprinkles west metro and up to 1/3″ the next 24 hours in the western Gorge.


Expect a brief soaking far east metro and west slopes of the Cascades later tonight and Tuesday morning.  All of us see sprinkles or light showers the next 24 hours but “wet” conditions will be mainly east metro.  Beyond that a weak northerly or northeast (offshore) flow takes over Wednesday through Friday.  Lots more sunshine and temps warming above normal once again.

Take a look at 10 day rain forecasts from the GFS, ECMWF, & GEM models.  All are drier than average for the end of April and early May.  In fact all three produce less than 1/2″ rain in much of the metro area through a week from Thursday.

That said, we’ll see a cool/showery upper-level trough move by just to our east coming up on Saturday/Sunday.


Then by 8 days from now it deepens into a cool trough along the West Coast

This is a cool pattern, but not very wet. The ECMWF 10 day precipitation anomaly shows a drier than average western USA.


This could be a setup for a late season frost in outlying areas early next week too with cool and dry air in place.  So don’t plant those warm weather veggies yet!

  • Posted

I haven’t heard any complaining yet, but if showers continue I think the whining will be just around the corner.  This first half of April has been VERY wet west of the Cascades, especially south of Portland.

Rain So Far This Month Or and Wa Earth Scene

East of the Cascades it hasn’t been exceptionally wet, but wetter than average.  By the way, when we say “average” that typically means a 30 year average.  We’ve seen measurable rain 13 of the first 15 days this month.

Spring weather has actually been warmer and drier than normal much of the time since 2012.  The last truly “chilly spring” was 2011.  Both 2016 and 2018 saw quite warm conditions in April/May.    Last May was the warmest on record in Portland and we saw very little rain from this point forward all the way through the summer!  So one could easily argue that we are overdue for a cool and wet spring.  It’s time.  But so far that hasn’t really been the case.

Spring Rain So Far2

March was quite dry, but that almost balances out the wet April so far.  March averaged out cool, and April has been a little warmer than average.  That’s a “normal” spring so far temperature-wise.

Typically we get (average) 30 days with measurable rain in Portland when you combine April and May together.  So far we’ve seen 12.  But only one of the past 5 springs has seen a greater than normal number of wet days

Spring Rain So Far

Again, we’ve had some real decent springs lately.

What’s ahead?  Big picture says there’s no sign of the rain suddenly shutting off.  But there will still be (lighter) showers at times over the next week.    The 10 day precipitation forecast from this morning’s Euro run shows less than 1″ rain now through late next week.  Much better than what we’ve been seeing the last couple of weeks


So enjoy the more reasonable weather the rest of this week.   Warmest day is Thursday as warm southerly flow and a warmer atmosphere sit just south of an approaching front.  South of Portland it’ll get well into the 70s, north of Portland more likely 60s.  We haven’t yet hit 70 this month.  Nothing too unusual, unless we don’t get there at all the next two weeks

April 70 Degree Days

Some good news on the flooding front too; the Army Corps of Engineers has been dumping water out of all those reservoirs in the Willamette Basin.  Detroit Lake has dropped 5 feet in the past 3-4 days.  Looks like we dodged a bullet as the heavy rain cut off just in time.  Rivers draining the Cascades (and Willamette) will continue to run high as more runoff continues to flow downstream

willamette reservoirs

  • Posted

We’ve just seen a few light showers today, but rain picks up west slopes of Cascades and in the Cascades themselves.    That has allowed many rivers to drop west of the Cascades.  Of the Willamette River tributaries, only the Pudding and Coast Fork Willamette River remain under flood warnings.  The Willamette itself crested early today in Eugene and now that crest is working its way downstream.  Highest water at Albany and Salem will be tomorrow.  In the metro area, the much lighter rain totals the past 4 days up here mean no flooding on the Willamette River, but it’s still running high with lots of logs and debris in the water

Mark Flood Willamette River Stats3

In Eastern Oregon the flooding has been more serious, especially in the John Day River basin.  At Service Creek the 3rd highest crest on record is forecast for tomorrow.  Some pics from ODOT

Warnings Flood Rivers 2

70% of Oregon’s population lives within the Willamette River Basin.  And it appears we have avoided a major flood event this time around.  That’s because 11 flood control reservoirs have been built since 1941.  It’s interesting to note that this same weather event pre-1941 would have produced a major flood in the Willamette River Basin.  The filling of those reservoirs has been amazing this week.  Take a look at current conditions

Flood Control Willamette Reservoirs 1

There is one reservoir that has filled beyond the “TOP OF FLOOD CONTROL” level; that’s Dorena.  It is spilling water “uncontrolled” today, which just means water is going over the spillway as it is designed to doduring a flood.  That DOESN’T mean water is going “over the top of the dam”.  That would be bad and that’s definitely not the case.

Then there are 5 reservoirs (in yellow) where water is within 2 feet of that spillway level.  Luckily at most of those the incoming water volume has slowed quite a bit.

There are 5 reservoirs (in green) with room to store more water.  At a few of those (Detroit Lake) water has been filling the lake rapidly.  Check out Detroit Lake

Flood Control Willamette Reservoirs 2

A 50 foot rise in the past week!  Right now the lake is up to just 8′ under its “full” summer level of 1563.5′.  That lake is still 15′ or so away from an uncontrolled spillway release; plenty of storage available.

If another atmospheric river event with many inches of rain were to show up in the next few days?  We’d see widespread flooding in the Willamette Valley due to little water storage left.  Luckily that is NOT the case.  Sure, there will be more rain in the upcoming week, but not too heavy.  RPM model shows 2-4″ rain in Cascades the next 3 days, then lighter totals through the weekend.

RPM Precipitation Accumulation

Rivers are going to continue to run very high as an unusually wet April continues…

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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?