Strongest April Windstorm in 50 Years Arriving

April 7, 2017


Wow!  That accelerated quickly….

Our models were correct and we have a major spring windstorm moving into the valley this morning.  Wind gusts are looking more like the strong models showed.  Hold on…it’s going to be a wild ride the next few hours.

The initial burst of wind has hit Portland…PDX has hit 53 mph, and Salem has a gust to 60.  54 at McMinnville.  I see a gust to 78 mph on the West Hills, a speed I haven’t seen at that location in at least 10 years.  A weather station on Chehalem Mtn. near Newberg has recorded a gust to 73 mph.

Widespread power outages have occurred of course.  I see PGE already reporting almost 50,000 out.  This is going to be an April storm to remember.

Satellite imagery shows the surface low just west of Tillamook so peak wind gusts should be between now at noon.

8:34am…Okay, generator is on…power went out partway through blog post.  Looks like up to 80,000 PGE customers now and a 56 mph gust at PDX.  61 at Hillsboro!  Wow, quite a storm.

Chief Meteorologist Mark Nelsen

First Wind Storm in 6 Months Friday

April 6, 2017

4pm Thursday

As mentioned in last night’s post, the last time we saw a deep low tracking up the coastline to give us strong south wind was way back in October.  All morning/midday models are in and show a windstorm both at the coast and likely for spots in the valley too.  The NWS is on board with high wind warnings up for the coastline and wind advisories for the valley.  Read the previous post for more detail since not much has changed.


Our forecast hasn’t changed much for the coast.  The wind appears to come in two waves out there.  First wind arrives right at sunrise (6am) or just before, then a 2nd stronger surge during the late morning hours:


All areas south of Portland should turn windy by sunrise with general 30-45 mph gusts then spreading INTO the metro area by mid-morning.

Between 10am-2pm bands of heavy showers and thunderstorms should mix even stronger wind gusts down to the surface (where we all live) in isolated spots.   This is a setup where some neighborhoods could get a 50-55 mph gusts and others stay down in the 30-40 mph range depending on where the heavy showers show up.  We can’t predict that well, but plan on some power outages and a few trees down.

In this pattern with cold air moving in overhead, a few thunderstorms, and some twisting in the atmosphere, it’s quite possible we get a few reports of funnel clouds.  Keep an eye on the sky tomorrow!

The screaming message here is that Friday should be a very active day (mainly before 3pm).  And for the first time in 6 months we get a southerly windstorm west of  the Cascades here in the valleys.


For the geeks:

A tough forecast for Friday since once again the isobar alignment for strong south wind in the valley is far from ideal (for strong wind).  In the past, without high-res models, I would have just forecast 30-40 mph gusts at best tomorrow.  But all models are very insistent on mixing down the strong south wind that we know will be just a couple thousand feet overhead.  Multiple models are showing 50-65 mph gusts in the north valley tomorrow morning.  Just one example from the NAM below.  If these models are correct, then this will be the strongest April windstorm in the valley since the 1960s!

For good reason our forecast didn’t go that extreme, but I bumped up the numbers slightly from what we were forecasting last night at this time.  We’ll see how it goes!

Chief Meteorologist Mark Nelsen


A Rare April Windstorm Possible Friday Morning

April 5, 2017

9pm Wednesday

This evening the maps & models are sure looking interesting for the first time in quite a while…

We had lots of snow/ice and cold east wind in December and January, plus the first part of February.  But there has been one weather pattern we’ve barely seen since that stormy period in October.  It’s our typical strong south wind or windstorm pattern when surface low pressure centers tracking north along the coastline.  When that happens a surge of southerly wind follows right behind as air rushes in to fill that vacuum (low pressure).   In a normal winter we see this pattern repeatedly but not this year.  We had that setup way back in mid-October (unusually early) and now it appears a similar event is about to happen on Friday (unusually late).


  • A High Wind Watch is up for the Oregon Coast for Friday
  • Strong wind arrives soon after daybreak out there…peak gusts 55-75 mph are likely.  Quite a storm for April!
  • No Watches/Warnings/Advisories yet for the Willamette Valley
  • Gusty wind (could be strong) arrives mid/late morning Friday
  • Peak gusts in the valley and metro area could be in the 40-50 mph range
  • A few models are STRONGER with the wind gusts…stay tuned in case we up those numbers above
  • Wind will die down Friday afternoon

If we do indeed see gusts that high, this will be the strongest (and only) windstorm since October.  What a way to bracket a cold rainy season, with a windstorm at the beginning and end.


Models first starting showing a strong low moving up the coastline yesterday evening and all morning runs showed the same thing.  Now evening models are almost exactly the same, which increases confidence that some sort of wind event (or storm) is on the way Friday.  Have we ever had an April windstorm?  Yes, but it’s extremely rare.  The last real one was before I was born; April 14th 1967.  Peak gusts reached 60-70 in the Willamette Valley and you can read about it on Wolf Read’s Storm King site.  An interesting quote from Wolf “Since 1972, there apparently haven’t been any significant April windstorms, which approximately coincides in time with the disappearance of the occasional October windstorm”.   Sure enough, I checked the numbers and PDX hasn’t seen a gust over 47 mph in April since this date…during the April 5th 1972 tornado.  The tornado just missed the far west end of Portland airport, near the wind sensor at the time.  A gust to 63 mph occurred with that one.

On Friday a 975-977mb low is forecast to ride north very quickly well offshore.  Here’s the 5am WRF-GFS model showing the deep low well west of Newport:

By 2pm it has moved straight north and is west of Forks, WA

Note this IS the classic path for windstorms in our region…the low appears to track around 127-128W longitude.  Compare this to the track of the October storm (thanks to Wolf Read again):

So this low looks to be slightly farther offshore and not as deep (strong).  Now you may remember that October storm was a bit of a strange one, producing far less wind than expected along the coast but forecasts were perfect for the metro area.  Peak gusts ended up like this:  

Take 5 mph off those gusts and that’s what I’m thinking for Friday at this point.  You see that in the forecasts above.

There ARE hints in models that the peak wind gusts could be stronger than forecast, that would be over 50 mph in the metro area and 70+ at the Coast.  For example note the WRF-GFS wind gust forecast.  Very clear signal showing 50-60 mph gusts in the Willamette Valley   

Another hint of stronger wind…GFS MOS (Model Output Statistics) forecasts 30 mph southerly wind…sustained during this time.  It’s rare to see such strong wind on MOS for the airport location.  3rd hint:  Very strong gusts on ECMWF model…50-60kts (60+ mph)…that’s at least as strong as what it showed for October storm.

One last note.  Even though the pressure gradient isn’t optimal for a big windstorm and isobars don’t have that perfect east/west orientation we like to see for that, the “warm” April atmosphere and good midday sun/mixing will likely make up for that.  We’ll see how it goes.

Chief Meteorologist Mark Nelsen

A Forecast Bust Today, More Showers Ahead

April 4, 2017

6pm Tuesday…

Well, we did hit 60 today and it sure did feel warmer.  That’s the positive news.  Of course we had off/on light showers the entire afternoon & evening in the metro area so that puts today’s report card in the BUST category.

To add to the cool/showery complaints, morning models came in much wetter for Wednesday, pushing a cold front right OVER western Oregon and Washington instead of lingering along the coastline.  The thinking has been (the past 2 days) we’d be in the warm air ahead of that front Wednesday, pushing our temps well into the 60s.  Instead, clouds and showers will sit right over us all day long.  Forget the 60s; we’ll only be in the 55-58 degree range tomorrow.  So it goes during this cool spring…

Speaking of…take a look at the 60 degree days through April 4th (today’s date) each of the past 10 springs.


Yep, we’re back into the 2011-2012 routine.  We’re seeing a total lack of warm spells from February through early-mid April.  Notice I haven’t talked about upper-level ridging across the Pacific Northwest at all since last fall?

At least we have seen 6 days with very little rain; I was able to plant my onions and a few other cold-weather veggies.  The soil was just barely dry enough.  Glad I got that done before those showers coming in tomorrow.

This brings up the question “Does this mean the rest of spring will be wet?”.  A very good question.  Take a look at the 5 wettest March’s on record here in Portland, then what followed rain-wise in April and May:



That’s quite a mixed bag.  Some wet, some dry.  The last La Nina winter/early spring (2012) remained wet through the spring.  The 10 day GFS meteogram, remember it’s only one model run from one model, turns us wetter again this weekend and beyond.  No sign of a warm & dry regime through mid-month.


Try to stay dry and don’t get too down about the rain.  Even though the natives are getting restless, I’m hoping they don’t need to sacrifice a local meteorologist…

Chief Meteorologist Mark Nelsen

April Is Here…70 Possible This Week

April 2, 2017

10pm Sunday…

I’m back at work and now we are finally finished with March.  It was a soaker with over 7″ of rain and our 4th consecutive cold/cool month.  At least it wasn’t unusually cool for March…just a notch or two below normal:

You can see that once again much of the USA had a warm month, especially in the West and Central sections of our country.  In fact about half of Oregon was above normal as well.

This cool and wet pattern in the Pacific Northwest is perfectly normal in late winter and early spring during La Nina events.  Yes, I know La Nina is now dead, but we had a weak La Nina through the winter and the early spring effects seem to be similar to 2008, 2011 & 2012.  Of course reality is extra harsh this year since we’re on a rebound from the past two very warm springs.  Remember last April?  It was freakishly warm the first week of the month and then a real heat wave arrived just after mid-month.  It was strange, but I know some of us just loved the “May in April” weather.  Check out the number of 70+ days the past few Aprils:

There is no sign that we’re about to head into a warm pattern, but there’s also no sign that we’re headed into an unusually cool April regime either.  Check out the temperature anomaly plot from the GEFS (GFS ensembles) for the next two weeks:

The “zero” line is a perfectly average temp.  You see warmer than normal conditions most of this week, then cooler than average this coming weekend and early next week, then warmer again.  The ECMWF is quite similar so I think it’s fair to say we have pretty typical early April conditions coming up.

By the way, we may hit 70 degrees for the first time this season on Wednesday.  The pattern looks “right” to me with a north/south front stalled offshore and possibly quite a bit of sunshine just ahead of it.  No onshore flow and a mild southerly wind could give us the boost for our first late spring feel outside.  Since I’m getting old and conservative, I decided to stick with a 67…but that might get revised after I check things out Monday.

I just took 6 days off work to do some travelling with the family for Spring Break.  We spent 4 days in Moab, UT for my son and I to do some mountain biking.  I survived the famous Slick Rock trail!  That was one of the weirdest mountain biking experiences ever.  Really tough, but still less than 3 hours long.  Then we drove through a snowy pass on the way to Zion National Park.  Now that place was incredible, but a bit too busy for me.  I had never made it to Zion but would love to go back during a slower time of the year…maybe September or October.  We moved on to two nights in Las Vegas on the Strip.  I figured it would be good for the teenage kids to see how wild it gets.  They weren’t let down!  What a strange place…definitely not my style, but briefly fun.  And, a big windstorm on Thursday was quite a highlight.  Screaming winds and a temperature drop from 79 to 60 in just a little over an hour as a cold front moved through.  Then it was a LONG drive up to Reno Friday and then Reno to home Saturday.  2,700 miles total for this trip.  It makes a huge difference having 3 available drivers in the car, I can’t believe I used to drive 10-14 hours in one day alone.

Chief Meteorologist Mark Nelsen