Confidence Growing in Good Eclipse Viewing For Most of Us

August 16, 2017

6pm Wednesday

We’re only 5.5 days away from the Great American Eclipse and things are looking good!  It appears MOST of us in the zone of totality, where 2 minutes of darkness will pass overhead, will have a clear view of the big event.  And if we forget about the eclipse for a moment…the weather itself looks GREAT across the region now through Tuesday.  Are you camping?  You’re in good shape…no need to worry about rain anywhere unless you get some drizzle along the coast.   Aren’t you glad we didn’t tell you it was going to be a rainy/cloudy/cool eclipse with snow up on Mt. Hood?  I just heard today that some of you received an alert saying that on your phones last week!

Over the past 3 days models have been advertising upper-level ridging of high pressure over our region later Sunday through early Tuesday.  Of course the eclipse falls right in the middle of that time period.  You can see the “ridge” in the upper-level flow over us Monday morning.  The opposite would be a dip in the flow.

In this case that means a warmer than normal atmosphere over us Monday.  It also means a lot of sinking motion overhead which warms/dries the airmass.  Thus little or no cloud cover overhead.  The ONE issue of course is the cool layer of marine air west of the Cascades.  Take a look at the WRF-GFS model depiction of that marine layer (green areas) Saturday afternoon (right side) to Wednesday afternoon (left side).  You can see a thin marine layer Sunday through Tuesday, then it thickens quite a bit Wednesday.  Those first three days it’s no thicker than 2,000′, which means you don’t have to worry about those low clouds if your viewing location is above that elevation.

Now check out Newport:

That’s pretty clear-cut, there is a high risk for morning/midday clouds right along the coastline in this pattern.  As we’ve been telling you for many months, planning to view the eclipse at the Coast is quite risky.  Two different models show a similar setup for low clouds Monday morning; likely at the coastline and just a possibility in the central Willamette Valley.  Note the ECMWF shows some intrusion into the Portland area but not down into the valley.  And you can see how the coastline is a bit iffy.

To wrap it all up, here are the forecasts we are using on-air tonight…


Episode 43: Oregon’s Total Solar Eclipse Preview

August 15, 2017

Time for an “Eclipse Podcast”! Lots of detailed information on what to expect on Monday. Enjoy.

Northwest Weather Podcast

Eclipse Background Shine

This week, the guys dedicate the entire episode to the upcoming solar eclipse that will be passing through Oregon on Monday, August 21, 2017.

What will you see? Where will be the best spots to catch it? What will the weather be like? What should you avoid doing? Mark and Brian will answer all of those questions and more.

We have you fully covered on! Click here for all of the latest news on the solar eclipse and how state and local governments are planning for it.

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Eclipse Weather Update & Thoughts from 26-Time Eclipse Chaser

August 14, 2017


24 hours have passed and now we’re less than 7 days from our once-in-a-lifetime eclipse in Oregon.  There have been encouraging trends in our long-range forecast models.

Eclipse Forecast 1

The GFS model has now come around and decided there will NOT be a cold upper-level trough swinging through the Pacific Northwest next Monday.  The ECMWF and GEM models have not been showing that anyway, so that trend is very good.  That’s point #1 on the graphic above.  One more reason you shouldn’t make a forecast 2 weeks out calling for a rainy and cloudy day!

Cloud Cover?

Assuming there is no organized weather system nearby, that leaves either: A) Scattered high clouds overhead, or B) Low morning stratus clouds somewhere between the coastline and west slopes of the Cascades as possible weather that could block eclipse viewing.

The GFS shows almost no cloud cover under high pressure and typical summertime weather.

GFS Clouds Rain

The ECMWF shows thin high clouds from an approaching system, although the contouring on this graphic makes that look a bit “intense”.


Neither implies significant marine cloud cover west of the Cascades, but THIS is the one weather feature that can easily change in the last 1-3 days before the event.

By the way, one of our regular readers just happens to be a HARDCORE eclipse chaser.  I assume Mike won’t mind me re-posting his info.  This is great stuff.  I hadn’t considered the possibility of low clouds re-developing during the eclipse in the moist coastal atmosphere as temps drop:

This is my 26th eclipse trip (16 TSEs seen, 6 annulars, 3 missed because of rain, clouds,and yes, wind). I’ve been using Jay Anderson (Environment Canada, retired meteorologist, who saved my eclipse in Australia by telling me to get off shore) and his blog eclipsophile, which already is looking at the 2 Jul 2019 eclipse. I have access to several other pages there, too, and can attest to what Mark has said regarding the uselessness of predicting cloudiness this far out. A couple of thoughts:

1. High clouds don’t ruin an eclipse; very few of my total viewings were in a clear sky. Puffy cumulus clouds drive you crazy, because you don’t know what they will do. Stratus, of course, is awful. Totally clear is rare; if you get it enjoy.

2. As the atmosphere cools during the partial phases, clouds may form. Then again, any convection (looking unlikely) gets shut off. The most I’ve seen the temp drop is 11 C (20 F). With moderately high dew points, the drop will probably be less.

3. Smoke is likely to be a concern for this eclipse, but the haze we had last week would have been OK, just not optimal, for viewing. I was camped out in northern Washington a week before, and you could barely see the Sun at all.

4. That said, I will be north of Ontario, about 1300 meters if I can (4200′), and have bail out plans in both directions, although it would have to be a major difference to consider going a long distance on eclipse AM. It wouldn’t be the first time. Hope all the eclipse virgins get to see it.

I’ve give a lot of talks from here to Prairie City, and tell people three things:

1. Totality is worth seeing. (Recent TED talk worth viewing).

2. Be safe, both in getting to the path and protecting your eyes.

3. If it’s your first, don’t take pictures. You’ll see better ones, mine have gathered dust, and every second spent looking at the camera takes away from the experience. This may be the only one you ever see. Enjoy it!



Eclipse Weather: A First Look

August 13, 2017

10pm Sunday

Now that we’re within 8 days of the eclipse, we can start to see a general weather pattern emerging.   The good news is that we don’t see a big wet weather pattern for next weekend and early the following week.  The (possibly) bad news is that SOME models keep trying to send a weak front or upper-level low quite close to us.  Of course that could possibly send lots of cloud cover overhead at the wrong time (for example…10:20am Monday the 21st).

Let’s check out the big picture:

  1. We don’t know YET if large parts of the Pacific Northwest will be covered in clouds OR just under high pressure with mainly sunny skies.
  2. Both of those possibilities (or perhaps something in-between) are still in play.
  3. There is no need to worry, or freak out, no matter where you area headed this weekend.  We’ll get a more detailed forecast as we go through the week.
  4. Do NOT alter your plans or viewing for now.  I know the hardcore folks have plans to move at the last minute if needed.  Don’t worry about that yet.

The general weather pattern for this calendar week is high pressure moving back over the West Coast, but this time it won’t be a big hot ridge of high pressure.  A weak jet stream will be just to our north later this week and through the upcoming weekend.  This is typically a nice weather pattern with varying amounts of morning clouds west of the Cascades.    On most models this continues through the early part of next week.

But SOME runs of SOME models have been trying to push a weak cold front or even an upper-level low through our area either Sunday or Monday.  The (less reliable) GFS model has been most persistent with this idea.  Take a look at its forecast for eclipse time in 8 days…very bad with a cold front moving onshore…solid cloud cover west of the Cascades, but just high clouds east of the mountains.


But then check out the ECMWF model:

Totally different with that weather system both staying to the north and also splitting apart well offshore.  This would say great viewing for the big event.  You can see why it would be a really BAD to make a specific cloud forecast at this point.

So is there anything else we could use to get an idea which model might be wrong, even this far out?  Yes, as I’ve mentioned in the past “ensemble forecasting” can help us out.  Take a look at the ensemble forecast from both the GFS and ECMWF for next Monday at about 18,000′.

You can see the GFS in general has slightly lower heights (more members that are giving us stronger upper-level troughing).  That said, even that 2nd map isn’t a wet or especially cloudy weather pattern.  Check out the GFS ensemble member rain accumulation forecast, each horizontal line representing one of those 21 members:

I see 5 members with a trace or more rain on eclipse that.  That’s about 1/4 of the members.  Obviously if we have rain there is cloud cover as well.  So it’s fair to quite a few members of this model have cloud cover over us on the big day.

How about that ECMWF?  The operational run of that model as you’ve seen above is quite nice.  Now look at the 51 ensemble members and their rain forecast:

Again each horizontal line represents one ensemble member.  I see 6 or 7 ( I also looked at all 51 maps!) members that would give us lots of clouds and even showers.  That’s a small percentage.  Odds are, based on this model, viewing might be just fine…but again it’s 8 days away.

One other model, the GEM (Canadian) looks pretty good as well.  It shows no sharp upper-level trough and just continues our fair weather pattern.

Of course I’ll be keeping on top of it all week-long.  I’m working each day through the eclipse…that last 2-3 down in Madras.

Chief Meteorologist Mark Nelsen

It Rained! Now Keep Watering Your Plants

August 13, 2017

5pm Sunday

I was camping with the family out at Stub Stewart State Park the last two days (very nice mountain bike trails!), and right at bedtime last night it started raining.  It was a rare summer sound to hear it raining all night, although I doubt it would have been real fun in a tent (we use a pop-up trailer).  Quite a change.

So of course the overnight rain ends our long dry spell in Portland.  This was the longest dry spell since the early 1980s in Portland

Brian Longest Dry Spells

Mark Dry Spells Summer Recent

We ended up with .06″ rain in Portland; just barely enough to settle the dust

2017 Data Bound Rain Today in Metro Only

Notice EVERYONE saw the rain west of the Cascades, just not a lot.  I’m pretty sure the Scappoose reading is incorrect since several stations within 1-5 miles had measurable rain.

We would need an inch of rain to even call it a “soaking” and what little we just had doesn’t go far into the ground.  So your plants/gardens/trees barely noticed.  Keep watering because we don’t see a soaking rain for at least the next 7-10 days.

The westerly flow and weak front have given us 3 big changes:

  1. No hot weather, today’s high of 75 was the coolest in almost a month.  We remain below 85 for the next week.
  2. Fire smoke is gone…it has moved east of the Cascades
  3. Humidity is back to normal.  After a week or so of humid weather, dewpoints are back into the 50s, a big improvement!

I’ll have another post later on eclipse weather…it’s only 8 days away now.

Chief Meteorologist Mark Nelsen

Thunderstorms In Valley Tonight

August 10, 2017

11:45pm Thursday

Our 12 day hot spell is ending this evening with a few flashes & bangs.  Thunderstorms over the Cascades are slipping westward into the Valley so you MIGHT see a flash the next few hours or wake up to thunder.  Of course as always it’s spotty and some spots will see it; some won’t

Here’s the latest chart showing cloud to ground strikes


So far nothing in the Portland metro area but that COULD change the next few hours…we’ll see.  It would be nice to see nighttime lightning at least once this summer!

Today was our 12th day with a high of 88+ in Portland and 13th at/above 90 in Salem.  But a thicker marine layer means many of us west of the Cascades will wake up to low clouds Friday AM.  This will keep highs below 90.

Fire smoke should start to dissipate tomorrow and be mainly gone Saturday as the airflow turns westerly at the surface and higher up as well.  It’s likely we’ll have our first measurable rain in almost 2 months Sunday as well.  Not a soaking, but at least enough to measure and turn streets wet at some point.

Chief Meteorologist Mark Nelsen

Eclipse Weather: Too Early For A Forecast

August 8, 2017


9am Tuesday

Have you seen a weather “forecast” or two for the eclipse?  There’s NO ONE that knows what it’s going to do on eclipse day yet.  If you’ve seen one of these, keep in mind it’s just a grab for clicks (online clickbait) or viewers (TV eyeballs) and has no basis in meteorology.

We won’t have a general idea of possible rain that day until around 7-9 days out.  As for cloud cover, which is far tougher to predict, we’ll start taking a stab at it this coming Sunday which will just be a general guess, and then hone in on a detailed forecast during the week leading up to the event itself on Monday the 21st.  Trust me, forecasting low marine clouds west of the Cascades is something we can easily get wrong just 3 days ahead of time.

As mentioned in the previous post, we DO have models that go out two full weeks like the GFS and ECMWF often referenced here.  But the “operational” versions of these models can flip around wildly with each run that comes in.  For example the 0z (evening run) GFS model looked like this on eclipse day:


That’s a cold upper-level trough just like we see in May or June.  That’s a showery and cool setup, but even in this pattern you can get large breaks in the cloud cover.  But wait!  6 hours later the overnight run of the GFS came in like this:

gfs_namer_324_500_vort_ht (1)

Much better, patchy morning clouds MAYBE west of the Cascades, otherwise all sunny and a very settled summer pattern with highs at least in the 80s.  In this model the trough is way up in SE Alaska.  You see the problem and why it would be ridiculous to make a forecast more than a week in advance?

That said, just as I mentioned in the last post, at least part of NEXT WEEK DOES FEATURE  A RARE COOL AND SHOWERY WEATHER PATTERN FOR MID AUGUST.  36 of 51 ECMWF model ensemble members (over 50%) project at least a tenth of an inch of rain over the metro area between now and eclipse day.  Some give us a half-inch or more.


Yet once again there is no need to panic…for now.  Take a look at 24hr rain totals from the same ensemble members:


You see a good percentage of the “rain action” happens Monday-Thursday next week.  There is a secondary smaller spike around the 21st/22nd (eclipse day), but only 7 of 51 ensemble members show more than .05″.  And this says very little about cloud cover, which of course is all we care about at 10:18am Monday the 21st.  Again, we won’t be able to start working on that one until about a week out.

To wrap it up, there is no need to panic/worry at this point.  We’ve got you covered here at FOX12; ignore any other “forecasts” you see in the next 5-6 days.  I’m right with all the rest of you watching the cloud forecast VERY carefully starting this coming Sunday/Monday!

Chief Meteorologist Mark Nelsen