Eclipse Weather: A First Look

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

7 Responses to Eclipse Weather: A First Look

  1. Dean Suhr says:

    Thanks for this eclipse focus, Mark. I’d like to see wind patterns, current fires, and smoke added to your daily overviews. I’d hate to be in Madras and find that the smoke from the Nena Springs or Whitewater fires obliterated the sky like happened in Portland last week.

  2. Mike says:

    I’ve been a faithful follower of this blog for a few years now but haven’t commented until now. I am one of the hard core eclipse chasers Mark Nelsen talks about. 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!

  3. Paul D says:

    It’s 50 degrees outside!! Very nice this morning! Gonna enjoy these cooler days.

  4. I wonder how behaved the crowds traveling to see the eclipse across the country will be. “Eclipse”, or some variation, could become slang for a messy, destructive crowd of tourists.

  5. Boydo3 N. Albany says:

    I like the last bit…” the last 2-3 down in Madras” worries and don’t change your plans. I will say that the last eclipse I saw in Hawaii, there were lots of folks from all over the world who missed it based on the the latest forecasts.Many were driving up the volcano to get above the clouds and got skunked. We, on on the other hand, just hung loose and got a great viewing spot and saw the whole event at a local supermarket parking lot. Mahalo!

    • Mark, that sly, old cat. He wants as many people as possible to stay in the valley or coast, to keep central Oregon from becoming (any more) crowded. If he told us directly that the weather will be a dud west of the Cascades, a good 100,000 or so would swamp central and eastern Oregon.

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