August 10, 2018

Major Change in Northwest Weather: Rain Moves in, Smoke Moves Out

A strong upper level trough will move inland over the region tonight and tomorrow morning bringing cooling weather, clouds, some precipitation, and the removable of the smoke layer aloft.

To start,  here are the upper-level (500-hPa, about 18,000 ft) charts for the next few days.

This morning  (5 AM) shows a big ridge over the western U.S., but a strong closed low/trough offshore.

Tomorrow morning at 5 AM, the trough/low is moving into our coast.

The trough moves through on Saturday and then moves northeastward into Canada on Sunday (11 PM Sunday is shown below)

The initial approach of the trough is associated with enhanced southerly flow that brought up smoke from California, but as it passes, the winds will turn more westerly, driving the smoke to the east.  This progression is shown by the HRRR-SMOKE model output. This morning at 10 AM, there was fairly dense smoke aloft (see figure), but far less at the surface.

But by 2 AM, western Washington is clear, as the densest smoke moves over eastern WA and Idaho.

 Precipitation should start moving in by 5 AM, illustrated by the UW WRF model precipitation for the 3-h period ending that time.
 Heavier rain is predicted during the subsequent three hours, particularly along the coast, the Olympics, and SW Washington.

The showers move to the Cascades during the afternoon.

  And continue while slowly declining during Saturday evening.

Seattle will not got a lot from this event and we do expect some embedded thunderstorms.   Sunday should be dry and warmer (around 80F).

Finally, it is interesting to look back at the temperatures at Seattle Tacoma Airport during the last 12 weeks compared to the normal highs (purple) and normal lows (cyan).  We have had a series of heat waves during the past two months, with some intervening cool periods.
Clearly, this summer was warmer than normal, something shown graphically with the following map of the temperature differences from normal over the past 60 days.  Western WA has been 1-3F above normal, with California being even warmer (perhaps 3-4F above normal for the period).


  1. So much for the "big cool down" the NWS folks were promising. I was greeted to 84F sunshine when I stepped-off the train in Edmonds at 5pm this evening. It was hot. It's still hot (65F @ UW and it's 1am). We'll see what tomorrow brings but I'm expecting to continue to be disappointed.

  2. this summer "was" warmer than normal? I am getting sick of everyone talking like summer is ending. we still have a ways to go...more beautiful 80 plus days, please!

  3. This upper level trough has brought cooler temps east of the mountains as well...along with lots of lightening and new fires and strong winds. Not good!

  4. Port Townsend received .76" in less than 2 hours this afternoon, closing down the farmers market a bit early. We had a few hair-raising lightning strikes too. Cool, fresh air this evening. Gotta love our local weather events!

  5. Cliff about a month ago you were predicting strongly that the fire season wouldn't be too bad in Washington state this year. You had your charts and readings and the like and while an impressive argument it didn't make sense to those of us non-scientists when we observed very dry, hot, windy conditions building. Also, the mainstream media was predicting a bad season (, and this seemed to bother you. Anyway, what do you make of the fire season now in Washington state?

  6. cliff: is your 1-3 degrees warmer than normal comment related to the highs? it sure looks like the low temp range was obliterated, again. i believe this is what kills glaciers the most and why 2012 onward has been a disaster for PNW glaciers.

  7. Give me cool nights with rain and hot days.

  8. Torrential rain and a mudslide blocking a lane on Highway 2 near Snohomish Saturday evening, and lightning. But dry in Duvall. I have monsoon envy!

  9. There were alot of new fire starts (all due to lightning) around and north of the Methow valley. Some have been contained. The thunderstorms had very little rain. I'm really looking forward to the fall rains but its going to be a very long August and perhaps September.

  10. Hi Cliff, Thanks again for all your work on this blog.

    Am I correct that "normal" is based on the last 30 years of data? Thus, when using "normal" it's hard to see dramatic changes. I'm guessing if we used the 30-yr period from 1955-1984, vs 1985-2014, we'd find this summer's avg temp (so far) is 3-5 degrees F above "normal" in W WA,if not more!

  11. Cliff:
    Just noticed that the sea surface temperatures off of Southern California are at record levels. Scripps Institution of Oceanography in San Diego recorded its highest ocean temperature ever, of 79.2 degrees Fahrenheit a few days ago. This might be an interesting topic to cover in the near future. Thanks...

  12. Well, Eastside got very little rain, .05" in our rain gage, and now it is very humid with a lot of smoke in the air. Sigh

  13. Deluge in Snohomish Saturday night...That was an intense hour Saturday night in the city of Snohomish! WeatherUnderground station listed 1.21" of rain for the day but I've read other reports saying 2" of rain in an hour. Started off with large hail (0.5 inch) followed by a waterfall of rain. Bands were going from the north (would hear then rain hitting the plastic pool on the north side of my house first) to the south. I think the convergence zone (if that's what it was?! funnel cloud? microburst?) occurred right over my house in the city. The northeast moving clouds rammed into a wall per se on the north side of Snohomish River Valley. Stars were still visible low on the horizon to the south but it was opaque right above Second Street in town.


  14. One of the most beautiful places in the world has been greatly diminished by climate change influenced weather this year.
    Look at google image results using a search of ‘mazama ridge paradise mount rainier’ and lupine is everywhere.
    “Possibly the most flowery place in the world,” reads the caption for the photo Bob Gibbons took on Mazama Ridge near Paradise MRNP, in his book 'Wildflower Wonders: The 50 Best Wildflower Sites in the World'.
    At Paradise this 1889 quote by John Muir is carved into the steps at Paradise: “… the most luxuriant and the most extravagantly beautiful of all the alpine gardens I have ever beheld in all my mountain-top wanderings.”
    This year there were almost no lupine flowers on Mazama Ridge at Paradise.
    There was an above average amount of snow at Paradise. Climate-change influenced weather this summer is almost certainly the cause of the failure of the lupine to flower. Seattle had the warmest July on record. From June 11th to August 9th Paradise was even warmer (compared to average) than Seattle. From May-July Seattle had .80 inches of rain compared to an average of 4.21, in July .05 of a .70 average.

  15. Dr. Mass, What happened to the onshore pattern you talked about yesterday that would be present through Saturday? I just went hiking in the N. Cascades and there was no sign of an onshore pattern. Just the opposite. Wind was prevalent from the East and was stacking smoke all the way up above 6,000'. Visibility was so bad, I couldn't see Mt. Baker from the top of Dock Butte.

    I have noticed a lot of misses over the last 3 years with regards to wind patterns. Not to pick on you specifically, I am really wondering if climate change is now occurring so rapidly that even though we have computers 1 MILLION times faster than those just 10 years ago, our models are NOT keeping up with how climate is changing. To me, that explains why, in my gut, I find weather prediction today to be no better than what I remember from 30 years ago.

    Interested in your thoughts and comments.


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