June 27, 2021

Even More Extreme: Extraordinary Record Highs Followed by Perhaps the Most Rapid Cooling in Northwest History

 If you are living west of the Cascade crest of Oregon and Washington, tomorrow will be a day you will never forget.

The latest model runs, all at very high resolution, show even more profound extremes than previously predicted.  And the end of the event will be extraordinary, with temperatures falling by as much as 50F within a few hours.

Our upcoming weather

Records Already Broken

   Many records fell yesterday, including a new all-time high temperature at Portland (108F) and daily or monthly records falling at dozens of stations.  But his is nothing compared to what will happen now.

Situation Right Now (Noon Sunday)

A fascinating plot (below, click on image to expand) shows you the 24-h temperature change--how we stack up temperature-wise compared to exactly one day ago.  

Along the SW WA coast, some locations are 15-30F warmer, because of the switch to easterly (from east) winds--pushing away the cool, ocean air.  But look at the Portland area...many locations are 10-15F warmer because of increased offshore flow, with the air warming by compression as it sinks over the western slopes of the Cascades.


The new 108F record at Portland is going to be OBLITERATED today.  115F is quite possible.

But north of Seattle temperatures were a bit cooler. 

 Ironically, it is connected with the warmth along the coast and around Portland!  To explain, here is the forecast sea-level pressure map at 5 PM today.  You can see the low-level winds and lines of constant pressure (isobars).  You will also notice an area of low pressure--the thermal trough--centered in the Willamette Valley.  It is the result of warm air produced by easterly flow descending the western Cascade slopes.  With low pressure to the south and high pressure to the north, the thermal trough produced northerly winds over the Puget Sound, with the air cooled as it moved over cooler water to the north.


But that low pressure is going to move northward overnight and Puget Sound will be "enjoy" the torrid conditions now burning Portland.

Here is the latest temperature forecast for 5 PM today.  You can see the very warm conditions around Portland (dark brown is 109-112) and you will see very warm conditions along the lower western slopes of the central Washington Cascades and nearby lowlands.  Near the water around Seattle near the water, it will ONLY be the upper 90s.


Tomorrow: The Day of Unimaginable Extremes

But tomorrow, it all goes horribly wrong.  The thermal trough moves northward and westward, pushing the strong easterly, downslope flow northward to over the central Cascades (see map for 11 AM Monday).  The sinking air will compress/warm as it sinks.


The burst of downslope, compressional heating will cause temperatures to warm beyond the experience of any living inhabitant of the region (see forecast temperatures at 5 PM Monday).  
Temperatures will rise above 112F on the eastside of Puget Sound and above 100F for everyone more than a few miles from the water.  Portland will be similarly warm.  And so will the lower elevations of the Columbia Basin.  

Heat apocalypse.   What more can be said?


You all know that looking at one forecast is not good enough.  We need to examine many (ensembles) to evaluate our confidence in the forecast.  Well, here are the high-resolution ensemble temperature forecasts at SeaTac airport.  Time is on the x-axis (00Z29 is 5 PM Monday).    Nearly every model run is taking SeaTac to around 112F.

And there is more.....after the temperature peaks around 5 PM it plummets steeply, like an insane meteorological roller coaster.   Some of you will be sweating in 110F temperates around dinner time, but looking for a light sweater around 6 AM.

The reasons for this profound shift?   The thermal trough will begin to move eastward over the Cascades, with an onshore marine push bringing in cool air off the Pacific (see forecast map at 2 AM Tuesday, green and blue colors indicate cool temperatures)


It will still get warm on Tuesday (80s for many), but the savage heat will be broken.  Good luck tomorrow.  You will be talking about it for a long time.

This is the "perfect storm" producing extreme temperatures for our region.  If you want to see how I feel, check out the video (go 60 seconds in)







47 comments:

  1. In that last line, you mean it will still get warm on Tuesday, right?

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    1. According to the just-issued NWS bulletin, it will now remain “in the upper 90s” through Tuesday. They don’t foresee much cooling Monday night, either.

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  2. Thanks Cliff! So we're in for a roller-coaster ride from Monday to Tuesday. What does this mean for winds? Will the rapid drop in temperature bring high winds or thunderstorms?

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  3. What would you call the probability of this event, both maximum temperature and this predicted massive change in temperature. 10-year? 100-year?500-year?1000-year?

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    1. No expert here...but considering that the last heat record in Seattle-103 in 2009--could suggest an interval of 10 to 20 years. The incredible Columbus Day storm (cat 2 hurricane really) that blew through the NW back in 1962, has been speculated as having been of a rare type of storm that likely will hit us around every 200 years...of course, that is an "apples vs oranges" comparison....I lived through that amazing storm...hopefully I will not be around for the next mega-heat event!

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  4. But didn't today disappoint the models as regards Puget Sound? I was hearing 110 for Seattle. Here in Fall City it is slightly cooler as of 2:30 than yesterday -- 100 by my car thermometer -- whereas it was 103 about this time yesterday. The recent forecast was for much hotter.

    The hottest place I can find right now is Concrete, at 110. One forecast I saw there was for 120, maybe tomorrow . . . Can concrete melt?

    Also, the wind is coming from the West.

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    1. that is true. It was predicted for 105 today in Seattle, and it ended up being between 95 to 101. It's a very real possibility that the 110 plus that was predicted will somewhere be between 100 to 105. However I think the models all indicate that it will be hot tomorrow before "boom cooldown

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    2. It did hit 104 at the Airport officially so that is pretty close to what was forecast.

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  5. Is it supposed to go from 73 at 6am, to 110 at 5pm, and then in 7hrs drop to 66 at midnight?

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  6. Would you care to comment on the NWS’s just-issued extension of the Excessive Heat Warning here to Tuesday at 11:00 P.M., saying that Tuesday temperatures would be in the upper 90s and Monday night/Tuesday morning cooling would be “poor” for Eastern Puget Sound? Sounds like a pretty direct contradiction of what you’ve written here.

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  7. What about Eastern Washington!? We want off the roller coaster too!

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  8. I'd be curious to hear your thoughts concerning the NWS bulletin, issued at 3:21 this afternoon, extending the Excessive Heat Warning for the Puget Sound region from Monday at 9:00 P.M. to Tuesday at 11:00 P.M.

    It predicts "Temperatures lingering in the upper 90s on Tuesday, with a potentially dangerously hot heat index of 111," and "Nighttime relief into Tuesday morning will be poor in Eastern Puget Sound and the adjacent Cascade foothills. Overnight lows will still be in the low 70s."

    Sounds like a direct contradiction to what you posted here. Is this based on dramatically changed data, or do you just think the NWS is wrong on this?

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  9. 103°/34% humidity 29.75 barometer here on East Hill in Kent at 3:45pm.

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  10. No relief in sight for Columbia Basin. Highs in the 100s for some time to come.

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  11. 103°/34% humidity 29.75 barometer here on East Hill in Kent at 3:45pm.

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  12. A heart-felt Thank you! Professor. Having the expert hand-holding us through this staves off the notion that we've arrived permanently at (Shakespeare) The Tempest: 'Hell is empty and all the devils are here.'

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  13. Yep David, same here in Lacey. Forecast for 106 - 107. Right now ... 102, same as yesterday. I'm not complaining, though, the sooner this temp madness is over with the better. :)

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  14. We are at 112 in SW WA (Salmon Creek- by Battle Ground) at 4:32pm. This is stupid hot.

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  15. I have to push back a bit. Of all the people who should know about the temperature extremes in this region, Cliff's the one. Yeah, Cliff, it's shaping up to be a big swing in Seattle, but it's nothing compared to the intraday change from 110F to -48F at the Mt. Adams sulfur mine (defunct since the late 1950s) on the Eastern Oregon town that awoke to a snowstorm on a July 2nd in the 1920s and saw the temp go over 90F that afternoon.

    There is HUGE natural variability in this region. Cycles within cycles. This weekend's "records" convey little historical information. Not only are many records missing because there were no reliable or precise measurements, but anyone who closely researches what records do exist would dial back the superlatives just a bit.

    Yes, this is a genuine weather event, and I don't even begin to castigate you for the focus, but this is within the normal parameters for a region characterized by very extreme weather. The fact that Seattle, in particular, pretty much swings between the high 30s or low 40s in winter (with the coldest days typically in the 20s) and 65 to 90 in summer (with occasional swings past those boundaries, in both directions) doesn't even begin to tell the story of the Pacific NW's normal weather or climate.

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    1. True. I've seen 'over 100' more than once here at the foot of Mt. Baker (admittedly, wasn't in June), and a winter so-cold (below zero, 1981) that Nooksack Falls froze and livestock had to be shipped to eastern Washington (Quincy) where water was still flowing. We do have wild extremes and anomalies, and "official records" are far from complete. Here's to blogs like this (and also online weather reporting - CoCoRaHS and Weather Underground (Wunderground)).

      In addition, unless I'm mistaken, many of the extremes seem to be driven by 'perfect storm' anomalies (polar, jet stream, etc) that are not driven by local mechanisms ... clearly well outside "range of normal."

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    2. I think it would be hard to find a spot in the world in recorded history that went from 110 to -48 in the same year. A day is just not believable. Has the top of Mt Adams ever hit 110 or -48 in the summer? Snow in the summer to 90s is plausible, 20s to 90s, 70 degree delta. Maybe 100 degree delta somewhere in history. 158 degree delta in 24 hours?

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    3. Placeholder with a bit of good wisdom when it comes to our microclimates and weather extremes here. Thank you.

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    4. Ted, you make a reasonable point, and in fact there are few official records for Adams; what do exist are from Trout Lake, a town near the base, and Potato Hill, whose records don't go back very far. Even if you therefore decide to ignore that one, the point still stands. There are HUGE temperature swings in this region, some of them in a single day.

      This is also true elsewhere in the West. On January 22, 1943, it was -4 at 7:30 a.m. in Spearfish, S.D.; two minutes later, it was 45 degrees; at 9 a.m., it was 54 degrees. By 9:27 a.m., it was back to -4.

      On January 25, 1872, it went from 46 to -20 in Denver. On January 14-15, 1972, Loma, Montana went from -54 to 49. Large swings in a short period of time are hardly unknown in the West. Certainly less common in Seattle and Portland, but many a 50-degree swing has happened within a day.

      There's a larger point to make. Seattle and Portland have large populations, but geographically speaking they are flies on a cow's back. OR and WA together span about 160,000 square miles, and there are more distinct climate zones in this region than anywhere I know of in the United States. More than a few west side yuppies have learned harsh lessons about that at times, including myself.

      In any case, a 50-degree swing in a day is certainly something to notice, just as the routine 30- to 40-degree swings in front of cold fronts made quite the impression on me when I was growing up in the Midwest. I completely understand Cliff's close attention to all of this, and have boatloads of respect for his scholarship, not to mention his courageous resistance to the "progressive" mobs at UW and Seattle in general.

      But no one's perfect. My criticism here is meant to be mild. A bit over his skis on this "all time" hoo-hah is what I'm trying to convey.

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    5. Yes, this is appreciated, Placeholder.

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  16. East of the Cascades, Monday is just the beginning. There will be even warmer temperatures Tuesday and temperatures 100-110 through the end of the week. So, there will only be respite for some.

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  17. My system is certainly n match for computational power you have access to, but my barometer has fallen steeply down to 1011 and is still falling. I’m doubting it’s suggestion of turbulence, but is there a chance the thermal trough has already begun to shift?

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    1. im wondering the same. If you go back to cliff mass's blog about the july 2009 heat event, there were thunderstorms accompanying the heat.

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  19. I dunno, 1:18 on the video seems pretty appropriate, too.

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  20. And all this mess is, of course, due to natural variability only. One giant fluctuation.

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  21. Wow - remarkably accurate today! (Sunday). I am impressed. According to the map (model), we'd see a break at about 5 pm, and woo-hoo that did happen. Had almost two hours wavering at 103-104 (instrument admittedly in full sun, from 2 to 4 pm). Now it's in the shade and at 5 temp had fallen to 93 F, currently 90 F at 6 pm.

    Keep the information coming. This is quite-something to follow, blow-by-blow.

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  22. 115°F at 5:30 p.m. June 27th in Sultan WA. Our location is typically more extreme weather in winter and summer than other places in our neighborhood. Ugh. Awful

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  23. I was thinking the same thing! Heat apocalypse, as I was looking out the window seeing neighbors with foil on their windows, reminding me of a scene out of a zombie movie or something. Also, this "perfect storm" makes me feel a little better about it not happening again...for awhile I hope.

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  24. It's supposed to get cooler the rest of the week but why is the forecast humidity so high? I thought down slope winds tended to dry out the air.

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  25. Here's some interesting data I pulled together from the National Weather Service data regarding average daily temperature departures from January 1, 2000-June 27, 2021 (preliminary). It helps show how extraordinary these temperatures the past few days around Seattle have been. Or at least at SeaTac. This data will be updated over the next several days.

    https://www.litterrocks.com/blog/2021/6/27/departures-from-normal

    My Capitol Hill house interior is still 91F at 10:00 PM. This event might be the one to finally push me towards A/C. Maybe next year.

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  26. It's all them Californians bringing their insane weather with them!

    107 in Graham on Sunday, 27 June @ 4:43 PM

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  27. It is just superb that weather computer models were able to predict this extreme weather event so many days in advance. An amazing accomplishment.

    During my career I had some contact with people who did computer modeling, which leads to my basic question. How do the weather models treat the vertical flow of air and water?

    I understand that for horizontal flow the computer models use a grid in the shape of rectangles, or triangles, or hexagons, and that the air moves horizontally from box to box using some elaborate form of the basic fluid equations. But if one takes a vertical slice through the models then the grids would look like a stack of pancakes, with the vertical spacing of the grids much smaller than the horizontal size. From what I understand about computer modeling of fluids, the computing time step would be too large to use fluid equations for vertical flow. If the fluid equations were used, they would produce artificial behavior such as acoustic waves.

    Which leads me back to my question. What kind of equations are used to accurately treat large-scale vertical flows of air and water in thunderstorms, or Hadley and Ferrel cells, etc.?

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  28. Hi Cliff,
    Welcome to my climate world! I've been reading your blog for a long while and am a Patreon subscriber because you provide clear and informative discussion as to the weather processes, but I'm located way down on the other side of the planet in the south eastern corner of Australia (there are many similarities between our weather patterns). Down here, this sort of drastic weather change is not the norm, but it isn't uncommon either. It is very hard on live stock which can suffer dreadfully and the shock can be deadly, but also as an ex-volunteer firefighter it is almost the worst sort of fire weather you'd ever want to experience. Small fire fronts can become long, wide and deadly fire fronts. Not good. Stay safe.
    Cheers
    Chris at Fernglade Farm

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  29. just shattering records here. nothing to see, people.

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  30. This quote from WSJ. I suspect Mr. Peterson wants to be seen as someone who knows everything. Soil moisture!? Really?

    "Drought conditions in states including Utah, Nevada and California helped prime the path for the Pacific Northwest’s brush with record temperatures, said Dan Petersen, a meteorologist at the National Weather Service’s Weather Prediction Center in College Park, Md. Water in soil typically absorbs a portion of the sun’s heat, lowering the overall temperature. But when there is a shortage of water, such as during a drought, heat builds up and temperatures typically remain higher, he said."

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  31. If I was not watching this unfold before my eyes, I would not have believed it. My home is near Lake Youngs SE of Renton. It was beginning to feel very hot. My trusty backyard thermometer read 98 at 0900. I thought something was wrong with the thermometer. Checked my local CWOP, EW0259, near Kentridge HS. The site was reporting 100F, and went to 101F at 0907. The adiabatic spillover has arrived with some serious punch.

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  32. Just wondering, with dewpoints in the low 60s, where is the moisture coming from?

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  33. Usually after July 4th through August is basically hot, dry, and cloudless all day. It feels like this summer just started it three weeks early with a major hear event. I hope cool and moisture arrive, but this could be the hottest driest summer in recorded history.

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  34. What's with the thunderstorms off the Oregon coast? Any chance they could come here?

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Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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