Friday, July 24, 2020

Heat Wave Coming to the Northwest

The past few days have been cooler than normal as marine air inundated the western side of our region.  But that is going to change over the weekend, and by Monday, Seattle may hit 90F and Portland could surge to 100F or more.   So get your fans and cool drinks ready.

Our current cool weather has been associated with an upper-level trough of low pressure over the region (see 500 hPa--about 18,000 ft--map below for 8 AM this morning).


But things change over the weekend as a significant ridge of high pressure and heights builds along the West Coast...check out the same map for Sunday at 2 PM... 180° change!


Ridging brings sinking and warming air over the region...and more important than that, inland pressure rises resulting in offshore (easterly) flow that cuts off western Washington and Oregon from the cool, coastal air.

Let me show you the predicted warm up! 

The forecast surface air temperatures and winds for 5 PM Saturday, shows 80sF in the Willamette Valley and the Columbia Basin, but cooling northerly flow over Puget Sound where temperatures only climb into the lower 70s.  Very nice day.  Good one for outdoor activity.


But the situation is considerably different, and more toasty, on Sunday at 5 PM.  Notice the development of easterly flow over southern WA and northern OR--easterly flow rapidly warms as it sinks and compresses on the western slopes of the Cascades.  Our big heat waves all have strong easterly flow crossing the mountains.  Portland jumps into the upper 90s, as does the Tri-Cities area.


 But the real show-stopper is on Monday (5 PM shown)--the warmest day of the sequence, except for the immediate coast.  The Columbia Basin and the Willamette Valley are torrid....with significant areas above 100F.  Seattle gets into the upper 80s to near 90F.    But look closely and you can see cool air moving inland from the coast.


There will be a weak marine push late Monday and Tuesday, with  modest cooling west of the Cascade crest.  And there will be major cooling...and the chance of rain later in the week.

27 comments:

  1. Bring it on! Love my central AC!

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  2. We have at least 1 heat wave every summer. Any guess on how many more we will have before the weather shifts for fall? I suspect at least 2 more in August.

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  3. No ac needed for a day or two. I’ll take the nice fresh air with a fan anyway.

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  4. The only time it gets over 75 in Port townsend, is when it's 90 in Seattle, kinda sad here. :(

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    1. It is sad. We're right across the water from you on Whidbay, and the national forecast is getting cooler, to just upper 60's on Sunday.

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  5. Thanks Cliff, you make it easy to understand!

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  6. Cliff,

    I'm glad to hear the 90 degree temperature is for just one day! We aren't accustomed to it including our pets. Heat exhaustion and heat stroke are very dangerous.

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  7. That's great to have AC if you aren't impacting your neighbors and are using it responsibly. I have a neighbor with a loud AC, it's on all the time, at night when it's in the 50's, during the day when it's in the 60's. It was on all day today and it was a cool day. Pretty much keeps us from having any peace outside and wakes us up at night. I can understand if it's in the mid to high 80s and above, otherwise using an AC is wasteful and contributes to global warming for no reason. There are very few days in Seattle where an AC is needed.

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    1. I couldn't agree more. We are surrounded by neighbors with heats pumps. Their noise completely ruins the otherwise peace and quit of the outdoors. I'd like to see them done away with - they are noise polluters.

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    2. Your neighbors need quieter heat pumps. Mine, installed in 2016, is many times quieter than the old unit it replaced. It's unobtrusive even when sitting 10-15 feet away from it.

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    3. Some of us live in spaces that trap heat even on days below 80. Don't assume it's not needed just because YOU don't need it.

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  8. 180 degree change? You mean it's going to be 240 degrees?

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  9. I live in a low-density residential area (lots are generally 0.25 ac and up) and I keep my small, old, but reasonably well-insulated house, at ~70F year-round. The AC runs occasionally starting in April or May and shuts off for the season typically during October. It's an efficient, modern unit with a quiet compressor/condenser. It runs, intermittently, at night only when the temperature fails to drop below 60F which happens infrequently at my location not far from the water in NW Bellingham. My electricity bill is quite reasonable during the summer and substantially lower during the winter as I heat using well-seasoned, locally, and sustainably-sourced firewood which I process by hand and burn using a high-efficiency catalytic stove.

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    1. My god are you proud or what lol

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    2. Loud and proud, brother! Ain't nothing wrong with that.

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  10. The minimum temperature this morning at my location in NW Bellingham was 48F - tied for minimum monthly temperature with a measurement on 7/5.

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  11. Is there any way to track the progress of the thermal trough? I had a link favorite to the visible satelite showing the marine layer on my phone, but it looks like its an expired link.

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  12. Is there a way to track the thermal trough via a visible satelite? I had a link as a favorite on my phone, but it doesn't look like it works anymore.

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  13. This comment has been removed by a blog administrator.

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  14. 90 F + wear mask everywhere outside your home according to new governor's directive. A lot of people in Seattle live in apartments with no AC.

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  15. The minimum temperature at my location in NW Bellingham yesterday morning was 48F - tied with a measurement from 7/5 for monthly minimum temperature. Today, the temperature reached 80F for the first time this month, the third time this year the and the first time since 5/10.

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  16. The temperature rose from a morning minimum of 51.5F to an afternoon maximum of 81.1F. This is an unusually large diurnal temperature range for mid-summer and the largest such that has occurred since the heat wave of 5/8-5/10. The maximum temperature of 81.1F is the second highest temperature I've measured this year after an 83F reading on 5/9.

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  17. This morning's minimum temperature at my location in NW Bellingham was 51.5F and the afternoon maximum was 81.1. This is the largest diurnal temperature variation since May and notably large for mid-summer. Also, the maximum temperature today is the second warmest of the year after a reading of 83F on 5/9.

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  18. The heat wave arrived as predicted here in the Rogue Valley of southern Oregon. It hit 103F this afternoon.

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  19. All I got to say is, right about now I'm glad I don't live in the Tri-Cities.

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