September 22, 2009

Big Daily Temperature Range and Foothills Heat


Today was hot, with many locations getting into the mid and upper 80s, and some foothills locations reaching into the 90s (see map of temps and winds at 5 PM). Why the foothills? The reason is we had fairly strong easterly flow today with downslope flow and compressional warming of the air descending the slopes. (see Seattle profiler winds and temps to see the easterly flow and warming aloft). North Bend is a favorite place for hot temps on such days because it is at the base of the Cascades and gets the maximum downslope heating. Hint: during the late fall it is sometimes MUCH warmer near North Bend and the foothills than anywhere else--good place for a hike or bike ride!

Last night there was good radiational cooling to space (since we had clear skies) and temperatures fell over most of the region...but near the foothills the temps really held up due to the downslope. See for yourself with the weather map at 7 AM. Over 70F in the foothills...but in the 50s and 40s elsewhere!
Another interesting aspect of temps today have been the large diurnal (daily) temperature range...something we frequently see in the fall under these conditions. With full sun and downslope offshore flow the temperatures can still get quite warm during the day, but the nights are getting much longer now (unfortunately for my tomatoes), and with clear skies there is good radiational cooling to space. Today, many locations were in the 40s this morning and skyrocketed to near 90F....nearly a 50F change over roughly six hours. That will crack some concrete! Don't believe me? Take a look at the temps at Shelton today (graph), where the temperature climbed from 41 to 89 over a few hours!
Tomorrow (Wed) will be slightly cooler and a marine push will occur tomorrow night....ending the heat wave. But no major weather in sight.

18 comments:

  1. Fascinating. A very warm evening here in Fremont, and we can clearly see the ash cloud over the Olympics that's been pushed out by the easterly winds over St Helens. Got to be a lot of nasty volcanic dust up there...

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  2. You wanna' talk diurnal swing, I think Sunriver this time of year is world class: http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KORSUNRI1&day=22&year=2009&month=9

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  3. That's very reminiscent of how some winters in FL would get. We could get frost overnight, dipping into the high thirties, and then during the day with full sun get well back up to 80 and beyond. Although I suspected it was the lack of moisture (which in turn caused clearer skies), now I know for sure.

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  4. My boss is down in Sunriver and he said the highs have been in the 80s, lows in the 20s. I would believe it in the high desert area. It's amazing to have it here. This has been like a Bay Area September...they get this clear, warm setup in Sept/Oct and you can see far out to the Farallons. But in Seattle...what a surprise! Sunrises and sunsets have looked amazing. Good time to move...if we stay dry on Oct. 3 I'll be happy. After that it can rain cats and dogs.

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  5. Tuesday was Portland's 24 day above 90 this summer, giving them a new record for 90 degree days in any one year.

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  6. I believe enough folks have now moved from California that it is affecting the weather. We are now an extension of Sonoma county. Please start referring to the DOL as the DMV and call initiatives , propositions.

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  7. I could not see Mt Rainier from the bus this morning. I was very interested to see why. Turns out there is quite a bit of smoke in the atmosphere.

    After a little research, this appears to be from some fires in southern Oregon.

    http://www.nwccweb.us/information/firemap.asp

    The 1km images shows the smoke pooling in the Okanogan valley in BC.

    http://www.atmos.washington.edu/images/vis1km/200909231715.gif

    Interesting that I could find no information about this on the air quality sites in either BC or Puget Sound. Actually got a clue from here.

    http://alg.umbc.edu/usaq/

    I think the air quality sites need to do a better job of communicating this type of situation. There is nothing but 'green' lights on this page.

    http://www.pscleanair.org/airq/aqi.aspx

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  8. "Smoke from Oregon Wildfires may impede clarity of vistas but is not expect to impact AQI."

    http://www.airnow.gov/index.cfm?action=airnow.showlocal&CityID=434

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  9. Tuesday's high was only 72 at our house on Bainbridge Island very close to Puget Sound as measured by our Davis weather station. Bremerton airport (also Kitsap County) is inland and reached 93.

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  10. How about Packwood... 94/39 yesterday

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  11. Blake,
    Glad to see you found our forecast discussion that was update yesterday morning. For future reference you can find it on our webs sites homepage or current air quality page:
    http://www.pscleanair.org/airq/aqi.aspx#
    Here is the full discussion from yesterday.

    Forecast discussion 23-28 Sept: Expect good mixing and dispersion of pollutants during the forecast period. Smoke from Oregon Wildfires may impede clarity of vistas but is not expect to impact AQI.

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  12. when i went to p/u my 15yo from young women at 8:30 it was cooling off nice and a WIND! It was so wonderful, i drove with the windows down and enjoyed being COLD!

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  13. I really noticed the temp differences on Monday. I was driving home to North Bend from downtown Seattle around midnight. It was 53 in Preston on I-90. At the North Bend Exit 31, the wind was blowing and the temp was 71. I live 3 miles north of North Bend around the other side of Mt Si where we are protected from the downslope winds. By the time I got to my house, it was 53 again.

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  14. Nice weather coming next week - finally!!

    Hint: The foothills in North Bend are not necessarily a good place for a hike or a bike ride in the fall, especially if you like fall. If you like the hotter weather, then yes, but not everyone does, so if you like the cooler weather, wait until later in the fall or in the winter - great times for low-elevation hikes and bike rides! - or go to higher elevations or closer to the water. Then there will be some great times for hiking and bike riding more to your liking, if you like the cooler temperatures... though it may be tough to avoid the sun.

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  15. One more fantastic weekend, warm and dry.

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  16. MONDAY LOOKS TO BE A TRANSITION DAY ...OF MOST INTEREST WITH THIS SYSTEM IS THE QUICK LOWERING OF
    HEIGHTS AFTER THE UPPER TROUGH PASSES. WASHINGTON WILL GO FROM
    HEIGHTS IN THE 580S TO THE 540S IN SHORT ORDER. THIS MEANS AT LEAST
    SOME OF THE PRECIPITATION MONDAY NIGHT AND TUESDAY IN THE MOUNTAINS
    WILL BE SNOW...PROBABLY DOWN TO 4000 FEET OR SO. THERE IS SOME
    REBOUNDING AFTER THAT BUT HEIGHTS ARE UNLIKELY TO GET AS HIGH AS
    THEY HAVE BEEN THIS WEEK...NOT UNTIL NEXT YEAR PROBABLY. BURKE

    Amen. Bring it.

    http://www.atmos.washington.edu/data/disc_report.html

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