Fall Arrives Next Monday

I hope you can forgive me for the click-baity, questionably accurate title. From an astronomical perspective, autumn will begin on 1:02 pm PDT Friday, September 22, 2017, and meteorological fall officially began on September 1st. But after a record-smashing streak of drier and hotter-than-average weather, we’ll finally get our first true taste of autumn next Monday as a strong cold front swings through the area.

We had some hors d’oeuvres to next Monday’s upcoming entree of liquid sunshine last Saturday, as a passing front dropped between a tenth and a quarter of an inch of rain over Western Washington and NW Oregon. That may seem insignificant for early/mid-September, but it was the most significant rainfall for our area since mid-June, and the only rainfall of the entire summer for the area apart from a very weak front in early-mid August. Late Sunday into Monday, a much stronger front will come through, dropping a half inch of rain throughout the Oregon lowlands and over an inch of rain along the Coast Range and Oregon Cascades.

24-hour precipitation from 5 pm Monday 9/18/2017 to 5 pm Tuesday 9/19/2017
24-hour precipitation from 5 pm Monday 9/18/2017 to 5 pm Tuesday 9/19/2017
Credit: Tropical Tidbits

This front will be associated with a mid-990s hPa low that should deliver a wide swath of small-craft-advisory winds to the offshore waters, with a smaller area of gale-force winds closer to the low center.

10-meter wind, SLP, 1000-500 hPa Thickness
Valid 5 AM PDT Monday, September 18

As luck would have it, I’m actually planning on being 60-70 miles off the Washington coast on Tuesday to go tuna fishing with my folks. With relatively strong winds along and in the wake of this cold front, seas could be as high as 3-4 meters. I’ll be sure to remember to bring the Dramamine… we don’t want any “chummers” on the trip!

Wave height and direction at 5 am Tuesday, September 19
Credit: NOAA Wave Watch 3

This low-pressure system is associated with a large upper-level trough that will stick around through the middle of the week. As the spaghetti plot below shows, models generally agree that we should see cooler and wetter-than-normal weather for much of next week.

Valid 5 am Monday September 18

I don’t know about you, but I’m DEFINITELY looking forward to a change towards cooler and wetter weather to give our firefighters some relief, help improve our air quality, and simply give us a change of pace from the hot and arid weather we’ve seen the past few months. It’s hard to believe that only have 1 1/2 half months to go until November!

Have a great Wednesday,
Charlie

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