Much Cooler Thursday Ahead; But A Very Nice September Start

August 29, 2018

7pm Wednesday

Hasn’t it been nice the past three days?  After the searing mid-summer heat this week has been glorious…definitely a late-summer or early fall feel out there.  Today we made it into the mid 80s after a comfortable morning mainly in the 50s and 60s.

High Temp Last 13 Days

The hot upper-level ridge of high pressure that’s been so persistent since mid-July has moved well offshore, taking the heat with it.   There is a weak upper-level system passing by the next 24 hours; it’ll give us a strong push of marine air tonight.  Expect plenty of cloud cover and even spots of drizzle Thursday morning.

Beyond tomorrow it appears we’ll be in a mild westerly flow through the foreseeable future.   That means comfortable warm temperatures most days and more sunshine than cloud cover.  Of course our Labor Day Weekend is looking good too.  Here’s a peek at the ECMWF ensemble temps for the next two weeks…a stable weather pattern for early September

KPDX_2018082912_eps_min_max_15

Of course we REALLY need a good soaking, but that doesn’t appear to be an option through at least the first week of September.  Salem will break its all-time dry days record tomorrow.  It’ll be the 80th day without measurable rainfall, today was day #79

Dry Spells Salem

Take a look at the ECMWF 24hr precip forecast from the ensembles and you see no support for anything other than sprinkles for at least the next week.  There are hints of some showers around the 8th-10th of the month, but that is quite a way out

KPDX_2018082912_eps24_precip_360

Luckily it was a somewhat wet weekend in the southern Washington and northern Oregon Cascades.  Some spots saw over 1/2″ of rain along the western slopes.  You can see the rise in moisture with the “1000-hour fuels” from the Log Creek RAWS site near Bull Run Lake

Fire Fuel Moisture Oregon

It’s a bit hard to read, but the black line shows decreasing moisture since the showers in mid June.  Then a quick bump up this past weekend brought moisture levels back to average for late August.  Notice last year (in yellow) moisture levels generally dropped through the first few days of September.  Then of course we had that miraculous deluge in the mountains mid-September, ending the fire season early.  We’ll see how it plays out this year.

You may be wondering…are we done with 90 degree weather?  Most likely not, although it’s not unheard of to stay below 90 in September.  Here’s a look at the past few years

Mark Last 90 Degree Day Heatwave

The average date is September 8th in Portland.  My guess is that we have another 90 degree day coming at some point next month since temperatures the next 10-14 days will likely run near to above average.

Chief Meteorologist Mark Nelsen