What A Change! Feels Like Fall

August 26, 2018

8pm Sunday

Weather forecast models did a great job showing our “endless summer” was about to…end last week.  Or at least summer will be taking a prolonged break.  Look at the last two weeks and you see the big change Thursday.

High Temp Last 13 Days

That high of 68 in Portland is the coolest day since June 13th.  And that continuously gray sky has been spitting a few light showers or drizzle at times…mainly central & east metro areas.  As of 6pm PDX has only received .01″ (Saturday evening) out of this big change

Rain Metro Today Databound

Of course what we REALLY need is a huge soaking.  It would be nice to see 2″ of rain followed by sunshine and 80 degree weather (personal opinion of course).

This is an incredible number that shows you how dry we’ve been.  The past 4 months…since May 1st.

Mark Dry Spell Summer

Only a little over 1″ of rain in Portland during an entire third of the year!

Mark Dry Spell Summer2

This dry spell (late spring through all of summer) is unprecedented in Portland, Salem, Olympia, & Seattle.  In all these locations it’s never been drier from late spring through the entire summer season.  In most years we get some sort of soaking rains in May, June, or later in August.  But not this year.  Records at Salem go back 126 years!

This is likely killing some native shrubs/bushes and has to be extremely rough on our native trees as well.  Let’s hope for some sort of soaking in September…

The ECMWF model is not encouraging for a soaking.  Here’s the 15 day 24 hour rainfall forecast from all its ensemble members.  Note the showers tonight, then hints of a shower or marine drizzle Thursday.  Af

ter that only a few members show some showers in the first week of the month, but just real light stuff.

KPDX_2018082612_eps24_precip_360

While I was taking a few days off we broke the 90 degree record of course, but other than a close call Tuesday I don’t see any 90 degree weather in sight

90 Degree Days Summer Heat

The ECMWF ensembles shows temperature about as normal as it gets for the last few days of August and early September

KPDX_2018082612_eps_min_max_15

The big pattern change?  Of course we have seen a hot upper-level ridge across much of the western USA through July and August.  Or at least upper-level heights have been higher than normal during this period.  But now it looks more like this:

ecmwf_z500a_noram_4

Higher than normal heights cover the Gulf of Alaska and cooler air is down over the Rockies, a pattern many of us would love to see in January!  Then see the forecast for this Friday:

ecmwf_fri

A similar setup with lower than normal heights over much of the western USA.  Nothing too unusual here; just that the hot ridge and high heights are gone for the next 7-10 days.

So enjoy the early taste of fall…in some years we plunge right into this weather from this point forward.  Other years the heat returns at times in September.  We’ll see.

Chief Meteorologist Mark Nelsen