Rain ahead, but October starts dry & warm

No sign of a wet or cool period through first week of the month
Published: Sep. 27, 2022 at 9:55 PM PDT
Email This Link
Share on Pinterest
Share on LinkedIn

Well this is exciting...we’re going to see some widespread (light) rain for much of the region. It’s been very dry; in the past 3 months Portland has only picked up about 1/4″ of rain! That’s very stressful for our native vegetation, even with that huge soaking all through the spring months. And this September has been something else...warmest on record in Portland and Salem, and one of the warmest in other areas.

(kptv)

Right now September in Portland is running about like an average July 10-20 years ago! High 81, low 58.

(kptv)

So what’s ahead? Light showers both tomorrow and early Thursday, then we’re heading back to unusually warm and dry weather for the first few days of October. A weakening front is approaching the coast. Technically it’s an “occluded” front, but for TV purposes I left it as a cold front. One surge of rain arrives around sunrise, then the surface low with it’s attendant showers arrives tomorrow evening and night. There should be a brief dry period DURING THE DAYTIME tomorrow.

(kptv)

That surface low dies and is replaced by building high pressure late Thursday and on into the weekend. What about rain? Just perusing many different models gives somewhere between .10″ and .50″ for the metro area

(kptv)

Areas NOT showing color means less than .10″ rain forecast. Here’s the 18z ECMWF model’s precipitation forecast

(kptv)

You can see many areas east of the Cascades will just get a few showers. The Cedar Creek Fire in the central Cascades should get a soaking once again. Smoke from that fire drifted into the Willamette Valley today; I could smell it a couple of times while running errands.

We’re headed back to dry weather Friday through at least early next week, and even later NEXT week doesn’t look very wet. That’s because upper-level heights will remain higher than normal the next 8-12 days. Take a look at the 500 millibar anomaly for days 2 to 12 from the ECMWF model ensembles. Above normal heights through October’s first week (or longer).

(kptv)

GFS model ensembles are quite similar

(kptv)

Clearly the “wet season” isn’t going to arrive in the next 1-2 weeks. You can expect a very warm first weekend of October, then drier than normal through much (or all?) of that first week of the month.

Enjoy the showers, and a warm/dry weekend. I’ll be off on vacation through Sunday the 9th; hopefully we don’t get any surprises. Time for a 25th anniversary trip with my wife!