October is already here; the month in Portland where we see the largest temperature swing. Today's average high is 70, by Halloween a typical day is only in the 50s! We don't see such a dramatic change (up or down) in any other month. We DO live in a climate dominated most of the time by the mild Pacific Ocean. West of the Cascades that keeps our winters warmer than at a similar latitude elsewhere. But summers are cooler than similar latitudes. We're sure not Denver with those wild daily swings in temps!
Today is the 2nd day of fire smoke streaming overhead from all those California fires. Luckily it has been the more typical "hazy/milky" sunshine without terrible air quality at the surface. This evening most areas are in the GOOD-MODERATE category.
Air quality will likely remain in this general range through Saturday. I see little or no air movement. On Sunday a push of northwest wind should clean things out not only at the lower elevations, but overhead as well.
Because of morning low clouds and fog in the valleys west of the Cascades we were a bit cooler today. 3 days in the 80s wrapped up September; then today we stayed in the 70s...still well above average for October 1st. But check out the heat at the higher elevations! Redmond's high of 91 was the warmest October day in 19 years!
September ended up well above normal west of the Cascades, especially in urban areas due to the warm nights. Portland ended up 3rd warmest on record. Without the early month smoke, it probably would have been our warmest September on record
What's ahead? Well last year we had a very dry October, but that was following a series of wet Octobers
The big message for this October is that the first week will be dry.
A ridge of high pressure is over the West Coast right now. Very warm airmass covers the whole region. This is the ECMWF ensemble forecast of 500 millibar heights. Color is the anomaly; MUCH warmer than normal tomorrow overhead. Technically the anomaly shown is much higher than average heights. But the effect is the same.
Next Tuesday isn't much different is it?
Ah, but a change late next week. Here's Friday the 9th. An upper-level trough and below normal heights over us. In October that means clouds and rain.
The ECMWF ensemble precipitation forecast chart shows the majority of ensembles are giving us rain at some point late next week. You'll definitely want to click for a closer view. Each horizontal line on the upper part of the chart represents ONE of the ensemble members. They all want to produce some significant rain NEXT WEEKEND, the 10th/11th.
To summarize, we've got about one more week of dry weather. But there are strong hints that we'll get soaked somewhere beyond next Thursday. Plan accordingly!