warm

Now that we’ve seen a nice soaking across most of the region, it’s time for some classic early fall weather. Cool nights and mornings plus briefly (very warm) afternoons. Fall in the Pacific Northwest is typically like this; rainy periods alternate with bright sunshine. The key messages…

  1. Expect dry conditions through at least next Saturday/Sunday
  2. Temperatures reach 80 degrees or warmer Monday through Friday
  3. A gusty east wind blowing out of the Gorge will arrive in the metro area tomorrow, then come and go through Friday.
  4. Fire smoke is unlikely to return in any significant fashion in the lowlands. But high-level smoke from California likely arrives Wednesday. Expect much hazier conditions Wednesday-Friday

Today was about as normal as it gets…we hit 51 last night and 75 today in the city. 1 and 3 degrees above the 30 year average. Strong high pressure is now in place overhead. Here’s the view for Tuesday…

The typical fall jet stream is diverted far to the north and then plunges south into the Great Lakes region. We go much above normal and they turn very chilly. It still looks similar NEXT Sunday, October 4th, although the ridge has “flattened” a bit. That could lead to onshore flow and areas of fog/clouds. We’ll see how that plays out.

Regardless, rain is not in the cards through at least next Sunday. Actually the GFS model ensembles (newly upgraded last week!) show the ridge popping up a bit again early-mid NEXT week. Here’s Wednesday the 7th (click for a better view). Warm colors indicate a positive (warm) upper-level height anomaly.

The ECMWF and Canadian models look the same. So confidence is relatively high that we have a dry (or mainly dry) 8-10 days ahead.

How warm? 850mb temps over Salem sit between 20-23 for the next six afternoons! This would be a major heat wave in summertime. But this time of year a “heat wave” is 80-90 degrees. We appear to have good offshore flow the next two days, then it backs off a bit Wednesday. A bit stronger again Thursday, weakening Friday. At no time do we have a strong east wind event. More of a typical “gusts 40-55 mph in the Gorge and breezes over the mountains” setup. That begins tomorrow. I’m going with these numbers…only Tuesday and Wednesday would be close to record highs.

If you don’t like warm/hot weather, at least this time of year long nights mean we’re back in the 60s soon after sunset. Lots of 40s/50s for overnight lows of course.

I just check past Portland weather stats to see how uncommon 5 days in the 80s is this time of year. Not unheard of, but somewhat unusual. So how many days have we made it to 80 AFTER this date? This will be the most since 2014-2015.

But you have to go all the way back to my first year in TV…1993 to find another early fall with this many 80 degree days. Definitely unusual. In 1987 we saw 8 days at/above 80 this late in the season, and 1991 was similar.

Everyone keeps asking me about smoke…will it come back? I think that’s a yes/no question.

  1. Little or no smoke was visible on the perfectly clear GOES-17 satellite image today. There’s no reason to believe any of our local fires will suddenly start raging out of control or even put up a big plume of smoke again. That’s due to wet forest, no strong wind forecast, and some good fire lines.
  2. But, communities close to those fires may be smelling smoke regularly again or we could even get a slight haze down here in the lowlands. That should be about it.
  3. MORE NOTICEABLE…As the upper-level high shifts slightly east of us late Tuesday, a southerly flow opens up overhead. This means Wednesday-Friday could see a lot of milky/hazy sky overhead with filtered sunshine. Hopefully that wouldn’t make it all the way down to the surface.

Here’s the GEOS-5 modelling that shows smoke about to arrive Tuesday evening. You can see the center of the upper-level high around La Pine at that time.

By the way, check out this 20 year span of Portland metro area PM2.5 pollution. Except for last year, our late summers have turned smokier; you aren’t crazy in thinking that’s the case. The poor air quality you regularly see in late fall and early winter is due to inversions; common due to weak sun angle and long nights. Data is from EPA

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