The Week Ahead – Here Come’s the Sun, but will the Smoke Stay Away?

Update: Wednesday 9/30/2020 6:43 am

Starting day with better air quality than yesterday.  Light easterlies overnight have kept fog away.  Winds shift this morning and expect the smoke aloft to move overhead by mid afternoon. Mixing to surface light, AQI not expected to exceed moderate (yellow).

Original post

What a wet start to Autumn. While we didn’t tally anywhere close to the ~8 inch monthly precipitation record (at Snoqualmie Falls) for September, it did rain 4”.  That's the third wettest over any 3-day period in September.  Had it not been for the dry first three weeks of the month we might have threatened the monthly rainfall record.  

Now let us talk about the big warmup on the way!  

A building ridge of high pressure should dominate, potentially sending highs into the 80°’s by mid-week.

With October fast approaching, this does beg the question if we’re going to break any heat records this week.  I was initially surprised by my finding.   Not Likely.  Turns out there was a massive thermal trough that sent the mercury to a blistering 95° on 10/1/1987. To check the likelihood this might be an error, I looked at official records at Sea-Tac on that day.  89°!  So probably legit (within acceptable margin of error).  I’d appreciate hearing from any of you living in the Valley that recall that record breaking heat.  

That one-day anomaly aside, October is not a total stranger to having a final gasp of summer-like warmth.  

Wx observations from Snoqualmie Falls

The really important question is will smoke return this week?  

Fortunately, barring any new major fires, that answer is unlikely.

Let’s check up on West Cost fires.  

WA and Oregon looking good, CA significantly improved.

As seen 9/27 9am PST. windy.com

However, California is going to heat up big time this week.  San Jose back into the mid-90°s.

There will be a light east wind/offshore flow developing this week, but importantly not a southerly wind that could bring up smoke from the existing fires.   As far as local fires, I'm hopeful considering there's no forecasted threat of lightning coupled with last week's drenching moisture that even reached eastern Washington to some extent.

Here's the smoke forecast as far out as available.  Wednesday is probably our hottest day.  For reference, a 50 AQI index (borderline "good" air quality) would equal 12 ug/m3

windy.com

Longer range, much cooler weather and rain looks set to return to the PNW around the following Monday (Oct 5).

Have a great week!

Almanac for September 28th (Snoqualmie Valley): 

Average High: 67° Average: Low 45°

Sunrise: 7:03 am Sunset: 6:51 pm Daylight: 11 hours 48 minutes

Moon Phase (current): Waxing Gibbous Full Moon: October 1st