Brief Cooldown, Much Above Average Temperatures Next Week

 FastCast—Friday, Sep. 23 to Tuesday, Sep. 27:

Onshore flow on Thursday brought much-improved air quality and cool, breezy conditions in Western Washington. Highs dropped from the upper 70s to the upper 60s/low 70s. Cooler conditions, with highs in the upper 60s to low 70s, will continue on Friday and Saturday. On Sunday, it will be mostly sunny, with highs increasing to the mid 70s. Monday and Tuesday will have highs of 10-20 degrees above average in the Pacific Northwest, reaching the upper 70s to low 80s in the lowlands and the mid 80s to low 90s in the Willamette Valley and Eastern Washington. This is very abnormal for late September, and daily records may be broken around the region. Additionally, flow will again turn offshore by late Saturday. This will potentially bring smoke from the Bolt Creek Fire back into the lowlands. Stay tuned for more information about smoke, air quality, and high temperatures. I will have an update on Friday night regarding Hurricane Fiona and its historic impacts to Atlantic Canada.

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Continue reading the full blog below!

After a couple very smoky days around Western Washington, fresh marine air returned on Thursday, bringing cooler temperatures, improved air quality, and a marine breeze (gusts 20-30 mph). Expect cooler temperatures in the upper 60s to low 70s on Friday and Saturday!

However, that cool and seasonable weather won’t last for long. A robust high pressure ridge will bring much warmer temperatures to the entire Pacific Northwest on Monday and Tuesday. Below is the European model, showing temperature departure from average on Monday afternoon.

On Monday afternoon, temperatures in the entirety of the Pacific Northwest will be 10-20 degrees above average. Western portions of Washington and Oregon will have highs an amazing 15-25 degrees above average. 

So…what will those highs be? The European model forecast for Monday is below.

Highs in the lowlands will be in the upper 70s to low 80s, a bit cooler near the water. Eastern Washington and the Willamette Valley will be quite hot, with highs in the mid 80s to low 90s. 

For the lowlands, temperatures over 80 degrees in the last week of September are rare, but not unprecedented. If you were wondering, “average” highs in the lowlands in late September are in the upper 60s.

It is more likely than not that above average temperatures will continue into October. Extremely above average temperatures like Monday and Tuesday don’t look likely as of now (but that can always change). The NOAA Climate Prediction Center outlook for September 28th to October 2nd is below.

There is a 40-60% chance of above average temperatures in Western Washington into the beginning of October. 

Stay tuned for a Friday night update on the historic impacts of Hurricane Fiona in Atlantic Canada, especially Nova Scotia. Updates on Fiona can be found at the National Hurricane Center and on all major news outlets.

Stay tuned this weekend for updates on the potential return of surface smoke with upcoming offshore flow.