8pm Monday...

I was on vacation last week and part of the previous week, but back in the forecasting saddle this week. What has changed? It’s been hot, except for a brief cool down Friday-Sunday. And a “big” .03″ rain fell at PDX, ending our 51-day dry spell

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Yesterday our own Jeff Forgeron (meteorologist on Good Day Oregon) married his best friend of 13 years under comfortable temperatures, low humidity, mainly sunny skies, and no smoke. A perfect afternoon for a “weather” wedding; Jeff nailed the timing, avoiding all the weather issues. Congrats Jeff & Katie! Here’s a nice pic of the weather team from Brian; the best team we’ve ever had!

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RECORD HOT SUMMER

I’ve just gone through the numbers, which are stunning:

  • #1 hottest summer on record at Portland, Salem, Eugene, Medford, Redmond, & Pendleton

This includes June 1st through August 8th. IF we have a cool 2nd half of August, that could knock us out of 1st place. For many stations, the previous “hottest summer” was 2015. Redmond’s previous hottest was 1968. Notice this includes BOTH stations where we’ve seen urban heating and others with little/no land change around the stations. This isn’t just about growing urban areas turning warmer (Example: Portland airport). We are living through a historically hot summer.

UNPRECEDENTED STRING OF HOT SUMMERS WEST OF CASCADES

  • Portland’s 5 hottest summers? All recent (in order too): 2021, 2015, 2018, 2017, 2009
  • Salem has a longer record that goes back to 1893. Hottest years are the same: 2021, 2015, 2018, 2017, 2009
  • Salem has seen 31 days at/above 90 so far; by Friday the new record should be 35 days there.
  • Pendleton is a bit different. The 5 hottest: 2021, 1967, 1961, 1958, 2015

RECORD DRY SPRING + SUMMER

Portland has only seen 3.80″ rain since March 1st. That’s 5.5 months! If that happened every year, we wouldn’t have green trees all around us. That tells you all our vegetation is very stressed, and of course fire danger is extreme throughout the region. This is the driest we’ve ever seen during this period. BUT, down at Salem, over 6″ has fallen. Still well below normal, but “just” 10th driest. Pendleton has only seen 1.34″ during this time = driest on record like Portland.

WHAT’S AHEAD?

Here we go again, just like in June (but not as intense); a strong upper-level ridge is developing just offshore. That means a dome of very warm air. Here’s the forecast for tomorrow; a 598dm ridge is highly unusual (again) at this latitude

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Then by Thursday it flops in over on top of the Pacific Northwest. At this point 594dm heights cover much of the region. This is major heatwave territory from June through mid-August.

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Now this model (WRF-GFS) quickly pushes a much cooler trough overhead Saturday and Sunday for dramatic cooling.

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Others keep the heat through Saturday; I think that’s a more likely outcome. Temperatures are forecast to peak around +25 to +27 (Celsius) Wednesday through Friday afternoons at 850mb. This is also major heatwave territory. Remember (until late June this year), the all-time high 850mb temp was +28.2. We will be close Thursday and Friday.

This will not be a heatwave with gusty easterly wind through the Gorge or into the western lowlands or OR/WA. That means two things. First, we won’t get as hot as we might get with a gusty east wind (106-108). And the coastline will remain reasonable, no hot east wind out there. Most likely even the north coast remains at/below 85 degrees this time around. You can see the weak/flat “thermal trough” straddling the western valleys and Cascades Thursday afternoon.

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This means no onshore cooling breezes, but no east wind either.

With all this in mind, we’re going for three days at/above 100 degrees Wednesday-Friday.

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In reality, we could end up with just (1) 100-degree day. Why? First, Wednesday we might end up at “just” 98-99. Second, fire smoke is a big issue the 2nd half of the week. Even just a moderate smoke layer overhead could easily keep us in the 90s Friday. NASA’s GEOS-5 smoke modeling shows lots of smoke over the region Friday afternoon/evening

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There are numerous small/moderate size fires burning in several complexes on the west slopes of the Cascades. We can assume they will burn more vigorously this week with heat and instability. As the upper-level ridge moves over/east of us Friday, that opens up southerly flow, bringing smoke north. Here’s the view this evening:

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That’s it for now; I’ll be working most of this week. Make sure you follow me on Facebook and Twitter for more frequent updates there: Twitter: @marknelsenKPTV and Facebook @marknelsenweather

Chief Meteorologist Mark Nelsen

Copyright 2021 KPTV-KPDX Broadcasting Corporation. All rights reserved. 

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