What a tremendous change the past week! Look at high temperatures in Portland. 100s to 90s to 80s to 70s. Today we just barely made it to 70, which means we spent the whole day in the 60s. This weekend was the coolest we’ve seen in over two months.
I had a few days off last week but working this weekend. I’ve had plenty of time to get up to speed and here’s what I’m seeing:
1. We had our usual two-month period of guaranteed warm/dry/sunny weather, but it was a bit early… June 15th to August 15th.
2. The heat of summer is gone, and there’s no sign it’s coming back. Endless days of sunshine are done for this year. Sure, we should have plenty of warm/dry weather ahead, but expect marine air to flood inland at times too. Just like this weekend, we will have cloudy or mostly cloudy & cool days mixed in.
3. We can still get up to 90 for about another month, but no model is projecting that for Portland through the rest of the month. We’re just 10 days away from September.
4. I don’t see a soaking rain, or even widespread showers, for the next week
With 9 days left in “meteorological summer”, we’re still on track for the hottest summer on record. That’s both in Portland and Salem, but it’s going to be close with this recent cooldown. It may end up the 2nd hottest. Regardless, both cities DID experience the warmest 2-month period on record from mid-June to mid-August.
One surprise, and a mild forecast bust, was the heavier than expected showers today. Many areas picked up measurable rain, and .05-.10″ was not uncommon. Almost all of it was central/east metro
That makes August 22nd the 2nd day with measurable rain this month at PDX.
WHY A COOL END TO AUGUST?
For at least half the time, we’ll be under weak upper level “troughing” or a dip in the jet stream through the end of the month. Right now, a chilly system is passing by to the north in British Columbia, excellent news with all the fires up there. Here’s the Canadian model’s representation of the current setup. Cool showers up north plus lots of cool northwesterly flow coming down the B.C. coastline into Oregon/Washington
That moves east, we warm up a bit tomorrow, then quite a bit Tuesday/Wednesday. But Wednesday night another “ripple” is moving by, pushing lots of clouds inland. We’ll likely see some drizzle again Thursday morning, and some models even produce real showers Wednesday night and Thursday A.M.
By Saturday, a warm ridge is developing to our west (zig-zag line) … that’s sunnier, warmer, and back to “summer weather”. NEXT WEEKEND LOOKS SIGNIFICANTLY WARMER/SUNNIER THAN WHAT WE JUST EXPERIENCED
But just four days later, another cool trough is approaching. This is Wednesday, September 1st
What about rain? As of now, there’s no sign of a significant cool/wet spell. The ECMWF ensemble forecast for the next two weeks doesn’t show that either. Although there could be drips/showers here and there (possibly Thursday/Friday).
SUMMER ISN’T OVER, but if you want lots of hot weather, that’s not happening in the next 10 days.
This is EXCELLENT news! The last outbreak of lightning was back in the first few days of the month, and I don’t see any ahead. It appears we’ve only had one large (over 1,000 acre) fire develop in the past two weeks. That is the Fox Complex near Lakeview.
- Cooler plus higher humidity with occasional onshore pushes means less chance for huge fire starts, plus existing fires grow slowly
- Westerly flow will continue send smoke east of the Cascades most of the time the next 10 days
- I don’t see a setup where we get significant smoke west of the mountains over the next week and beyond
- This weather pattern does not produce the dangerous easterly wind with its low humidity and high temps
The largest fires (or complexes) burning right now in Oregon
It’s good that we don’t have any sort of hot easterly wind event in sight…6 of those fires are burning on the west slopes of the Cascades! That’s right where the historic mega-fires burned last September.
I’ve said for years that what the weather does DURING fire season is far more important than the lead up in the spring. Remember we had our driest spring on record and most of Oregon is in severe drought. BUT, if we keep lightning away, humans don’t start fires, and we get occasional cooldowns/showers, we can make it through the rest of the season…fingers crossed!
Chief Meteorologist Mark Nelsen
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