BIG SIGNS OF FALL IN THE CRYSTAL BALL...
A welcome cold front will bring the recent siege of summer weather to an end over the coming weekend. It was quite a run though with 6 consecutive 90 degree days in much of my area. Cedar Rapids has not been below 92 for a high since last Sunday. That's quite a reversal from the start of the month when we began with 5 highs in the 70s. Typically you would expect to see just the opposite in August with the cooler weather back loaded.
These are the daily temperature departures for August. That last week was a burner with highs averaging about 12 degrees above normal
The front bringing the relief did spark some thunderstorms along with a watch and several warnings. Garrison, Iowa hard hit by the derecho had 60 mph winds and 1" hail. Hopkinton also reported some tree damage but that's about all I've seen for reports. However, as I was concerned about in my previous post most areas missed out on much needed beneficial rains. The Doppler estimates look like this. Very little in my area south of HWY 30. The big winners for the most widespread rain were Buchanan, Delaware, and Jones counties.
Where the rain came down in buckets was in central Wisconsin where estimates of 5-10"+ are showing along I-94 northwest of Portage. Too bad we couldn't spread that around like butter.
The big theme in the Midwest weather going forward is much cooler temperatures the next couple of weeks.That's well supported by the MJO which is projected to cycle into phases 3 and 4 going into September.
Below are the phase 3 and 4 temperature analogs in September.
The GFS is really ambitious with the cool air showing temperature departures that look like like this in 5 day increments.
Days 5-10 September 2-7th
Days 10-15 September 7-12th
Here's the trough the GFS develops September 9th that delivers the coldest air. We are getting out a couple weeks here so we need to be cautious with this solution. If by chance it verifies it would bring a pretty spectacular early season preview of fall.
How spectacular you say? Well these are the highs September 8th...mid 40s in NC Wisconsin.
Are you sitting down? Here are the lows the next morning. Freezing as far south as Dubuque and Waterloo. That's at least 5 weeks ahead of the average first freeze.
Now the grand finale, snow reaching into the north shore of Lake Superior!
Let me say this about all of that. I personally have serious reservations anything that drastic ends up happening. However, the trend of much cooler conditions is well supported and the Climate Prediction Center is on board with an 8-14 day outlook that shows this.
They even indicate a high risk of hazardous temperatures September 8-10th. That implies at least a 60 percent chance of much below normal temperatures.