Climate models for years have been projecting major increases in summer temperatures here in the heartland of the nation. In a contradiction, the data Dr. Roy Spencer has compiled shows that so far the trend has not developed. You can see how the models predictions in red and green, are much greater than the actual observations NOAA recorded. Since 1970 summer temperature departures have only gone up 0.4 degrees with the the models anticipating a range of 1.6 to 2.4 degrees.
Overall, what has increased is corn yields which have continued to trend higher thanks to improved hybrids, farming practices, increased CO2 and mostly good growingl weather. Dips have occured from major droughts such as occurred in 2012 and parts of 2013. Yields in excessive flooding years like 1993 and to some degree 2019 also tend to be below trend line.
Here are the summer rainfall totals since 1993 in Cedar Rapids and the Quad Cities. While temperature trends have been fairly constant precipitation shows much more year to year variability.
Speaking of variability, these are the precipitation departures since June 1st. It's been feast or famine around the central Midwest. The graphic shows nearly a 10" difference in departures between Ames and Waterloo, Iowa since June 1st, a distance of 75 miles as the crow flies.
In fact, after a very wet April and early May in northern Illinois, much of that state is now experiencing abnormally dry conditions. Western Iowa is also in on the dry soil conditions which have grown worse since the report was issued June 30th
Prospects for rain of a more widespread nature will go up over my area Thursday but not before another steamy day Wednesday. Highs near 90 and dew points in the mid to upper 70s will create a very tropical environment. The NWS has issued a heat advisory for much of my are Wednesday for the combination of heat and humidity that will make if feel close to 100 degrees from 11:00 AM through the early evening..
Thursday a slow moving cool front will cut into the instability generating showers and thunderstorms that will end in the north Thursday night and in the south Friday morning. As has been the case this severe weather season, vertical shear is meager which keeps the threat of severe storms low. A few downbursts are possible but the primary concern looks to be spotty locally heavy rains. Storm movement should be relatively slow and water vapor gets into the 1.5 to 2.00 inch range. That should produce some good downpours in the spots where the stronger updrafts occur.
The Storm Prediction Center has a slight risk outlook for a few strong storms Thursday.
The GFS and EURO show this for total rain through Friday.
Following the front, temperatures and dew points will lower significantly to more tolerable levels for the coming weekend. Hopefully the rains fall where they are needed most. Stay cool my friends "a motto I adhere to at all times" Roll weather...TS