FROM THE STOVE TO THE FRIDGE...
We've got some big changes coming on the thermometer in the next 24 hours, just in time for the official start of fall. Before I get to the potential of near record heat, a couple comments about the past weekend. First and foremost, a recap of the rains which in the SW half of my area were significant and beneficial from several rounds of storms both Saturday and Sunday. Here's the Doppler estimates of what fell. Many areas from I-80 south picked up 1-3" totals over the two day period. Even larger amounts were measured in a band from SE of Des Moines to roughly Ft. Madison.
Here's what fell in Sunday's storms.
The rains were a reason to celebrate from SC Iowa to WC Illinois, an area suffering from moderate to extreme drought conditions. Some places in the extreme drought category in southern Iowa saw more rain in 36 hours than they had in the previous 3 months.
Unfortunately, some of the downpours came with hail and high winds. Here's some storm reports compiled by the NWS around the central Midwest. There were 2 distinct bands of concentrated severe weather.
This radar image shows two clusters of severe storms rolling through parts of SE Iowa and WC Illinois around 9:15 Sunday evening (significant hail was found in both). Within the red rectangular box a tornado watch is in effect over southern Iowa.
That disturbance quickly departed Monday leaving sunshine and mild temperatures with highs of 80-84 degrees to start the week.
ONE DAY SHOT OF HEAT...
Tuesday a short lived burst of heat arrives on the scene allowing temperatures to reach 90 in much of the area, perhaps 94 in a few spots.
Readings that warm would be close to the records for the date.
RECORD HIGHS FOR TUESDAY SEPTEMBER 20th.
Burlington.........94 in 2018
Moline...............94 in 2017
Cedar Rapids...93, in1931
Making matters worse will be dew points that are likely to reach or top 70.
That's expected to create heat index values in the mid to upper 90s which will make for a very steamy September day, especially with winds only in the 5-15 mph range.
A capped atmosphere will allow abundant sunshine and no threat of storms despite some decent instability.
A BIG CHANGE TO FALL...
Tuesday night a potent cold front will dive into the region bringing with it a sharp change to cooler conditions by late Wednesday. Moisture is expected to be minimal so only a slight chance of rain is indicated with the frontal passage. If showers do develop they are likely to be post frontal, light in nature, and focused on the area south of I-80. Here's what models are suggesting for rain totals Tuesday night through Wednesday night.