A weakening band of showers and thunderstorms will roll through the area near or just before sunrise. These storms will be capable of some gusty winds, brief downpours and lightning. However, they will also be fading/weakening as they move through so severe weather is not a big concern with the morning activity.
However, new storms will start to ramp up along and southeast of I-44 in Missouri, up into the metro St. Louis area by early afternoon and increase in coverage and intensity as they move to the east and northeast during the afternoon. These storms will have the potential to produce strong winds, large hail and possibly a couple of tornadoes, especially in areas southeast of St. Louis.
The region of greatest concern for severe weather (and especially tornadoes) will be along and east of Hwy 67 in Missouri up into metro St. Louis, especially metro east and then along and southeast of I-55 in Illinois.
Timing for this severe threat will be after 2 p.m. and lasting through sunset. It is important to note that if the morning rain lingers longer than expected that could help mitigate this severe threat somewhat but I will not have a good handle on that until at least mid-morning.
In addition to the potential for severe weather, these storms will be efficient rain producers and heavy rain is likely in many spots, even for those that do not see severe storms.
Rainfall totals by late Wednesday evening will range from 1-3" across the viewing area, with a few spots possibly reaching 4".