As we go into this coming week, model guidance continues to remain quite consistent on the pattern growing more active across portions of the Midwest, including here in Illinois. This will be due to a trough establishing itself to the west with a strong upper ridge across the Midwest and eastern U.S. This then promotes warmer than normal temperatures across a good portion of the region along with favorable trajectories off the Gulf of Mexico for moisture to advect northward. Those downstate on the warm side of the frontal boundary will see both above normal temperatures and the potential for multiple waves of rain, leading to heavy rainfall totals this coming week.
Shown in the loop below is the available moisture content in the atmosphere and the higher the values, the more potential there is for the heavy rain to fall. The higher values initially are located well to the southwest but with the favorable wind pattern to the southwest across the southern plains, that higher moisture is able to advect northeast into the southern Midwest.
The brunt of expected waves of rainfall looks to be in the Tuesday night through Thursday night time-frame as things look now. As you can see in the loop below centered on those times, multiple waves of precipitation (in the form) of rain falls on portions of central and southern Illinois. Further north as mentioned in yesterdays article, northern Illinois could be cold enough for several chances of wintry precipitation.
We are still several days away from these rounds of potentially heavy rainfall but if we were to try to pin down the day for the heaviest rain, it currently looks like Thursday as there is good model agreement for the heaviest rain during that time-frame.
With all that has been mentioned above, the Weather Prediction Center is already forecasting a large area of 2-4" of rain between now and Friday, with the brunt of that expected in the Tuesday through Thursday night period. We will continue to send out updates regarding the heavy rainfall and potential flooding later this coming week.