Southern IL Forecast

Headlines heading into the weekend remain the same – rain. We’ve had some scattered shower activity across parts of southern IL this afternoon but activity will continue to increase in coverage, especially as we head into Friday afternoon/evening as a warm front reinforces and further destabilizes the column. Lack of instability will preclude the severe weather risk but hearing some rumbles of thunder shouldn’t be a surprise. In terms of precipitation totals, I think 0.75-1.25″ is a good widespread rainfall total for the region with the highest totals falling in the northeast section of southern IL tapering off to the southwest as outlined in the image above. In the circled region, a general precipitation minimum may occur with totals ranging from 0.4-0.75″. These finer details will be ironed out once we get a better handle on where exactly boundary sets up so expect some slight adjustments to general forecast track and totals as we move forward. 

Canadian depition of warm front location Saturday showing sharp temperature gradient from generally north to south.
NAM depiction of warm front location Saturday showing sharp temperature gradient from generally north to south.

Friday – Highs area-wide should hover with a degree or two of 50F. Scattered shower activity will exist throughout the day with widespread activity developing in the evening to overnight hours. Overnight lows should fall into the low-mid 40s.

Saturday – Highs will range from near 50F to 62F (potentially mid 60s) depending on where the warm front resides Saturday. It looks to setup just south of Mt. Vernon so areas south of the Warm front will see upper 50s to low 60s and locations north will only rise into the low 50s (as seen on the graphics above) Showers are likely throughout the day and will begin tapering off in the evening/overnight hours.

Sunday – After the warm front sinks south of the IL overnight Saturday, temperatures should be consistent area-wide with highs in the lower 50s. It will be dry though!