Historically speaking, April is one of Illinois’ leading months for seeing severe weather including tornadoes, damaging winds, and large hail. While many Illinoisan’s are still wondering how and why 6″ of snow fell on April Fools Day, we’re focusing on the potential for a few severe storms to hit that very same area and points south and east Tuesday. We’re not looking for any major severe weather outbreak, but a fair amount of damage reports may accumulate by late tomorrow evening across mainly eastern and southeastern Illinois.
As shown above, we are looking at an elevated risk of severe thunderstorms for mainly a Robinson, Olney, and Carmi line and east into Indiana. Elevated thunderstorms overnight tonight may produce hail up to the size of quarters across central and southern Illinois, but the main severe weather risk would evolve from mid to late afternoon through the evening hours.
The main threat with any thunderstorms tomorrow will be the capability of near quarter sized hail. The main severe threat with any storms tomorrow will be winds of 60 to 65 MPH. Due to the proximity of the low pressure system as well as a warm front draped over the area, an isolated tornado is possible with any supercell that forms and/or associated with any notches in the QLCS that will likely develop along the cold front during the mid-evening.
Shown above is the projected radar image from the 18z 3km NAM around 3:00 P.M. tomorrow. This is only ONE possible scenario, but also one that I have fairly high confidence in. We see scattered convection across far south eastern Illinois into Indiana and our developing squall line across central and southwestern Illinois. Wind shear will be strong with this system, but instability is a bit lacking which will preclude a much large severe weather threat across the state. Nevertheless, plenty of MUCAPE exist with very steep mid level lapse rates, so any sustained updrafts will easily be capable of producing copious amounts of hail [some severe].
Bottom line is that tomorrow will be an active weather day across the region with a chance at some severe storms. These storms, again, will be confined mainly south of I-72 and east of I-57. A couple of weak tornadoes are POSSIBLE, several reports of hail LIKELY, and a few damaging winds report POSSIBLE. Stay tuned for further updates and possible warnings.