NWS Lincoln, IL -- SWOP event summary

March 31, 2023

Analysis from 8:30 am March 31^st shows a 995 mb low near the Iowa/Nebraska border with a warm front advancing to Illinois from the southwest. The low then deepened to 989 mb by 8:30 pm that same day. When the warm front passed through, the central Illinois region was in the warm sector of this system which brought the first round of severe weather in the early afternoon. Within the warm sector, the environment was energized and unstable. The surface-based CAPE was 1000+ J/kg with dewpoints near 60 degrees.

As the low passed to the northwest of Illinois, a strong cold front progressed through the area. The surface map below depicts the set up as of 8:30 pm as the storms were ongoing. As this cold front brought us a strong line of thunderstorms and a couple discrete supercells the surface-based CAPE was still over 1000 J/kg with dewpoints nearing 70 degrees and 63 knots of surface to 6 km winds shear which is extremely strong and energized. This line and the cells associated went on the produce several tornadoes, strong wind gusts in excess of 60 mph, and large hail. The high temperatures were in the 70s for central and southeastern Illinois with dewpoints in or near the 60s.

SURFACE WEATHER MAP 8:30PM CDT MAR 31

This system continued to produce very strong winds, hail, and several more tornadoes. Surveys are being done and as they are completed more storm reports will be sent out. This system spanned from northern Iowa/Illinois all the way down to mid-eastern Arkansas. Some of the reports from central Illinois were amazing. The report shown below was of baseball size hail near Banner, IL! Another report that was of interest was a measured 71 mph wind gust from Champaign airport.

SEVERE WEATHER REPORTS MARCH 31, 2023 (W=WIND, T=Tornado)

Rainfall from this system wasn’t as extreme as previous systems this month but it came down quickly and intensely due to the thunderstorms it was associated with. The image below depicts the rainfall amounts across central and southeastern Illinois.

RAINFALL MARCH 31, 2023