textproduct: Central Illinois

KEY MESSAGES

- A Flood Watch continues until 4 am cdt over central IL where moderate to locally heavy rain is possible early this morning east of I-55.

- Breezy northwest winds gusting up to around 30 mph today and Sunday will bring in much cooler air to the area this weekend. Lows in the 30s tonight and Sunday night will likely result in frost development during the overnight and early morning hours over central IL. Some areas from I-74 northeast could even get to near freezing Sunday night.

DISCUSSION

Issued at 330 AM CDT Sat Apr 18 2026

A major severe weather event affected central and northern IL from I-72 north Fri afternoon/evening with several reports of damaging winds, large hail along with several tornadoes. At least 7 confirmed tornadoes in central IL so far, over Fulton, Mason, Tazewell, Logan, McLean and Champaign counties. Bloomington/Normal had a lot of wind damage reports including some structural damage. Three survey teams will be conducted today in central IL. The storms weakened during late Fri evening with outflow boundary from the storms passing just southeast of Lawrence county. The cold front had just passed east of I-55 with widespread moderate showers and isolated thunderstorms from I-55 east. Between 1-2 inches of rain had fallen over much of the IL river valley and 1 inch or more of rain as far east as Springfield and Lincoln. Springfield set a daily rainfall record of 1.36 inches on Fri/Apr 17th beating the 1.13 inches set in 1912. We will allow the flood watch to expire at 4 am over central IL as the heaviest rainfall with thunderstorms appears to be ending in east central IL.

The cold front just east of I-55 will sweep through eastcentral and se IL by mid morning (14Z/9 am) with showers diminishing from east of I-55 during this morning. Clouds to decrease over the IL river valley during mid/late morning and over the rest of central and se IL during this afternoon as skies become mostly sunny. Breezy nw winds will gust to around 30 mph today bringing in much cooler temperatures today. Temps have fallen into the mid to upper 40s west of I-55 while milder temps still in the 60s in southeast IL ahead of the front. Temps should mostly be in the low to mid 50s much of this afternoon, mildest in southeast IL.

The next forecast concern will be frost and freeze potential over CWA overnight and Sunday night. High pressure over the central Rockies to ridge into the Ozarks and mid MS river valley by dawn Sunday. Breezy nw winds at sunset to diminish during the evening and veer WSW overnight. Lows overnight in the mid to upper 30s, coldest from Macomb to Bloomington north where frost more likely to develop during overnight and early Sunday morning. But there may be enough wind to keep the frost from getting as widespread and held off on issuing a frost advisory overnight, but may need to readdress this especially for northern CWA if wind gets lighter.

Another cold front drops southward over IL during Sunday with some increase in clouds as skies become partly sunny and breezy nw winds gusting around 30 mph by Sunday afternoon. Highs Sunday in the upper 50s/lower 60s and coolest from I-74 northeast. Canadian high pressure over the central Canadian Prairies drops down into southern Lake MI by dawn Monday and to bring clear skies and lighter winds. Feel Sunday night will have more widespread frost over central IL and maybe even temps near freezing from I-74 northeast. We will likely need a frost advisory overnight Sunday night and early Mon morning and maybe even a freeze warning over ne CWA.

Ample sunshine Monday with south winds 5-10 mph by Monday afternoon. Highs Monday in the upper 50s/lower 60s and mildest in southeast IL and western CWA. Southerly flow Monday night to keep it from getting as cold as warm front lifts east of IL by late Mon night as high pressure builds into New England and the mid Atlantic States. More seasonable lows in the mid to upper 40s Mon night.Warmer on Tue with breezy sw winds gusting 25-30 mph and highs in the mid to upper 70s with partly to mostly sunny skies.

We have some slight chances of convection Tue night into Wed as a cold front drops down across northern IL overnight Tue night into early Wed morning. Though moisture and lift is limited with this boundary so most areas will likely stay dry. Mild highs Wed in the upper 70s to near 80F and lighter west to sw winds 5-10 mph with partly to mostly sunny skies. So overall a pretty nice day expected on Wednesday. Forecast models show a stronger storm system moving into the MS river valley Thu night and Fri bringing the next best chance of showers and thunderstorms. Warm highs in the lower 80s Thu with breezy SSW winds gusting 25-30 mph. Highs in the 70s Fri and cooling into the 60s next Saturday with a 20-30% chance of lingering showers per NBM/WPC. Though GEM and Ecmwf models are much wetter over IL next Saturday while GFS model is drier.

The Climate Prediction Center (CPC) 6-10 Day Outlook for Apr 23-27th has a 50-60% chance of above normal temperatures over central and southeast IL, and a 40-45% chance of above normal precipitation.

AVIATION /12Z TAFS THROUGH 12Z SUNDAY/

Issued at 616 AM CDT Sat Apr 18 2026

A cold front has pushed through the region. Any lingering rain and MVFR ceilings associated with the front should clear the area by mid morning with VFR conditions expected to prevail the remainder of the period. Gusty NW winds will be in place through the day with gusts in the 20-30 kt range, peaking this afternoon and early evening. Winds will drop off after sunset this evening and gradually back to the SW late in the period.

ILX WATCHES/WARNINGS/ADVISORIES

None.