textproduct: Central Illinois

KEY MESSAGES

- Scattered showers and thunderstorms are expected through this evening, and into the overnight hours southeast of the IL river. Damaging winds, hail, heavy rains and localized flooding is in play today. A Flood Watch is posted until 1 am tonight from Fulton to Macon to Vermilion counties north where 1-2 inches and locally 2-4 inches of rain possible. - A persistent northwest flow will keep temperatures and humidity levels in check the next several days, with seasonable highs in the upper 70s to mid 80s.

DISCUSSION

Issued at 245 PM CDT Wed Aug 19 2026

We continued the Flood Watch through 1 am tonight from Fulton, Mason, Menard, Logan, Macon, Piatt, Champaign and Vermilion counties north. Some areas could see 1-2 inches of rain through early overnight in central IL with pockets of 2-4 inches possible. PWATs are in the 1.6-2 inch range over CWA (highest over southern CWA) and supports heavy rain threat next several hours. Parts of the flood watch area has already seen 5-10 inches of rain since last Sunday Aug 9th.

Radar mosaic shows a few cells developing along a frontal trof from southern Fulton county into central parts of McLean and Ford county. Had a recent report and photo of a funnel clouds in Bloomington and Galva (southern Henry county). Moderately unstable tropical airmass over CWA with SB CAPES of 2-3k j/kg, and highest over northern/nw CWa. The 0-6 km bulk shear values are at moderate levels too from 35-45 kts over CWA and highest over southern/sw CWA. A cold front over northern/nw IL will push se thru CWA during tonight, while an associated short wave trof over western Iowa tracks se through IL during tonight. This will interact with the tropical air mass to likely produce scattered showers and thunderstorms. SPC Day1 outlook has marginal risk of severe storms over CWA for large hail and damaging winds while tornado threat is over southern IL south of CWA though a few more funnels may occur along weak trof over northern CWA through 00Z/7 pm.

Quieter weather expected on Thursday and Thu night as cold front nearing the Ohio river by sunrise Thu pushes into central KY. Highs in the lower 80s Thu with dewpoints in the mid to upper 60s. A northern stream system approached IL on Friday bringing 20-40% chance of convection over northern cWA Fri afternoon and across central IL friday night especially Fri evening. SPC keeps severe risk west nw of IL on Fri with slight risk of Nebraska and northeast KS. Highs in the low to mid 80s Friday with dewpoints sneaking up into the upper 60s/lower 70s by Fri afternoon.

Fairly quiet weather this weekend into early next week with just slight pops at times while most areas should stay dry. Another cold front to sweep through IL early Saturday and bringing in less humid air during this weekend. Lows Saturday night in the lower 60s and lows in upper 50s to around 60F Sunday night making for more comfortable nights ahead. Highs Sat 80-85 (warmest in southeast IL) and upper 70s/lower 80s Sunday/Monday. Still pretty not much weather expected into middle of next week with some moderation of temperatures and dewpoints to more summerlike readings.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 1250 PM CDT Wed Aug 19 2026

Scattered convection is forecast to develop during mid/late afternoon and continue through this evening, and early overnight se of the IL River with MVFR conditions possible. There is also a chance of IFR condtions with thunderstorms with heavier rains later this afternoon into this evening. A weak east/west trof was just south of PIA and near BMI early this afternoon with east to NE winds near 5 kts north of this boundary and south to SW winds near 5 kts south of the boundary. Main cold front over northern IL to push southward into the IL river valley/PIA late afternoon and thru rest of central IL during this evening, keeping convection chances going for several hours. We have MVFR vsbys possible overnight into early Thu morning from patchy fog after the convection chances end. Winds to stay fairly light next 24 hours under 10 kts and veer NE during tonight into Thu morning.

ILX WATCHES/WARNINGS/ADVISORIES

Flood Watch until 1 AM CDT Thursday for ILZ027>031-036>038- 041>046-048-053.