393 FXUS63 KILX 130456 AFDILXArea Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 1156 PM CDT Fri Sep 12 2025
.KEY MESSAGES...
- An extended period of well above normal temperatures continues across central and southeast IL through next Friday with highs in the upper 80s to mid 90s expected through at least Thursday.
- Isolated showers and thunderstorms are possible north of I-74 overnight. There is a 20-40% chance of showers and thunderstorms thunderstorms northeast of a Peoria to Terre Haute line on Saturday and along and east of highway 51 during Saturday night. Otherwise much of area will see dry conditions into the middle of next week.
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.DISCUSSION... Issued at 245 PM CDT Fri Sep 12 2025
A warm front was over central Iowa and northeast MO, just sw of IL at mid afternoon. Partly to mostly sunny skies prevailed over central and southeast IL with more scattered cumulus clouds in eastern IL east of highway 51, along with some passing cirrus clouds. Warm temps were in the mid to upper 80s with Pittsfield 91F and Quincy 90F. Dewpoints were mostly in the 50s with dewpoints around 60F in west central IL and at Olney. PW values had risen to 1.2-1.4 inches in west central IL closer to approaching warm front. Nearest convection was over central IA and few isolated cells in north central MO.
Latest CAMs show most of convection tonight to be focused over the upper MS river valley on nose of low level jet as warm front lifts ne across central IL during late evening and overnight. But some CAM members like HRRR and FV3 show isolated convection dropping se toward I-74 late tonight. So added slight pops mainly after 2 am tonight north of I-74. CAMs have trended further south with a cluster of convection dropping SSE into northeast and east central IL on Sat morning as it weakens. Could see isolated convection develop along lingering outflow boundaries during Sat afternoon further south into central IL as MUCAPEs rise to 1500-3000 j/kg and 0-6 km bulk shear values are 25-30 kts in ne/eastern CWA. More clusters of convection projected to drop southward over IN and possibly into eastern IL, especially east of I-57 during Sat night especially overnight hours. SPC added marginal risk of severe storms for wind and hail ne of a Henry to Bloomington to Charleston line on Saturday and Sat night.
Lows overnight in the low to mid 60s with areas near the Indiana border around 60F. Highs Sat in the upper 80s and lower 90s, coolest ne CWA and warmest from Springfield SW where highs approaching 95F. Highs in the low to mid 90s on Sunday with mid 90s more common especially from I-57 west where more sunshine expected. Heat indices to peak around 100F Sunday afternoon over the IL river valley where dewpoints reach upper 60s to near 70F.
A strong subtropical upper level ridge extending from Texas into the central/eastern Plains will be over IL from this weekend into middle of next week, keeping it hot with highs in the low to mid 90s Mon through Wed and upper 80s/lower 90s Thu. Convection chances will be low Sunday through Wed night, with some uptick in convection chances Thu/Fri as upper level trof approaches from the west.
The Climate Prediction Center (CPC) 6-10 Day outlook for Sep 18-22 has 60-70% chance of above normal temperatures over central/se IL. CPC 8-14 Day Outlook for Sep 20-26 has 55-60% chance of above normal temps over central/southeast IL. So the late summer heat looks to continue for awhile.
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.AVIATION... (For the 06z TAFs through 06z Saturday Night) Issued at 1156 PM CDT Fri Sep 12 2025
VFR for most central IL terminals through the period with southeast to south winds near/under 10 kt. High resolution models show an area of thunderstorms developing over northern IL this morning, dropping southeast into east central IL this afternoon. Confidence on timing/placement of storms is low at this range, so went with PROB30 group for TSRA at KBMI-KCMI and will watch trends for refinement on later forecasts.
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.ILX WATCHES/WARNINGS/ADVISORIES... None. &&
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NWS ILX Office Area Forecast Discussion