textproduct: Central Illinois

KEY MESSAGES

- There is a Marginal Risk (level 1 of 5) for severe weather along and east of I-57 this afternoon with a Slight Risk (level 2 of 5) now over the Wabash river valley.

- Blustery and colder conditions are expected for Thursday and Friday as high temperatures dip below normal into the 40s.

DISCUSSION

Issued at 230 PM CST Wed Nov 11 2026

At 20Z/2 pm, a deepening 1006 mb low pressure was near Clinton IL in DeWitt county with cold front passing east of I-55 early this afternoon. Temperatures had warmed into the upper 60s/lower 70s in eastern IL ahead of the cold front. Models continue to show some increase in moisture from the sw with steepening lapse rates with cold air aloft arriving with approaching upper level trof. SB CAPEs increase to 600-1100 J/kg in eastern IL during this afternoon while effective wind shear values are 25-35 kts in eastern IL and get to 35-50 kts in southern/se IL into western KY, just south of CWA. Higher storm relative helicities of 100-150 m2/s2 are over the Wabash river valley and eastward into IN where marginal risk of tornadoes are. SPC continues a marginal risk of severe storms 5-15% large hail and damaging winds in eastern IL mainly east of I-57, and upgraded the Wabash river valley to a slight risk over much of Lawrence and eastern parts of Clark and Crawford counties through 6 pm where 15% risk of large hail and damaging winds. SPC has a 2% to less than 5% risk of tornadoes near the Wabash river valley. See SPC recent mesoscale discussion Number 2449 for eastern IL for further details.

Low pressure to continue to deepen as it tracks quickly ESE into west central IN by mid evening and into sw Ohio by midnight. As the low deepens and tracks into the Ohio River Valley, winds will become breezy north to NW and bring in much colder temperatures next few days. Lows overnight in the upper 30s and lower 40s coolest nw CWA. A 2nd strong northern stream short wave trough over central Ontario Province will drop southward across the central Great Lakes and Ohio Valley on Thu and will keep more low clouds around along with isolated to scattered showers especially in eastern IL on Thu. Band of lake enhanced showers off Lake Michigan late Thu and Thu night to mostly be ne of CWA, but may affect far ne Vermilion county by Hoopeston where even snowflakes possible. Brisk NNW winds gusting 20-30 mph Thu (NBM has 20-30% chance of gust over 30 mph especially from Lincoln northeast). High temperatures Thu in the mid to upper 40s central IL and lower 50s in southeast IL and only in the low to mid 40s Friday (likely the coldest day of the season so far) despite partly to mostly sunny skies Friday. The brisk winds will make it feel colder both Thursday and Friday. Lows Thu night in the upper 20s/lower 30s, coldest in western CWA. Widespread hard freeze expected over CWA during Friday and Sat nights with lows in the mid 20s (even lower 20s western CWA Friday night). Still chilly Saturday with highs in the mid to upper 40s.

The seasonably cool weather likely lingers early next week with highs in the upper 40s/lower 50s Sunday and Monday as dry weather prevails. Large mid/upper level trof over the Eastern US late this week gradually shift away from IL during early next week with weak upper level ridging into the MS river valley and Eastern Plains. Surface high pressure of 1030-1034 mb to settle near IL by Monday and shift into the mid Atlantic States by middle of next week. Temperatures to slowly moderate back to near or slightly above normal in the middle to upper 50s by next Wednesday, and near 60F next Thursday.

AVIATION /18Z TAFS THROUGH 18Z THURSDAY/

Issued at 1150 AM CST Wed Nov 11 2026

1009 mb low pressure near PIA will continue to deepen as it tracks ESE into west central IN by early evening as associated short wave trof tracks quickly from NW IL at midday into Indiana by mid evening. This will bring isolated to scattered convection to areas mainly east of PIA and SPI into mid afternoon, especially at BMI and CMI with MVFR visibilities and ceilings possible. A period of MVFR ceilings also possible at PIA and SPI outside the convection. Will need to watch for possible stronger winds with convection at CMI which is in the marginal risk of severe storms during mid/late afternoon. MVFR ceilings will be most likely in eastern terminals this evening then MVFR ceilings possible across area on Thu morning as next strong short wave trof digs into central IL from lower MI. Added VCSH after 13-14Z Thu over eastern airports (BMI, DEC and CMI). Winds have recently shifts to NW at PIA while south to SW winds near 10 kts early this afternoon over rest of central IL airports to shift north to NW during the afternoon and increase to 12-17 kts with gusts 20-25 kts. Winds veer more NW and temporarily weaken to around 10 kts later this evening and overnight before increasing to 12-18 kts and gusts 18-27 kts after 14Z Thu.

ILX WATCHES/WARNINGS/ADVISORIES

None.