textproduct: Central Illinois

KEY MESSAGES

- Areas of fog, with a few spots having visibilities of a mile or less, will continue to lift over portions of central IL late this morning. More fog will likely re-develop across central IL tonight as a warm front approaches from the south. There is a 50-80% chance that visibilities will once again drop below 1 mile.

- After a windy and warm day with highs well into the 70s on Friday, a cold front will trigger a broken line of thunderstorms Friday night. There is a Slight Risk (15-30% chance) of severe weather...with the primary risk being damaging wind gusts.

UPDATE

Issued at 1055 AM CST Thu Mar 5 2026

We allowed the Flood Watch in southeast IL to expire at 9 am. Between 1 and 2 inches of rain fell in past 24 hours from I-70 south causing flood warnings on the Little Wabash river at Clay City (already in flood) and Embarras river at Lawrenceville (forecast to reach flood stage by mid afternoon). Scattered showers lingered along and southeast of a Louisville to Robinson line at late morning and lifting northeast. The HRRR shows isolated to scattered showers persisting into this afternoon in east central and southeast IL, mainly east of I-57 with an isolated thunderstorm possible in southeast IL. This in response to a frontal boundary from Danville to Charleston to west of Effingham that pushes into southern IL during this afternoon. SPC day1 outlook keeps marginal risk of severe storms se of IL over KY, southern Ohio and WV for 5% risk of damaging winds. A larger marginal risk area this afternoon and tonight is west of IL over nw MO into central and sw Iowa.

Allowed the Dense Fog Advisory to expire at 9 am from I-72 north, but issued a special weather statement for areas of fog lingering until noon especially from I-55 nw. But CAMS show widespread fog developing during tonight from the IL river to I-70 and gradually shifting northward late tonight into mid Friday morning as pressure gradient increases with passage of warm front. This warm front could be accompanied by a scattered to broken band of showers and thunderstorms lifting ne over CWA overnight into mid Friday morning.

Highs today range from upper 50s north of I-72 and mid to upper 60s in southeast IL which stays in warm sector longer today. Should see some breaks in low clouds develop during this afternoon especially north of I-72.

07

LONG TERM

(Saturday through Wednesday) Issued at 354 AM CST Thu Mar 5 2026

The cold front will work its way across central Illinois Saturday morning, followed by a return to dry and slightly cooler weather for Saturday afternoon and Sunday. After chilly morning lows in the 30s, the dry Pacific-origin airmass will heat sufficiently to produce Sunday afternoon highs in the upper 50s and lower 60s. After that, warmer conditions will return early next week thanks to southwesterly flow. Highs will climb back into the 70s on Monday and Tuesday...and rain chances will return as well. While there are still some timing discrepancies among the synoptic models at that range, consensus points to Monday night through Wednesday morning as the wettest period as another storm system traverses the region.

Barnes

AVIATION

(For the 12z TAFs through 12z Friday Morning) Issued at 543 AM CST Thu Mar 5 2026

IFR ceilings/visbys will persist at the central Illinois terminals through midday. 1/4 to 1/2 mile fog will continue through 15z before gradually improving and becoming unrestricted by 18z/19z. While the fog will eventually clear, the low clouds will not. Forecast soundings suggest ceilings may rise to MVFR late this afternoon into early evening before once again lowering to IFR after dark. Given ample low-level moisture and only light E/SE winds developing ahead of a slowly approaching warm front, fog will re-develop tonight. CAMs vary on the exact timing and how low visbys will become, but the synoptic pattern suggests another foggy night. Have lowered all sites to 1 mile after 05z/06z accordingly, but these may need to be adjusted down if trends persist.

Barnes

ILX WATCHES/WARNINGS/ADVISORIES

None.