textproduct: Central Illinois

KEY MESSAGES

- Scattered storms progress from west to east this morning, exiting eastern Illinois by midday. Isolated damaging wind gusts and small hail can't be ruled out.

- Temperatures start off in the 60s early this morning, but will cool during the day as a cold front moves through. Above normal temperatures are likely Sunday (60s) into early next week (70s).

- Another system arrives mid-week, bringing more beneficial rainfall Tuesday into Wednesday. There is a 60-80% chance of at least 1" of rain. Some of the storms could be strong to severe.

DISCUSSION

Issued at 107 AM CST Sat Mar 7 2026

*** SATURDAY ***

At 1230am/0630z Sat morning, a 1004-mb sfc low was analyzed near western WI, with a sharp cold front extending SW to near Des Moines, IA, and Kansas City, MO. Sfc obs capture a sharp temperature gradient, with areas just ahead of the front still in the mid 60s while areas behind the front have plunged into the mid 30s. Regional radar mosaics depict two corridors of rain/storms, one out ahead of the sfc front (extending from near Springfield, MO, to Galesburg, IL, to Milwaukee, WI, as of 1230am/0630z), and the other along the cold front.

While storms have generally been sub-severe over the last several hours, the KILX VWP is sampling a robust and strengthening LLJ with wind speeds approaching 70 kts at 1km AGL. Forecast soundings show a strong low-level warm nose in response to this LLJ, so storms are unlikely to be sfc-based overnight, but can't rule out downward transport of stronger winds to the sfc. There were reports of 50-60 mph winds in Moline, IL, as showers went through earlier, highlighting the potential to mix these stronger LLJ winds to the sfc.

CAMs suggest the western edge of precip activity pushing east of I- 55 by 6am/12z this morning, continuing to progress across eastern IL before departing to the east by 12pm/18z. The NAM suite still highlights modest MUCAPE values across eastern IL (around 1000 J/kg), and these areas were not worked over by Fri afternoon storms so this depiction seems plausible. Can't rule out some strengthening as scattered showers/storms track into eastern IL this morning, but the diurnal timing still appears unfavorable (most CAMs bring the leading edge of precip to the IL/IN border around 6am/12z).

As that strong front moves across the area, non-diurnal temp trends are likely. Highs will occur this morning when temps are still in the 60s across the warm sector, then falling temps are expected after the frontal passage. A sfc ridge axis will be draped from OK towards MI tonight, with cloud cover decreasing from northwest to southeast in time. Clear skies, weak winds, and the cooler post-frontal airmass should result in lows in the mid 30s across most of the forecast area. The exception is far eastern/southeastern IL, where the lingering cloud cover could keep lows near 40 degF.

*** SUNDAY INTO NEXT WEEK ***

The sfc high shifts east by Sun, reestablishing SW flow across the local area. Above normal temps persist, with highs likely to be in the 60s on Sun (60-90% chance, highest west of the IL River), then into the 70s for Mon-Tues. Moisture return will be slow at first, as Gulf moisture remains blocked by a cold front over the deep south. With dewpoints only in the 30s on Sun, may need to keep an eye on fire wx concerns. The concern is low at this point though, as gusts of 20-25 mph are fairly low, minimum RH values are above 30%, and fuel moisture may be higher after recent rains. The Gulf becomes unblocked early next week, with return flow pushing dewpoints into the 50s by Mon, and potentially into the 60s by Tues.

The cut-off low near the SW US remains progged to lift NE towards the plains by Tues, while a phased northern stream wave deepens to its north. These features favor strong synoptic scale ascent downstream, which in conjunction with the Gulf moisture advection set the stage for another round of widespread showers/storms from Tues eve into Wed. The severe storm potential will need to be monitored. The latest LREF Grand Ensemble has the joint probabilities of MUCAPE over 1000 J/kg and deep layer shear over 40 kts at 40-60%. Machine learning guidance sources broadly highlight the warm sector of this system as posing some degree of severe storm threat, but vary on the exact probabilities. At the least, this system should offer another chance for beneficial rainfall, with a 60-80% chance of at least 1" of rain per the NBM, and a 20-40% chance for over 2".

Following another cold front associated with this mid-week system, temps are expected to trend cooler for Thurs, with the ensemble interquartile range showing highs in the mid 40s to mid 50s.

Erwin

AVIATION

(For the 12z TAFs through 12z Sunday Morning) Issued at 519 AM CST Sat Mar 7 2026

Rain will come to an end from west to east this morning, followed shortly after by a cold front that shifts winds from southwesterly to northwesterly. A few rumbles of embedded thunder could still develop, but chances were too low to include in the TAF and observations across the region show decreasing lightning coverage upstream of the central IL terminals. Lower ceilings (primarily MVFR) will push in with the front and persist through the daytime hours. An hour or two of IFR ceilings can't be ruled out, with the best chance being at KPIA/KBMI, where a TEMPO group was included. Ceilings should return to VFR tonight, with cloud coverage thinning through the night.

Erwin

ILX WATCHES/WARNINGS/ADVISORIES

None.