textproduct: Central Illinois

KEY MESSAGES

- A dangerous severe weather outbreak is projected for for central IL today, capable of strong/intense tornadoes (EF2-EF3+ damage), damaging wind gusts of 75+ mph, and 2+ inch hail.

- Heavy rainfall rates will create a risk of localized flash flooding today. There is a Flood Watch out for the areas along and north of a Fulton County to McLean County line from 7am to 10pm.

- Strong, non-convective gradient winds are anticipated this afternoon, with widespread southwest gusts near 50 mph, particularly for areas near and south of I-72. A Wind Advisory will be in effect from 12pm to 7pm.

DISCUSSION

Issued at 307 AM CDT Wed Jun 17 2026

Bottom Line Up Front: Stay weather aware all day long today and know where your safest shelter is when/if a warning is issued for your location today. An outbreak of severe weather is expected later today.

SPC has maintained a moderate risk (level 4 of 5) with an enhanced risk (level 3 of 5) over (basically) the rest of the forecast area. A warm front will push north, lifting better moisture (dewpoints in the 70s and PWATS ~2 inches) into central and southeastern IL. A morning round of convection will travel along and north of the warm front associated with the strong LLJ this morning. If a supercell can latch onto the warm front, tornadoes can be possible. Otherwise, large hail and damaging winds are the concern for the morning round. This round will enter the northern part of the forecast area by 13z (8am) and will travel east across the state. There is some uncertainty of how far south that area of storms will make it but some guidance is now suggesting as far south as I-70. There is some overlap in timing with the afternoon "big show". The early round will be exiting the east/southeast counties by ~20z (4pm), which is about the time the line of storms will be developing in western IL.

Some uncertainty on how far north the warm front will get still exists. Guidance is still showing it lifting somewhere between I-74 and I-80. If the warm front doesn't get as far north as I-80, then the moderate risk threat could possibly be pushed further south for the cold frontal passage and associated thunderstorms in the afternoon from 20z-05z (3pm-12am). The environment will be very volatile and capable of strong/intense tornadoes (EF2-EF3+ damage), damaging wind gusts of 75+ mph, and 2+ inch hail. CAPE values 2000- 3000 J/kg, insane amount of effective bulk shear values (60-70 knots), and SRH 0-1 km of ~250-450 m2/s2. Mid level lapse rates are more than sufficient for large to very large hail (7.6-8.1 C/km). Supercells are the expected mode through most of the event this afternoon into evening, but may begin to evolve into a fast moving linear system as it nears exiting the southeastern counties. The supercells have the perfect environment to be long-lived. These storms are going to be moving very fast, with storm motions nearly due east at 50-60 knots.

WPC has kept an excessive rainfall high-end slight risk for central and southeastern IL today, but our northern most counties have been clipped by the moderate risk area. PWATs of 1.8-2.1 inches are forecast. The storms today would likely have torrential rain within them, but will be moving fairly fast, which would hopefully help curb the flooding threat for most places. With many rivers/streams already at or near flood and saturated soils, flooding could become a concern through the event. There is a Flood Watch out for the areas along and north of a Fulton County to McLean County line from 12z to 03z (7am-10pm) today. Remember, turn around, don't drown!

Outside of the severe weather today, there are very strong winds associated with this system. There is a Wind Advisory in place from Schuyler County to Vermilion County from 18z to 00z (1pm-7pm) today. Southerly winds will gust to 35-45 mph during that time.

After today, it looks like we get two days of a break. Friday and Saturday appear to be pleasant with highs in the upper 70s to mid 80s and plenty of sunshine. Additional rain chances return to the forecast for Sunday into Monday.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 609 AM CDT Wed Jun 17 2026

VFR conditions will prevail at all sites for the start. However, two rounds of showers/storms will move across each site next 16hrs. First round will be in morning and will have TEMPO at at all sites and MVFR ceilings within the TEMPO group. Vis will be around 3sm. After a brief break in the afternoon, the second around moves through all sites in the afternoon to early evening. Will have TEMPO group for all sites and MVFR ceilings and vis for when storms move through. After line of storms moves through, ceilings should return to VFR.

Winds will become southeasterly this morning with gusts of 20-25kts. Afternoon winds become southwesterly with gusts pushing 35-40kts at all sites. Once storms and front moves through, winds become westerly with gusts around 20-25kts.

ILX WATCHES/WARNINGS/ADVISORIES

Flood Watch through this evening for ILZ027>031-036>038. Wind Advisory from 1 PM this afternoon to 7 PM CDT this evening for ILZ040>057-061>063-066>068-071>073.