759
FXUS63 KILX 161905
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
205 PM CDT WED SEP 16 2026
KEY MESSAGES
- A HEAT ADVISORY HAS BEEN ISSUED FOR AREAS SOUTH OF I-70
THROUGH THURSDAY, WITH AFTERNOON HEAT INDEX VALUES NEAR 105
DEGREES. WHILE HUMIDITY LEVELS DROP OFF A BIT LATE IN THE
WEEK, HIGHS IN THE 90S ARE LIKELY TO PREVAIL IN THIS AREA
THROUGH THE WEEKEND.
- AFTER HEAVY RAIN OCCURRED LAST NIGHT OVER THE NORTHERN PARTS
OF THE FORECAST AREA, POTENTIAL EXISTS FOR ADDITIONAL HEAVY
RAIN TONIGHT. WHILE THE GREATEST THREAT IS CLOSER TO I-80, A
FLOOD WATCH HAS BEEN ISSUED FOR KNOX, STARK AND MARSHALL
COUNTIES.
DISCUSSION
ISSUED AT 205 PM CDT WED SEP 16 2026
LATEST SURFACE MAP SHOWS THE FRONT DRAPED JUST NORTH OF I-70. A
LARGE TEMPERATURE RANGE IS IN PLACE OVER THE FORECAST AREA EARLY
THIS AFTERNOON, RANGING FROM THE LOWER 70S NEAR GALESBURG, TO
THE MID 90S SOUTH OF I-70. CONVECTION HAS RECENTLY BEEN FIRING
SOUTH OF I-70, ALONG AN AXIS OF SBCAPE OVER 3000 J/KG, WHILE
SCATTERED SHOWERS PERSIST OVER THE NORTHERN THIRD OF THE
FORECAST AREA.
NOT A LOT OF MOVEMENT IS EXPECTED WITH THE FRONT THE NEXT FEW
DAYS, REMAINING DRAPED OVER CENTRAL ILLINOIS COURTESY OF A LARGE
UPPER HIGH OVER THE SOUTHEAST U.S. GULF MOISTURE HAS BEEN
FEEDING INTO THE MID MISSISSIPPI VALLEY DUE TO THE HIGH'S
CIRCULATION, AND UNSEASONABLY HIGH PRECIPITABLE WATER VALUES
OVER 2 INCHES WILL REMAIN POOLED JUST NORTH OF THE BOUNDARY. TWO
CONSEQUENCES OF THIS PATTERN: 1) UNSEASONABLY HOT WEATHER WITH
HIGHS IN THE 90S (MAINLY SOUTH OF I-70) CONTINUING INTO THE
WEEKEND, AND 2) POTENTIAL FOR ADDITIONAL HEAVY RAIN ACROSS
NORTHERN ILLINOIS TONIGHT.
- HEAT CONCERNS: A HEAT ADVISORY HAS BEEN ISSUED FOR AREAS
SOUTH OF I-70 THROUGH THURSDAY. DEW POINTS IN THE LOWER 70S
WILL RESULT IN HEAT INDICES APPROACHING 105 DEGREES BOTH THIS
AFTERNOON AND THURSDAY AFTERNOON. AS THE BOUNDARY SLIPS A
LITTLE FURTHER SOUTH THURSDAY NIGHT, SLIGHTLY LOWER
TEMPERATURES AND DEW POINTS SHOULD KEEP THE HEAT INDEX JUST
UNDER 100 DEGREES ON FRIDAY.
- RAIN CONCERNS: MORNING MODEL SUITE HAS BEEN ADVERTISING DEVELOPMENT
OF AN MCS ACROSS SOUTHEAST IOWA LATER THIS EVENING, TRACKING
EASTWARD ACROSS NORTHERN ILLINOIS OVERNIGHT INTO EARLY
THURSDAY. WITH THE EXCESSIVE PRECIPITABLE WATER VALUES AND
TRAINING STORMS, POTENTIAL FOR AREAS OF FLASH FLOODING IS
HIGH. HEAVY RAIN LAST NIGHT OF 2-4 INCHES FELL FROM THE
SOUTHEAST TIP OF IOWA TO NORTH OF PEORIA. WHILE THE CORE OF
THE HEAVIEST RAIN TONIGHT IS EXPECTED CLOSER TO I-80, A NUMBER
OF CAM'S DO SHOW STORMS POTENTIALLY TRACKING AS FAR SOUTH AS
I-74. HREF AND REFS LPMM BOTH SUGGEST AMOUNTS AROUND 2 INCHES
FROM GALESBURG TO LACON ARE NOT OUT OF THE QUESTION. THUS, A
FLOOD WATCH HAS BEEN ISSUED FOR KNOX, STARK AND MARSHALL
COUNTIES UNTIL 10 AM THURSDAY.
GOING FURTHER OUT IN TIME, WHILE THE FRONT BEGINS LIFTING BACK
NORTH AS A WARM FRONT FRIDAY NIGHT, THE BOUNDARY NEVER FULLY
EXITS THE REGION UNTIL EARLY NEXT WEEK. AT THAT POINT, A STRONG
SHORTWAVE OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY
SHOULD FINALLY KICK THE FRONT EASTWARD. UNTIL THEN, RAIN CHANCES
WILL PERSIST, WITH THE HIGHEST CHANCES FROM SATURDAY NIGHT INTO
SUNDAY NIGHT.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1201 PM CDT WED SEP 16 2026
IFR CEILINGS CONTINUE TO LIFT NORTH, WITH LOW MVFR EXPECTED AT
KPIA/KBMI FOR ANOTHER HOUR OR TWO. WHILE VFR CONDITIONS PREVAIL
INTO THE EVENING, SOME VISIBILITY RESTRICTIONS MAY BECOME AN
ISSUE AT THESE SITES, DEPENDING ON HOW MUCH CLEARING TAKES
PLACE. TOWARD DAYBREAK, CLUSTERS OF SHOWERS AND THUNDERSTORMS
MAY GRAZE THESE SITES AS WELL, THOUGH MOST WILL BE FURTHER
NORTH.
SOUTH OF THERE, CEILINGS HAVE LIFTED TO AROUND 7000 FEET OR
HIGHER, AND VFR CONDITIONS WILL PREVAIL THROUGH THURSDAY
MORNING.
ILX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM 10 PM CDT THIS EVENING THROUGH THURSDAY
MORNING FOR ILZ027-028-030.
HEAT ADVISORY UNTIL 7 PM CDT THURSDAY FOR ILZ066>068-071>073.
KEY MESSAGES...GEELHART
DISCUSSION...GEELHART
AVIATION...GEELHART
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