691
FXUS63 KILX 091722
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1222 PM CDT WED SEP 9 2026
KEY MESSAGES
- ISOLATED STRONG TO SEVERE THUNDERSTORMS SOUTH OF INTERSTATE 70
THIS AFTERNOON CARRY A RISK OF LOCALIZED DAMAGING WIND GUSTS.
- LOCALIZED HEAVY RAINFALL TONIGHT WILL YIELD POCKETS OF 1 TO 2
INCH TOTALS NEAR AND SOUTH OF I-70, LEADING TO POTENTIAL
PONDING IN LOW-LYING AREAS.
DISCUSSION
ISSUED AT 1222 PM CDT WED SEP 9 2026
REGIONAL RADAR MOSAIC INDICATES A BAND OF SHOWERS ALONG A
CONFLUENCE ZONE DISSIPATING AS IT TRACKS EAST NEAR I-55 EARLY
THIS AFTERNOON. AN OUTFLOW BOUNDARY WELL AHEAD OF THIS ACTIVITY
WAS TRACKING TOWARD SE IL, AND APPEARS TO BE THE FOCUS FOR
ISOLATED THUNDERSTORM DEVELOPMENT THIS AFTERNOON. THERMODYNAMIC
ANALYSIS INDICATES MLCAPE VALUES BUILDING TO AROUND 1000-1500
J/KG ACROSS SOUTHERN PORTIONS OF THE FORECAST AREA, PRIMARILY
NEAR AND SOUTH OF INTERSTATE 70. WEAK 0–6 KM BULK SHEAR AROUND
20-25 KNOTS WILL TEND TO LIMIT STORM ORGANIZATION, BUT STEEP
LOW- LEVEL LAPSE RATES DRIVING DCAPE NEAR 1000 J/KG WILL LEAD TO
PULSEY DOWNBURST WINDS IN ANY THUNDERSTORMS THAT MANAGE TO
DEVELOP MID- LATE AFTERNOON. THIS ACTIVITY SHOULD QUICKLY FADE
EARLY EVENING WITH DIMINISHING INSTABILITY.
MOISTURE TRANSPORT RAMPS UP AGAIN OVERNIGHT, AHEAD OF A
SHORTWAVE DIVING SOUTHEAST FROM THE PLAINS. PRECIPITABLE WATER
(PWAT) VALUES WILL CLIMB TO 1.8–2.0 INCHES ALONG AN ELEVATED
BOUNDARY STRETCHED WEST-EAST OVER CENTRAL IL, WELL ABOVE THE
90TH PERCENTILE FOR EARLY SEPTEMBER. HI-RES MODEL GUIDANCE
DEPICT CLUSTERED CONVECTIVE DEVELOPMENT TRACKING EASTWARD
LATE TONIGHT AND THURSDAY MORNING, MAINLY SOUTH OF THE I-72
CORRIDOR. PROBABILITIES FROM THE HREF REVEAL A 70 PERCENT CHANCE
OF RAINFALL EXCEEDING 1.0 INCH SOUTH OF THE I-70 CORRIDOR, WITH
LOCALIZED MAXIMA UP TO 2.0 INCHES ACROSS SOUTHEAST ILLINOIS BY
THURSDAY MORNING. PAVEMENT PONDING AND LOCALIZED NUISANCE URBAN
FLOODING WILL BE THE PRIMARY IMPACTS.
SHOWERS ARE EXPECTED TO DISSIPATE OVER THE SOUTH HALF OF THE
AREA THURSDAY MORNING. LIGHT WINDS WILL PREVAIL AS THE FRONTAL
ZONE SLOWLY SINKS SOUTH, LEADING TO ANOTHER DAY OF MODERATE
HUMIDITY LEVELS, ESPECIALLY SOUTH OF I-72. DRY AND MILD WEATHER
WILL DOMINATE FRIDAY AS HIGH PRESSURE BUILDS THROUGH THE
EASTERN GREAT LAKES.
ENSEMBLE GUIDANCE GENERALLY AGREES ON THE NEXT FRONT REACHING
CENTRAL IL THIS WEEKEND. UPPER LEVEL SUPPORT DOESN'T LOOK GREAT
AND WE APPEAR TO BE NEAR THE TAIL END OF THE FRONT, SO WE
MAINTAIN LOW CHANCE POPS FOR SATURDAY AND SATURDAY NIGHT.
TEMPERATURES WILL AVERAGE A BIT ABOVE NORMAL SAT-SUN WITH HIGHS
IN THE MID- UPPER 80S. A BUILDING UPPER- LEVEL RIDGE ACROSS THE
CENTRAL CONUS EARLY NEXT WEEK WILL FOSTER A FURTHER WARMING
TREND FOR MONDAY AND TUESDAY, PUSHING HIGH TEMPERATURES INTO THE
LOWER 90S. FURTHERMORE, THE CLIMATE PREDICTION CENTER (CPC)
6-10 DAY OUTLOOK INDICATES A 40 TO 70 PERCENT PROBABILITY OF
ABOVE-NORMAL TEMPERATURES ACROSS CENTRAL ILLINOIS THROUGH
SEPTEMBER 18TH.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1222 PM CDT WED SEP 9 2026
AN AREA OF -SHRA WAS DISSIPATING OVER CENTRAL IL AT MIDDAY, AND
WILL POSE NO AVIATION IMPACTS. THE NEXT ROUND OF -SHRA IS
FORECAST TO DEVELOP LATE TONIGHT, IMPACTING THE KSPI-KDEC-KCMI
CORRIDOR THROUGH THURSDAY MORNING WITH MVFR CEILINGS, AND AT
TIMES MVFR VISIBILITY. THERE IS AROUND A 30% CHANCE OF IFR
CEILINGS AT THESE TERMINALS, BUT KEPT THIS OUT OF THE FORECAST
FOR NOW AND WILL MONITOR TRENDS. FARTHER NORTH AT KPIA-KBMI,
MVFR CEILINGS ARE LIKELY 09-18Z. THESE SITES WILL BE NEAR THE
NORTH EDGE OF THE -SHRA, SO WENT WITH VCSH FOR NOW. WNW WINDS
NEAR/UNDER 10 KT THIS AFTERNOON WILL GO LIGHT AND VARIABLE
TONIGHT AND THURSDAY MORNING AS THE FRONTAL ZONE MOVES IN.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...25
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