717
FXUS63 KILX 101740
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1240 PM CDT THU SEP 10 2026
KEY MESSAGES
- SCATTERED RAIN SHOWERS ACROSS CENTRAL AND SOUTHEAST ILLINOIS
WILL DIMINISH LATE THIS AFTERNOON.
- UNSEASONABLY WARM CONDITIONS RETURN SATURDAY THROUGH TUESDAY,
SENDING AFTERNOON TEMPERATURES INTO THE UPPER 80S AND LOWER
90S.
DISCUSSION
ISSUED AT 1240 PM CDT THU SEP 10 2026
A SHORTWAVE TROUGH AND ASSOCIATED FRONTAL BOUNDARY CURRENTLY
TRAVERSING THE AREA HAS BROUGHT WIDESPREAD RAIN SHOWERS TO
CENTRAL AND SOUTHEAST ILLINOIS THROUGH MIDDAY. SYNOPTIC SCALE
ASCENT HAS WEAKENED OVER THE PAST FEW HOURS AND THIS TREND IS
EXPECTED TO CONTINUE, CAUSING THE SHOWERS TO SCATTER OUT AND
EVENTUALLY DIMINISH BY EARLY EVENING OVER SOUTHEAST IL.
SINKING MOTION AND SURFACE HIGH PRESSURE BUILDING ACROSS THE
GREAT LAKES WILL PROMOTE CLEARING SKIES TONIGHT AND FRIDAY
MORNING. HIGH TEMPERATURES ON FRIDAY REBOUND INTO THE LOWER TO
MID 80S AS BROAD SOUTHEASTERLY FLOW RESUMES.
TWO LOW CHANCES OF RAIN DEVELOP FOR LATE FRIDAY THROUGH
SUNDAY. THE FIRST IS ASSOCIATED WITH A WEAK UPPER WAVE PASSING
TO OUR SOUTH, WHICH COULD SPREAD SCATTERED SHOWERS AS FAR NORTH
AS SOUTHEAST TO EAST CENTRAL IL FRIDAY AFTERNOON AND FRIDAY
NIGHT. SEPARATELY, A FRONTAL BOUNDARY OVER THE UPPER MIDWEST
MAKES SOME PROGRESS SOUTHEAST ON SATURDAY NIGHT INTO SUNDAY,
AND THIS BRINGS LOW CHANCE POPS INTO THE WESTERN CWA.
HIGH CONFIDENCE RESIDES IN A SUBSTANTIAL WARMING TREND SATURDAY
THROUGH TUESDAY (SEP 12-15). AN UPPER-LEVEL RIDGE AMPLIFIES
ACROSS THE CENTRAL TO EASTERN CONUS, SUPPORTED BY STRONG
AGREEMENT BETWEEN DETERMINISTIC AND ENSEMBLE MEAN GUIDANCE. NBM
BLENDED GUIDANCE PROJECTS DAILY HIGH TEMPERATURES CLIMBING INTO
THE UPPER 80S TO LOWER 90S THROUGH THIS PERIOD. THE ECMWF
EXTREME FORECAST INDEX (EFI) HIGHLIGHTS MAXIMUM TEMPERATURE
VALUES RANGING FROM 0.70 TO 0.85 ACROSS CENTRAL ILLINOIS,
INDICATING CLIMATOLOGICALLY UNUSUAL WARMTH FOR MID- SEPTEMBER.
GUIDANCE SUPPORTS DEW POINTS GENERALLY IN THE 60S THOUGH THIS
STRETCH, WHICH WOULD KEEP DAILY PEAK HEAT INDICES BELOW 100
DEGREES.
THE NEXT CHANCE FOR APPRECIABLE RAIN HOLDS OFF UNTIL SOME POINT
NEXT WEEK WHEN THE NEXT COLD FRONT MOVES INTO THE MIDWEST.
THE GUIDANCE ENVELOPE SHOWS A LARGE SPREAD IN TIMING, WHICH IS
EXPECTED AS THE SYSTEM IS MOVING INTO A STRONG RIDGE. AS A
RESULT, NBM'S CHANCE TO LIKELY POPS STRETCH THROUGH MON-THU.
ML/AI SEVERE OUTLOOK PRODUCE SHOW A LOW (5%) RISK AREA CENTERED
AROUND TUESDAY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1240 PM CDT THU SEP 10 2026
SHRA AND VARIABLE CEILINGS ASSOCIATED WERE ASSOCIATED WITH A
FRONTAL BOUNDARY STRETCHED ACROSS CENTRAL IL AT MIDDAY. -SHRA
WILL DIMINISH THIS AFTERNOON ALONG WITH IMPROVING CEILINGS. DUE
TO THE MOIST GROUND AND LIGHT WINDS, ANOTHER ROUND OF REDUCED
CEILINGS AND VISIBILITIES IS LIKELY LATE TONIGHT, AT LEAST FOR
PARTS OF THE AREA LATE TONIGHT. CURRENT GUIDANCE SHOWS IFR
CONDITIONS MOST LIKELY AT KSPI WITH LOWER PROBABILITIES OF
REDUCED CATEGORIES FOR TERMINALS FARTHER NORTHEAST.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...25
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