464
FXUS63 KILX 011726
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1226 PM CDT TUE SEP 1 2026
KEY MESSAGES
- DANGEROUS HEAT WAVE CONTINUES: HIGHS REACHING THE MID-90S TO
NEAR 100 DEGREES WILL COMBINE WITH LINGERING HUMIDITY TO
PRODUCE HEAT INDEX VALUES OF 100 TO 105+ DEGREES THROUGH
SATURDAY. HIGHEST PROBABILITIES (40-80%) FOR TRIPLE-DIGIT HEAT
FOCUS SOUTH OF I-74 THROUGH WEDNESDAY.
- ISOLATED STORM THREAT: A LOW PROBABILITY (LESS THAN 20%)
EXISTS THURSDAY FOR AN ISOLATED POP-UP AFTERNOON OR EVENING
THUNDERSTORM. WHILE COVERAGE WILL BE SPARSE, STRONG
INSTABILITY COULD SUPPORT AN ISOLATED SEVERE STORM WITH
LOCALIZED WIND OR HAIL IMPACTS.
DISCUSSION
ISSUED AT 1223 PM CDT TUE SEP 1 2026
LATE SUMMER HEAT WAVE
UPPER-LEVEL RIDGING REMAINS DOMINANT ACROSS THE MIDWEST,
ANCHORED BY A ROBUST 596 DAM 500MB HIGH CENTERED OVER THE MID-
MISSISSIPPI AND TENNESSEE VALLEYS THROUGH WEDNESDAY. THIS RIDGE
AXIS IS PROGGED TO SHIFT TOWARD THE SOUTHEASTERN CONUS BY LATE
WEEK. AN 850MB THERMAL RIDGE CONTINUES TO RUN WELL ABOVE THE
90TH PERCENTILE; WITH A 12Z MORNING SOUNDING RECORDING 23C,
GUIDANCE CONTINUES TO ADVERTISE 23-26C TEMPERATURES OVER THE
REGION THROUGH SATURDAY.
SURFACE TEMPERATURES WILL REMAIN WELL ABOVE NORMAL THROUGH THE
WEEKEND. WHILE DEW POINTS ARE EXPECTED TO PERSIST IN THE UPPER
60S TO LOWER 70S, WE ARE SEEING A SEASONAL DECLINE IN LOW-LEVEL
MOISTURE CONTRIBUTION FROM EVAPOTRANSPIRATION. THIS REDUCTION,
COUPLED WITH DEEP MIXING INTO A DRIER COLUMN, WILL HELP KEEP DEW
POINTS SOMEWHAT IN CHECK, THOUGH TEMPERATURES HAVE A
SIGNIFICANT CHANCE OF REACHING THE 100-DEGREE MARK. NBM
PROBABILITIES FOR HITTING TRIPLE DIGITS ARE DECENT ACROSS
CENTRAL ILLINOIS SOUTH OF I-74 THROUGH SATURDAY, WITH THE
HIGHEST PROBABILITIES (40-80%) OCCURRING TODAY AND TOMORROW.
THESE PROBABILITIES LOWER SLIGHTLY THURSDAY THROUGH SATURDAY
(30-60%) FOR THE SOUTHWESTERN HALF OF THE CWA. DAILY HEAT
INDICES WILL GENERALLY RANGE FROM 100-105 DEGREES THROUGH
SATURDAY. A HEAT ADVISORY REMAINS IN EFFECT UNTIL THURSDAY AND
WILL LIKELY REQUIRE AN EXTENSION FOR AT LEAST PORTIONS OF
CENTRAL ILLINOIS.
CONVECTIVE CHANCES REMAIN LARGELY CONFINED TO NORTHERN ILLINOIS
AND THE GREAT LAKES, CLOSER TO THE JET STREAM, THROUGH THE
REMAINDER OF THE WORK WEEK. HOWEVER, AN ISOLATED
AFTERNOON/EVENING POP-UP STORM CANNOT BE RULED OUT AS SURFACE
TEMPERATURES APPROACH CONVECTIVE THRESHOLDS DAILY. GIVEN THE
LACK OF NOTABLE SYNOPTIC-SCALE FORCING, THE PROBABILITY REMAINS
LOW (LESS THAN 20%), THOUGH SOME CAMS, SUCH AS THE RRFS,
HIGHLIGHT THIS POTENTIAL. SHOULD DEVELOPMENT OCCUR, MLCAPE
VALUES OF 2000-2500 J/KG AND DEEP-LAYER SHEAR OF 25-30 KT
WEDNESDAY AND THURSDAY WOULD SUPPORT STRONGER STORM ACTIVITY.
SLOW PATTERN STARTING THIS WEEKEND
A CLOSED UPPER LOW NEAR HUDSON BAY WILL DIG TOWARD NEW ENGLAND
BY LATE WEEK INTO THE WEEKEND, CARVING OUT A DEEP LONGWAVE
TROUGH OVER THE EASTERN CONUS. THIS WILL SHUNT THE UPPER RIDGE
AXIS BACK WEST ACROSS THE CENTRAL GREAT PLAINS, TRANSITIONING
CENTRAL ILLINOIS INTO A NORTHWEST FLOW REGIME. AT THE SURFACE,
CANADIAN HIGH PRESSURE BUILDING ACROSS QUEBEC WILL DRIVE A
BACKDOOR COLD FRONT INTO ILLINOIS, SERVING AS THE FOCUS FOR
PRECIPITATION CHANCES OVER THE WEEKEND. TEMPERATURES WILL
MODERATE FROM THE 90S AHEAD OF THE FRONT TO THE LOWER-TO-MID 80S
IN ITS WAKE. THIS TRANSITION APPEARS SLOW, RESULTING IN A
TEMPERATURE GRADIENT FROM THE LOW 90S IN THE SOUTHERN COUNTIES
TO THE LOWER/MID 80S IN THE NORTHERN CWA BY EARLY NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1158 AM CDT TUE SEP 1 2026
CENTRAL ILLINOIS WILL REMAIN BETWEEN HIGH PRESSURE OVER THE
SOUTHEAST CONUS AND LOW PRESSURE TRACKING SLOWLY EAST ACROSS
ONTARIO RESULTING IN A MODEST SWERLY BREEZE. WINDS WILL PICK UP
INTO THE 8-12KT RANGE DURING THE DAYTIME HOURS, AND DROP OFF
BELOW 10 KT DURING THE NIGHTTIME HOURS. VFR CONDITIONS ARE
EXPECTED THROUGH THE PERIOD.
CLIMATE
ISSUED AT 440 PM CDT MON AUG 31 2026
RECORD HIGH TEMPERATURES THIS WEEK:
LOCATION TUE 9/1 WED 9/2 THU 9/3
======== ======== ======== ========
BLOOMINGTON 102/1894 101/2011 102/1913
CHAMPAIGN 102/2011 101/2011 99/2011
CHARLESTON 99/2011 103/1953 100/1925
DANVILLE 101/1953 101/1953 99/1913
DECATUR 102/1953 102/1953 102/1913
JACKSONVILLE 103/1913 103/2011 101/2011
LINCOLN 102/1953 101/1953 100/1913
OLNEY 105/1953 106/1953 105/1925
PARIS 101/1953 102/1953 101/1913
PEORIA 101/1913 100/1913 99/1913
SPRINGFIELD 102/2011 101/2011 100/2011
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 7 PM CDT THURSDAY FOR ILZ027>029-036-037-
040>044-047>056-061>063-066>068-071>073.
HEAT ADVISORY UNTIL 7 PM CDT THURSDAY FOR ILZ030-031-038-045-
046-057.
KEY MESSAGES...DEUBELBEISS
DISCUSSION...DEUBELBEISS
AVIATION...DEUBELBEISS
CLIMATE...07/GEELHART
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