017
FXUS63 KILX 040512
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1212 AM CDT FRI SEP 4 2026
KEY MESSAGES
- AN EXTREME HEAT WARNING REMAINS IN EFFECT AREAWIDE THROUGH
FRIDAY AND FOR PARTS OF THE AREA SATURDAY WITH DANGEROUS
HEAT INDEX VALUES BETWEEN 100 AND 109 DEGREES.
- THERE IS A VERY LOW CHANCE (10-15%) FOR AN ISOLATED SEVERE
THUNDERSTORM LATE THIS AFTERNOON AND EVENING AND AGAIN FRIDAY
AFTERNOON AND EVENING. THE PRIMARY THREAT WILL BE DAMAGING
WIND GUSTS. A MARGINAL SEVERE RISK LINGERS OVER PORTIONS OF
EAST CENTRAL ILLINOIS SATURDAY.
DISCUSSION
ISSUED AT 142 PM CDT THU SEP 3 2026
EXCESSIVE HEAT
A ROBUST 595 DAM 500MB RIDGE REMAINS ANCHORED OVER THE SOUTHERN
APPALACHIANS, WITH RIDGING EXTENDING ACROSS CENTRAL ILLINOIS
INTO THE UPPER MIDWEST. THE 12Z KILX SOUNDING SAMPLED 850MB
TEMPERATURES JUST ABOVE 22C, WELL ABOVE THE 90TH PERCENTILE
(18.6C) FOR EARLY SEPTEMBER CLIMATOLOGY. THIS PATTERN CONTINUES
TO DRIVE THE ONGOING HEAT WAVE, WITH HEAT INDICES CONSISTENTLY
RANGING BETWEEN 100-109F OVER THE PAST COUPLE DAYS. AN EXTREME
HEAT WARNING REMAINS IN EFFECT AREAWIDE THROUGH FRIDAY. MODEST
RELIEF IS EXPECTED BY SATURDAY AS THE UPPER RIDGE RETROGRADES,
THOUGH THE EXTREME HEAT WARNING WILL BE MAINTAINED FOR THE
SOUTHERN TIER OR TWO OF COUNTIES (ROUGHLY RUSHVILLE TO ROBINSON
SOUTH) WHERE PEAK INDICES WILL LINGER NEAR 105F.
CONVECTIVE RISK AND SEVERE POTENTIAL
THE REGION REMAINS ON THE PERIPHERY OF THE UPPER RIDGE, WHERE A
RING OF FIRE PATTERN PERSISTS. AN OUTFLOW BOUNDARY FROM EARLIER
CONVECTION ACROSS FAR NORTHERN ILLINOIS HAS DRIFTED INTO
PORTIONS OF CENTRAL ILLINOIS, POTENTIALLY FOCUSING ISOLATED
DEVELOPMENT LATE THIS AFTERNOON OR EVENING. WHILE A STOUT 650MB
WARM NOSE CURRENTLY ACTS AS A CAPPING MECHANISM, LOCALIZED
FORCING FROM THE OUTFLOW COULD ALLOW FOR CONVECTIVE INITIATION.
WHERE SURFACE-BASED INSTABILITY CAN OVERCOME THE CAP, PROGGED
MLCAPE VALUES OF 3000 J/KG AND DEEP-LAYER SHEAR OF 25-35KT COULD
SUPPORT ISOLATED SUPERCELL STRUCTURES, THOUGH WEAK LOW-LEVEL
SHEAR AND MARGINAL LCL HEIGHTS SUGGEST THE TORNADO THREAT
REMAINS NEGLIGIBLE.
HEADING INTO FRIDAY, THE FOCUS SHIFTS TO CONVECTIVE OUTFLOW
FROM AN MCS POTENTIALLY TRAVERSING THE UPPER MIDWEST INTO THE
SOUTHERN GREAT LAKES. SHOULD AN OUTFLOW BOUNDARY REACH THE LOCAL
AREA, PULSE-SEVERE STORMS ARE POSSIBLE IN AN ENVIRONMENT OF
HIGH INSTABILITY (>3000 J/KG) AND WEAK SHEAR (15-20KT), WITH
DAMAGING WIND GUSTS SERVING AS THE PRIMARY HAZARD.
EXTENDED OUTLOOK
A TRANSITION IN THE SYNOPTIC PATTERN IS ANTICIPATED THIS
WEEKEND AS THE UPPER RIDGE AXIS RETROGRADES TOWARD THE CENTRAL
GREAT PLAINS, AMPLIFYING AS AN UPPER TROUGH DIGS ACROSS THE
CANADIAN MARITIMES AND NEW ENGLAND FORMING AN OMEGA BLOCK. THIS
WILL SHIFT CENTRAL ILLINOIS INTO A NORTHWEST FLOW REGIME BY
EARLY THIS WEEKEND. AN 850MB BAROCLINIC ZONE WILL STRADDLE THE
REGION, WITH A BACKDOOR COLD FRONT PROVIDING A MODEST COOLING
TREND IN NORTHEAST ILLINOIS; TEMPERATURES WILL DROP FROM THE 90S
INTO THE MID-TO- UPPER 80S SUNDAY AND MONDAY FOR PARTS OF THE
AREA THAT SEE FRONTAL PASSAGE. FURTHER SOUTH, AN EXTREME HEAT
WARNING REMAINS IN EFFECT. THIS REPRIEVE IN OUR NORTHEAST
COUNTIES WILL BE SHORT-LIVED, HOWEVER, AS THE RIDGE AXIS BUILDS
BACK EAST EARLY NEXT WEEK, SUPPORTING A RETURN OF WIDESPREAD
90-DEGREE HEAT BY TUESDAY AND WEDNESDAY.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1211 AM CDT FRI SEP 4 2026
VFR CONDITIONS EXPECTED THE NEXT 24 HOURS, WITH MAINLY SOME
HIGHER BASED (6-7KFT) DIURNAL CUMULUS DEVELOPMENT TOWARD MIDDAY.
SOUTH WINDS WILL TREND MORE TOWARD THE WEST FOR A TIME LATE
MORNING INTO AFTERNOON.
CLIMATE
ISSUED AT 1211 AM CDT FRI SEP 4 2026
RECORD HIGH TEMPERATURES THROUGH SATURDAY:
LOCATION FRI 9/4 SAT 9/5
======== ======== ========
BLOOMINGTON 100/1925 103/1899
CHAMPAIGN 100/1954 102/1899
CHARLESTON 98/1925 102/1954
DANVILLE 101/1954 102/1954
DECATUR 103/1913 104/1954
JACKSONVILLE 103/1899 104/1899
LINCOLN 102/1954 103/1954
OLNEY 103/1954 106/1925
PARIS 104/1954 105/1954
PEORIA 98/2015 104/1899
SPRINGFIELD 100/1954 99/1954
ILX WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR
ILZ027>031-036>038-041>046-053>057-063.
EXTREME HEAT WARNING UNTIL 7 PM CDT SATURDAY FOR ILZ040-
047>052-061-062-066>068-071>073.
KEY MESSAGES...DEUBELBEISS
DISCUSSION...DEUBELBEISS
AVIATION...GEELHART
CLIMATE...GEELHART
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