815
FXUS63 KILX 061814
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
114 PM CDT THU AUG 6 2026
KEY MESSAGES
- BUILDING HEAT (SUNDAY–MONDAY): HIGHS IN THE UPPER 80S TO
LOWER 90S COMBINED WITH HIGH HUMIDITY WILL CREATE TRIPLE-DIGIT
HEAT INDEX VALUES. THERE IS A 40% CHANCE OF HEAT INDICES
REACHING OR EXCEEDING 100 DEGREES ACROSS PORTIONS OF THE LOWER
ILLINOIS RIVER VALLEY ON SUNDAY, EXPANDING TO AREAS SOUTH OF
CANTON TO CASEY ON MONDAY.
- STORM CHANCES: STORMS WILL BE POSSIBLE EACH NIGHT FRIDAY NIGHT
THROUGH MUCH OF NEXT WEEK. SATURDAY NIGHT INTO SUNDAY MORNING
CURRENTLY CARRIES THE HIGHEST LIKELIHOOD (60%) FOR WIDESPREAD
THUNDERSTORM ACTIVITY ACROSS CENTRAL ILLINOIS.
DISCUSSION
ISSUED AT 102 PM CDT THU AUG 6 2026
SHORT TERM (TODAY THROUGH TONIGHT)
AREA OBSERVATIONS AND SATELLITE IMAGERY REVEALS A BAGGY,
LOOSELY ORGANIZED TROUGH CENTERED OVER CENTRAL AND SOUTHERN
ILLINOIS THIS AFTERNOON. IN THE VICINITY OF THIS FEATURE, DEW
POINTS HAVE POOLED INTO THE LOWER 70S, WHICH, COMBINED WITH
TEMPERATURES IN THE UPPER 70S, IS CONTRIBUTING TO A MODESTLY
UNSTABLE ENVIRONMENT. RAP ANALYSIS INDICATES MLCAPE VALUES OF
1000-1500 J/KG WITHIN A WEAKLY SHEARED ENVIRONMENT (0-6KM SHEAR
OF 15-25 KT). FORCING REMAINS NEBULOUS THIS AFTERNOON, PRIMARILY
DRIVEN BY WEAK WARM AIR ADVECTION BUT THUNDERSTORM CHANCES ARE
TEMPERED BY LINGERING CONVECTIVE DEBRIS, LIMITING ACTIVITY TO
ISOLATED OR WIDELY SCATTERED (20-30% COVERAGE) SHOWERS AND
STORMS.
FORCING IS PROGGED TO INCREASE LATE THIS EVENING AND OVERNIGHT
AS A LOW-LEVEL JET (LLJ) STRENGTHENS ACROSS SOUTHEAST MISSOURI.
STRONG CONVERGENCE AT THE NOSE OF THE LLJ IS EXPECTED TO
MAXIMIZE NEAR THE I-72 CORRIDOR, RESULTING IN AN INCREASE IN
CONVECTIVE COVERAGE. WEAK CORFIDI VECTORS (BELOW 5-10 KT)
ORIENTED OUT OF THE NORTH SUGGEST THE POTENTIAL FOR BACKBUILDING
CELLS CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL. WHILE HREF
LPMM GUIDANCE INDICATES LOCALIZED TOTALS IN EXCESS OF 2-3
INCHES, LOW HREF PROBABILITIES (<15%) FOR EXCEEDING 2 INCHES
LEND LOWER CONFIDENCE IN WIDESPREAD FLASH FLOODING, AS TOTALS
SHOULD REMAIN BELOW 3-4 IN/6 HR FLASH FLOOD GUIDANCE.
LONG TERM (FRIDAY THROUGH NEXT WEEK)
THE UPPER-LEVEL PATTERN SHIFTS FRIDAY AS AN EXPANSIVE RIDGE
CENTERED NEAR THE FOUR CORNERS BUILDS INTO THE GREAT PLAINS. A
STALLED SURFACE FRONT OVER SOUTHERN ILLINOIS MAY SUPPORT
LINGERING MORNING SHOWERS, BUT THE TREND FOR CENTRAL ILLINOIS
HAS BEEN DRIER AS SURFACE RIDGING BUILDS IN FROM THE NORTH.
HIGHS WILL REACH THE MID-80S WITH DEW POINTS IN THE MID-70S
MAINTAINING A HUMID AIR MASS. HEAT WILL INTENSIFY THROUGH THE
WEEKEND IN RESPONSE TO THE EXPANDING UPPER RIDGE, WITH TRIPLE-
DIGIT HEAT INDICES POSSIBLE BY SUNDAY AND MONDAY AS TEMPERATURES
CLIMB INTO THE UPPER 80S TO LOWER 90S. THE CHANCE FOR REACHING
AND EXCEEDING 100F HEAT INDEX SUNDAY IS AROUND 40% ACROSS
PORTIONS OF THE LOWER ILLINOIS RIVER VALLEY (SOUTHWEST OF HAVANA
TO SPRINGFIELD) AND 40% SOUTH OF A CANTON TO CASEY LINE MONDAY.
A RING OF FIRE PATTERN WILL DOMINATE THIS WEEKEND THROUGH EARLY
NEXT WEEK, WITH NOCTURNAL MCS ACTIVITY RIDING THE PERIPHERY OF
THE RIDGE. WHILE THERE IS A CHANCE FOR STORMS IN THE FORECAST
EACH NIGHT, SATURDAY NIGHT APPEARS MOST FAVORABLE FOR WIDESPREAD
CONVECTION ACROSS CENTRAL ILLINOIS AS THE INSTABILITY GRADIENT
DRAPES OVERHEAD. BY MONDAY, THE RIDGE BEGINS TO BREAK DOWN,
ALLOWING AN EFFECTIVE FRONTAL BOUNDARY TO GRADUALLY SLIDE BACK
SOUTH THROUGH THE WEEK. THIS WILL INITIATE A GRADUAL COOLING
TREND, WITH HIGHS IN THE 90S MONDAY YIELDING TO THE MID-80S BY
THURSDAY AS POPS TREND SOUTHWARD WITH THE ADVANCING BOUNDARY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 100 PM CDT THU AUG 6 2026
A WEAKENING FRONTAL BOUNDARY OVER THE REGION WILL RESULT IN
LIGHT WINDS UNDER 10 KT THROUGH THE PERIOD. A FEW SPOTTY
(20-30% COVERAGE) SHOWERS AND STORMS ARE POSSIBLE THIS AFTERNOON
AND EVENING WITH CHANCES DIMINISHING FROM THE NORTH LATE TONIGHT.
SOME PATCHY FOG IS POSSIBLE LATE TONIGHT INTO FRIDAY MORNING,
ESPECIALLY NEAR THE I-74 CORRIDOR. MVFR CEILINGS MAY BRIEFLY
OCCUR FRIDAY MORNING AS DIURNAL CUMULUS DEVELOPS, BUT SHOULD
LIFT BACK TO VFR AROUND OR SHORTLY AFTER THE END OF THE CURRENT
VALID PERIOD.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...DEUBELBEISS
DISCUSSION...DEUBELBEISS
AVIATION...DEUBELBEISS
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