471
FXUS63 KILX 250543
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1243 AM CDT THU JUN 25 2026
KEY MESSAGES
- ISOLATED SEVERE STORMS THROUGH THURSDAY: SCATTERED
THUNDERSTORMS LATE THIS AFTERNOON THROUGH THURSDAY EVENING
BRING A THREAT OF ISOLATED DAMAGING WIND GUSTS AND LARGE HAIL.
THESE HAZARDS SHIFT FROM CENTRAL ILLINOIS TODAY TO AREAS
SOUTH OF INTERSTATE 70 ON THURSDAY.
- HEAVY RAINFALL AND FLOODING: MULTIPLE ROUNDS OF STORMS BRING A
HEAVY RAINFALL AND FLOOD THREAT FROM THURSDAY NIGHT THROUGH
FRIDAY NIGHT. THERE IS A 75% CHANCE THAT RAINFALL TOTALS WILL
EXCEED 2 INCHES FOR LOCATIONS SOUTH OF INTERSTATE 72.
- DANGEROUS HEAT NEXT WEEK: A PROLONGED PERIOD OF OPPRESSIVE
HEAT AND HUMIDITY BUILDS INTO THE REGION SUNDAY THROUGH
WEDNESDAY. HIGH CONFIDENCE EXISTS THAT DAILY HEAT INDEX VALUES
WILL CONSISTENTLY EXCEED 100 DEGREES ACROSS THE ENTIRE AREA.
DISCUSSION
ISSUED AT 1159 AM CDT WED JUN 24 2026
THROUGH TONIGHT: MARGINAL SEVERE RISK & CONVECTIVE TRENDS...
WATER VAPOR IMAGERY THIS AFTERNOON CAPTURES A COMPACT MID-LEVEL
SHORTWAVE TROUGH PIVOTING ACROSS THE UPPER MISSISSIPPI VALLEY,
FORCING AN ASSOCIATED COLD FRONT INTO CENTRAL WISCONSIN. FURTHER
SOUTH, SEVERAL SUBTLE SHORTWAVE IMPULSES EMBEDDED WITHIN BROAD
MERIDIONAL FLOW ARE TRACKING SOUTHEASTWARD TOWARD NORTHERN
ILLINOIS AND EASTERN IOWA. THIS COMBINED FORCING WILL GENERATE
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS THE LOCAL AREA FROM
LATE THIS AFTERNOON THROUGH THE EVENING HOURS.
THE OVERALL OUTLOOK FOR SEVERE WEATHER REMAINS MARGINAL (LEVEL
1 OF 5) DUE TO A FEW THERMODYNAMIC LIMITING FACTORS.
THERMODYNAMICS & INSTABILITY: BOUNDARY LAYER INSTABILITY WILL
PEAK LATE THIS AFTERNOON AS SURFACE TEMPERATURES CLIMB INTO THE
LOWER 80S OVER MID-60S DEWPOINTS. THIS WILL YIELD MLCAPE VALUES
OF 15002000 J/KG, EXTENDING AS FAR EAST AS THE INTERSTATE 55
CORRIDOR.
KINEMATICS: DEEP-LAYER SHEAR WILL SEE A MODEST INCREASE TO
AROUND 40 KNOTS (06 KM BULK SHEAR) AS A 500-MB JET CORE SKIRTS
THE REGION.
CAPPING & LAPSE RATES: UPDRAFT ACCELERATION WILL FACE HEADWINDS
FROM WEAK MID-LEVEL LAPSE RATES (6C/KM) AND A NOTABLE WARM
LAYER BELOW 500 MB SAMPLED BY THE 12Z ILX SOUNDING.
WHILE THE PRIMARY SYNOPTIC ASCENT AND HIGHEST STORM COVERAGE
WILL REMAIN FOCUSED TO OUR NORTH AND WEST IN CLOSER PROXIMITY TO
THE COLD FRONT, THERE IS SUFFICIENT MESOSCALE SUPPORT FOR A FEW
STRONG TO SEVERE CELLS LATE TODAY. ELONGATED AND SOMEWHAT WAVY
HODOGRAPHS SUGGEST MULTI-CELL STRUCTURES WITH ISOLATED DAMAGING
WIND GUSTS AND LARGE HAIL AS THE PRIMARY THREATS, WHILE THE
TORNADO THREAT REMAINS NEGLIGIBLE. VIGOROUS MULTI-CELL CLUSTERS
SHOULD BE MONITORED THROUGH MID-EVENING AS FAR SOUTH AS THE
INTERSTATE 72/DANVILLE CORRIDOR BEFORE NOCTURNAL STABILIZATION
SETS IN.
THURSDAY: FRONTAL PROGRESSION SHIFTS HAZARDS SOUTH...
OVERNIGHT AND INTO THURSDAY, THE SURFACE COLD FRONT IS
PROJECTED TO SAG SLOWLY SOUTHWARD THROUGH THE FORECAST AREA.
THIS SPATIAL PROGRESSION WILL COMPRESS THE SEVERE WEATHER THREAT
FURTHER SOUTH, RESTRICTING AFTERNOON SHOWER AND THUNDERSTORM
POTENTIAL PRIMARILY TO AREAS ALONG AND SOUTH OF THE INTERSTATE
70 CORRIDOR.
BECAUSE BOUNDARY LAYER CONDITIONS NEAR THIS SLOW- MOVING
FRONTAL ZONE ARE EXPECTED TO MIRROR TODAY'S ENVIRONMENT,
ISOLATED STRONG TO SEVERE THUNDERSTORMS WILL REMAIN POSSIBLE.
CLOSE MONITORING WILL BE REQUIRED FOR ANY ROBUST CELLS CAPABLE
OF PRODUCING LOCALIZED DAMAGING WIND GUSTS AND LARGE HAIL.
THURSDAY NIGHT THROUGH FRIDAY NIGHT: RAINFALL & FLOODING
THREAT...
BY THURSDAY NIGHT, THE SURFACE FRONT IS ANTICIPATED TO STALL
OUT BETWEEN THE INTERSTATE 70 AND INTERSTATE 72 CORRIDORS AS THE
PRIMARY UPPER-LEVEL FORCING SHIFTS TOWARD THE EASTERN GREAT
LAKES. THE FORECAST FOCUS WILL QUICKLY TRANSITION TO A
HEAVY RAINFALL AND HYDROLOGIC THREAT ALONG THIS STATIONARY
BOUNDARY. A TRAIN OF MULTIPLE UPPER-LEVEL SHORTWAVES AND WEAK
SURFACE LOW-PRESSURE SYSTEMS WILL TRAVERSE THE STALLED FRONT
FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT, INTERACTING WITH A
DEEPLY SATURATED TROPICAL AIRMASS.
PRECIPITATION TOTALS: LATEST NBM GUIDANCE INDICATES AN
IMPRESSIVE 75% CHANCE OF RAINFALL TOTALS EXCEEDING 2 INCHES BY
SATURDAY MORNING ALONG A CORRIDOR EXTENDING FROM PITTSFIELD TO
LAWRENCEVILLE.
HYDROLOGIC CONTEXT: SATURATED ANTECEDENT SOIL CONDITIONS FROM
RECENT ACTIVE WEATHER WILL MAXIMIZE RUNOFF POTENTIAL, ELEVATING
FLASH FLOOD AND RIVER FLOODING CONCERNS.
HEADLINES: GIVEN THE HIGH CONFIDENCE IN MULTI-ROUND CONVECTIVE
RAINFALL OVER VULNERABLE BASINS, A FLOOD WATCH HAS BEEN ISSUED
FOR AREAS SOUTH OF I-72 FROM THURSDAY AFTERNOON TO SATURDAY
AFTERNOON.
SATURDAY THROUGH NEXT WEEK: BUILDING HEAT DOME & OPPRESSIVE
HUMIDITY...
PRECIPITATION CHANCES WILL DIMINISH SIGNIFICANTLY BY SATURDAY
AFTERNOON AS THE SYNOPTIC PATTERN UNDERGOES MAJOR AMPLIFICATION.
A PERSISTENT AND HIGHLY ANOMALOUS UPPER-LEVEL TROUGH DIGGING
OVER WESTERN NORTH AMERICA WILL TRIGGER ROBUST DOWNSTREAM RISING
HEIGHTS, ESTABLISHING A FORMIDABLE HEAT DOME DIRECTLY ACROSS
THE MIDWEST.
TEMPERATURES: DAILY MAXIMUM TEMPERATURES WILL ROUTINELY REACH
THE LOWER 90S STARTING SUNDAY.
HEAT INDICES: COMBINED WITH HIGH AMBIENT HUMIDITY AND POOLING
BOUNDARY LAYER MOISTURE, LATEST NBM GUIDANCE INDICATES THAT HEAT
INDEX VALUES MAY CONSISTENTLY EXCEED 100F FROM SUNDAY THROUGH
WEDNESDAY OF NEXT WEEK.
HEADLINES: THIS PROLONGED PERIOD OF OPPRESSIVE HEAT WILL LIKELY
NECESSITATE A SERIES OF EXCESSIVE HEAT ADVISORIES OR WARNINGS
FOR THE ENTIRE REGION HEADING INTO NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1243 AM CDT THU JUN 25 2026
SCATTERED THUNDERSTORMS AHEAD OF AN APPROACHING FRONTAL BOUNDARY
WILL AFFECT THE I-72 TERMINALS KSPI-KDEC-KCMI FOR THE FIRST FEW
HOURS OF THE 06Z TAF PERIOD, THEN PROGRESS SOUTH OF THE AREA FOR
THE REMAINDER OF THE FORECAST PERIOD. AS THE FRONTAL BOUNDARY
STALLS TO THE SOUTH AND BEGINS TO SHIFT NORTHWARD WITH AN
APPROACHING DISTURBANCE FROM THE WEST ALONG THE FRONT,
INCREASING LOW CLOUD COVER WILL DEVELOP LATE IN THE PERIOD. RAIN
AND EMBEDDED THUNDERSTORMS WILL LIKELY DEVELOP IN THE NEXT FEW
TO SEVERAL HOURS AFTER 06Z FRIDAY. WINDS BECOMING LIGHT AND
VARIABLE OVERNIGHT, THEN NW 5-10 KTS BY AROUND 18Z. WINDS
DECREASING AGAIN AFTER 00Z FRIDAY.
ILX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH FROM THIS AFTERNOON THROUGH SATURDAY AFTERNOON FOR
ILZ052-054-056-061>063-066>068-071>073.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...37
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