775
FXUS63 KILX 051757
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1257 PM CDT SUN JUL 5 2026
KEY MESSAGES
- A FEW BRIEF AFTERNOON THUNDERSTORMS ARE POSSIBLE (30-40%
CHANCE) ACROSS CENTRAL ILLINOIS THIS AFTERNOON AND EARLY
EVENING. SEVERE WEATHER IS NOT EXPECTED, AND STORM ACTIVITY
WILL FADE QUICKLY AFTER SUNSET.
- DRY AND SEASONABLY WARM CONDITIONS RETURN MONDAY THROUGH
WEDNESDAY, WITH AFTERNOON TEMPERATURES PEAKING IN THE 80S.
- THUNDERSTORMS RETURN THURSDAY AND FRIDAY (60% CHANCE).
TORRENTIAL DOWNPOURS WILL BRING A LOCALIZED FLASH FLOODING
RISK AND A CHANCE OF ISOLATED DAMAGING WIND GUSTS.
- A DANGEROUS PERIOD OF EXCESSIVE HEAT COULD RE-DEVELOP ACROSS
THE REGION BY THE MIDDLE OF NEXT WEEK (JULY 12TH ONWARD).
DISCUSSION
ISSUED AT 213 AM CDT SUN JUL 5 2026
TODAY: ISOLATED DIURNAL CONVECTION
EARLY MORNING WATER VAPOR IMAGERY DEPICTS MULTIPLE SUBTLE
SHORTWAVES DIGGING THROUGH THE CORN BELT WITHIN A BROADER
LONGWAVE TROUGH AXIS CENTERED OVER THE CENTRAL PLAINS. THESE
SUBTLE IMPULSES ARE PUSHING A DIFFUSE SURFACE BOUNDARY SOUTHWARD
INTO CENTRAL ILLINOIS. A WEAK 1012 MB SURFACE LOW IS ANALYZED
OVER CENTRAL INDIANA EARLY THIS MORNING. WERE IT NOT FOR GOES
NIGHTTIME MICROPHYSICS RGB IMAGERY SHOWING AN EAST-WEST
EXPANSION OF LOW STRATUS ACROSS THE ILX CWA, IT WOULD BE
DIFFICULT TO PINPOINT THE EXACT POSITION OF THE FRONT BASED ON
SURFACE OBSERVATIONS ALONE; WIND AND DEWPOINT GRADIENTS ACROSS
THE BOUNDARY REMAIN REMARKABLY NEGLIGIBLE.
AS THIS CHAOTIC MID-LEVEL PATTERN EVOLVES TODAY, THE WEAK
SHORTWAVES WILL PROVIDE THE PRIMARY FOCUS FOR ISOLATED,
DIURNALLY DRIVEN STORMS. OWING TO THE WASHED-OUT NATURE OF THE
SURFACE FRONT, DIFFERENTIAL HEATING WILL ALLOW FOR THE BUILDING
OF AROUND 1000 J/KG OF SBCAPE ON EITHER SIDE OF THE BOUNDARY
THIS AFTERNOON. IN THIS WEAKLY FORCED, WEAKLY SHEARED
ENVIRONMENT (BULK SHEAR LESS THAN 15 KNOTS), CONVECTIVE
ORGANIZATION WILL BE SEVERELY LIMITED. WHILE SEVERE WEATHER AND
FLASH FLOODING RISKS ARE LOW, THE COMBINATION OF A MODESTLY
BUOYANT AIRMASS AND WEAK UPPER-LEVEL SUPPORT WARRANTS
MAINTAINING CHANCE POPS (30-40%) FOR BRIEF, SINGLE-CELL PULSE
STORMS ACROSS THE REGION TODAY. ANY ACTIVITY WILL QUICKLY
DIMINISH AFTER SUNSET WITH LOSS OF DAYTIME HEATING.
MONDAY THROUGH WEDNESDAY: MOSTLY DRY
SHORT-RANGE DETERMINISTIC AND ENSEMBLE GUIDANCE REMAINS
SOMEWHAT SPLIT ON THE PRECISE EVOLUTION OF THE UPPER-LEVEL
PATTERN THROUGH MIDWEEK, THOUGH SENSIBLE WEATHER IMPACTS REMAIN
LARGELY SIMILAR. THE ECMWF AND ITS EPS SUITE FAVOR CONSOLIDATING
THE SHORTWAVES OVER THE OZARKS, PINCHING THE ENERGY OFF FROM
THE MAIN BELT OF WESTERLIES. CONVERSELY, THE GFS AND GEFS
PROGRESS THIS CONSOLIDATED TROUGH STEADILY EASTWARD.
REGARDLESS OF THE CAMP THAT VERIFIES, THE NET OUTCOME FAVORS
SHORTWAVE RIDGING NOSING INTO CENTRAL ILLINOIS FROM MONDAY
THROUGH WEDNESDAY, KEEPING THE AREA DRY AND SEASONABLY WARM WITH
HIGHS IN THE MID-TO-UPPER 80S. THE LONE EXCEPTION WOULD BE IF
THE SLOWER ECMWF SOLUTION VERIFIES, WHICH COULD SUPPORT DAILY
LOW-CHANCE (25%), ISOLATED AFTERNOON THUNDERSTORMS ACROSS
SOUTHEAST ILLINOIS. GIVEN THAT THE BROADER ENVELOPE OF GLOBAL
GUIDANCE FAVORS A MORE PROGRESSIVE EVOLUTION, THE FORECAST LEANS
TOWARD THE DRIER GFS/GEFS CONSENSUS.
THURSDAY AND FRIDAY: UNSETTLED WEATHER RETURNS
BY WEDNESDAY EVENING, A MORE POTENT SHORTWAVE TROUGH IS
FORECAST TO DIG ACROSS THE NORTHERN PLAINS AND INTO THE GREAT
LAKES. THIS WILL EFFECTIVELY BREAK DOWN THE MID-LEVEL RIDGE AND
PUSH ANOTHER WEAK COLD FRONT INTO THE GREAT LAKES AND MIDWEST BY
THURSDAY. AS IS COMMON DURING MID-SUMMER, THE PARENT UPPER-
LEVEL FORCING WILL QUICKLY RACE EASTWARD, LEAVING THE SURFACE
FRONT TO BECOME SHEARED OUT AND STALL OVER CENTRAL ILLINOIS BY
FRIDAY.
THIS BOUNDARY WILL BECOME THE FOCUS FOR A RETURN TO WET AND
UNSETTLED WEATHER FOR THE BACK HALF OF THE WEEK. THERMODYNAMIC
PROFILES AHEAD OF THE FRONT WILL BECOME MODERATELY BUOYANT,
CHARACTERIZED BY 2000-3000 J/KG OF MUCAPE. HOWEVER, KINEMATICS
REMAIN WEAK WITH DEEP-LAYER SHEAR HOLDING UNDER 25 KNOTS ON
THURSDAY, WEAKENING FURTHER BY FRIDAY. WHILE ORGANIZED SEVERE
WEATHER IS UNLIKELY GIVEN THE POOR SHEAR PROFILES, HIGHLY
EFFICIENT WARM- RAIN PROCESSES DRIVEN BY ANOMALOUS MOISTURE
(PWATS CLIMBING NEAR OR ABOVE 2.0 INCHES) WILL INTRODUCE A
LOCALIZED FLASH FLOODING RISK. TORRENTIAL RAINFALL AND WET
DOWNBURSTS CAPABLE OF ISOLATED DAMAGING WIND GUSTS WILL BE THE
PRIMARY THREATS TO MONITOR.
SATURDAY AND BEYOND: STRONG SIGNALS FOR HIGH HEAT
AS THE LATE-WEEK BOUNDARY WASHES OUT, MEDIUM-RANGE GUIDANCE IS
IN REMARKABLY STRONG AGREEMENT REGARDING THE BUILDING OF A HIGH-
AMPLITUDE SUBTROPICAL RIDGE ACROSS THE CENTRAL US INTO THE
FOLLOWING WEEK. WHILE EXACT DETAILS ON THE CORE AMPLITUDE AND
POSITIONING WILL CHANGE, LONG-RANGE ENSEMBLES (GEFS/EPS/GEPS)
CONSISTENTLY TRACK AN ANOMALOUS 600-MB UPPER-LEVEL HIGH
DIRECTLY INTO THE CORN BELT IN THE 7 TO 10 DAY WINDOW (JULY
12-15).
IF CENTRAL ILLINOIS REMAINS ON THE PERIPHERY OF THIS RIDGE,
ACTIVE NORTHWEST FLOW COULD SEND PERIODIC MCS RIDGE-RIDERS
THROUGH THE REGION TO TEMPER THE HEAT. HOWEVER, IF THE CORE OF
THE RIDGE CENTERS DIRECTLY OVER THE MIDWEST AS CURRENT TRENDS
SUGGEST, ANOTHER STRETCH OF DANGEROUS, EXCESSIVE HEAT WILL BE
LIKELY FOR THE MIDDLE OF JULY.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1255 PM CDT SUN JUL 5 2026
BROKEN CUMULUS CLOUDS WITH MVFR CEILINGS POSSIBLE EARLY THIS
AFTERNOON TO LIFT TO VFR DURING MID/LATE AFTERNOON. ISOLATED
SHOWERS AND THUNDERSTORMS POSSIBLE IN EASTERN IL FROM 20-24Z AND
CARRIED VCSH AT BMI, DEC AND CMI WITH PROB30 GROUP AT CMI.
LATEST HRRR RUN IS SHOWING PATCHES OF LOW CLOUDS WITH MVFR BASES
MOVING BACK INTO PARTS OF CENTRAL AND EASTERN IL DURING
OVERNIGHT INTO MID MON MORNING, THOUGH NOT AS EXTENSIVE AS LAST
NIGHT AND THIS PAST MORNING. NNW WINDS 5-10 KTS VEER NNE TONIGHT
INTO MONDAY.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...07
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