960
FXUS63 KILX 081748
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1248 PM CDT WED JUL 8 2026
KEY MESSAGES
- ISOLATED STORMS TODAY: ISOLATED AFTERNOON THUNDERSTORMS (20%
TO 30% CHANCE) MAY DEVELOP SOUTH OF INTERSTATE 72 TODAY,
ENDING QUICKLY AFTER SUNSET.
- HEAVY RAIN AND FLASH FLOOD RISK THURSDAY THROUGH SATURDAY: A
STALLED FRONT BRINGS A 60% TO 70% CHANCE OF RAIN AND STORMS TO
CENTRAL AND SOUTHERN ILLINOIS. SLOW- MOVING STORMS COULD
TRIGGER LOCALIZED FLASH FLOODING, WITH A 30% CHANCE OF
RAINFALL EXCEEDING 2 INCHES SOUTH OF INTERSTATE 72.
- EXTREME HEAT OR ACTIVE STORMS NEXT WEEK: HIGH UNCERTAINTY
EXISTS FOR MID-JULY. A SHIFTING HIGH-PRESSURE SYSTEM COULD
BRING EITHER DANGEROUS HEAT AND HUMIDITY OR PERIODIC STORM
COMPLEXES.
DISCUSSION
ISSUED AT 318 AM CDT WED JUL 8 2026
TODAY THROUGH TONIGHT
THE DOMINANT FEATURE THIS MORNING REMAINS A PESKY, CUT-OFF
UPPER-LEVEL LOW SPINNING NEAR THE LOWER OHIO RIVER VALLEY. AS A
DOWNSTREAM RIDGE AXIS SHIFTS EASTWARD, SLIGHT LOW-LEVEL WARMING
WILL TAKE PLACE WITH 850 MB TEMPERATURES NUDGING UPWARD. THIS
WILL TRANSLATE TO AFTERNOON HIGHS CLIMBING INTO THE UPPER 80S
TO NEAR 90F. DIURNAL HEATING COMBINED WITH RESIDUAL LOW-LEVEL
MOISTURE WILL SUPPORT ISOLATED AFTERNOON THUNDERSTORMS (20-30%
CHANCE), PRIMARILY GRIDDED SOUTH OF THE INTERSTATE 72 CORRIDOR
CLOSER TO THE DEPARTING LOW'S PERIPHERY. ANY ACTIVITY SHOULD
QUICKLY DIMINISH AFTER SUNSET WITH THE LOSS OF DAYTIME HEATING.
THURSDAY THROUGH SATURDAY NIGHT
A NOTABLE SHIFT IN THE SYNOPTIC PATTERN IS ANTICIPATED BY
THURSDAY AS STRONG SHORTWAVE ENERGY DIGS INTO THE UPPER MIDWEST.
THIS WILL GUIDE A WEAKENING MESOSCALE CONVECTIVE VORTEX (MCV)
AND PUSH A SURFACE COLD FRONT INTO CENTRAL ILLINOIS BY THURSDAY
AFTERNOON, ULTIMATELY BREAKING DOWN THE PERSISTENT RIDGE.
HOWEVER, SINCE THE MAIN UPPER-LEVEL DYNAMICS ARE FORECAST TO
OUTPACE THE SURFACE FRONT, THE BOUNDARY WILL LIKELY ALIGN
PARALLEL TO THE MID-LEVEL FLOW. CONSEQUENTLY, THE FRONT IS
EXPECTED TO SHEAR OUT AND STALL OVER CENTRAL OR SOUTHERN
ILLINOIS FROM FRIDAY INTO SATURDAY.
THIS STALLED BOUNDARY WILL SERVE AS THE PRIMARY FOCAL POINT FOR
UNSETTLED WEATHER TO CLOSE OUT THE WEEK, YIELDING HIGH
PROBABILITIES (60-70%) FOR RAIN. AHEAD OF THE FRONT, A
MODERATELY TO STRONGLY UNSTABLE ENVIRONMENT WILL MATERIALIZE,
WITH MUCAPE VALUES CLIMBING INTO THE 2000-3000 J/KG RANGE. DEEP-
LAYER VERTICAL WIND SHEAR IS PROGGED TO PEAK NEAR A MODEST 30
KNOTS THURSDAY AFTERNOON BEFORE WEAKENING INTO FRIDAY.
WHILE THE ENHANCED SHEAR PROFILES ON THURSDAY COULD SUPPORT
LOCALIZED, PULSE-LIKE DOWNBURSTS CAPABLE OF ISOLATED DAMAGING
WIND GUSTS, THE PRIMARY OPERATIONAL CONCERN IS SHIFTING TOWARD
FLASH FLOODING DRIVEN BY HIGHLY EFFICIENT WARM-CLOUD PROCESSES.
PRECIPITABLE WATER (PWAT) VALUES ARE FORECAST TO SURGE ABOVE
2.0 INCHES, WHICH SITS WELL ABOVE THE 90TH PERCENTILE FOR JULY
CLIMATOLOGY. CONSEQUENTLY, TRAINING AND BACK-BUILDING CONVECTIVE
CELLS PRODUCING TORRENTIAL RAINFALL RATES WILL BE THE MAIN
HAZARD TO MONITOR, ESPECIALLY LATE THURSDAY NIGHT INTO FRIDAY
WHEN CORFIDI UPSHEAR VECTORS DRAMATICALLY LOWER IN MAGNITUDE,
SIGNALING SLOW-MOVING OR ANCHORING STORM STRUCTURES.
AND YET, MODEL GUIDANCE CONTINUES TO EXHIBIT NOTABLE VARIANCE
REGARDING THE EXACT SPATIAL PLACEMENT OF THIS BOUNDARY. SOLUTION
A (GEFS/GEPS) KEEPS THE SURFACE BOUNDARY AND MULTIPLE WAVES OF
HEAVY RAIN FURTHER NORTH SQUARELY ACROSS OUR CWA, WHICH WOULD
MAXIMIZE THE LOCAL FLASH FLOOD RISK. SOLUTION B (ECMWF/EPS) HAS
BEEN STEADFAST IN PUSHING THE SURFACE BOUNDARY CONSIDERABLY
FURTHER SOUTH BY FRIDAY AND SATURDAY, WHICH WOULD KEEP MUCH OF
OUR CWA DRY TO FINISH THE WEEK.
BLENDED (NBM) AND ENSEMBLE (LREF) GUIDANCE LEAN TOWARD A
PROLIFIC, POTENTIALLY MULTI-DAY RAINFALL EVENT, SHOWING ABOUT A
30% CHANCE OF EXCEEDING 2 INCHES OF RAINFALL THROUGH SUNDAY
MORNING, PRIMARILY FOR AREAS SOUTH OF I-72. GIVEN THE MODEL
DIVERGENCE, WE WILL CONTINUE TO MESSAGE THIS AS A LOW-
PROBABILITY, BUT POTENTIALLY HIGH-IMPACT RAINFALL EVENT.
SUNDAY THROUGH WEDNESDAY
ONCE THE STALLED FRONT FINALLY DISSIPATES OR SHUNTS SOUTH LATE
IN THE WEEKEND, LONG-RANGE GUIDANCE EXHIBITS EXCELLENT AGREEMENT
REGARDING THE RAPID EXPANSION OF A HIGH-AMPLITUDE SUBTROPICAL
RIDGE OVER THE CENTRAL UNITED STATES. MEDIUM-RANGE ENSEMBLES
(GEFS/EPS/GEPS) CONSISTENTLY PROJECT AN ANOMALOUS UPPER-LEVEL
HIGH CENTERING OVER THE CENTRAL PLAINS DURING THE JULY 13-16
TIMEFRAME.
SENSIBLE WEATHER ACROSS CENTRAL ILLINOIS DURING THIS EXTENDED
PERIOD WILL DEPEND HEAVILY ON THE EXACT LONGITUDINAL POSITIONING
OF THIS RIDGE CORE. A MORE WESTERN RIDGE ORIENTATION WOULD
PLACE THE LOCAL AREA UNDER ACTIVE, NORTHWEST FLOW ALOFT. THIS
PATTERN WOULD OPEN THE DOOR FOR PERIODIC, RIDGE-RIDING MESOSCALE
CONVECTIVE SYSTEMS (MCSS) THAT WOULD TEMPER AFTERNOON
TEMPERATURES VIA PERSISTENT CLOUD COVER AND CONVECTIVE DEBRIS.
CONVERSELY, IF THE RIDGE CORE MIGRATES FURTHER EASTWARD DIRECTLY
INTO THE CORN BELT, A SPELL OF DANGEROUS, EXCESSIVE HEAT AND
HUMIDITY COULD RAPIDLY DEVELOP BY MID-JULY. GIVEN THE TYPICAL
MODEL VARIANCE AT DAY 6 AND DAY 7, TRENDS WILL BE MONITORED
CLOSELY OVER THE COMING FORECAST CYCLES.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 1248 PM CDT WED JUL 8 2026
VFR CONDITIONS ARE LARGELY ANTICIPATED TO CONTINUE AT ALL TAF
SITES THROUGH 18Z THURSDAY. BRIEF MVFR CEILINGS MAY OCCUR EARLY
THIS AFTERNOON. OTHERWISE, THERE IS A LOW (~20%) PROBABILITY OF
CEILINGS BELOW 6 KFT AFTER 12Z THURSDAY MORNING AS DECAYING
STORMS APPROACH FROM THE NORTHWEST. LOW CONFIDENCE IN ANY FOG
DEVELOPMENT THURSDAY MORNING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...AAT
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