469
FXUS63 KILX 060829
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
329 AM CDT MON JUL 6 2026
KEY MESSAGES
- COMFORTABLE AND MOSTLY DRY THROUGH WEDNESDAY: GENERALLY
PLEASANT CONDITIONS WILL PERSIST ACROSS CENTRAL ILLINOIS,
WITH ONLY A LOW (20% TO 30%) CHANCE OF ISOLATED AFTERNOON
SHOWERS AND STORMS.
- HEAVY RAIN AND LOCALIZED FLOODING RISK THURSDAY AND FRIDAY: A
STALLING WEATHER FRONT COULD BRING WIDESPREAD STORMS LATE
THIS WEEK (60% CHANCE). WHILE WIDESPREAD SEVERE WEATHER IS
UNLIKELY, HEAVY DOWNPOURS WILL INTRODUCE A LOCALIZED RISK OF
FLASH FLOODING AND ISOLATED DAMAGING WIND GUSTS.
- POTENTIAL FOR INTENSE HEAT BY MID-JULY: A POWERFUL HIGH-
PRESSURE SYSTEM BUILDING OVER THE CENTRAL UNITED STATES MAY
BRING A PROLONGED PERIOD OF DANGEROUS, EXCESSIVE HEAT TO THE
REGION NEXT WEEK, THOUGH EXACT TIMING REMAINS UNCERTAIN.
DISCUSSION
ISSUED AT 326 AM CDT MON JUL 6 2026
SHORT TERM (TODAY THROUGH WEDNESDAY)
EARLY MORNING WATER VAPOR IMAGERY DEPICTS A COMPACT, CUT-OFF
UPPER-LEVEL LOW TWIRLING OVER THE MISSOURI OZARKS, DETACHED FROM
THE MAIN BELT OF THE WESTERLIES. MEANWHILE, FURTHER NORTH
ACROSS THE CORN BELT, THE AXIS OF A SHORTWAVE RIDGE HAS BEGUN TO
NOSE INTO THE REGION FROM THE WEST. WITH CENTRAL ILLINOIS
POSITIONED IN THE TRANSITION ZONE BETWEEN THESE TWO FEATURES,
NEAR-TERM SENSIBLE WEATHER IS SHAPING UP TO BE FAIRLY BENIGN.
WHILE OUR PROXIMITY TO THE OUTER PERIPHERY OF THE UPPER LOW
JUSTIFIES MAINTAINING LOW-END POPS (20-30%) FOR ISOLATED
AFTERNOON SHOWERS, THE BUILDING RIDGE AXIS TO OUR WEST PRESENTS
A STRONG COUNTERCASE FOR A COMPLETELY DRY DAY FOR MOST OF THE
FORECAST AREA. REGARDLESS OF ISOLATED PRECIP POTENTIAL, TODAY
WILL OFFER A HIGHLY COMFORTABLE AIRMASS BY JULY STANDARDS.
AFTERNOON HIGHS ARE FORECAST TO REACH THE LOW-TO-MID 80S. WHEN
COUPLED WITH DEWPOINTS IN THE UPPER 60S TO NEAR 70F, HEAT INDEX
VALUES WILL TOP OUT IN THE UPPER 80S.
A SIMILAR, BLOCKY PATTERN WILL PERSIST THROUGH TUESDAY AND
WEDNESDAY AS THE SLUGGISH UPPER LOW DRIFTS TOWARD THE CONFLUENCE
OF THE MISSISSIPPI AND OHIO RIVER VALLEYS. IF ANYTHING, 850-MB
TEMPERATURES WILL WARM SLIGHTLY ACROSS CENTRAL ILLINOIS AS THE
RIDGE EDGES EASTWARD, LIFTING AFTERNOON SURFACE TEMPERATURES
INTO THE MID-TO-UPPER 80S MID-WEEK. ISOLATED TO WIDELY SCATTERED
THUNDERSTORM CHANCES (20-30%) WILL LINGER THROUGH WEDNESDAY
AFTERNOON, WITH THE HIGHEST RELATIVE COVERAGE FOCUSED SOUTH OF
THE INTERSTATE 72 CORRIDOR.
THURSDAY THROUGH FRIDAY NIGHT
BY MID-WEEK, A POTENT SHORTWAVE TROUGH IS FORECAST TO DIG
ACROSS THE NORTHERN PLAINS AND INTO THE GREAT LAKES, EFFECTIVELY
BREAKING DOWN THE MID-LEVEL RIDGE AND DRIVING A WEAK COLD FRONT
TOWARD THE LOCAL AREA ON THURSDAY. AS IS CHARACTERISTIC OF MID-
SUMMER SYSTEMS, THE PRIMARY UPPER-LEVEL FORCING WILL QUICKLY
OUTRUN THE BOUNDARY AND RACE EASTWARD INTO CANADA. THIS WILL
LEAVE THE SURFACE FRONT TO BECOME SHEARED OUT AND INCREASINGLY
PARALLEL TO THE MID-LEVEL FLOW, ULTIMATELY STALLING OVER CENTRAL
ILLINOIS BY FRIDAY.
THIS LINGERING BOUNDARY WILL SERVE AS THE PRIMARY FOCUS FOR A
RETURN TO WET AND UNSETTLED WEATHER FOR THE BACK HALF OF THE
WEEK. AMBIENT THERMODYNAMIC PROFILES WILL BECOME MODERATELY TO
STRONGLY BUOYANT, CHARACTERIZED BY MUCAPE VALUES SURGING INTO
THE 2000-3000 J/KG RANGE. KINEMATICS WILL ALSO IMPROVE BY
THURSDAY, WITH DEEP-LAYER VERTICAL WIND SHEAR INCREASING TO 30
KNOTS ON THURSDAY BEFORE DECAYING BY FRIDAY.
WHILE ORGANIZED SEVERE WEATHER IS PLAUSIBLE GIVEN THE IMPROVED
SHEAR PROFILES, HIGHLY EFFICIENT WARM-RAIN PROCESSES DRIVEN BY
ANOMALOUS ATMOSPHERIC MOISTURE–WITH PWATS CLIMBING ABOVE 2.0
INCHES (ABOVE THE 90TH PERCENTILE FOR JULY)--WILL INTRODUCE A
MORE CONCERNING FLASH FLOODING RISK. TORRENTIAL RAINFALL RATES
AND WET DOWNBURSTS CAPABLE OF ISOLATED DAMAGING WIND GUSTS WILL
BE THE PRIMARY THREATS TO MONITOR.
EXTENDED OUTLOOK (SATURDAY THROUGH MONDAY)
AS THE LATE-WEEK BOUNDARY WASHES OUT, MEDIUM-RANGE
DETERMINISTIC AND ENSEMBLE GUIDANCE IS IN REMARKABLY STRONG
AGREEMENT REGARDING THE BUILDING OF A HIGH-AMPLITUDE SUBTROPICAL
RIDGE OVER THE CENTRAL UNITED STATES HEADING INTO THE FOLLOWING
WEEK. WHILE EXACT DETAILS REGARDING CORE AMPLITUDE AND SPATIAL
POSITIONING WILL INEVITABLY FLUCTUATE, LONG-RANGE ENSEMBLES
(GEFS/EPS/GEPS) CONSISTENTLY TRACK AN ANOMALOUS 600-MB UPPER-
LEVEL HIGH DIRECTLY OVER THE ROCKIES IN THE 7 TO 10 DAY WINDOW
(JULY 13-16).
THE ULTIMATE SENSIBLE WEATHER IMPACTS FOR CENTRAL ILLINOIS WILL
HINGE ENTIRELY ON THE PLACEMENT OF THIS RIDGE. IF THE LOCAL
AREA REMAINS ON THE EASTERN PERIPHERY OF THE HIGH, ACTIVE
NORTHWEST FLOW WOULD LIKELY SEND PERIODIC MCS RIDGE-RIDERS
THROUGH THE REGION, WHICH WOULD ACT TO TEMPER THE HEAT WITH
CLOUD COVER AND CONVECTIVE DEBRIS. HOWEVER, SHOULD THE CORE OF
THE RIDGE DRIFT FURTHER EAST INTO THE CORN BELT AS SOME LONG-
RANGE MEMBERS SUGGEST, A PROLONGED PERIOD OF DANGEROUS,
EXCESSIVE HEAT WOULD BECOME INCREASINGLY LIKELY FOR THE MIDDLE
OF JULY.
AVIATION /06Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 1222 AM CDT MON JUL 6 2026
PATCHY MVFR CEILINGS ARE EXPECTED TO SPREAD SW ACROSS CENTRAL
ILLINOIS AND BECOME MORE WIDESPREAD OVERNIGHT. CEILINGS WILL
LIFT DIURNALLY FROM NEAR IFR TO HIGH END MVFR MID MORNING THEN
BACK TO VFR BY EARLY TO MID AFTERNOON. WINDS WILL BE OUT OF THE
NORTH TO NORTHEAST AT 10 KT OR LESS THROUGH THE PERIOD.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...DEUBELBEISS
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