307
FXUS63 KILX 030728
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
228 AM CDT FRI JUL 3 2026
KEY MESSAGES
- OPPRESSIVE HUMIDITY WILL PUSH HEAT INDEX VALUES BETWEEN
100-105 F ACROSS CENTRAL AND SOUTHEASTERN ILLINOIS. AN
EXCESSIVE HEAT WARNING REMAINS IN EFFECT TODAY, FOLLOWED BY A
HEAT ADVISORY SOUTH OF INTERSTATE 72 ON SATURDAY AFTERNOON.
- ISOLATED SEVERE STORMS MAY DEVELOP THIS AFTERNOON AND
EVENING, PRIMARILY NORTH OF INTERSTATE 72. WHILE WIDESPREAD
SEVERE WEATHER IS UNLIKELY, ANY STORM COULD PRODUCE LOCALIZED
TORRENTIAL RAINFALL AND BRIEF, DAMAGING WIND GUSTS.
- A FRONT WILL PUSH THROUGH THE REGION ON SUNDAY, BRINGING A
WELCOME END TO THE HEAT WAVE. COOLER, LESS HUMID, AND DRY
CONDITIONS ARE FORECAST MONDAY THROUGH WEDNESDAY.
DISCUSSION
ISSUED AT 223 AM CDT FRI JUL 3 2026
..HEAT AND HUMIDITY
SUMMERTIME HEAT AND HUMIDITY WILL CONTINUE TO BUILD ACROSS THE
REGION TODAY AS CENTRAL ILLINOIS REMAINS POSITIONED ON THE
EASTERN PERIPHERY OF A POTENT 594-MB UPPER- LEVEL HEAT RIDGE.
UPSTREAM CONVECTIVE DEBRIS MAY INTRODUCE MORE WIDESPREAD CLOUD
COVER THAN PREVIOUS DAYS, WHICH COULD MARGINALLY SUPPRESS DEEP
BOUNDARY LAYER MIXING THIS AFTERNOON. WHILE THIS MAY
INADVERTENTLY CAP AFTERNOON HIGHS IN THE UPPER 80S, THE TRADE-
OFF WILL BE DEWPOINTS POOLING EFFICIENTLY IN THE MID- TO UPPER
70S. THE NET RESULT YIELDS ANOTHER DAY OF OPPRESSIVE HEAT INDEX
VALUES HOVERING AROUND 100 F ACROSS CENTRAL AND SOUTHEAST
ILLINOIS. GIVEN THE CUMULATIVE IMPACTS OF THIS PROLONGED HEAT
WAVE, AN EXCESSIVE HEAT WARNING REMAINS FIRMLY IN EFFECT THROUGH
THIS EVENING.
BY SATURDAY, A SERIES OF SHORTWAVE TROUGHS EXITING THE GREAT
PLAINS WILL BEGIN FLATTENING THE PERSISTENT RIDGE, SHUNTING IT
TOWARD THE EASTERN SEABOARD AND PUSHING A WEAK SURFACE FRONT
SOUTHWARD. IF EARLY AFTERNOON CONVECTION DISSIPATES OR MISSES
THE AREA TO THE NORTH, CENTRAL AND SOUTHEAST ILLINOIS WILL ONCE
AGAIN BECOME ENTRENCHED IN STAGNANT, TROPICAL AIR WITH HEAT
INDICES APPROACHING 100 F. DUE TO THIS CONTINUED THREAT, A HEAT
ADVISORY HAS BEEN ISSUED FOR SATURDAY AFTERNOON FOR LOCATIONS
NEAR AND SOUTH OF A DANVILLE TO INTERSTATE 72 LINE.
..CONVECTIVE POTENTIAL & SEVERE RISKS
THE PRIMARY FORECAST CHALLENGE REVOLVES AROUND CONVECTIVE
TRENDS AND MESOSCALE BOUNDARIES. EARLY MORNING RADAR REVEALS
MULTIPLE CONVECTIVE COMPLEXES ACTIVE ACROSS THE CORN BELT NEAR
THE INTERSTATE 80 CORRIDOR, SENDING OUTFLOWS DIVING SOUTHWARD.
WHILE THESE OUTFLOWS ARE EXPECTED TO STALL AND MIX BACK
NORTHWARD UNDER THE INFLUENCE OF SOUTHERLY MEAN FLOW, THEY--
ALONG WITH DIFFERENTIAL HEATING BOUNDARIES--WILL SERVE AS FOCAL
POINTS FOR RENEWED DEVELOPMENT THIS AFTERNOON. THIS IS
PARTICULARLY TRUE AS A CONVECTIVELY-AUGMENTED SHORTWAVE TROUGH
TRACKS OUT OF EASTERN IOWA AND INTO NORTHERN ILLINOIS.
ENVIRONMENTS NEAR AND NORTH OF I-72 WILL BE CHARACTERIZED BY
EXTREME INSTABILITY, WITH MLCAPE VALUES PROGGED IN THE 3000–4000
J/KG RANGE. WHILE THE AMBIENT WIND PROFILE REMAINS WEAK, THE
SHORTWAVE COULD LOCALLY ENHANCE DEEP-LAYER SHEAR TOWARD 30
KNOTS. WIDESPREAD ORGANIZED SEVERE WEATHER IS NOT ANTICIPATED;
HOWEVER, WITHIN A HIGH-PWAT, TROPICAL AIRMASS, HIGH
PRECIPITATION EFFICIENCY WILL FAVOR PULSE CONVECTION OR
TRANSIENT, DISORGANIZED CLUSTERS. THE PRIMARY HAZARDS WILL BE
LOCALIZED TORRENTIAL DOWNPOURS AND WET MICROBURSTS. AREAS SOUTH
OF I-72 WILL LIKELY REMAIN TOO FAR REMOVED FROM THIS MESOSCALE
FORCING, RENDERING THEM DRY AND HOT.
A SIMILAR SETUP UNFOLDS FRIDAY NIGHT INTO SATURDAY. NOCTURNAL
CONVECTION BLOSSOMING TO OUR WEST WILL NEED TO BE MONITORED
CLOSELY, AS DECAYING MCVS OR RESIDUAL OUTFLOW BOUNDARIES COULD
TRACK PERILOUSLY CLOSE TO THE FA AHEAD OF THE SAGGING SURFACE
FRONT. THE THERMODYNAMIC PROFILE REMAINS VIRTUALLY IDENTICAL FOR
SATURDAY, MAINTAINING A LOCALIZED THREAT FOR HEAVY RAINFALL AND
LOCALIZED DAMAGING WIND GUSTS IN WATER-LOADED DOWNDRAFTS.
..NEXT WEEK
A PATTERN SHIFT FINALLY ARRIVES BY THE LATTER HALF OF THE
WEEKEND. A STRONGER, MUCH MORE PROGRESSIVE SHORTWAVE IS FORECAST
TO EMERGE FROM THE NORTHERN ROCKIES ON SUNDAY, PROVIDING THE
NECESSARY STEERING FLOW TO ACCELERATE A SECONDARY COLD FRONT
COMPLETELY THROUGH THE STATE. THIS BOUNDARY WILL EFFECTIVELY
SCOUR OUT THE MULTI-DAY TROPICAL AIRMASS, DROPPING DEWPOINTS
BACK INTO THE COMFORTABLE MID-60S TO LOWER 70S BY MONDAY.
A WELCOME STRETCH OF SEASONABLE, DRY WEATHER IS ANTICIPATED
FROM MONDAY THROUGH WEDNESDAY AS A TRANSIENT SHORTWAVE RIDGE
BUILDS ACROSS THE MIDWEST. THE RESPITE LOOKS TO BE SHORT-LIVED,
HOWEVER, AS LONG-RANGE GUIDANCE HINTS AT UNSETTLED WEATHER
RETURNING BY LATE NEXT WEEK. A WELL-DEFINED TROUGH IS PROJECTED
TO DIG ACROSS THE UPPER MIDWEST, DRAGGING ITS ATTENDANT COLD
FRONT INTO THE REGION AND REINTRODUCING CHANCES FOR SHOWERS AND
THUNDERSTORMS.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 1201 AM CDT FRI JUL 3 2026
THUNDERSTORMS OVER NORTHERN ILLINOIS HAVE KICKED OUT AN OUTFLOW
BOUNDARY SOUTH INTO PORTIONS OF CENTRAL ILLINOIS. IT IS
POSSIBLE A FEW ADDITIONAL STORMS FORM ALONG THIS BOUNDARY
OVERNIGHT, ESPECIALLY FURTHER NORTH AT PIA AND POSSIBLY BMI,
BUT CONFIDENCE IS TOO LOW TO INCLUDE MENTION IN THE TAF.
OTHERWISE, LIGHT SOUTH WINDS AND VFR CONDITIONS ARE EXPECTED TO
PREVAIL OVERNIGHT INTO MOST OF FRIDAY WITH WINDS VEERING TO SW
BY LATE MORNING. ADDITIONAL SCATTERED SHOWERS AND STORMS ARE
EXPECTED TO DEVELOP OVER CENTRAL ILLINOIS FRIDAY EVENING. LOW
CONFIDENCE IN PLACEMENT AND EXPECTED ISOLATED TO SCATTERED
COVERAGE PRECLUDES MORE THAN A PROB30 MENTION AT THIS TIME.
ILX WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR
ILZ027>031-036>038-040>057-061>063-066>068-071>073.
HEAT ADVISORY FROM 11 AM TO 7 PM CDT SATURDAY FOR ILZ049>057-
061>063-066>068-071>073.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...DEUBELBEISS
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