776
FXUS63 KILX 071838
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
138 PM CDT SUN JUN 7 2026
KEY MESSAGES
- ISOLATED LOCALLY HEAVY RAIN WILL OCCUR ACROSS PARTS OF CENTRAL
IL THIS AFTERNOON AND AGAIN MONDAY AFTERNOON AND EVENING.
- HIGH HEAT AND HUMIDITY WILL BUILD ACROSS THE REGION TUESDAY
THROUGH THURSDAY, DRIVING AFTERNOON HEAT INDEX VALUES AROUND
100 DEGREES.
- A SEVERE THUNDERSTORM RISK ACCOMPANIES A COLD FRONTAL PASSAGE
ON THURSDAY.
DISCUSSION
ISSUED AT 138 PM CDT SUN JUN 7 2026
AN UNSEASONABLY MOIST AIRMASS REMAINS ANCHORED OVER CENTRAL AND
SOUTHEAST ILLINOIS. 12Z ILX SOUNDING INDICATED PRECIPITABLE
WATER VALUES (PWAT) AT 1.95", JUST SHY OF A RECORD FOR THE DATE.
THE MOIST ENVIRONMENT AND LONG SKINNY CAPE PROFILES PROMOTE
HIGHLY EFFICIENT WARM-RAIN PROCESSES. WHILE OVERALL FORCING IS
WEAK, IT HAS BEEN AIDED BY CONVERGENCE BANDS LIFTING NORTH, EAST
OF A BAGGY MID LEVEL LOW OVER THE CENTRAL PLAINS. CONVECTIVE
ELEMENTS HAVE BEEN SLOW MOVING DUE TO WINDS <20 KT THROUGH THE
DEPTH OF THE PROFILE, BUT GENERALLY HAVE BEEN TRACKING NORTH AND
MAINLY LIMITED TO THE NORTHERN CWA AND POINTS NORTH TODAY.
SHORT RANGE CAMS INDICATE THIS TREND TOWARDS HIGHER COVERAGE
WILL CONTINUE NEAR AND NORTH OF I-74 INTO EARLY THIS EVENING,
BEFORE COVERAGE DIMINISHES WITH THE LOSS OF DIURNAL HEATING.
ON MONDAY, A SIMILAR SETUP REMAINS IN PLACE, THOUGH THE UPPER
WAVE MOVES OVERHEAD, PROMOTING A HIGHER COVERAGE OF SHOWERS AND
STORMS FROM LATE MORNING INTO THE EVENING. GUIDANCE SHOWS PWATS
RISING OVER 2" WITH LIGHT WINDS ALOFT, PROMOTING EFFICIENT SLOW
MOVING CONVECTIVE ELEMENTS. THE 12Z HREF LPMM 24-HR RAINFALL
THROUGH 00Z TUE SHOWS ISOLATED AREAS OF 2-5" (MOST LIKELY WORST
CASE SCENARIO) OVER PORTIONS OF THE CENTRAL TO NORTHERN CWA. IF
THIS WERE TO OCCUR OVER URBAN AREAS OR ISOLATED AREAS THAT SAW
HEAVY RAIN LAST NIGHT AND THIS MORNING, FLASH FLOODING WILL BE A
CONCERN. THOUGH OVERALL ANTECEDENT DRY CONDITIONS AND ISOLATED
NATURE OF THE PROJECTED HEAVY RAIN PRECLUDE WIDESPREAD FLASH
FLOOD CONCERNS AND WATCH ISSUANCE AT THIS TIME.
THE UPPER LOW PUSHES EAST AS SUBTROPICAL RIDGING EXPANDS ACROSS
THE OHIO VALLEY TUESDAY AND WEDNESDAY, LEADING TO A HOT AND
HUMID PERIOD. THE ECMWF EXTREME FORECAST INDEX (EFI) HIGHLIGHTS
THIS PERIOD WITH VALUES BETWEEN 0.7 AND 0.8 FOR MAXIMUM
TEMPERATURES, SIGNALING A CLIMATOLOGICALLY UNUSUAL HEAT EVENT
FOR EARLY JUNE. THE NATIONAL BLEND OF MODELS (NBM) PROJECTS
AFTERNOON HIGHS IN THE LOW TO MID-90S. COMBINING THESE
TEMPERATURES WITH DEWPOINTS IN THE LOWER 70S YIELDS HEAT INDICES
OVER 100 DEGREES. LREF PROBS INDICATE A 70 TO 80 PERCENT
PROBABILITY OF HEAT INDEX VALUES EXCEEDING 100 DEGREES, HIGHEST
ON WEDNESDAY AFTERNOON. SOUTHWEST WINDS WILL INCREASE WED AMID A
TIGHTENING MSLP GRADIENT, WITH DIURNAL MIXING SUPPORTING WIND
GUSTS OVER 25 MPH.
ATTENTION THEN SHIFTS TO THURSDAY AS AN UPPER-LEVEL TROUGH
MOVES ACROSS THE UPPER MIDWEST, DRAGGING A COLD FRONT INTO THE
REGION. WHILE SOME TIMING DIFFERENCES ARE NOTED AMONG THE
ENSEMBLE SUITE, THE BETTER DYNAMICS APPEAR TO OVERLAP FAVORABLY
WITH DIURNAL HEATING, INCREASING THE SEVERE THUNDERSTORM RISK.
SPC'S 15% RISK AREA (EQUIVALENT TO SLIGHT RISK) FOR THURSDAY
HIGHLIGHTS THE AREA NORTH OF I-70. THIS IS SUPPORTED BY A NUMBER
OF AI/ML COMPOSITE SEVERE PRODUCTS. HEAT WILL ALSO BE A CONCERN
TO THE SOUTHEAST OF CONVECTIVE CLOUD COVER/RAIN COOLED
OUTFLOWS, WHERE HEAT INDICES WILL LIKELY REACH AROUND 100
DEGREES.
BEHIND THE FRONT FOR FRIDAY AND SATURDAY, HIGH PRESSURE BUILDS
SOUTHEAST FROM CANADA, DELIVERING A MORE SEASONABLE AND LESS
HUMID AIRMASS. LOOKING FURTHER AHEAD, THE CPC 6-10 AND 8-14 DAY
OUTLOOK INDICATE A TREND FOR NEAR TO BELOW-NORMAL TEMPERATURES.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1217 PM CDT SUN JUN 7 2026
TSRA WILL BE SCATTERED AROUND THE CENTRAL IL TERMINALS INTO
EARLY THIS EVENING WITH AROUND 10-30% COVERAGE. OUTSIDE OF THAT
CONDITIONS WILL PRIMARILY BE VFR UNTIL AN MVFR CLOUD DECK MOVES
IN FROM THE SOUTH LATE TONIGHT (08-10Z). CONFIDENCE IS HIGH IN
THESE CEILINGS THROUGH MUCH OF MONDAY MORNING, WITH AROUND
20-30% PROBS OF IFR CEILINGS - SO LEFT THAT MENTION OUT FOR NOW.
ANOTHER ROUND OF SCATTERED TSRA LOOKS TO DEVELOP BY LATE
MORNING. ANY STORMS TODAY AND MONDAY HAVE TO POTENTIAL TO
BRIEFLY REDUCE TO IFR VISIBILITY IN +RA. WINDS WILL GENERALLY BE
SOUTHEAST UNDER 10 KT THROUGH TONIGHT, WITH SOME INCREASE IN
SPEED EXPECTED TOWARD MIDDAY MONDAY.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...25
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