219
FXUS63 KILX 211047
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
547 AM CDT SUN JUN 21 2026
KEY MESSAGES
- WIDESPREAD RAIN WILL OCCUR ACROSS CENTRAL AND SOUTHEAST ILLINOIS
TODAY. AMOUNTS OF 1 TO 2 INCHES WILL BE COMMON. ISOLATED
HIGHER AMOUNTS OVER 3 INCHES COULD RESULT IN FLASH FLOODING.
- THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER ALONG
AND SOUTH OF A JACKSONVILLE TO DANVILLE LINE FROM 2 PM TO 10
PM TODAY.
DISCUSSION
ISSUED AT 155 AM CDT SUN JUN 21 2026
THE 00Z HIGH-RESOLUTION GUIDANCE INDICATES DUAL-THREATS TODAY
CONSISTING OF HEAVY RAINFALL AND A SEVERE WEATHER RISK THIS
AFTERNOON AND EVENING. THE PRIMARY FORECAST UNCERTAINTY REVOLVES
AROUND THE DEGREE OF DESTABILIZATION FOLLOWING THIS MORNINGS
INITIAL CONVECTIVE ACTIVITY, AND THE LOCATION OF THE RESULTING
OUTFLOW BOUNDARY/EFFECTIVE WARM FRONT. HIGH- RESOLUTION MODELS
SHOW A CLEAR SIGNAL THAT THE NORTHERN PORTION OF THE FORECAST
AREA WILL REMAIN OVERTURNED AND STABLE. HOWEVER, NEAR AND SOUTH
OF THE I-72 CORRIDOR, GUIDANCE SUPPORTS STRONGER
DESTABILIZATION.
..SEVERE RISK TODAY
THE RAP AND HRRR PROJECT MLCAPE VALUES SURGING OVER 1000 J/KG
LATE AFTERNOON SOUTH OF THE WARM FRONT. THIS HIGHER-INSTABILITY
RESERVOIR WILL COUPLE WITH FAVORABLE KINEMATICS, AS AN UPPER-
LEVEL JET STREAK PROVIDES 35 TO 45 KNOTS OF EFFECTIVE BULK
SHEAR. UPDRAFT HELICITY (UH) SWATHS SHOW A DISTINCT CLUSTERING
ACROSS THE SOUTHERN HALF OF THE FORECAST AREA AFTER 19Z. THIS
ENVIRONMENT FAVORS MULTI-CELL CLUSTERS AND TRANSIENT SUPERCELLS
CAPABLE OF PRODUCING DAMAGING DOWNBURST WINDS AND LARGE HAIL.
LOW-LEVEL HODOGRAPHS CURVE SUFFICIENTLY NEAR THE SURFACE
BOUNDARY TO SUPPORT A LOCALIZED TORNADO THREAT, REFLECTED IN
SPC'S 5% TORNADO RISK. THE PRIMARY FORECAST SOLUTION FAVORS A
TARGETED SEVERE THREAT AREA FOCUSED ALONG AND SOUTH OF A LINE
FROM JACKSONVILLE TO LINCOLN TO DANVILLE, PEAKING BETWEEN 19Z
AND 03Z, BEFORE THE INSTABILITY AXIS IS SHUNTED EAST INTO
INDIANA.
..HEAVY RAIN TODAY
ANOMALOUS ATMOSPHERIC MOISTURE IS SURGING NORTHWARD INTO
CENTRAL ILLINOIS EARLY THIS MORNING AHEAD OF AN APPROACHING
SHORTWAVE. HIGH-RESOLUTION GUIDANCE SHOWS PRECIPITABLE WATER
VALUES CLIMBING INTO THE 2-2.25-INCH RANGE, WHICH APPROACHES
CLIMATOLOGICAL MAXIMUMS FOR LATE JUNE. THIS DEEP TROPICAL
MOISTURE WILL INTERACT WITH A 40-50 KT LOW-LEVEL JET STREAK,
WITH ITS CONVERGENT NOSE AIMED AT CENTRAL IL THIS AFTERNOON. AS
A RESULT, THUNDERSTORMS WILL BECOME HIGHLY EFFICIENT RAINFALL
PRODUCERS. THE 00Z HREF PROBABILITY-MATCHED MEAN (PMM) INDICATES
A WIDESPREAD SWATH OF 1-3 INCHES OF RAIN ACROSS CENTRAL AND
SOUTHEAST ILLINOIS, WITH LOCALIZED TOTALS EXCEEDING 4 INCHES
WHERE STORMS TRAIN OVER THE SAME AREAS. GIVEN ANTECEDENT
SATURATED SOILS, THIS RAIN WILL RAPIDLY CONVERT TO RUNOFF. THE
WEATHER PREDICTION CENTER (WPC) MAINTAINS A MODERATE RISK (LEVEL
3 OF 4) IN THE EXCESSIVE RAINFALL OUTLOOK (ERO) FOR TODAY.
FLASH FLOODING IS A PRIMARY THREAT, PARTICULARLY IN URBAN AND
LOW-LYING AREAS.
..NEXT WEEK
LINGERING RAIN SHOWERS REMAIN POSSIBLE OVER EASTERN IL INTO
MONDAY MORNING AS THE UPPER- LEVEL TROUGH CROSSES THE REGION.
COOLER, DRIER AIR FILTERS IN ON MONDAY AFTERNOON ON NORTHWEST
WINDS, WITH HIGHS ONLY IN THE MID-70S.
SURFACE HIGH PRESSURE BUILDS OVER THE MIDWEST ON TUESDAY,
BRINGING DRY CONDITIONS AND SEASONABLY MILD TEMPERATURES WITH
HIGHS IN THE UPPER 70S TO LOWER 80S.
FOR THE MID-TO-LATE WEEK PERIOD, THE OFFICIAL FORECAST RELIES
CLOSELY ON NBM GUIDANCE, THOUGH CONFIDENCE DROPS DUE TO NOTABLE
MODEL DISAGREEMENTS. THE MAIN FORECAST PERIODS OF PRECIP ARE
ASSOCIATED A FRONTAL PASSAGE LATE WEDNESDAY, AND A STRONGER
SHORTWAVE PROJECTED OVER THE MIDWEST LATE FRIDAY INTO SATURDAY.
ENSEMBLE GUIDANCE SHOW A GENERAL TREND TOWARD RISING GEOPOTENTIAL
HEIGHTS NEXT WEEKEND, SUGGESTING WARMING TEMPERATURES.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 547 AM CDT SUN JUN 21 2026
A WEATHER SYSTEM WILL BRING DETERIORATING AVIATION CONDITIONS
LATER THIS MORNING AND AFTERNOON WITH LOWERING CEILINGS, RA, AND
EMBEDDED TSRA. WE EXPECT MVFR CONDITIONS TO BECOME WIDESPREAD BY
EARLY AFTERNOON, WITH IFR CONDITIONS LIKELY BY EVENING AND
CONTINUING OVERNIGHT. SE WINDS WILL INCREASE THIS MORNING AND
BECOME GUSTY THIS AFTERNOON OVER 20 KT. WINDS WILL GRADUALLY
BACK NORTHEAST AT KPAI-KBMI THIS EVENING, AND NORTHWEST AT
KSPI-KDEC-KCMI, WITH GUSTS BECOMING LESS COMMON.
ILX WATCHES/WARNINGS/ADVISORIES
FLOOD WATCH THROUGH LATE TONIGHT FOR ILZ027>031-036>038-
040>057-061>063-066>068-071>073.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...25
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page