108
FXUS63 KILX 181120 CCC
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
620 AM CDT WED JUN 18 2025
KEY MESSAGES
- THERE IS A RISK FOR SEVERE WEATHER AND FLOODING ACROSS ALL OF
CENTRAL ILLINOIS TODAY BETWEEN 10AM AND 5PM...WITH THE GREATEST
RISK (LEVEL 3 OF 5) FOCUSED ALONG AND SOUTHEAST OF A BLOOMINGTON
TO TAYLORVILLE LINE WHERE ALL HAZARDS (TORNADO, WIND AND HAIL)
ARE POSSIBLE.
- HOT AND HUMID WEATHER WILL DEVELOP BY THE END OF THE WEEK. HIGH
TEMPERATURES ARE FORECAST TO RISE INTO THE LOWER TO MIDDLE 90S
BOTH SATURDAY AND SUNDAY, RESULTING IN PEAK HEAT INDEX READINGS
ABOVE 100 DEGREES.
DISCUSSION
ISSUED AT 222 AM CDT WED JUN 18 2025
EARLY MORNING RADAR TRENDS REVEAL SCATTERED SHOWERS AND
THUNDERSTORMS DEVELOPING ACROSS CENTRAL ILLINOIS, AS AN INCREASING
LLJ LIFTS OVERTOP A WARM FRONT. THIS EARLY MORNING ACTIVITY IS
ELEVATED IN NATURE AND POSES LITTLE RISK OF BECOMING SEVERE.
FURTHER UPSTREAM ACROSS THE OZARKS, A MATURE MCS IS PUSHING
EASTWARD AHEAD OF A SFC COLD FRONT. SHORT-TERM MODEL GUIDANCE
REMAINS IN REASONABLE AGREEMENT IN THE EVOLUTION OF THE UPSTREAM
MCS, WITH IT DECAYING AS IT LIFTS NORTHWARD TOWARD THE MID-
MISSISSIPPI VALLEY BY SUNRISE.
THE RISK FOR FLOODING AND SEVERE WEATHER COULD EMERGE AS EARLY AS
LATE MORNING ACROSS WEST CENTRAL ILLINOIS, AS BOTH LOW- AND MID-
LEVEL FLOW INCREASE AHEAD OF A COMPACT MID-LEVEL SHORTWAVE AND ITS
ATTENDANT SFC-LOW/DECAYING MCV.
STRONG CONVERGENCE AND FRONTOGENESIS ALONG THE NORTHERN PERIPHERY
OF THE COMMA HEAD MAY LEND ITSELF TO A NARROW BAND OF HEAVY
RAINFALL. THE MOST RECENT SUITE OF HI-RES GUIDANCE ALL POINT TO A
NARROW CORRIDOR OF HEAVY QPF NEAR OR NORTH OF THE ILLINOIS RIVER
VALLEY, WITH HREF LPMM QPF OFFERING ANYWHERE BETWEEN 1-4”.
THE PLACEMENT OF CONVECTIVE INITIATION REMAINS SOMEWHAT MORE MURKY
THAN THE TIMING. RECENT TRENDS FROM THE HRRR HAVE SHIFTED THE SFC
LOW A LITTLE FURTHER SOUTH OF THE ILLINOIS RIVER VALLEY, WHICH
WOULD FOCUS INITIATION MORE NEAR THE I-72 CORRIDOR. TIMING HAS
REMAINED MORE CONSISTENT WITH INITIATION OCCURRING BETWEEN
16Z-18Z/11AM-1PM.
THE CAPE/SHEAR PROFILE WILL SUPPORT DISCRETE SUPERCELLS AT THE
ONSET WITH SHEAR VECTORS SOMEWHAT PERPENDICULAR TO THE LINE OF
FORCING. HODOGRAPHS WILL BECOME MORE ELONGATED BY AFTERNOON AS
BOTH LOW- AND MID-LEVEL JET CORES VEER IN AHEAD OF THE COLD FRONT.
THE TORNADO POTENTIAL WILL BE GREATEST IN THE VICINITY OF THE WARM
FRONT, WHERE BACKED SFC WINDS AND ENHANCED 0-1 KM SRH ARE
SUPPORTIVE OF STP VALUES > 2. LOW LCLS WILL ALSO SUPPORT AN
INCREASED TORNADO THREAT IN THE VICINITY OF THE WARM FRONT AS IT
QUICKLY LIFTS ACROSS CENTRAL ILLINOIS EARLY THIS AFTERNOON.
FURTHER SOUTH ACROSS THE WARM SECTOR, THE HODOGRAPH APPEARS TO
STRAIGHTEN OUT, MORE SUGGESTIVE OF A LARGE HAIL THREAT AS
SUPERCELLS WILL HAVE A TENDENCY TO WANT TO SPLIT. BUT, WITH ONE OR
MORE CONVECTIVE OUTFLOWS LURKING AHEAD OF THE COLD FRONT, THE SIG
TOR THREAT CANNOT BE DISCOUNTED FURTHER SOUTH ACROSS THE WARM
SECTOR, EITHER.
LATEST TRENDS SHOW THE MAIN CONVECTIVE THREAT EXITING EASTERN
ILLINOIS BY 21Z/4PM AS THE MAIN UPPER FORCING DEPARTS TOWARD THE
GREAT LAKES REGION. STILL, SHOWERS AND STORMS MAY LINGER ALONG THE
DECAYING COLD FRONT BEFORE ACTIVITY FADES WITH THE LOSS OF DAYTIME
HEATING.
A STRETCH OF HOT AND HUMID WEATHER BEGINS TO TAKE SHAPE BY FRIDAY
AS A 588-MB RIDGE BUILDS ACROSS THE PLAINS. NBM DETERMINISTIC
GUIDANCE SUGGESTS AFTERNOON HIGHS IN THE MID-TO-UPPER 80S ACROSS
THE REGION. TEMPERATURES ARE THEN FORECAST TO QUICKLY RATCHET
UPWARD INTO THE 90S BY THE WEEKEND AS THE UPPER-LEVEL RIDGE
AMPLIFIES (TO 594 MB) WITH THE EMERGENCE OF A DEEP WESTERN TROUGH.
THE DAILY HEAT INDEX VALUE IS ANTICIPATED TO SURGE BETWEEN 100-105
F EACH DAY BETWEEN SATURDAY AND TUESDAY AS SFC DEWPOINTS ROUTINELY
HOVER IN THE LOW-TO-MID 70S. THE PROLONGED NATURE OF THE HEAT
FORECAST COULD POTENTIALLY PROMPT OUR FIRST EXTREME HEAT WATCH OF
THE SUMMER.
BOTH BLENDED (NBM) AND ENSEMBLE (LREF) GUIDANCE CURRENTLY EXHIBIT
VERY LOW (< 20%) RAIN CHANCES EACH DAY FROM FRIDAY TO MONDAY. IN
THIS SUMMERTIME AIRMASS, IT’S HARD TO IMAGINE US NOT GETTING AT
LEAST ISOLATED SHOWER AND STORM ACTIVITY DURING PEAK DIURNAL
HEATING. IT WOULD BE MORE UNUSUAL THAT WE DIDN’T. BUT, IT’S NOT
UNTIL MONDAY OR TUESDAY THAT MID-LEVEL CAPPING AND DRY AIR
ENTRAINMENT ERODE ENOUGH TO SUPPORT THE RETURN OF ISOLATED
SHOWER/STORM ACTIVITY.
MJA
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 603 AM CDT WED JUN 18 2025
SCATTERED SHOWERS AND VFR CONDITIONS WILL GIVE WAY TO MORE
WIDESPREAD THUNDERSTORMS THIS MORNING AS A DISTURBANCE MOVES
NORTHEASTWARD INTO THE AREA. HAVE INCLUDED PROB30 GROUPS FOR THESE
THUNDERSTORMS, ALONG WITH MVFR CIGS/VSBYS FROM AROUND 14Z-20Z,
HOWEVER TIMING OF THIS DISTURBANCE REMAINS SOMEWHAT UNCERTAIN, AND
IT COULD HAVE LINGERING IMPACTS PAST 20Z. ADDITIONAL THUNDERSTORM RE-
DEVELOPMENT WILL BE POSSIBLE SHORTLY AFTER THIS INITIAL DISTURBANCE
MOVES OUT OF THE AREA AS A FRONTAL BOUNDARY CONTINUES TO PROGRESS
EASTWARD ACROSS THE AREA. AN ADDITIONAL PROB30 GROUP HAS BEEN ADDED
TO ALL TERMINALS BY 23Z-01Z. ADDITIONAL CONCERNS INVOLVE CIG
HEIGHTS, WHICH COULD LOWER TO IFR AT KDEC AND KCMI BEYOND 05Z. WINDS
BECOMING S 10 KTS THIS MORNING, INCREASING TO 20G30 KTS FROM THE SW
AFTER 18Z-20Z.
MJA/37
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
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