923
FXUS63 KILX 260505
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1205 AM CDT SUN JUL 26 2026
KEY MESSAGES
- OPPRESSIVE HEAT AND HUMIDITY RETURN SUNDAY AND MONDAY WITH
HEAT INDICES PEAKING BETWEEN 100 AND 110 DEGREES.
- SEVERE WEATHER PROBABILITIES INCREASE SUNDAY INTO MONDAY WITH
MONDAY PRESENTING THE MOST FAVORABLE CONVECTIVE WINDOW AHEAD
OF AN APPROACHING COLD FRONT.
UPDATE
ISSUED AT 941 PM CDT SAT JUL 25 2026
ADDED CHANCES FOR THUNDERSTORMS STARTING AROUND GALESBURG AT 5
AM AND QUICKLY SPREADING SOUTHEASTWARD THROUGH MOST OF THE AREA
BY LATE MORNING AS A CLUSTER OF THUNDERSTORMS CURRENTLY MOVING
INTO NW IA APPEARS POISED TO FOLLOW A CORRIDOR OF HIGH CAPE
(FEW THOUSAND J/KG MUCAPE) AND SHEAR (AROUND 50 KTS EFFECTIVE
BULK SHEAR) TOWARD WEST CENTRAL IL OVERNIGHT. 00Z HIGH-RES MODEL
RUNS JUST ARE CONSISTENT WITH THIS GENERAL TRACK, ALTHOUGH MOST
WEAKEN THUNDERSTORMS QUITE A BIT AS THEY APPROACH CENTRAL IL.
THEY COULD HOLD TOGETHER BETTER THAN FORECAST WITH THE
FAVORABLE ENVIRONMENT THEY ARE MOVING INTO, AND THINK SOME
SEVERE STORM ACTIVITY IS POSSIBLE, CONSISTENT WITH SPC'S
MARGINAL RISK THROUGH 12Z FROM LINCOLN NORTHWESTWARD, AND
THROUGH THE ENTIRE FORECAST AREA FRIDAY.
DISCUSSION
ISSUED AT 240 PM CDT SAT JUL 25 2026
LINGERING CLOUD COVER HAS HELD TEMPERATURES DOWN SEVERAL DEGREES SO
FAR TODAY WITH 2 PM READINGS RANGING FROM THE LOW 70S TO NEAR 80
DEGREES. CLOUDS WILL SLOWLY ERODE FROM WEST TO EAST THROUGH EARLY
EVENING, THOUGH TEMPERATURES HAVE BEEN FURTHER REDUCED WITH HIGHS
THROUGH THE REMAINDER OF TODAY PEAKING IN THE LOW 80S IN WESTERN IL
AND MIDDLE TO UPPER 70S IN EASTERN IL. AFTER A BRIEF BREAK FROM THE
LOW CLOUDS THIS EVENING, STRONG WARM AIR ADVECTION AHEAD OF AN
APPROACHING WARM FRONT WILL BRING ANOTHER PERIOD OF LOW STRATUS
OVERNIGHT INTO SUNDAY MORNING AS MOISTURE GETS TRAPPED BENEATH A LOW-
LEVEL INVERSION. POCKETS OF LOWER VISIBILITY ARE ALSO POSSIBLE WITH
A LOW TO MEDIUM CHANCE (20-40%) FOR DENSE FOG.
MID-LEVEL HEIGHTS RISE HEADING INTO SUNDAY AS THE UPPER RIDGE
AMPLIFIES OVER THE WEST-CENTRAL US, SENDING 20-25C 850 MB
TEMPERATURES INTO THE MIDDLE MISSISSIPPI VALLEY. SURFACE
TEMPERATURES WILL SURGE INTO THE UPPER 80S TO LOW 90S ON SUNDAY, AND
THEN THE LOW TO MIDDLE 90S ON MONDAY. DEWPOINTS IN THE UPPER 70S TO
80 DEGREES WILL EQUATE TO HEAT INDICES OF 100 TO 110 DEGREES THE
NEXT TWO DAYS WITH MONDAY BEING THE HOTTEST. A HEAT ADVISORY REMAINS
IN EFFECT FOR COUNTIES WEST OF I-57 SUNDAY AFTERNOON THROUGH MONDAY
WHERE CONFIDENCE HAS REMAINED HIGHEST IN CRITERIA BEING MET (HEAT
INDEX 105 DEGREES). AN EXPANSION EASTWARD MAY BE NEEDED FOR SOME ON
MONDAY.
ONE COMPLICATING FACTOR TO THE HEAT IS CONVECTION AND CLOUD COVER.
CENTRAL ILLINOIS IS POSITIONED ON THE EASTERN PERIPHERY OF THE UPPER
RIDGE, MAKING US A PRIME TARGET FOR NORTHWEST FLOW/SHORTWAVE TROUGH
ACTIVITY. OUR FIRST OPPORTUNITY COMES DURING THE DAY ON SUNDAY
IF THE WAVE IS STRONG ENOUGH TO OVERCOME OUR CAPPING INVERSION.
ADDITIONAL OPPORTUNITIES EXIST SUNDAY NIGHT THROUGH MONDAY NIGHT
AS A COUPLE MORE SHORTWAVES AND AN APPROACHING COLD FRONT SERVE
AS OUR FORCING MECHANISMS. HOWEVER, PLACEMENT AND TIMING OF
ACTIVITY REMAINS HIGHLY UNCERTAIN WITH CAMS PROVIDING LITTLE
HELP. ANY STORMS THAT DO DEVELOP WILL HAVE THE POTENTIAL TO
BECOME SEVERE AS THEY MOVE THROUGH AN ENVIRONMENT CHARACTERIZED
BY STRONG INSTABILITY (3500+ J/KG SBCAPE) AND SUFFICIENT
VERTICAL WIND SHEAR (~30 KTS). HAZARDS WITH ANY SEVERE STORMS
WOULD BE DAMAGING WINDS, LARGE HAIL, AND HEAVY RAINFALL.
TEMPERATURES AND DEWPOINTS DROP CLOSER TO SEASONAL NORMALS FOR THE
MIDDLE TO END OF THE WEEK BEHIND A COLD FRONT. NORTHWEST FLOW
REMAINS POSITIONED ALOFT THROUGH THE UPCOMING WEEK AND MAY OPEN THE
DOOR FOR OCCASIONAL PRECIPITATION OPPORTUNITIES THROUGH NEXT
WEEKEND. HOWEVER, DETAILS REMAIN UNCERTAIN.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1205 AM CDT SUN JUL 26 2026
WIDESPREAD MVFR CEILINGS ARE IN PLACE AT 05Z. A GAP IN THE
CLOUDS ACROSS EASTERN ILLINOIS SHOULD PROMOTE DEVELOPMENT OF
STRATUS OVER THE NEXT FEW HOURS, DROPPING CEILINGS TO AROUND
500 FEET FROM KBMI-KDEC EASTWARD. SOME LOWER VISIBILITIES BELOW
A COUPLE MILES ARE ALSO A CONCERN, MAINLY AT KCMI. SOME
IMPROVEMENT IS EXPECTED FROM WEST TO EAST MID TO LATE MORNING,
AND ALL SITES SHOULD BE VFR BY 18Z.
CLUSTER OF THUNDERSTORMS OVER NORTHWEST IOWA HAS SIGNIFICANTLY
WEAKENED, AND ITS REMNANTS SHOULD REACH PORTIONS OF CENTRAL
ILLINOIS TOWARD DAYBREAK. HOWEVER, CONFIDENCE IN ANY THUNDER
REACHING THIS FAR SOUTHEAST IS MUCH LOWER THAN EARLIER. WILL
ONLY INCLUDE KPIA IN A PROB30 MENTION FOR THUNDER IN THE NEW TAF
SET.
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM NOON TODAY TO 9 PM CDT MONDAY FOR
ILZ027>031-036>038-040>044-047>054-061.
KEY MESSAGES...NMA
UPDATE...37
DISCUSSION...NMA
AVIATION...GEELHART
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