176
FXUS63 KILX 251741
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1241 PM CDT SAT JUL 25 2026
KEY MESSAGES
- MORNING SHOWERS AND ISOLATED THUNDER WILL TAPER OFF BY
MIDDAY, LEAVING BEHIND WIDESPREAD LOW CLOUDS AND A SHARP
TEMPERATURE GRADIENT THIS AFTERNOON (70S EAST, MID 80S WEST).
- OPPRESSIVE HEAT AND HUMIDITY ARRIVE SUNDAY AND MONDAY WITH
HEAT INDEX VALUES CLIMBING TO 100-110F. EXISTING HEAT
ADVISORIES WILL LIKELY BE EXPANDED AND UPGRADED FOR MONDAY
SHOULD CURRENT FORECAST TRENDS HOLD.
- SEVERE WEATHER PROBABILITIES INCREASE SUNDAY INTO MONDAY
ALONG THE PERIPHERY OF THE RIDGE (RING OF FIRE / NORTHWEST
FLOW SETUP), WITH MONDAY PRESENTING THE MOST FAVORABLE
CONVECTIVE WINDOW AHEAD OF AN APPROACHING COLD FRONT.
DISCUSSION
ISSUED AT 300 AM CDT SAT JUL 25 2026
TODAY THROUGH TONIGHT
A WARM FRONT STRETCHING FROM EASTERN SOUTH DAKOTA DOWN INTO THE
MISSOURI OZARKS CONTINUES TO DRIVE ROBUST WARM-AIR ADVECTION
(WAA) AND ISENTROPIC LIFTING ACROSS OUR FORECAST AREA. EXPECT
SCATTERED LIGHT RAIN SHOWERS AND PERHAPS AN ISOLATED EMBEDDED
THUNDERSTORM TO TRACK ACROSS THE REGION THIS MORNING, PRIMARILY
FOCUSED ALONG AND SOUTH OF THE I-72 CORRIDOR.
BY MIDDAY, AN INCOMING ELEVATED MIXED LAYER (EML) WILL RAPIDLY
STRIP MID-LEVEL COLUMN MOISTURE, SHUTTING OFF PRECIPITATION FROM
NORTHWEST TO SOUTHEAST. HOWEVER, LOW-LEVEL MOISTURE WON'T CLEAR
AS QUICKLY; PERSISTENT 850 MB WAA OVERRUNNING THE COOL SIDE OF
THE SURFACE BOUNDARY WILL KEEP A BLANKET OF STRATUS LOCKED IN
PLACE INTO THE LATE AFTERNOON AND EVENING, ESPECIALLY ACROSS
EASTERN ILLINOIS. TO ACCOUNT FOR THIS, HIGH TEMPERATURES HAVE
BEEN NUDGED DOWN A BIT. THIS SETS UP A STARK EAST-TO-WEST
TEMPERATURE GRADIENT ACROSS CENTRAL ILLINOIS TODAY: UPPER 70S
WHERE CLOUDS REMAIN LOCKED IN (EAST), RANGING TO MID 80S WHERE
PARTIAL CLEARING OCCURS (WEST).
OVERNIGHT, STRATUS WILL RE-EXPAND AND LOWER AS THE SURFACE WARM
FRONT APPROACHES AND MOISTURE GETS TRAPPED BENEATH A SHARP,
LOW- LEVEL INVERSION. CLOUD COVER AND ELEVATED BOUNDARY-LAYER
MOISTURE WILL SEVERELY LIMIT DIURNAL COOLING, KEEPING OVERNIGHT
LOWS MUGGY IN THE LOWER 70S.
.SUNDAY THROUGH MONDAY NIGHT (EXTREME HEAT & SEVERE
POTENTIAL)...
THE MID-LEVEL RIDGE AXIS CROSSES DIRECTLY OVERHEAD SUNDAY AND
MONDAY, BRINGING THE MOST OPPRESSIVE HEAT WAVE OF THE SUMMER SO
FAR. ENSEMBLE GUIDANCE (GEFS/ECE/CMC) EXHIBITS REMARKABLE
CLUSTERING, BRINGING TOP-TIER 850 MB TEMPERATURES (23-25C)
DIRECTLY INTO THE MIDWEST. AFTERNOON HIGHS WILL EASILY REACH THE
LOWER-TO-MID 90S BOTH DAYS. WHEN COUPLED WITH RICH GULF
MOISTURE DRIVING SURFACE DEWPOINTS INTO THE UPPER 70S TO NEAR
80F, HEAT INDEX VALUES WILL SOAR INTO THE 100-110F RANGE BOTH
AFTERNOONS.
A HEAT ADVISORY REMAINS IN EFFECT FOR COUNTIES EAST OF I-57 ON
SUNDAY. GIVEN MEDIUM-HIGH CONFIDENCE IN PEAK HEAT INDEX VALUES
BETWEEN 105-110F ACROSS THE ENTIRE FORECAST AREA ON MONDAY,
HEADLINES WILL ALMOST CERTAINLY BE UPGRADED AND EXPANDED IN
UPCOMING FORECAST PACKAGES.
BEYOND THE HEAT CONCERNS, A REPRESENTATIVE "RING OF FIRE"
CONVECTIVE ENVIRONMENT IS ANTICIPATED ALONG THE NORTHERN FLANK
OF THE ESTABLISHED RIDGE. ALTHOUGH ROBUST THERMODYNAMIC
PROFILES WILL MATERIALIZE, WITH SBCAPE VALUES LIKELY SURPASSING
4000 J/KG, SUBSIDENCE/CAPPING SHOULD SUPPRESS MOST DEVELOPMENT
THROUGH SUNDAY DAYLIGHT HOURS. THE WINDOW FOR HIGHER-IMPACT
CONVECTION OPENS MONDAY AFTERNOON AS A DUO OF SHORTWAVE IMPULSES
CREST THE RIDGE AND PROPEL A SURFACE COLD FRONT TOWARD THE
AREA. WHILE FORECAST CONFIDENCE REGARDING EXACT CONVECTIVE
EVOLUTION REMAINS LOW, ANY ORGANIZED CLUSTERS (MCS) THAT
SUCCESSFULLY BREACH THE CAP WILL ENCOUNTER AN ENVIRONMENT
CONDUCIVE TO SIGNIFICANT DAMAGING WINDS, LARGE HAIL, AND
LOCALIZED FLASH FLOODING.
TUESDAY THROUGH FRIDAY
THE COLD FRONT IS MODELED TO PUSH SLOWLY SOUTH ACROSS CENTRAL
ILLINOIS ON TUESDAY. THIS WILL BEGIN THE PROCESS OF FLUSHING OUT
THE OPPRESSIVE AIRMASS, THOUGH LINGERING HEAT AND HIGH HUMIDITY
(DEWPOINTS HOLDING IN THE 70S) WILL HANG ON ACROSS SOUTHEAST
ILLINOIS THROUGH TUESDAY AFTERNOON. HIGHS TUESDAY WILL TOP OUT
IN THE UPPER 80S TO NEAR 90F.
FROM WEDNESDAY THROUGH THE END OF THE WEEK, CENTRAL ILLINOIS
SHIFTS INTO CLASSIC SUMMER NORTHWEST FLOW ON THE EASTERN FLANK
OF THE AMPLIFIED CENTRAL US RIDGE. WHILE EXTREME THERMODYNAMIC
PROFILES EASE OFF, NORTHWEST-FLOW REGIMES IN LATE JULY
NOTORIOUSLY FOSTER UPSTREAM CONVECTIVE COMPLEXES TRACKING TOWARD
THE REGION. EXPECT TEMPERATURES AND HUMIDITY TO RETURN TO NEAR
SEASONAL NORMS (HIGHS IN THE UPPER 80S, HEAT INDICES MID 90S)
WITH PERIODIC, EPISODIC STORM CHANCES.
AVIATION /18Z TAFS THROUGH 18Z SUNDAY/
ISSUED AT 1241 PM CDT SAT JUL 25 2026
IFR TO MVFR CEILINGS WILL SLOWLY IMPROVE FROM WEST TO EAST THROUGH
EARLY EVENING. AFTER A BRIEF PERIOD OF VFR CONDITIONS THIS EVENING,
CLOUDS WILL EXPAND AND LOWER ONCE AGAIN AS MOISTURE RAPIDLY ADVECTS
NORTHWARD AHEAD OF AN APPROACHING WARM FRONT. THE LATEST NEAR TERM
GUIDANCE SHOWS MVFR TO IFR CEILINGS/VISBYS DEVELOPING OVERNIGHT AND
LINGERING INTO SUNDAY MORNING AT MOST AIRFIELDS. CEILINGS SHOULD
IMPROVE BY LATE MORNING/EARLY AFTERNOON. ISOLATED SHOWERS AND STORMS
(20% CHANCE) ARE POSSIBLE IN WEST-CENTRAL IL LATE SUNDAY MORNING,
BUT CONFIDENCE IN PLACEMENT AND COVERAGE REMAINS FAR TOO LOW TO
MENTION AT KPIA.
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM NOON SUNDAY TO 9 PM CDT MONDAY FOR
ILZ027>031-036>038-040>044-047>054-061.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...NMA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page