432
FXUS63 KILX 230650
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
150 AM CDT THU JUL 23 2026
KEY MESSAGES
- THERE IS A MEDIUM (30-50%) CHANCE OF LIGHT RAIN FRIDAY
AFTERNOON INTO FRIDAY NIGHT, MAINLY SOUTH OF A LINE FROM
MACOMB TO PARIS.
- DANGEROUS HEAT BUILDS SUNDAY AND MONDAY, WITH AFTERNOON HEAT
INDEX VALUES NEARING 105 F ACROSS THE AREA.
- A LOW (20-30%) CHANCE OF SEVERE THUNDERSTORMS AND HEAVY RAIN
EXISTS LATE SUNDAY THROUGH MONDAY NIGHT.
DISCUSSION
ISSUED AT 141 AM CDT THU JUL 23 2026
TODAY THROUGH FRIDAY NIGHT
TODAY, THE WELCOME MID-SUMMER REPRIEVE WILL BE SUSTAINED AS A
CONTINENTAL POLAR HIGH SETTLES ACROSS THE LOWER GREAT LAKES.
AFTERNOON HIGHS WILL BE CAPPED IN THE UPPER 70S DUE TO LIGHT
SURFACE FLOW, ALONGSIDE COMFORTABLE DEWPOINTS IN THE 50S. THIS
PLEASANT AIR MASS IS FORECAST TO HOLD THROUGH EARLY FRIDAY,
THOUGH LOW-LEVEL WINDS WILL TURN SOUTHERLY AND MOISTURE
ADVECTION WILL BEGIN LATE IN THE DAY AS THE SURFACE HIGH SHIFTS
TOWARD THE MID-ATLANTIC.
MEANWHILE, A MID-LEVEL SHORTWAVE DIGGING ACROSS THE CENTRAL
PLAINS WILL FLATTEN THE PERSISTENT UPPER RIDGE. ISENTROPIC
ASCENT ALONG THE DEVELOPING WARM FRONT TO OUR SOUTHWEST IS
EXPECTED TO SEED AN ORGANIZED MESOSCALE CONVECTIVE SYSTEM (MCS)
OR STORM CLUSTER. WHILE CENTRAL AND NORTHERN ILLINOIS STAY
MOSTLY DRY, NBM POPS MAINTAIN A 30-50% CORRIDOR FOR SHOWERS
SOUTH OF A MACOMB-TO-PARIS LINE FRIDAY AFTERNOON INTO FRIDAY
NIGHT. FORECAST SOUNDINGS DEPICT MEAGER SHEAR AND POOR MID-LEVEL
LAPSE RATES ALONG THIS GRADIENT, SO THUNDERSTORM DEVELOPMENT IS
UNLIKELY, KEEPING PRECIPITATION PRIMARILY AS LIGHT RAIN OR
VIRGA.
SATURDAY THROUGH MONDAY
SUBSIDENCE BEHIND FRIDAY'S WAVE, PAIRED WITH BUILDING UPPER-
LEVEL HEIGHTS AS THE RIDGE EXPANDS EASTWARD, WILL SET THE STAGE
FOR A SHARP WEEKEND WARMING TREND. TEMPS JUMP INTO THE MID-TO-
UPPER 80S ON SATURDAY AS SURFACE DEWPOINTS CREEP BACK INTO THE
LOWER 70S.
A PRONOUNCED MID-SUMMER WARMING TREND TAKES CENTER STAGE SUNDAY
AND MONDAY AS A SURFACE WARM FRONT ADVANCES NORTHWARD THROUGH
THE REGION. BACKED BY ENSEMBLE DATA SHOWING 850-MB TEMPERATURES
CLIMBING INTO THE 22-24C RANGE, DAYTIME HIGHS ARE EXPECTED TO
REACH THE LOWER TO MIDDLE 90S. WHEN PAIRED WITH RICH GULF
MOISTURE DRIVING DEWPOINTS INTO THE UPPER 70S, RESULTING HEAT
INDICES ARE PROJECTED TO APPROACH 105F ACROSS BOTH DAYS. SHOULD
THESE TRENDS HOLD, A HEAT ADVISORY COULD BECOME NECESSARY.
SIMULTANEOUSLY, A LOW-PROBABILITY, HIGH-IMPACT SEVERE WEATHER
POTENTIAL IS MATERIALIZING FROM LATE SUNDAY INTO MONDAY NIGHT.
ACCORDING TO GRAND ENSEMBLE GUIDANCE (LREF), THERE IS A 20-30%
JOINT PROBABILITY OF SBCAPE EXCEEDING 2500 J/KG, MINIMAL CAPPING
(SBCIN > -50 J/KG), AND DEEP-LAYER SHEAR (0-6 KM BULK SHEAR)
TOPPING 30 KTS. A COMPACT SHORTWAVE TROUGH AND AN ASSOCIATED
COLD FRONT DROPPING SOUTHWARD OUT OF THE UPPER MIDWEST ARE
EXPECTED TO ACT AS THE PRIMARY TRIGGERS. IF STORMS MANAGE TO
INITIATE WITHIN THIS VOLATILE AND MODERATELY SHEARED ATMOSPHERE,
LOCALIZED HEAVY RAINFALL AND SEVERE CONVECTIVE HAZARDS WILL
BECOME DISTINCT POSSIBILITIES. SIGNIFICANT MESOSCALE VARIABLES,
INCLUDING THE PRECISE TIMING OF THE FRONT AND SUBSEQUENT MCV
INTERACTIONS, KEEP FORECAST UNCERTAINTY HIGH AT THIS POINT.
TUESDAY THROUGH MID-NEXT WEEK
RELIEF ARRIVES TUESDAY AS THE COLD FRONT PUSHES SOUTH OF
CENTRAL ILLINOIS, SCOURING OUT THE HIGH HUMIDITY AND RETURNING
DEWPOINTS TO THE 60S. HIGH TEMPERATURES WILL RECEDE BACK INTO
THE MID-TO-UPPER 80S, EFFECTIVELY LOWERING THE OVERALL HEAT
RISK. WHILE NORTHWEST FLOW IN THE WAKE OF THE DEPARTING TROUGH
WILL NEED TO BE WATCHED FOR ANY UPSTREAM MIGRATORY SHORTWAVES,
STRONG ENSEMBLE CONSENSUS POINTS TOWARD A STRETCH OF DRY AND
SEASONABLY WARM WEATHER PREVAILING THROUGH MID-WEEK.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1215 AM CDT THU JUL 23 2026
VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES NEXT 24HRS. SKIES
SHOULD BE MOSTLY CLEAR BUT SOME CIRRUS WILL BE FLOATING BY
THROUGH THE NIGHT. EXPECTING DIURNAL CU TO DEVELOP AGAIN DURING
THE DAY AROUND 4-5KFT BUT THEN DISSIPATE IN THE EVENING, LEAVING
SCATTERED CIRRUS. WINDS WILL BE LESS THAN 10KTS THROUGH THE
PERIOD, WITH A EASTERLY DIRECTION AT ALL SITES.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...AUTEN
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