540
FXUS63 KILX 270507
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1207 AM CDT THU AUG 27 2026
KEY MESSAGES
- COMFORTABLE AND DRY WEATHER IS ANTICIPATED THURSDAY THROUGH
SATURDAY, FOLLOWED BY THE RETURN OF SUMMER-LIKE HEAT EARLY
NEXT WEEK.
UPDATE
ISSUED AT 711 PM CDT WED AUG 26 2026
7 PM SURFACE MAP SHOWS THE COLD FRONT HAS REACHED I-70.
SCATTERED SHOWERS AND STORMS AHEAD OF THE FRONT HAVE BEEN WANING
RECENTLY WITH IMPENDING LOSS OF DAYTIME HEATING, AND AND
RESIDUAL SHOWERS IN SOUTHEAST ILLINOIS SHOULD END IN THE NEXT
HOUR OR SO. WITH DRIER AIR FILTERING INTO THE REGION,
TEMPERATURES IN MOST AREAS SHOULD REACH THE MID 60S BY DAYBREAK,
WITH SOME LOWER 60S NEAR I-74.
DISCUSSION
ISSUED AT 1212 PM CDT WED AUG 26 2026
A SURFACE COLD FRONT CURRENTLY STRETCHES NEAR THE I-55 CORRIDOR
IN CENTRAL IL, HIGHLIGHTED BY AND AGITATED CU FIELD ON VISIBLE
SATELLITE IMAGERY. RECENT RADAR AND SATELLITE TRENDS SUGGEST
THAT CONVECTIVE INITIATION IS ALREADY UNDERWAY, A COUPLE HOURS
AHEAD OF WHAT THE HIGH-RES MODELS HAVE BEEN SUGGESTING. AHEAD OF
THE FRONT, SURFACE DEW POINTS IN THE UPPER 60S TO LOWER 70S
SUPPORT A MODERATELY UNSTABLE ENVIRONMENT, WITH RAP AND HRRR
SOUNDINGS INDICATING MLCAPE VALUES REACHING NEAR 2500 J/KG BY
MID- AFTERNOON. 0-6 KM BULK SHEAR PROFILES OF 35 KT, AUGMENTED
BY A SUBTLE 500 MB SPEED MAX TRANSLATING EASTWARD ACROSS CENTRAL
ILLINOIS, CREATE AN ENVIRONMENT FAVORABLE FOR SUPERCELLS,
PARTICULARLY OVER EAST CENTRAL IL. THE LIMITING FACTOR IN STORM
COVERAGE WILL BE A LACK OF FORCING FOR ASCENT, WHICH WILL BE
TIED TO WEAK LOW LEVEL CONVERGENCE AND LIFT AHEAD OF THE MID
LEVEL WAVE. SUITE OF CAMS GENERALLY SHOW LITTLE OR NO
DEVELOPMENT (HRRR, HRW, NAM NEST), WITH A COUPLE NOTABLE
EXCEPTIONS (RRFS/FV3) SHOWING MORE ROBUST COVERAGE OVER EAST
CENTRAL IL. GIVEN THE CAPE/SHEAR PROFILES, SUFFICIENT LAPSE
RATES, AND DCAPE UP TO 1400 J/KG, DAMAGING WIND GUSTS AND LARGE
HAIL ARE THE PRIMARY SEVERE HAZARDS. SPC MAINTAINS A 2% TORNADO
RISK WHICH WOULD LIKELY BE TIED TO STORM SCALE INTERACTIONS. ANY
CONVECTION SHOULD TRACK SOUTHEAST AROUND 30 MPH, AND EXIT INTO
INDIANA BY 9-10 PM.
SURFACE HIGH PRESSURE BUILDS SOUTHWARD FROM THE UPPER MIDWEST
ACROSS THE GREAT LAKES REGION THURSDAY AND FRIDAY. THIS WILL
BRING A NICE STRETCH OF WEATHER TO THE REGION WITH COMFORTABLE
TEMPS AND HUMIDITY FOR LATE AUG. CONFIDENCE REMAINS GOOD IN DRY
CONDITIONS PERSISTING THROUGH SATURDAY. RETURN SOUTHERLY FLOW
AROUND THE EXITING SURFACE HIGH BRINGS HIGH TEMPERATURES INTO
THE MID-80S WITH OVERNIGHT LOWS IN THE LOW 60S.
MODEL DIVERGENCE INCREASES REGARDING A SHORTWAVE TROUGH
TRAVERSING THE NORTHERN STREAM SUNDAY INTO EARLY NEXT WEEK.
DETERMINISTIC GFS RUNS FEATURE A DEEPER MID-LEVEL TROUGH DRIVING
A COLD FRONT INTO ILLINOIS. IN CONTRAST, DETERMINISTIC ECMWF
AND ECMWF-AI RUNS MAINTAIN A FLATTER, DISPLACED TROUGH
STRUCTURE, KEEPING MAINLY DRY CONDITIONS GOING. CONSEQUENTLY,
THE FORECAST RELIES HEAVILY ON NBM BLEND GUIDANCE, MAINTAINING
SLIGHT CHANCE (20%) POPS, PRIMARILY OVER THE NORTHERN CWA.
UPPER RIDGING BUILDS ACROSS THE MIDWEST EARLY NEXT WEEK,
BRINGING A RETURN TO HEAT AND HUMIDITY AS SURFACE FLOW BECOMES
SOUTHERLY. HIGHS ARE PROJECTED TO REACH THE UPPER 80 TO MID 90S,
WITH HEAT INDICES PEAKING IN THE UPPER 90S TO AROUND 100 MON-WED.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 1206 AM CDT THU AUG 27 2026
HIGH PRESSURE CURRENTLY OVER THE NORTHERN GREAT PLAINS WILL
SHIFT TO THE UPPER MIDWEST BY LATE IN THE PERIOD. A MODEST
NORTHWEST BREEZE WILL BE IN PLACE ACROSS CENTRAL ILLINOIS DURING
THE DAY THURSDAY, BUT WINDS ARE EXPECTED TO GO LIGHT AND
VARIABLE AFTER SUNSET AS THE RIDGE AXIS MOVES OVERHEAD. DIURNAL
CUMULUS FORMING THURSDAY MORNING MAY BRIEFLY RESULT IN MVFR
CEILINGS, BUT VFR CONDITIONS ARE OTHERWISE FAVORED THROUGH THE
PERIOD.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25/GEELHART
UPDATE...GEELHART
DISCUSSION...25
AVIATION...DEUBELBEISS
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