310
FXUS63 KILX 261713
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1213 PM CDT WED AUG 26 2026
KEY MESSAGES
- A CONDITIONAL SEVERE THUNDERSTORM RISK EXISTS MID AFTERNOON TO
EARLY EVENING MAINLY NEAR AND EAST OF INTERSTATE 57, CAPABLE
OF LOCALIZED DAMAGING WIND GUSTS AND LARGE HAIL.
- COMFORTABLE AND DRY WEATHER IS ANTICIPATED THURSDAY THROUGH
SATURDAY, FOLLOWED BY THE RETURN OF SUMMER-LIKE HEAT EARLY
NEXT WEEK.
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 /12Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1212 PM CDT WED AUG 26 2026
A COLD FRONT WAS NEARING I-55 AT MIDDAY, ASSOCIATED WITH SCT-BKN
CU AT 2500-3500 FT. ANALYSIS AND TRENDS SUGGEST THAT KCMI IS
THE ONLY TERMINAL THAT HAS A DECENT CHANCE OF SEEING TSRA THIS
AFTERNOON, SO LIMITED PROB30 TO THAT SITE ONLY. OTHERWISE WINDS
VEER TO THE WNW BEHIND THE FRONT, BECOMING LIGHT THIS EVENING
WITH MOSTLY CLEAR SKIES. A ROBUST CU FIELD IS FORECAST TO FORM
LATE THURSDAY MORNING. THIS COULD INITIALLY BE BELOW 3000 FEET,
HOWEVER CONFIDENCE IS TOO LOW FOR MVFR AT THIS RANGE.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25
DISCUSSION...25
AVIATION...25
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