450
FXUS63 KILX 021727
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1227 PM CDT SUN AUG 2 2026
KEY MESSAGES
- QUIET WEATHER AND LOW HUMIDITY: EXPECT COMFORTABLE WEATHER
WITH LOW HUMIDITY AND BELOW-NORMAL HIGHS IN THE LOW-TO-MID 80S
THROUGH TUESDAY.
- MID-WEEK HEAT SURGE: HEAT AND HUMIDITY RETURN WEDNESDAY AHEAD
OF A COLD FRONT, WITH HEAT INDEX VALUES PUSHING INTO THE
LOWER 90S.
- SEVERE STORM POTENTIAL MID-WEEK: WIDESPREAD SHOWERS AND
THUNDERSTORMS ARE LIKELY (50-80% CHANCE) LATE WEDNESDAY NIGHT
THROUGH THURSDAY AS THE FRONT PASSES. THERE IS AN ISOLATED
THREAT FOR SEVERE WEATHER DURING THIS TIME, PRIMARILY DRIVEN
BY DAMAGING WIND GUSTS AND HAIL.
- DRIER NEXT WEEKEND: HIGH CONFIDENCE REMAINS FOR BUILDING HIGH
PRESSURE AND A RETURN TO DRY CONDITIONS WITH HIGHS NEAR 90F
BY NEXT WEEKEND.
DISCUSSION
ISSUED AT 1223 PM CDT SUN AUG 2 2026
SHORT TERM
(REST OF TODAY THROUGH TUESDAY NIGHT)
LOW-LEVEL STRATUS AND LINGERING CLOUD COVER ASSOCIATED WITH THE
DEPARTING SYNOPTIC SYSTEM WILL GRADUALLY LIFT AND SCATTER OUT
FROM WEST TO EAST THROUGH THE REMAINDER OF THIS AFTERNOON,
GIVING WAY TO LATE-DAY SUNSHINE. AT THE SURFACE, A SURFACE HIGH
IS BUILDING ACROSS THE UPPER MIDWEST AND MID-MISSISSIPPI VALLEY
BENEATH THE WESTERN PERIPHERY OF AN UPPER- LEVEL RIDGE AXIS.
DRIER AIR ADVECTION IS ALREADY UNDERWAY, AS EVIDENCED BY
DROPPING SURFACE DEWPOINTS UPSTREAM ACROSS IOWA AND NORTHERN
ILLINOIS.
MODEL GUIDANCE REMAINS IN STRONG AGREEMENT REGARDING THE
EVOLUTION OF THE UPPER-LEVEL PATTERN OVER THE NEXT 48 HOURS.
THE ADVANCING UPPER RIDGE AXIS WILL EXPERIENCE A SLOW EASTWARD
PROGRESSION AS A PIECE OF SHORTWAVE ENERGY FROM THE DEPARTING
LOW BECOMES CUT OFF FROM THE MAIN BELT OF WESTERLIES AND
RETROGRADES SOUTHWESTWARD ACROSS THE TENNESSEE VALLEY THROUGH
MIDWEEK. THE NET RESULT FOR CENTRAL AND EASTERN ILLINOIS WILL
BE A STRETCH OF PROTOTYPICAL EARLY AUGUST WEATHER. EXPECT
MOSTLY CLEAR SKIES, LOW HUMIDITY (DEWPOINTS REMAINING
COMFORTABLY IN THE 60S), AND AFTERNOON HIGH TEMPERATURES
TOPPING OUT IN THE LOW-TO-MID 80S BOTH MONDAY AND TUESDAY--
ABOUT 2 TO 4 DEGREES BELOW SEASONAL NORMALS.
LONG TERM
(WEDNESDAY THROUGH SUNDAY)
THE SYNOPTIC REGIME UNDERGOES A NOTABLE TRANSITION BY MID-WEEK
AS A STRONG NORTHERN-STREAM TROUGH PIVOTS ACROSS SOUTH-CENTRAL
CANADA, FORCING A WEAKLY DRIVEN COLD FRONT SOUTH TOWARD THE
UPPER MIDWEST. BY WEDNESDAY AFTERNOON, THE FRONTAL BOUNDARY IS
PROJECTED TO LAY OUT EAST-TO-WEST NEAR THE SOUTHERN WISCONSIN
AND EASTERN IOWA BORDER. SOUTH-SOUTHWESTERLY RETURN FLOW AHEAD
OF THE BOUNDARY WILL TAP INTO A PLUME OF GULF MOISTURE, DRIVING
A REBOUND IN BOTH HEAT AND HUMIDITY ACROSS THE MID-MISSISSIPPI
VALLEY. EXPECT HIGHS TO REACH THE MID-TO-UPPER 80S WEDNESDAY
AFTERNOON, WHILE SURFACE DEWPOINTS POOL INTO THE LOW-TO-MID 70S,
YIELDING HEAT INDICES PUSHING INTO THE LOWER 90S.
THE MAIN FORECAST CHALLENGE AND POTENTIAL IMPACT PERIOD ARRIVES
LATE WEDNESDAY NIGHT INTO THURSDAY. ADDITIONAL SHORTWAVE
ENERGY DIGGING ACROSS THE CORN BELT WILL REINVIGORATE THE
SURFACE FRONT, PROVIDING THE NECESSARY SYNOPTIC ASCENT TO DRIVE
THE BOUNDARY THROUGH CENTRAL ILLINOIS DURING THE DAY THURSDAY.
WIDESPREAD SHOWERS AND THUNDERSTORMS ARE EXPECTED TO ACCOMPANY
THE FRONTAL PASSAGE. MODEL SOUNDINGS CONTINUE TO HIGHLIGHT A
PARAMETER SPACE FAVORABLE FOR ORGANIZED CONVECTION, FEATURING
SURFACE-BASED CAPE VALUES OF 1500-2500 J/KG AND 0-6 KM BULK
SHEAR ON THE ORDER OF 20-30 KNOTS ALONG THE FRONTAL ZONE. A
MARGINAL THREAT FOR SEVERE WEATHER (PRIMARILY ISOLATED DAMAGING
WIND GUSTS AND HAIL) APPEARS PLAUSIBLE DURING THE PEAK HEATING
HOURS ON THURSDAY, AND THIS THREAT WILL CONTINUE TO BE
MONITORED AS HIGH-RESOLUTION GUIDANCE COMES INTO RANGE.
GUIDANCE CONTINUES TO DEMONSTRATE SOME DISPARITY REGARDING POST-
FRONTAL TIMING AND BOUNDARY ORIENTATION HEADING INTO FRIDAY:
1. FAST/PROGRESSIVE SOLUTION: ONE ENSEMBLE SUBSET PUSHES THE
COLD FRONT ENTIRELY SOUTH OF THE KILX CWA BY THURSDAY EVENING,
ALLOWING A SECONDARY BUBBLE OF WEAK SURFACE HIGH PRESSURE TO
BUILD IN. THIS SCENARIO WOULD FAVOR DRIER CONDITIONS FOR FRIDAY
AND SATURDAY.
2. HUNG-UP WAVE SOLUTION: AN ALTERNATE CAMP KEEPS THE SURFACE
BOUNDARY STALLED OR DRAPED ACROSS SOUTHERN/CENTRAL ILLINOIS INTO
FRIDAY. A TRAILING SHORTWAVE MIGRATING ALONG THE BOUNDARY WOULD
MAINTAIN SHOWER AND THUNDERSTORM CHANCES THROUGH FRIDAY
AFTERNOON BEFORE FINALLY PUSHING THE BAROCLINIC ZONE SOUTH.
REGARDLESS OF LATE-WEEK TIMING NUANCES, GLOBAL ENSEMBLES SHOW
GENERAL CONSENSUS ON UPPER-LEVEL RIDGING BUILDING BACK ACROSS
THE MIDWEST BY NEXT WEEKEND. THIS SHOULD SUPPORT A RETURN TO
MOSTLY DRY CONDITIONS FOR MOST OF THE AREA, WITH TEMPERATURES
TRENDING BACK TOWARD THE 90F MARK TO KICK OFF THE SECOND WEEK OF
AUGUST.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1151 AM CDT SUN AUG 2 2026
BKN STRATOCU WILL DOMINATE THE CENTRAL IL TERMINALS THIS
AFTERNOON, WITH BASES RISING ABOVE 3K FEET OVER THE NEXT FEW
HOURS. BEYOND THIS, A PERIOD OF MVFR VISIBILITY IS LIKELY EARLY
MONDAY MORNING DUE TO LIGHT FOG. NNE WINDS WILL GUST NEAR 20 KT
AT TIMES THIS AFTERNOON THEN DIMINISH BY EARLY EVENING,
REMAINING LIGHT THROUGH MIDDAY MONDAY.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...25
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