062
FXUS63 KILX 291912
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
212 PM CDT TUE JUL 29 2025
KEY MESSAGES
- A HEAT ADVISORY REMAINS IN EFFECT FOR CENTRAL IL INTO THIS
EVENING, AND ACROSS SOUTHEAST ILLINOIS THROUGH WEDNESDAY
AFTERNOON.
- THUNDERSTORMS WILL DEVELOP ALONG A SLOW-MOVING COLD FRONT
WEDNESDAY, BRINGING A RISK OF STRONG STORMS AND TORRENTIAL
RAINFALL.
- COOLER AND LESS HUMID AIR FOLLOWS THE FRONTAL PASSAGE FOR
THURSDAY INTO THE WEEKEND.
DISCUSSION
ISSUED AT 212 PM CDT TUE JUL 29 2025
OUTFLOW FROM LAST NIGHT'S UPPER MIDWEST DERECHO HAD CLEARED THE
ENTIRE CWA BY LATE MORNING. TEMPORARY NORTH WINDS IN ITS WAKE
MIXED SLIGHTLY LOWER DEW POINTS DOWN TO THE SURFACE, MAINLY LOW-
MID 70S, THOUGH STILL UPPER 70S ALONG/SOUTH OF I-70. SO WHILE
PEAK HEAT INDICES THIS AFTERNOON ARE A FEW DEGREES LOWER THAN
YESTERDAY, STILL LOOKING AT WIDESPREAD 100-105, ANOTHER DANGEROUS
DAY FOR THOSE VULNERABLE TO HEAT STRESS.
OVERALL QUIET WEATHER IS EXPECTED ACROSS THE LOCAL AREA THROUGH
TONIGHT. HAVE A WEARY EYE TO THE NORTHWEST, WHERE A COUPLE
THUNDERSTORM COMPLEXES HAVE DEVELOPED OVER NORTHERN IA TODAY ALONG
A SHARP CAPE GRADIENT. CONVECTIVE ALLOWING MODELS HAVE HAD A POOR
HANDLE ON THIS, AND THOUGH THE DOWNSTREAM ENVIRONMENT IS LESS
FAVORABLE FOR ORGANIZED CONVECTION, THIS WILL BEAR WATCHING GIVEN
STRONG INSTABILITY BUILDING ACROSS SOUTHERN IA AND RESULTING CAPE
GRADIENT JUST TO OUR NW LATE THIS AFTERNOON AND EVENING.
SHORTWAVE ENERGY ENTERING THE PLAINS THIS EVENING ALONG A FIRMING
FRONTAL ZONE WILL LIKELY DEVELOP ANOTHER LARGE MCS ACROSS EASTERN
NE AND WESTERN IA, SPREADING INTO WESTERN IL AFTER DAYBREAK WED. A
WEAKENING LOW LEVEL JET AND UNFAVORABLE DIURNAL TIMING SHOULD
CAUSE THESE STORMS TO DISSIPATE AS THEY MOVE INTO THE CWA. HOWEVER
WITH INCREASING AFTERNOON INSTABILITY, FESTERING CLUSTERS OF
LOOSELY ORGANIZED STORMS APPEAR LIKELY, GIVEN 20-30 KT DEEP LAYER
SHEAR. ISOLATED DAMAGING WIND GUSTS ARE THE PRIMARY SEVERE RISK,
AS NOTED BY SPC'S DAY 2 MARGINAL RISK FOR ALL OF CENTRAL/SE IL.
LOCALLY HEAVY RAIN WILL ALSO BE A CONCERN GIVEN VERY HIGH PWATS
NEAR 2.2" (FOR REFERENCE 2.4" IS THE RECORD HIGH FOR ILX
SOUNDINGS). HREF LPMM SHOWS POCKETS OF 2-3" 3-HOUR QPF WED
AFTERNOON AND EVENING NORTH OF I-72, SO A LOCALIZED FLASH FLOOD
THREAT EXISTS, HIGHLIGHTED IN WPC'S DAY 2 SLIGHT RISK.
HEAT WILL AGAIN BE A CONCERN WED, THOUGH WITH LOWER CONFIDENCE ON
LOCATION THAN RECENT DAYS DUE TO INCREASED CLOUD COVER AND
CONVECTIVE OUTFLOW FROM THE NORTH. CURRENT GRIDDED FORECAST SHOWS
HEAT INDICES PEAKING AT 100-105F AS FAR NORTH AS A TAYLORVILLE TO
PARIS LINE. IN COLLABORATION WITH ADJACENT WFOS, EXTENDED THE
CURRENT HEAT ADVISORY FOR THESE AREAS THROUGH WEDNESDAY AFTERNOON.
THE FRONTAL ZONE GRADUALLY WORKS SOUTHEAST THROUGH THE CWA WED
NIGHT AND THU, WITH WAVES OF SHOWERS AND STORMS DIMINISHING FROM
THE NORTH THROUGH TIME. MAJOR PATTERN SHIFT BEHIND THE FRONT DUE
TO AMPLIFYING UPPER RIDGING OVER THE ROCKIES AND A DEEPENING
EASTERN CONUS TROUGH. THIS TO BRING NORTHWEST UPPER FLOW TO THE
REGION, USHERING CANADIAN HIGH PRESSURE INTO THE GREAT LAKES
THROUGH THIS WEEKEND, AND A PLEASANT AIRMASS WE HAVEN'T SEEN
SINCE EARLY JUNE. NBM CONTINUES TO ADVERTISE 75-80F HIGHS THU-SAT
WITH LOWS DROPPING INTO THE UPPER 50S.
25
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1205 PM CDT TUE JUL 29 2025
MAINLY CLEAR SKIES AND LIGHT WINDS THROUGH TONIGHT. THIS SHOULD
ALLOW PATCHY MVFR FOG TO DEVELOP LATE, SO INCLUDED TEMPO GROUP FOR
THIS. AFTER SUNRISE, WILL BE WATCHING FOR AN AREA OF SCATTERED
STORMS TRACKING SOUTHEAST OUT OF IA. WITH CONCERNS ON TIMING AND
COVERAGE, WENT WITH PROB30 GROUP FOR TSRA DURING THE LATE MORNING.
25
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR ILZ027-029-036-037-
040>051-053.
HEAT ADVISORY UNTIL 7 PM CDT WEDNESDAY FOR ILZ052-054>057-
061>063-066>068-071>073.
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