689
FXUS63 KILX 281734
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
1234 PM CDT SUN JUN 28 2026
KEY MESSAGES
- ISOLATED STORM THREAT TODAY: THERE IS A VERY LOW CHANCE
(UNDER 20%) FOR STRONG TO SEVERE THUNDERSTORMS TO DEVELOP LATE
THIS AFTERNOON AND EVENING NEAR AND NORTH OF THE INTERSTATE
74 CORRIDOR.
- DANGEROUS HEAT WAVE: A PROLONGED HEAT WAVE WILL BRING
DANGEROUS HEAT INDEX VALUES OF 100 TO 105 DEGREES DAILY ACROSS
ALL OF CENTRAL ILLINOIS THROUGH THURSDAY.
- HOLIDAY WEEKEND STORMS: DAILY THUNDERSTORM CHANCES RETURN
THURSDAY AND LAST THROUGH THE HOLIDAY WEEKEND, BRINGING A RISK
OF LOCALIZED HEAVY RAINFALL AND ISOLATED STRONG STORMS.
DISCUSSION
ISSUED AT 1230 PM CDT SUN JUN 28 2026
NEAR TERM (THIS AFTERNOON AND EVENING):
A DIFFUSE SURFACE WARM FRONT IS CURRENTLY ANALYZED ACROSS THE
AREA, STRETCHING ROUGHLY FROM NEAR THE QUAD CITIES SOUTHEASTWARD
TOWARD TERRE HAUTE. DOWNSTREAM OF AN ENERGETIC UPPER-LEVEL LOW
PIVOTING OVER THE WESTERN UNITED STATES, A CONVECTIVELY ENHANCED
SHORTWAVE IS TRACKING ACROSS THE UPPER MISSISSIPPI VALLEY. THESE
FEATURES WILL PROVIDE ENOUGH SYNOPTIC IMPETUS TO LIFT THE
SURFACE FRONT NORTHWARD THROUGH THIS EVENING.
THE PRIMARY FORECAST CHALLENGE REVOLVES AROUND A DECAYING
MESOSCALE CONVECTIVE SYSTEM (MCS) CURRENTLY CHURNING THROUGH
EASTERN IOWA. HIGH-RESOLUTION CONVECTIVE-ALLOWING MODELS (CAMS)
SUGGEST THIS SYSTEM COULD MAINTAIN ENOUGH INTEGRITY TO PUSH AN
OUTFLOW BOUNDARY INTO OUR NECK OF THE WOODS. IF THIS OUTFLOW
INTERSECTS THE NORTHWARD-LIFTING WARM FRONT NEAR THE I-74
CORRIDOR, IT COULD SERVE AS THE FOCAL POINT FOR NEW CONVECTIVE
INITIATION LATER TODAY. WHILE THE OVERALL PROBABILITY OF
OCCURRENCE REMAINS VERY LOW (20% CHANCE OR LESS), THE
ENVIRONMENT CANNOT BE IGNORED; SUBSTANTIAL THERMODYNAMIC
INSTABILITY PAIRED WITH MID- LEVEL BULK SHEAR EXCEEDING 30 KNOTS
WOULD EASILY SUPPORT A STRONG TO SEVERE THUNDERSTORM THREAT FOR
ANY UPDRAFTS THAT MANAGE TO ACCELERATE PAST A 750-MB WARM
LAYER.
OUTSIDE OF THIS LOCALIZED CONDITIONAL THREAT ALONG AND
NORTH OF THE I-74 CORRIDOR, PRECIPITATION CHANCES HAVE FALLEN
OFF A CLIFF FOR THE REST OF THE CWA AS THE SYNOPTIC PATTERN
AMPLIFIES.
MIDWEEK HEAT WAVE (MONDAY THROUGH THURSDAY):
THE AFOREMENTIONED WESTERN TROUGH IS DRIVING ROBUST HEIGHT
RISES DOWNSTREAM, CEMENTING A POTENT, HIGHLY ANOMALOUS HEAT DOME
OVER THE OHIO RIVER VALLEY AND THE MIDWEST. THIS DEEP LAYER
RIDGE WILL GOVERN OUR WEATHER THROUGH THE MIDDLE OF THE WEEK,
RESULTING IN A PROLONGED PERIOD OF DANGEROUS HEAT.
DAILY HIGH TEMPERATURES WILL CONSISTENTLY CLIMB INTO THE LOW
90S. WHILE RAW TEMPERATURES ARE NOTEWORTHY, THE REAL STORY WILL
BE THE OPPRESSIVE HUMIDITY. SIGNIFICANT MOISTURE POOLING WITHIN
THE BOUNDARY LAYER WILL PUSH DEWPOINTS WELL INTO THE 70S. NBM
GUIDANCE HEAVILY FAVORS WIDESPREAD HEAT INDICES CLIMBING INTO
THE 100-105 F RANGE DAILY FROM TODAY STRAIGHT THROUGH THURSDAY.
GIVEN THE LACK OF NOCTURNAL RELIEF AND THE MULTI-DAY DURATION
OF THIS EVENT, AN EXCESSIVE HEAT ADVISORY REMAINS IN EFFECT FOR
ALL OF CENTRAL ILLINOIS THROUGH THURSDAY.
END OF WEEK AND THE HOLIDAY WEEKEND:
BY THURSDAY INTO FRIDAY, THE CORE OF THE UPPER-LEVEL RIDGE IS
PROGGED TO MIGRATE TOWARD THE MID-ATLANTIC COAST. THIS EASTWARD
SHIFT WILL OPEN THE DOOR TO A BROADER, MORE ACTIVE SOUTHWEST
FLOW ALOFT ACROSS THE MID-MISSISSIPPI RIVER VALLEY.
A SERIES OF SUBTLE SHORTWAVES EJECTING OUT OF THE SOUTHERN
PLAINS WILL TRAVERSE THIS FLOW, BRINGING A RETURN OF DAILY
THUNDERSTORM CHANCES TO THE FORECAST. WHILE DEEP-LAYER SHEAR
WILL BE SEASONALLY WEAK AS THE STRONGER JET DYNAMICS STAY WELL
TO OUR NORTH, THE COMBINATION OF RICH BOUNDARY-LAYER INSTABILITY
AND MINOR SYNOPTIC ASCENT WILL BE SUFFICIENT TO WARRANT CLOSE
MONITORING. ISOLATED SEVERE WEATHER AND HEAVY DOWNPOURS CANNOT
BE RULED OUT LATE THIS WEEK AND HEADING INTO THE HOLIDAY
WEEKEND.
AVIATION /18Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 1155 AM CDT SUN JUN 28 2026
CEILINGS ARE QUICKLY LIFTING AND BREAKING THIS AFTERNOON AS A
SURFACE WARM FRONT LIFTS ACROSS THE REGIONAL TERMINALS. MOSTLY
CLEAR SKIES WILL RETURN ACROSS THE BOARD LATER THIS AFTERNOON AS
A PRONOUNCED RIDGE ASSERTS ITSELF OVER THE MIDWEST. SURFACE
WINDS WILL GRADUALLY VEER SOUTHERLY AND INCREASE MONDAY MORNING
AS THE PRESSURE GRADIENT TIGHTENS OVER THE CENTRAL U.S.,
OCCASIONALLY GUSTING TO 20 KTS.
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR ILZ027>029-036-
037-040>042-047>054-061-062-066>068-071>073.
HEAT ADVISORY FROM 11 AM MONDAY TO MIDNIGHT CDT THURSDAY NIGHT
FOR ILZ027>031-036>038-040>057-061>063-066>068-071>073.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...MJA
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