676
FXUS63 KILX 291045
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
545 AM CDT MON JUN 29 2026
KEY MESSAGES
- A HEAT ADVISORY IS IN EFFECT FROM TODAY THROUGH THURSDAY AS
HEAT INDEX READINGS PEAK AT 105-110 DEGREES EACH AFTERNOON.
- THUNDERSTORM CHANCES WILL GRADUALLY INCREASE FRIDAY INTO THE
UPCOMING HOLIDAY WEEKEND.
DISCUSSION
ISSUED AT 347 AM CDT MON JUN 29 2026
**** HOT AND HUMID WEATHER ****
08Z/3AM WATER VAPOR IMAGERY SHOWS A PRONOUNCED UPPER TROUGH
ALONG/WEST OF THE ROCKIES WITH A CORRESPONDING DOWNSTREAM RIDGE
CENTERED FROM THE GULF COAST NORTHWARD TO THE GREAT LAKES.
THANKS TO RISING UPPER HEIGHTS, THE PERSISTENT FRONTAL BOUNDARY
THAT BROUGHT SEVERAL DAYS OF SHOWERS/STORMS TO SOUTHERN ILLINOIS
AND THE OHIO RIVER VALLEY HAS LIFTED NORTHWARD TO THE I-74
CORRIDOR. THE FRONT WILL CONTINUE ITS NORTHWARD TREK INTO THE
UPPER MIDWEST/GREAT LAKES TODAY, PLACING ALL OF CENTRAL AND
SOUTHEAST ILLINOIS SQUARELY IN A HOT/HUMID AIRMASS. PARTIAL
CLOUD COVER WILL DO LITTLE TO MITIGATE THE WARMING, AS FORECAST
SOUNDINGS AND NUMERIC GUIDANCE SUGGEST AFTERNOON HIGHS CLIMBING
INTO THE LOWER 90S. EVEN HOTTER CONDITIONS WILL BE ON TAP FOR
TUESDAY AND WEDNESDAY: HOWEVER, GUIDANCE INCLUDING THE
MET/MAV/NBM APPEAR TO BE A FEW DEGREES TOO WARM IN THE UPPER
90S. AS THE RIDGE AXIS SHIFTS EASTWARD, 500MB HEIGHTS WILL DROP
INTO THE 592-594DM RANGE OVER CENTRAL ILLINOIS. IN ADDITION,
PLENTIFUL BOUNDARY LAYER MOISTURE WITH DEWPOINTS IN THE MIDDLE
70S WILL TEMPER THE HEATING. AS A RESULT, THINK HIGHS WILL ONLY
RISE A COUPLE OF DEGREES INTO THE MIDDLE 90S FOR TUESDAY THROUGH
THURSDAY. NONETHELESS, AFTERNOON HEAT INDEX VALUES WILL EXCEED
105 DEGREES WHILE OVERNIGHT READINGS ONLY DROP INTO THE MIDDLE
TO UPPER 70S. WHILE THESE CONDITIONS ARE CERTAINLY NOT OUT OF
THE ORDINARY FOR THIS TIME OF YEAR, THIS IS THE FIRST TIME THIS
SUMMER THE REGION WILL EXPERIENCE A PROLONGED PERIOD OF
HEAT/HUMIDITY. AS A RESULT, THE HEAT ADVISORY WILL CONTINUE
THROUGH THURSDAY. INCREASING CLOUD COVER AND CONVECTION CHANCES
WILL LIKELY RESULT IN A SLIGHT COOLING BY FRIDAY, ALTHOUGH THE
ADVISORY MAY EVENTUALLY NEED TO BE EXTENDED FOR LOCATIONS
ALONG/SOUTH OF THE I-70 CORRIDOR IF TRENDS CONTINUE.
**** THUNDERSTORM CHANCES RETURN BY THE END OF THE WEEK ****
A SERIES OF SHORT-WAVE TROUGHS EJECTING NORTHEASTWARD OUT OF THE
ROCKIES WILL GRADUALLY FLATTEN THE PREVAILING UPPER RIDGE BY THE
END OF THE WEEK. WHILE THE MAIN BAROCLINIC ZONE WILL REMAIN
FOCUSED FROM MICHIGAN SOUTHWESTWARD TO NEBRASKA, A MORE
SIGNIFICANT WAVE MAY NUDGE THE FRONT A BIT SOUTHWARD AND BRING
AN INCREASED RAIN CHANCE TO AT LEAST THE NORTHERN HALF OF THE
KILX CWA ON FRIDAY. THE 00Z JUN 29 GFS/ECMWF/GEM ARE ALL IN
EXCELLENT AGREEMENT CONCERNING THIS PROCESS, SO HAVE THEREFORE
INTRODUCED 30-40 POPS ACROSS THE AREA. WILL NEED TO KEEP AN EYE
ON HOW FAR SOUTH THE FRONT GETS NUDGED, AS THE LATEST WPC
OUTLOOK INDICATES A MARGINAL RISK (5-15% CHANCE) FOR EXCESSIVE
RAINFALL AS FAR SOUTH AS GALESBURG AND LACON.
ONCE THE FRIDAY SHORT-WAVE EXITS, A FLAT WEST-TO-EAST ZONAL FLOW
PATTERN WILL PREVAIL ACROSS THE MIDWEST AS ALL MODELS SHOW THE
RIDGE RETROGRADING WESTWARD TOWARD THE DESERT SOUTHWEST. IT IS
DIFFICULT TO PINPOINT/TIME ANY SUBTLE SHORT-WAVES EMBEDDED
WITHIN THE FLOW AT THAT TIME RANGE, SO FORECAST CONFIDENCE FOR
THE 4TH OF JULY REMAINS POOR. THE CURRENT MODEL SUITE DOES NOT
SHOW ANY DISTINCT FORCING MECHANISM OTHER THAN PERHAPS LINGERING
OUTFLOW BOUNDARIES, SO RAIN CHANCES SHOULD BE LOW. AFTER THAT,
ANOTHER STRONGER SHORT-WAVE WILL TRACK ACROSS THE PLAINS AND DIG
SOUTHEASTWARD INTO THE OHIO RIVER VALLEY. THIS WILL PUSH A COLD
FRONT THROUGH CENTRAL ILLINOIS ON SUNDAY, FOLLOWED BY A RETURN
OF MORE SEASONABLE TEMPERATURES IN THE UPPER 80S BY EARLY NEXT
WEEK.
AVIATION /12Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 545 AM CDT MON JUN 29 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 12Z TAF PERIOD.
1030Z/530AM SATELLITE IMAGERY SHOWS A FEW PATCHES OF MID-LEVEL
CLOUDS AT AROUND 15,000FT DRIFTING ACROSS THE SKY. NAM/RAP
FORECAST SOUNDINGS SUGGEST SCT DIURNAL CU AT 2500-3500FT
DEVELOPING AFTER 15Z...WITH THE CLOUD COVER FADING AWAY PRIOR
TO SUNSET. WINDS WILL INITIALLY BE S/SE AT LESS THAN 10KT EARLY
THIS MORNING, THEN WILL VEER TO S/SW AND GUST TO AROUND 20KT
FROM LATE MORNING THROUGH THE AFTERNOON.
ILX WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY FROM 11 AM THIS MORNING TO MIDNIGHT CDT THURSDAY
NIGHT FOR ILZ027>031-036>038-040>057-061>063-066>068-071>073.
KEY MESSAGES...BARNES
DISCUSSION...BARNES
AVIATION...BARNES
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