727
FXUS63 KILX 231950
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
250 PM CDT TUE JUN 23 2026
KEY MESSAGES
- THERE IS A MARGINAL RISK (5-15% CHANCE) OF EXCESSIVE RAINFALL
ALONG AND SOUTH OF A DANVILLE TO BEARDSTOWN LINE THURSDAY
THROUGH FRIDAY.
- A MAJOR PATTERN CHANGE WILL BRING A RETURN TO TYPICAL
SUMMERTIME HEAT AND HUMIDITY BY EARLY NEXT WEEK. THE LATEST
NBM INDICATES AN 80-100% CHANCE OF HIGH TEMPERATURES CLIMBING
ABOVE 90 DEGREES BY NEXT MONDAY AND TUESDAY.
DISCUSSION
ISSUED AT 250 PM CDT TUE JUN 23 2026
*** SCATTERED THUNDERSTORMS WEDNESDAY ***
A COLD FRONT CURRENTLY EXTENDING FROM THE DAKOTAS TO COLORADO
WILL SINK SOUTHEASTWARD OVER THE NEXT 24 HOURS. THE PRE-FRONTAL
AIRMASS ACROSS CENTRAL ILLINOIS WILL INITIALLY BE DRY/SUBSIDENT:
HOWEVER, SOUTHWESTERLY FLOW AHEAD OF THE BOUNDARY WILL LEAD TO
DEWPOINTS CLIMBING INTO THE MIDDLE 60S AND PRECIPITABLE WATER
VALUES INCREASING TO 1.25-1.50 BY WEDNESDAY AFTERNOON. DUE TO
THE LACK OF BOUNDARY LAYER MOISTURE, INSTABILITY WILL REMAIN
WEAK...WITH SBCAPES LESS THAN 1000J/KG ACROSS MUCH OF CENTRAL
ILLINOIS. THE EXCEPTION WILL BE IN A NARROW CORRIDOR CLOSER TO
THE FRONT ALONG/NORTHWEST OF THE ILLINOIS RIVER WHERE DEWPOINTS
MAY REACH THE UPPER 60S AND SBCAPES WILL CLIMB INTO THE
1000-2000J/KG RANGE. DEEP-LAYER SHEAR WILL ALSO BE MAXIMIZED
WITHIN THIS CORRIDOR AS EVIDENCED BY NAM 0-6KM SHEAR VALUES OF
AROUND 40KT. AS A RESULT, THINK SCATTERED SHOWERS AND
THUNDERSTORMS WILL DEVELOP WEDNESDAY AFTERNOON...MAINLY WEST OF
THE I-57 CORRIDOR. WHILE SPC HAS NOT YET HIGHLIGHTED A SEVERE
RISK FOR ANY PART OF CENTRAL ILLINOIS, A FEW OF THE CELLS
ALONG/WEST OF THE ILLINOIS RIVER MAY CONTAIN GUSTY WINDS AND
SMALL HAIL DURING THE LATE AFTERNOON/EARLY EVENING. THE
SCATTERED SHOWERS/THUNDER WILL SPREAD FURTHER EAST ACROSS THE
REMAINDER OF CENTRAL ILLINOIS WEDNESDAY NIGHT, THEN WILL DEPART
INTO INDIANA BY THURSDAY MORNING.
*** HEAVY RAINFALL RISK THURSDAY INTO FRIDAY ***
THE MID-WEEK COLD FRONT WILL BECOME PARALLEL WITH THE PREVAILING
ZONAL FLOW PATTERN AND WILL GRADUALLY STALL ACROSS SOUTH-CENTRAL
ILLINOIS ON THURSDAY. AS A SERIES OF SHORT-WAVE TROUGHS EJECTING
EASTWARD FROM THE PLAINS INTERACTS WITH THE STALLED BOUNDARY,
PERIODS OF SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS MAINLY
THE SOUTHERN TWO-THIRDS OF THE KILX CWA THURSDAY AFTERNOON
THROUGH FRIDAY NIGHT. WITH A 40-50KT 850MB JET STREAK PROGGED TO
DEVELOP FROM TEXAS NORTHEASTWARD INTO SOUTHERN ILLINOIS AND THE
OHIO RIVER VALLEY, PRECIPITABLE WATER VALUES WILL SURGE INTO
THE 2.00-2.50 RANGE ALONG/SOUTH OF THE I-72 CORRIDOR THURSDAY
NIGHT. AS A RESULT, SHOWERS AND THUNDERSTORMS WILL BECOME
WIDESPREAD AND HEAVY RAINFALL WILL BE LIKELY. ONCE THE INITIAL
WAVE PASSES, A SECOND DISTURBANCE WILL BRING ANOTHER ROUND OF
RAIN FRIDAY NIGHT INTO SATURDAY MORNING. THE EXACT LOCATION OF
THE SECOND ROUND IS STILL SOMEWHAT IN QUESTION AND MAY BE
SLIGHTLY FURTHER SOUTH THAN THE INITIAL THURSDAY NIGHT RAINFALL:
HOWEVER, ALL INDICATIONS STRONGLY SUGGEST THE HIGHEST AMOUNTS OF
2 TO 3.50 INCHES WILL FOCUS ALONG/SOUTH OF A PARIS TO PITTSFIELD
LINE. RAINFALL OF THIS MAGNITUDE OCCURRING ON ALREADY SATURATED
SOILS/WATER-LOGGED FIELDS WILL LEAD TO STEEP RISES ON AREA
STREAMS AND MAY POSE A LOCALIZED FLASH FLOOD RISK. AS A RESULT,
A FLOOD WATCH WILL NEED TO BE CAREFULLY CONSIDERED OVER THE NEXT
COUPLE OF FORECAST CYCLES. FURTHER NORTH AWAY FROM THE
STRONGEST FORCING AND DEEPEST MOISTURE, RAINFALL WILL BE
CONSIDERABLY LIGHTER...WITH LOCATIONS ALONG/NORTH OF A MACOMB TO
BLOOMINGTON LINE SEEING LESS THAN 1 INCH.
*** SUMMERTIME HEAT AND HUMIDITY EARLY NEXT WEEK ***
A STRONG JET STREAM OVER THE NORTHERN PACIFIC WILL NUDGE A DEEP
UPPER LOW OVER THE GULF OF ALASKA SOUTHEASTWARD LATER THIS WEEK.
MODELS HAVE BEEN CONSISTENTLY SHOWING THIS FEATURE DIGGING WEST
OF THE ROCKIES, RESULTING IN DOWNSTREAM RIDGING OVER THE MIDWEST
BY EARLY NEXT WEEK. AS UPPER HEIGHTS RISE, THE PERSISTENT
FRONTAL BOUNDARY FROM MISSOURI INTO THE OHIO RIVER VALLEY WILL
GRADUALLY GET SHIFTED NORTHWARD OVER THE WEEKEND...RESULTING IN
A CONTINUED RISK FOR A FEW SHOWERS AND THUNDERSTORMS, BUT ALSO
AN INCREASE IN HEAT AND HUMIDITY. HIGH TEMPERATURES WILL REACH
THE UPPER 80S/LOWER 90S BY SUNDAY, THEN AS THE RIDGE BECOMES
MORE PROMINENT ACROSS THE AREA, THE 12Z NBM INDICATES AN 80-100%
CHANCE OF TEMPS CLIMBING ABOVE 90 DEGREES BY NEXT MONDAY AND
TUESDAY. GIVEN DEWPOINTS IN THE MIDDLE TO UPPER 70S, CORRESPONDING
HEAT INDEX READINGS WILL EXCEED 100 DEGREES. AS A RESULT, THE
LATEST PROBABILISTIC HEAT RISK SHOWS A 60-90% CHANCE OF REACHING
THE MAJOR CATEGORY ACROSS NEARLY ALL OF CENTRAL AND SOUTHEAST
ILLINOIS FOR BOTH DAYS.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 1247 PM CDT TUE JUN 23 2026
VFR CONDITIONS WILL PREVAIL THROUGH THE ENTIRE 18Z TAF PERIOD.
FEW-SCT DIURNAL CU AT 4000-5000FT WILL DEVELOP EAST OF THE
ILLINOIS RIVER THIS AFTERNOON...WITH PERHAPS A FEW PERIODS OF
BKN CU ALONG/WEST OF THE RIVER. ONCE THESE CLOUDS FADE AWAY
PRIOR TO SUNSET, A HIGH/THIN OVERCAST WILL BE OBSERVED EARLY
THIS EVENING BEFORE NAM/HRRR FORECAST SOUNDINGS INDICATE A
BKN-OVC MID-LEVEL DECK AT AROUND 12,000FT WILL SPREAD ACROSS THE
AREA OVERNIGHT INTO WEDNESDAY MORNING. A FEW SHOWERS/THUNDERSTORMS
MAY DEVELOP ALONG/WEST OF I-55 IN ADVANCE OF A COLD FRONT
TOWARD MIDDAY WEDNESDAY, BUT OPTED TO LEAVE PRECIP MENTION OUT
OF THE TAFS UNTIL MODEL/RADAR TRENDS DICTATE. WINDS WILL
INITIALLY BE LIGHT/VARIABLE, THEN WILL BECOME S/SW AT 8-12KT BY
WEDNESDAY MORNING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...25/BARNES
DISCUSSION...BARNES
AVIATION...BARNES
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