517
FXUS63 KILX 200757
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
257 AM CDT WED MAY 20 2026
KEY MESSAGES
- COOLER AND DRIER WEATHER SETTLES INTO THE REGION THROUGH
THURSDAY, THOUGH A FEW LIGHT MORNING SHOWERS REMAIN SOUTH OF
INTERSTATE 72. DAYTIME HIGH TEMPERATURES WILL STAY NEAR 70
DEGREES.
- WIDESPREAD RAIN WILL MOVE ACROSS CENTRAL ILLINOIS FRIDAY
AFTERNOON AND EVENING. WHILE RAIN IS HIGHLY LIKELY, TOTAL
AMOUNTS REMAIN UNCERTAIN AND COULD RANGE BETWEEN 0.10 AND 0.90
INCHES.
- TEMPERATURES WARM INTO THE UPPER 70S THIS WEEKEND AND CONTINUE
TO CLIMB NEXT WEEK. HIGH CONFIDENCE EXISTS THAT AFTERNOON HEAT
IN THE MID 80S WILL RETURN BY THE MIDDLE OF NEXT WEEK.
DISCUSSION
ISSUED AT 252 AM CDT WED MAY 20 2026
SCATTERED SHOWERS MAY PERSIST THROUGH LATE MORNING FOR AREAS
NEAR AND SOUTH OF INTERSTATE 72 AS A MID-LEVEL SHORTWAVE TROUGH
OVER SE MISSOURI TRACKS NORTHEAST ALONG A BAGGY BAROCLINIC ZONE.
WITH THE PRIMARY AXIS OF INSTABILITY NOW SHIFTED TOWARD THE
OHIO RIVER VALLEY, ANY RESULTING PRECIPITATION SHOULD REMAIN
LIGHT, WITH A MINIMAL RISK OF THUNDERSTORMS.
ALTHOUGH HREF CAM GUIDANCE VARIES, WITH SOME MODELS DEPICTING
DRY CONDITIONS, THE MEAN HREF QPF SUGGESTS TOTALS UP TO ONE-
TENTH OF AN INCH NEAR I-72, WITH UP TO ONE-QUARTER OF AN INCH
POSSIBLE SOUTH OF A TAYLORVILLE-TO-PARIS LINE.
OTHERWISE, A COOLER AND DRIER TREND IS TAKING SHAPE TODAY AND
THURSDAY AS SURFACE HIGH PRESSURE SETTLES OVER THE GREAT LAKES
REGION. HIGH TEMPERATURES MAY STRUGGLE TO REACH 70 DEGREES,
WHILE OVERNIGHT LOWS DROP INTO THE UPPER 40S AND LOWER 50S. SOME
FORECAST MODELS ALSO INDICATE THAT A LAKE BREEZE FROM LAKE
MICHIGAN MAY PENETRATE AS FAR INLAND AS THE I-74 CORRIDOR LATE
THIS AFTERNOON AND AGAIN TOMORROW, LIKELY RESULTING IN A COOLER
FEEL DURING THE EVENING HOURS.
THE PERIOD OF DRY WEATHER WILL BE SHORT-LIVED. BY FRIDAY
MORNING, A SERIES OF SHORTWAVE IMPULSES IS EXPECTED TO MOVE
NORTHWARD FROM THE LOWER-MISSISSIPPI VALLEY, PRECEDING A MORE
SIGNIFICANT TROUGH MOVING THROUGH THE CENTRAL UNITED STATES.
THIS SHIFT IN THE ATMOSPHERIC PATTERN WILL PUSH A SURFACE FRONT
INTO CENTRAL ILLINOIS AROUND MIDDAY FRIDAY. CONSEQUENTLY,
WIDESPREAD SHOWERS ARE ANTICIPATED ACROSS THE FORECAST AREA
FRIDAY AFTERNOON AND EVENING, DRIVEN BY ISENTROPIC ASCENT AND
WARM-AIR ADVECTION. WHILE LIMITED INSTABILITY SHOULD PREVENT
SEVERE CONVECTIVE WEATHER, HIGH PRECIPITABLE WATER (PWAT) VALUES
MAY LEAD TO HIGH RAINFALL EFFICIENCY. FORECASTED RAINFALL
TOTALS REMAIN UNCERTAIN; THE 100-MEMBER LREF GLOBAL ENSEMBLE
SHOWS A 25TH-75TH PERCENTILE RANGE OF 0.10 TO 0.90 INCHES FOR
OUR FORECAST AREA. WHILE CONFIDENCE IN THE OCCURRENCE OF RAIN IS
HIGH, THE SPECIFIC ACCUMULATION AMOUNTS AMONG MODEL GUIDANCE
REMAIN HIGHLY VARIABLE. THOUGH, IT IS WORTH NOTING THAT THIS
SAME GUIDANCE CURRENTLY FOCUSES THE HIGHER QPF ACROSS SE
ILLINOIS. AS THE FRONT SHIFTS NORTHWARD THROUGH THE REGION ON
FRIDAY, TEMPERATURES ARE EXPECTED TO SURGE THIS WEEKEND, WITH
HIGHS REACHING THE UPPER 70S BOTH SATURDAY AND SUNDAY.
THE MAIN UPPER TROUGH AXIS SWINGING THROUGH THE MIDWEST MAY
TRIGGER ADDITIONAL SCATTERED SHOWERS OVER THE WEEKEND. HOWEVER,
FOLLOWING THE PASSAGE OF THE INITIAL FRONTAL ZONE ON FRIDAY,
MID-LEVEL RH PROFILES APPEAR SIGNIFICANTLY DRIER, RESULTING IN
SUBSTANTIALLY LOWER QPF FOR SATURDAY AND SUNDAY.
HEADING INTO NEXT WEEK, GLOBAL DETERMINISTIC MODELS SUGGEST THE
DEVELOPMENT OF A REX BLOCK OVER THE PLAINS. THE PROGRESSION OF
THE ASSOCIATED UPPER LOW WILL ULTIMATELY DICTATE RAIN AND STORM
POTENTIAL THROUGH EARLY NEXT WEEK. CURRENT INDICATIONS SUGGEST
THAT AREAS SOUTH OF I-72 ARE BEST POSITIONED FOR RAINFALL AS THE
LOW PORTION OF THE BLOCK PIVOTS UP THE MISSISSIPPI VALLEY WHILE
THE HIGH-PRESSURE SIDE LOITERS OVER THE CORN BELT. THERE IS
STRONGER MODEL AGREEMENT REGARDING TEMPERATURES, WITH MID-TO-
UPPER 80S HEAT FORECAST TO RETURN BY THE MIDDLE OF NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1144 PM CDT TUE MAY 19 2026
A COOLER, DRIER CONTINENTAL AIRMASS IS SETTLING OVER THE GREAT
LAKES REGION BEHIND A COLD FRONT. THIS WILL GRADUALLY SHIFT THE
BACK EDGE OF MVFR CEILINGS SOUTH OF THE CENTRAL ILLINOIS
TERMINALS OVERNIGHT. WINDS WILL GENERALLY REMAIN NORTHERLY
THROUGH WEDNESDAY MORNING, SHIFTING NORTHEAST PRIOR TO SUNSET.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...MJA
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