942
FXUS63 KILX 211055
AFDILX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LINCOLN IL
555 AM CDT THU MAY 21 2026
KEY MESSAGES
- A COOL DAY TODAY WITH TEMPERATURES PEAKING NEAR 70 DEGREES
WILL GIVE WAY TO A WARMING TREND THIS WEEKEND, WITH HIGHS
RISING INTO THE UPPER 70S.
- HIGH UNCERTAINTY SURROUNDS A STORM SYSTEM FRIDAY. WHILE A
DRIER OUTCOME IS EXPECTED FOR MOST OF CENTRAL ILLINOIS WITH
UNDER A QUARTER-INCH OF RAIN, A SOAKING RAINFALL REMAINS
POSSIBLE IF THE STORM TRACKS FURTHER NORTH.
- SUMMER-LIKE HEAT RETURNS BY THE MIDDLE OF NEXT WEEK AS
TEMPERATURES CLIMB INTO THE MID-TO- UPPER 80S. ANY RAIN NEXT
WEEK COULD FOCUS PRIMARILY SOUTH OF INTERSTATE 72.
DISCUSSION
ISSUED AT 322 AM CDT THU MAY 21 2026
A COOLER AND DRIER PATTERN WILL PERSIST THROUGH TODAY AS
SURFACE HIGH PRESSURE LINGERS OVER THE GREAT LAKES REGION. HIGH
TEMPERATURES MAY STRUGGLE TO REACH 70 DEGREES. SOME FORECAST
MODELS INDICATE THAT A LAKE BREEZE MAY PENETRATE AS FAR INLAND
AS THE I-74 CORRIDOR AGAIN THIS EVENING, LIKELY RESULTING IN
ANOTHER CHILLY LATE SPRING NIGHT WITH LOWS IN THE 50S.
A SERIES OF PROGRESSIVE SHORTWAVE IMPULSES IS MODELED TO EJECT
FROM THE SOUTHERN PLAINS FRIDAY MORNING AHEAD OF A BROADER,
DEEP-LAYER TROUGH AXIS PIVOTING ACROSS THE CENTRAL PLAINS. THIS
SYNOPTIC FORCING WILL LIFT A SURFACE LOW-PRESSURE SYSTEM INTO
THE LOWER OHIO RIVER VALLEY BY MIDDAY FRIDAY.
MODEL GUIDANCE DISPLAYS CONSIDERABLE SPREAD REGARDING THE EXACT
TRACK OF THIS LOW, WHICH YIELDS HIGH UNCERTAINTY FOR LOCAL QPF.
RECENT ITERATIONS OF THE GLOBAL DETERMINISTIC SUITES
(GFS/ECMWF) HAVE CONSISTENTLY SHIFTED THE TRACK OF THE SURFACE
LOW FURTHER SOUTHEAST. THIS TRACKS THE DEEPER MOISTURE AXIS AWAY
FROM OUR CWA, SUBSTANTIALLY LOWERING RAIN COVERAGE AND QPF
ACROSS CENTRAL ILLINOIS.
THE CANADIAN MODEL (CMC) CONTINUES TO BUCK THE CONSENSUS,
REMAINING A WESTERN OUTLIER BY PULLING THE SURFACE LOW DIRECTLY
THROUGH CENTRAL ILLINOIS AND BRINGING WIDESPREAD SOAKING RAINS.
HIGH-RESOLUTION ENSEMBLE FORECAST (HREF) MEMBERS REFLECT A
SIMILAR DICHOTOMY. THE HRRR AND NAMNEST RESTRICT MEANINGFUL RAIN
COVERAGE TO THE OHIO RIVER VALLEY, KEEPING CENTRAL ILLINOIS
LESS WET. CONVERSELY, THE NSSL WRF, ARW, AND FV3 DEPICT A MUCH
FURTHER NORTH EXPANSION OF THE RAIN SHIELD INTO OUR AREA.
LEANING HEAVILY ON THE BROADER GLOBAL DETERMINISTIC AND ENSEMBLE
TRENDS, A DRIER OUTCOME APPEARS MOST PROBABLE FOR THE BULK OF
THE ILX FORECAST AREA. THE HREF PROBABILITY MATCHED MEAN (PMM)
POSITIONS THE HEAVY RAINFALL AXIS (0.50 TO 1.50 INCHES) STRICTLY
ALONG AND SOUTH OF THE OHIO RIVER. MUCH OF CENTRAL ILLINOIS IS
HIGHLIGHTED TO RECEIVE LESS THAN 0.10 INCHES.
FURTHERMORE, MID-LEVEL WATER VAPOR AND FORECAST RH PLOTS REVEAL
A PERSISTENT POCKET OF DRY AIR CENTERED NEAR 700 MB THAT COULD
SEVERELY LIMIT COLUMN SATURATION. BARRING ANY UNEXPECTED
MESOSCALE FGEN (FRONTOGENETICAL) BANDING ON THE NORTHWEST FLANK
OF THE SYSTEM, AREAS NORTH OF INTERSTATE 70 WILL LIKELY STRUGGLE
TO SEE MORE THAN 0.25 INCHES OF TOTAL RAINFALL.
WEEKEND CONDITIONS WILL BE INFLUENCED BY AN UPPER TROUGH AXIS
MOVING THROUGH THE MIDWEST, WHICH MIGHT SPARK SOME SCATTERED
SHOWERS. HOWEVER, MID-LEVEL RH PROFILES LOOK NOTABLY DRIER
FOLLOWING FRIDAYS SURFACE LOW PASSAGE, LEADING TO MUCH LOWER QPF
AND POPS FOR SATURDAY AND SUNDAY. THE PRIMARY IMPACT OF THIS
SETUP WILL BE A WARMING TREND, WITH AFTERNOON HIGHS CLIMBING
INTO THE UPPER 70S THROUGHOUT THE WEEKEND. OTHERWISE, WITH A
DIFFUSE SURFACE BOUNDARY LINGERING OVER THE REGION, ITS NOT
DIFFICULT TO HALLUCINATE ABOUT LANDSPOUT ACTIVITY.
LOOKING AHEAD TO NEXT WEEK, DETERMINISTIC GLOBAL MODELS
INDICATE A REX BLOCK FORMING OVER THE PLAINS. THE MOVEMENT OF
THE RELATED UPPER-LEVEL LOW WILL BE THE DECIDING FACTOR FOR
PRECIPITATION AND THUNDERSTORM CHANCES THROUGH THE EARLY PART OF
THE WEEK. AS THE LOWER PORTION OF THE BLOCK MOVES UP THE
MISSISSIPPI VALLEY AND HIGH PRESSURE STAYS ANCHORED OVER THE
CORN BELT, CURRENT DATA SUGGESTS LOCATIONS SOUTH OF I-72 HAVE
THE HIGHEST PROBABILITY OF RAIN. WHILE THE EXACT PROGRESSION OF
THIS BLOCKING PATTERN REMAINS SOMEWHAT UNCERTAIN, MODELS SHOW
STRONG CONSENSUS ON A RETURN TO HEAT, WITH TEMPERATURES EXPECTED
TO REACH THE MID-TO- UPPER 80S BY MID-WEEK.
AVIATION /12Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 532 AM CDT THU MAY 21 2026
MID-LEVEL CLOUDS HAVE SPREAD INTO CENTRAL ILLINOIS EARLY THIS
MORNING IN THE FACE OF SURFACE HIGH PRESSURE ANCHORED OVER THE
GREAT LAKES. SHORT- TERM GUIDANCE IS SHOWING THESE CLOUDS
SCATTERING OUT BY MID-TO- LATE MORNING, WHICH SEEMS REASONABLE
GIVEN SOME RESIDUAL SUBSIDENCE OVER THE AREA.
CLOUDS ARE ANTICIPATED TO INCREASE AND LOWER THIS EVENING AHEAD
OF A FRONTAL SYSTEM. GUIDANCE SUPPORTS MVFR CEILINGS AT KSPI
AND KDEC BETWEEN 06Z-12Z, EVENTUALLY REACHING KCMI, KBMI AND
KPIA BY THE END OF THE TAF PERIOD.
OTHERWISE, SURFACE WINDS WILL MAINTAIN ITS EAST COMPONENT
THROUGHOUT THE DAY, OCCASIONALLY GUSTING NEAR 20 KTS BEFORE
DIMINISHING THIS EVENING.
ILX WATCHES/WARNINGS/ADVISORIES
NONE.
KEY MESSAGES...MJA
DISCUSSION...MJA
AVIATION...MJA
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