511
FXUS63 KLOT 181810
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
110 PM CDT MON MAY 18 2026
KEY MESSAGES
- A FEW ADDITIONAL ROUNDS OF SHOWERS AND THUNDERSTORMS TODAY AND
TUESDAY, SOME OF WHICH COULD BE STRONG TO SEVERE MAINLY DURING
THE AFTERNOON HOURS.
- SUMMER-LIKE WARMTH AND BREEZY WINDS AT TIMES WILL PREVAIL
THROUGH TUESDAY, THEN COOLER TEMPERATURES RETURN FOR THE
MIDDLE OF THE WEEK.
- MILDER WEATHER RETURNS HEADING INTO THE WEEKEND, THOUGH WITH
AT LEAST INTERMITTENT SHOWER/THUNDERSTORM POTENTIAL.
DISCUSSION
ISSUED AT 347 AM CDT MON MAY 18 2026
REGIONAL RADAR MOSAIC SHOWS A LINEAR MCS MOVING ACROSS THE
MISSISSIPPI RIVER INTO WESTERN WI/IL EARLY THIS MORNING. THERE
HAS BEEN A NOTABLE WEAKENING TREND TO THE CONVECTION OVER THE
PAST FEW HOURS AS THE COMPLEX PROPAGATES INTO A REGION OF
DECREASING DEEP- LAYER SHEAR AND LOW-LEVEL INSTABILITY, THOUGH
STORMS SHOULD CONTINUE TO SPREAD EASTWARD THIS MORNING ALONG A
COMPOSITE OUTFLOW BOUNDARY AT THE LEADING EDGE OF THE
CONVECTION. IN FACT, RECENT RADAR TRENDS INDICATE A FEW NEW
CELLS DEVELOPING AHEAD OF THE LINE NEAR THE QUAD CITIES, PERHAPS
AIDED BY ENHANCED ASCENT ASSOCIATED WITH ONE OR MORE AN
APPARENT MCVS NEAR THE IA/IL/MO BORDER. GUSTY WINDS OF 30-40 MPH
WITH THE OUTFLOW AND SOME SMALL HAIL ARE POSSIBLE WITH THESE
STORMS EARLY THIS MORNING, THOUGH THE OVERALL THREAT OF
ORGANIZED SEVERE WEATHER APPEARS LOW FOR THE NEXT SEVERAL HOURS.
LATER THIS MORNING HOWEVER, DIURNAL WARMING AND ASSOCIATED
DESTABILIZATION ALONG THE EAST/SOUTHEAST PERIPHERY OF THE
COMPLEX REMNANTS AND OUTFLOW BOUNDARY MAY SUPPORT RENEWED
DEVELOPMENT/STRENGTHENING OF CONVECTION WITH MORE OF A SEVERE
THREAT INTO THIS AFTERNOON. THOUGH DEPENDING ON HOW FAR THE
OUTFLOW BOUNDARY MAKES IT THIS MORNING, THIS WOULD LIKELY BE
ACROSS THE SOUTH/FAR EAST PORTIONS OF THE FORECAST AREA. FARTHER
NORTH/NORTHWEST, LINGERING STRATIFORM RAIN AND CLOUD COVER THIS
MORNING LOOKS TO LIMIT DESTABILIZATION AND RECENT CAM TRENDS
HAVE BEEN CONSISTENTLY DRY THERE DURING THE DAY/EVENING.
FARTHER TO THE WEST, EARLY MORNING GOES VAPOR IMAGERY INDICATES
ANOTHER MID-LEVEL SHORT WAVE ROUNDING THE BASE OF A WESTERN
CONUS LONG-WAVE TROUGH. WIDESPREAD STRONG CONVECTION IS PROGGED
TO DEVELOP LATE THIS AFTERNOON AND EVENING ACROSS KS/NE/IA ONCE
AGAIN IN RESPONSE, EVENTUALLY GROWING UPSCALE INTO ANOTHER
EASTWARD- PROPAGATING LINEAR MCS. SIMILARLY TO THIS MORNING, CAM
RUNS CONTINUE TO DEPICT A SIMILAR WEAKENING OF THIS SYSTEM AS
IT REACHES THE MISSISSIPPI RIVER AND SPREADS INTO WI/IL EARLY
TUESDAY MORNING WITH ASSOCIATED RELATIVELY LOW SEVERE POTENTIAL.
THE LINGERING MCS COLD POOL FOOTPRINT AND RESIDUAL CLOUDINESS
WILL LIKELY DELAY DESTABILIZATION INTO MIDDAY TUESDAY, THOUGH
ADDITIONAL STORM DEVELOPMENT APPEARS POSSIBLE ACROSS THE
SOUTHEAST HALF OF THE FORECAST AREA TUESDAY AFTERNOON/EVENING AS
THE COLD FRONT FINALLY PUSHES THROUGH THE FORECAST AREA.
STRONGER MID-LEVEL FLOW ON THE SOUTHEASTERN PERIPHERY OF THE
AFOREMENTIONED SHORT WAVE WILL LIKELY SUPPORT ENOUGH STORM
ORGANIZATION FOR A HAIL/WIND THREAT DURING THIS TIME.
FOLLOWING THE COLD FRONT, SURFACE HIGH PRESSURE IS PROGGED TO
BUILD EAST INTO THE WESTERN GREAT LAKES REGION WEDNESDAY AND
THURSDAY. DRY, BUT BREEZY AND COOLER WEATHER IS EXPECTED BOTH
DAYS, WITH TEMPS MAINLY IN THE 60S, BUT ONLY IN THE 50S NEAR
LAKE MICHIGAN WITH NORTHEAST-EAST FLOW OFF THE LAKE. NIGHTTIME
LOWS IN THE 40S ARE EXPECTED. THE HIGH THEN DRIFTS OFF TO THE
EAST THURSDAY NIGHT, WITH THE UPPER LEVEL PATTERN FAVORING A
SERIES OF MID-LEVEL DISTURBANCES TRACKING THROUGH THE AREA
FRIDAY INTO THE WEEKEND. THIS WILL SUPPORT MILDER TEMPERATURES,
BUT ALSO SOME OCCASIONAL SHOWER/THUNDERSTORM CHANCES INTO THE
HOLIDAY WEEKEND.
RATZER
AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 109 PM CDT MON MAY 18 2026
WIND FIELD HAS BEEN SUBSTANTIALLY ALTERED BY STORMS THIS
MORNING, BUT WILL REVERT BACK TO A SOUTH-SOUTHWEST DIRECTION
EARLY THIS AFTERNOON. PRESSURE GRADIENT IS BAGGIER IN THE WAKE
OF THE STORMS THAN ORIGINALLY FORECAST, SO GUSTINESS OF THE
WINDS MAY BE SLOWER TO DEVELOP TODAY THAN INDICATED IN THE TAFS.
SHOWERS AND STORMS THAT DEVELOP OVER THE CENTRAL PLAINS TODAY
WILL MOVE EAST AND LIKELY REACH NORTHERN ILLINOIS IN A QUICKLY
DECAYING STATE LATE TONIGHT/EARLY TUESDAY MORNING. CONFIDENCE IS
LOW IN WHETHER THIS ACTIVITY WILL REACH THE TERMINALS, SO OPTED
TO JUST HANG ONTO A PROB30 IN THE TAFS.
FINALLY, CONFIDENCE IN WINDS TUESDAY IS ON THE LOWER END OF THE
SPECTRUM. THERE IS A CHANCE WIND FIELDS COULD BE ALTERED BY
DIMINISHING STORMS, WHICH COULD PLAY HAVOC ON DIRECTIONS AND
SPEEDS. HOWEVER, IF WIND FIELDS AREN'T SIGNIFICANTLY ALTERED,
THEN WINDS WILL LIKELY BE EVEN STRONGER THAN INDICATED IN THE
TAFS.
- IZZI
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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