632
FXUS63 KLOT 151158
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
658 AM CDT WED APR 15 2026
KEY MESSAGES
- ADDITIONAL WAVES OF SHOWERS AND THUNDERSTORMS ARE EXPECTED
EARLY THIS MORNING THROUGH TONIGHT. SOME COULD BE SEVERE AND
PRODUCE HEAVY RAINFALL LEADING TO FLASH FLOODING.
- A BRIEF BREAK IN THE PATTERN IS EXPECTED LATE THURSDAY INTO
THE DAY ON FRIDAY BEFORE ANOTHER STORM SYSTEM ARRIVES FRIDAY
EVENING INTO EARLY SATURDAY.
- COOLER AIR ARRIVES INTO EARLY NEXT WEEK AND MAY BRING
FROST/FREEZE CONCERNS EARLY SUNDAY AND MONDAY MORNINGS.
DISCUSSION
ISSUED AT 343 AM CDT WED APR 15 2026
THROUGH TONIGHT:
AN ELONGATED AXIS OF ELEVATED SHOWERS AND THUNDERSTORMS
CONTINUES EARLY THIS MORNING FROM SOUTHEAST NEBRASKA THROUGH
SOUTHERN MICHIGAN. SOME OF THESE STORMS HAVE TAKEN ADVANTAGE OF
A SMALL AREA OF STEEPER MID-LEVEL LAPSE RATES AMIDST STRONG
EFFECTIVE SHEAR TO 50 KT AND MANAGED TO PRODUCE SEVERE HAIL.
ISOLATED STRONG TO SEVERE STORMS WILL REMAIN POSSIBLE THROUGH
EARLY THIS MORNING.
THERE REMAINS A FAIR AMOUNT OF UNCERTAINTY WITH RESPECT TO HOW
CONVECTIVE TRENDS UNFOLD THE REMAINDER OF THE DAY OWING TO THE
POTENTIAL FOR MULTIPLE "WAVES" OF SHOWERS AND STORMS. EACH
MODEL AND THEIR RESPECTIVE RUNS VARY ON THE DETAILS, INCLUDING
TIMING AND PLACEMENT OF THE DIFFERENT BANDS OF STORMS AND HOW
THEY INTERACT WITH EACH OTHER (OUTFLOWS, COLD POOLS, ETC.). IT
DOES APPEAR THAT AFTER THIS INITIAL ROUND OF STRONGER STORMS
EARLY THIS MORNINGS SAGS FARTHER EAST AND SOUTHEAST THERE MAY BE
A TEMPORARY DECREASE IN THE THUNDERSTORM COVERAGE DURING THE
REST OF THE MORNING HOURS WHEN LAPSE RATES HERE LOCALLY
DECREASE.
ONCE WE GET INTO THE AFTERNOON HOURS THE THREAT OF SEVERE
WEATHER INCREASES AGAIN AS LAPSE RATES STEEPEN ALLOWING
INSTABILITY TO QUICKLY BUILD OVER THE AREA (MLCAPE OF 2000+
J/KG) AMIDST AMPLE DEEP LAYER SHEAR. THE STORM PREDICTION
CENTER HAS UPGRADED THE REST OF THE AREA TO A LEVEL 2 OF 5
SEVERE THUNDERSTORM RISK WHICH SEEMS APPROPRIATE, WITH THE
PRIMARY HAZARD BEING DAMAGING WIND GUSTS WITH ANY EMBEDDED
BOWING SEGMENTS. A LOCALLY HIGHER HAIL THREAT MAY MATERIALIZE
WITH ANY EMBEDDED SEMI-DISCRETE SUPERCELLS. ANOTHER CONCERN FOR
TODAY IS THE POTENTIAL FOR FLASH FLOODING AS ADDITIONAL WAVES
OF HEAVY RAINFALL POTENTIALLY OCCUR OVER THE SAME AREAS. HAVE
EXTENDED THE FLOOD WATCH IN DURATION AND AREA TO ACCOUNT FOR
THIS.
THURSDAY:
A COMPACT SHORTWAVE AND ASSOCIATED WEAK SURFACE LOW/MCV IS
FORECAST TO MOVE ACROSS OR NEAR THE AREA DURING THE DAY ON
THURSDAY WHICH WILL LIKELY BE ACCOMPANIED BY ADDITIONAL
SCATTERED SHOWERS AND NON-SEVERE THUNDERSTORMS. ONCE THAT MOVES
OFF TO THE EAST A VERY BRIEF BREAK IN THE WET AND STORMY
PATTERN IS EXPECTED THURSDAY NIGHT THROUGH THE DAY ON FRIDAY.
TEMPERATURES ON THURSDAY WILL ALSO END UP COOLER (ALBEIT STILL
UNSEASONABLY WARM) WITH HIGHS IN THE MID 60S TO MID 70S, COOLEST
ACROSS FAR NORTHEAST ILLINOIS.
FRIDAY - SATURDAY:
STRONG SOUTHERLY WARM AND MOIST CONVECTION WILL RETURN INTO THE
DAY ON FRIDAY AHEAD OF AN APPROACHING COLD FRONT. THIS BOUNDARY
IS EXPECTED TO PROGRESS ACROSS THE AREA SOMETIME LATE FRIDAY INTO
EARLY SATURDAY MORNING PAIRED WITH A LINE OF THUNDERSTORMS,
SOME OF WHICH COULD BE SEVERE. SUSPECT THAT LESS FAVORABLE
DIURNAL TIMING OF ANY LINGERING STORMS INTO THE MORNING ON
SATURDAY MAY LIMIT THE OVERALL SEVERE THREAT HERE LOCALLY BEFORE
STORMS REINTENSIFY EAST OF THE AREA INTO THE REST OF THE DAY.
STAY TUNED!
SATURDAY NIGHT ONWARD:
IN THE WAKE OF THE EARLY SATURDAY COLD FRONT, A MUCH COLDER
AIRMASS (RELATIVE TO WHAT WE HAVE HAD OVER THE PAST SEVERAL
DAYS) WILL SETTLE INTO THE REGION OVER THE WEEKEND. OVERNIGHT
LOW TEMPERATURES MAY DROP INTO THE 30S, WITH SOME NEAR TO SUB-
FREEZING TEMPERATURES POSSIBLE ACROSS INTERIOR NORTHERN
ILLINOIS. LIGHTER WINDS IN PLACE SUNDAY NIGHT MAY ALLOW FOR
FROST DEVELOPMENT OUTSIDE OF CHICAGO AND WILL BE SOMETHING FOR
THOSE WITH AGRICULTURAL INTERESTS TO MONITOR OVER THE NEXT FEW
DAYS.
THE COOLER CONDITIONS WILL BE RATHER SHORT-LIVED WITH EXTENDED
GUIDANCE FAVORING A RETURN TOWARD HIGH AMPLITUDE RIDGING ACROSS
THE CENTRAL CONUS AND UNSEASONABLY WARM TEMPERATURES RETURNING
TO THE REGION BY MIDWEEK NEXT WEEK.
PETR
AVIATION /12Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 658 AM CDT WED APR 15 2026
MAIN CONCERNS:
- IN THE WAKE OF MORNING SHRA AND ISOLATED EMBEDDED TS, THE
POTENTIAL EXISTS FOR ADDITIONAL SHRA/TSRA THIS AFTERNOON AND
EVENING, WITH LOW CONFIDENCE IN SPECIFICS.
A FAIRLY COHERENT AREA OF SHOWERS EXTENDS BACK TO ABOUT THE MS
RIVER AS OF THIS WRITING. INCLUDED VCTS UNTIL MID MORNING FOR
THE CHICAGO METRO TERMINALS TO ACCOUNT FOR A FEW TALLER
CONVECTIVE CORES THAT MAY PRODUCE SPORADIC LIGHTNING. MORE
WIDESPREAD TS OVER FAR WESTERN IL SHOULD REMAIN SAFELY SOUTH OF
THE TAF SITES AS THEY LIFTS NORTHEAST THROUGH THE MORNING.
IN THE WAKE OF THE MORNING ACTIVITY, THERE SHOULD BE A FEW TO
SEVERAL HOUR WINDOW WITH ISOLATED TO SCATTERED SHRA AT MOST NEAR
THE TERMINALS. IT REMAINS QUITE UNCLEAR WHERE ADDITIONAL
SHRA/TSRA WILL DEVELOP THIS AFTERNOON. MORE RECENT GUIDANCE HAS
TENDED TO FAVOR SOUTH OF THE TERMINALS THIS AFTERNOON, WITH A
BETTER CHANCE OF TS HOLDING OFF UNTIL THIS EVENING. GIVEN THE
AFOREMENTIONED LOWER CONFIDENCE IN SPECIFICS, OPTED TO
TRANSITION BACK TO A BROADER PROB30 WHILE MAINTAINING THE VCTS
FROM PREVIOUS ISSUANCES. VARIABLE/ERRATIC AND STRONG/GUSTY
WINDS MAY OCCUR IN ANY ON STATION TS IMPACTS. WIND VARIABILITY
IN THE WAKE OF THE STORMS WOULD LIKELY FOLLOW. OUTSIDE OF
CONVECTION, WINDS WILL FAVOR A SOUTHWEST TO WEST DIRECTION
THROUGH THURSDAY MORNING, WITH OCCASIONAL GUSTS TO ~20 KT.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH THROUGH LATE TONIGHT FOR ILZ003-ILZ004-ILZ005-
ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-
ILZ021-ILZ023-ILZ032-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
ILZ108.
IN...FLOOD WATCH THROUGH LATE TONIGHT FOR INZ001-INZ002-INZ010-
INZ011.
LM...NONE.
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