477
FXUS63 KLOT 150843
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
343 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 COULD 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 FAVORING AREAS NEAR AND NORTH OF I-80.
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 WITH A LOCALLY HIGHER HAIL THREAT ACROSS
NORTHERN/NORTHWEST ILLINOIS, INCLUDING THE ROCKFORD AREA WHERE
EMBEDDED SUPERCELLS OR SEMI-DISCRETE STORM MODE CAN'T BE RULED
OUT. ANOTHER CONCERN FOR TODAY IS THE POTENTIAL FOR FLASH
FLOODING AS ADDITIONAL WAVES OF HEAVY RAINFALL POTENTIALLY OCCUR
OVER THE SAME AREAS. WILL LIKELY END UP NEEDING TO EXTEND THE
CURRENT 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 /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 1210 AM CDT WED APR 15 2026
AVIATION FORECAST CONCERNS FOR THE 06Z TAFS:
- PERIODS OF TSRA, PARTICULARLY REMAINDER OF OVERNIGHT, AND
AGAIN LATE WEDNESDAY AFTERNOON/EVENING. BRIEF IFR/MVFR
POSSIBLE IN PRECIPITATION. SCATTERED SHRA POSSIBLE AT OTHER
TIMES.
- WINDS LIKELY CONVECTIVELY DISTURBED WITH SOMEWHAT VARIABLE
DIRECTIONS FOR THE NEXT SEVERAL HOURS, OTHERWISE MAINLY
SOUTHWEST TO SOUTH WINDS (BREEZY AT TIMES WITH GUSTS 20-25 KTS).
LATE EVENING SURFACE ANALYSIS DEPICTS AN AREA OF LOW PRESSURE
OVER NORTH-CENTRAL KS, WITH A QUASI-STATIONARY FRONTAL BOUNDARY
EXTENDING NORTHEAST ACROSS IA INTO SOUTHERN WI. A THUNDERSTORM
COMPLEX WHICH MOVED ACROSS NORTHERN IL LATE TUESDAY EVENING WAS
MOVING EAST ACROSS LOWER MI, THOUGH STORMS CONTINUE TO
REDEVELOP BACK ACROSS NORTHWEST IN/NORTHEAST IL ALONG AND
NORTHEAST OF A WEST-EAST ORIENTED OUTFLOW BOUNDARY TRAILING THE
AFOREMENTIONED COMPLEX. ADDITIONAL THUNDERSTORMS HAVE DEVELOPED
ALONG THE STATIONARY FRONT ROUGHLY ALONG A A KOMA-KDSM-KCID
LINE.
EXPECTATION IS THAT SCATTERED TS WILL CONTINUE TO REDEVELOP
ACROSS THE CHICAGO TERMINALS AS THE LOW-LEVEL JET ASCENDS ATOP
THE WEST-EAST OUTFLOW BOUNDARY, AT LEAST FOR ANOTHER 2-3 HOURS
OR SO. HIGH-RES GUIDANCE (RRFS/HREF) INDICATES IA TSRA WILL
SPREAD INTO PARTS OF NORTHERN IL AFTER 09-10Z, POTENTIALLY
LINGERING THROUGH DAYBREAK OR SLIGHTLY LATER BEFORE WEAKENING
AND MOVING EAST OF THE AREA. TERMINALS WILL REMAIN WITHIN A
REGION OF BROAD SOUTHWEST WARM/MOIST ADVECTION HOWEVER, WHICH
COULD RESULT IN ISOLATED/SCATTERED SHRA JUST ABOUT ANY TIME
WEDNESDAY. CAN'T RULE OUT SOME ISOLATED TS DURING THE DAY,
THOUGH THE NEXT BEST WINDOW FOR GREATER TSRA COVERAGE APPEARS TO
BE LATE WEDNESDAY AFTERNOON INTO WEDNESDAY EVENING/NIGHT.
SURFACE WINDS HAVE BECOME CONVECTIVELY DISTURBED ACROSS NORTHERN
IL AT THIS TIME IN THE WAKE OF THE DEPARTING COMPLEX. WHILE
WINDS SHOULD EVENTUALLY SETTLE BACK TO A SOUTH-SOUTHWEST,
CURRENT WINDS DO HAVE SOME VARIABILITY IN DIRECTION NORTH OF
THE AFOREMENTIONED OUTFLOW BOUNDARY. ONCE WINDS DO SHIFT BACK TO
THE SOUTH-SOUTHWEST, BREEZY CONDITIONS ARE LIKELY WITH GUSTS
20-25 KTS AT TIMES.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH UNTIL 6 AM CDT EARLY THIS MORNING FOR ILZ003-
ILZ004-ILZ005-ILZ006-ILZ008-ILZ011-ILZ012-ILZ013-ILZ020-
ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...FLOOD WATCH UNTIL 6 AM CDT EARLY THIS MORNING FOR INZ001.
LM...NONE.
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