766
FXUS63 KLOT 301759
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1259 PM CDT WED JUL 30 2025
KEY MESSAGES
- A FLOOD WATCH REMAINS IN EFFECT FOR THE ENTIRE AREA THROUGH 1
PM TOMORROW AFTERNOON. A PORTION OR ALL OF IT MAY BE ABLE TO
BE CANCELLED EARLY.
- PERIODS OF RAIN ARE EXPECTED THIS EVENING AND OVERNIGHT AS A
SLOW-MOVING WEATHER SYSTEM MOVES OVERHEAD.
- HIGH WAVES AND RIP CURRENTS WILL LEAD TO A HIGH SWIM RISKS AT
ALL LAKE MICHIGAN BEACHES THROUGH AT LEAST FRIDAY AFTERNOON.
- COOLER TEMPERATURES AND MORE COMFORTABLE HUMIDITY LEVELS WILL
ARRIVE TOMORROW AND LAST THROUGH THE WEEKEND.
DISCUSSION
ISSUED AT 1259 PM CDT WED JUL 30 2025
THROUGH THURSDAY:
RECENT RADAR IMAGERY DEPICTS SHOWERS AND STORMS MOVING EASTWARD
ACROSS THE AREA AT PRESS TIME AHEAD OF AN MCV/SHORTWAVE MOVING
EASTWARD ACROSS THE MISSISSIPPI RIVER. MEANWHILE, A SECOND AREA
OF SHOWERS AND EMBEDDED THUNDERSTORMS STRETCHES FROM FAR
NORTHERN IOWA EASTWARD THROUGH MUCH OF SOUTHERN WISCONSIN ALONG
THE NORTHERN FLANK OF THE MCV AND ALONG A BROAD FRONTAL ZONE
DRIFTING SOUTHWARD THROUGH THE GREAT LAKES. BETWEEN BOTH
FEATURES, RELATIVELY TRANQUIL CONDITIONS RESIDE WITH BROKEN
CLOUD COVER AND TEMPERATURES IN THE MID 70S.
OVER THE COMING HOURS, THE EXPECTATION IS FOR THE MAIN AXIS OF
SHOWERS AND STORMS TO SHIFT EASTWARD OUT OF OUR AREA ONLY TO BE
REPLACED BY THE SECONDARY AREA OF SHOWERS AND EMBEDDED STORMS
DROPPING SOUTHWARD OUT OF WISCONSIN. A BROAD AREA OF UPPER-
LEVEL DIFFLUENCE IN THE RIGHT ENTRANCE REGION OF A PASSING JET
STREAK IN TANDEM WITH PWATS NEAR 2" SHOULD AFFORD SURPRISINGLY
EFFICIENT RAIN RATES THIS EVENING PARTICULARLY WHERE POCKETS OF
INSTABILITY STILL RESIDE. AS A RESULT, WILL MAINTAIN THE
INHERITED FLOOD WATCH THROUGH THE AREA (THOUGH DO BELIEVE IT MAY
BE ABLE TO BE CANCELLED EARLY FOR PORTIONS OF THE AREA
OVERNIGHT). MEANWHILE, INCREASING NORTH TO NORTHEASTERLY FLOW
OFF THE LAKE WILL LEAD TO BUILDING WAVES ON LAKE MICHIGAN,
RESULTING IN A HIGH SWIM RISK THIS EVENING ONWARD AT ALL LAKE
MICHIGAN BEACHES.
TOMORROW, THE BACK EDGE OF THE SHORTWAVE WILL SHIFT EASTWARD
CAUSING SHOWERS TO TAPER FROM NORTHEAST TO SOUTHEAST. SHOWERS OR
SPRINKLES MAY LAST THE LONGEST AT LAKESHORE LOCATIONS WHERE
ONSHORE FLOW AND TUMBLING 850MB TEMPERATURES MAY AFFORD MODEST
LAKE INSTABILITY BEFORE DRY AIR RUSHES INTO THE REGION. OUTSIDE
TAPERING RAIN CHANCES, TOMORROW WILL FEEL QUITE DIFFERENT
COMPARED TO THE PAST WEEK WITH HIGHS ONLY IN THE LOW TO MID 70S
AND MUCH LOWER HUMIDITY LEVELS. CONTINUED NORTH TO NORTHEASTERLY
ONSHORE WINDS WILL MAINTAIN A HIGH SWIM RISK AT ALL LAKE
MICHIGAN BEACHES. FINALLY, HAVE INTRODUCED NEAR-SURFACE SMOKE TO
THE FORECAST OWING TO UPSTREAM OBSERVATIONS OF 2-5 MILE
VISIBILITIES ACROSS THE UPPER GREAT LAKES (THAT AIRMASS WILL
COME OUR WAY BEHIND THE FRONT TOMORROW).
BORCHARDT
THURSDAY NIGHT THROUGH WEDNESDAY:
A BROAD SURFACE HIGH IS EXPECTED TO BE PARKED OVER THE GREAT
LAKES THURSDAY NIGHT AND REMAIN IN PLACE THROUGH THE WEEKEND. AS
A RESULT, DRY CONDITIONS WITH PLENTIFUL SUNSHINE ARE IN STORE
FOR US. AS AN ADDED BONUS, PERSISTENT NORTHWEST FLOW ALOFT ON
THE BACK SIDE OF AN UPPER TROUGH OVER THE NORTHEAST CONUS AND
NORTHEAST WINDS AT THE SURFACE WILL KEEP TEMPERATURES AND
HUMIDITY IN A MORE COMFORTABLE RANGE WITH DAILY HIGHS IN THE
MID-70S TO AROUND 80 AND OVERNIGHT LOWS IN THE 50S TO AROUND 60.
HOWEVER, BREEZIER WINDS ARE LIKELY TO PERSIST THROUGH FRIDAY
EVENING ESPECIALLY OVER THE OPEN WATERS OF LAKE MICHIGAN WHICH
WILL RESULT IN CONTINUED HIGH WAVES AND LIFE THREATENING RIP
CURRENTS AT AREA BEACHES. WHILE OUR CURRENT BEACH HAZARD
STATEMENT RUNS THROUGH FRIDAY AFTERNOON, THERE IS A CHANCE WE
MAY NEED TO EXTEND IT IF THE FORECAST CONTINUES TO TREND AS
EXPECTED. THAT SAID, ANYONE WITH PLANS TO HEAD TO THE BEACH
FRIDAY SHOULD PLAN ON STAYING OUT OF THE WATER UNTIL WINDS AND
WAVES SUBSIDE.
HEADING INTO NEXT WEEK, THE DRY WEATHER DOES LOOK TO LINGER
THROUGH AT LEAST MONDAY BEFORE THE UPPER PATTERN SHIFTS BACK TO
AN ACTIVE SOUTHWEST FLOW REGIME TOWARDS THE MIDDLE OF THE WEEK.
THIS PATTERN SHIFT WILL RESULT IN TEMPERATURES AND HUMIDITY
LEVELS RETURNING TO MORE TYPICAL AUGUST READINGS (HIGHS IN THE
80S AND DEW POINTS IN THE 60S TO NEAR 70) AND OF COURSE CHANCES
FOR SHOWERS AND THUNDERSTORMS. WHILE THERE IS SOME UNCERTAINTY
AS TO WHEN EXACTLY THE RAIN RETURNS, IT LOOKS LIKE CHANCES WILL
BE INCREASING MONDAY NIGHT ONWARD.
YACK
AVIATION /18Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 1235 PM CDT WED JUL 30 2025
CONCERNS:
-SHOWERS AND THUNDERSTORMS THROUGH EARLY-MID AFTERNOON
-IFR OR EVEN BRIEF LIFR VISIBILITY IN HEAVY DOWNPOURS
-POTENTIAL FOR IFR CEILINGS LATER TODAY AND TONIGHT
A COMPLEX OF THUNDERSTORMS WILL CONTINUE TO SLIDE BY JUST TO THE
SOUTH OF THE CHICAGOLAND TERMINALS. KMDW WILL GET GRAZED BY
LIGHTNING, WITH ABOUT A 40-50% PERCENT CHANCE OF DIRECT TERMINAL
IMPACTS, FOR KORD VCTS MORE LIKELY TELLS THE STORY. FOR BOTH
TERMINALS, HEAVY SHOWERS MAY STILL REDUCE VISIBILITY TO IFR (1
1/2-2SM), THOUGH LIFR MAY BRIEFLY OCCUR. THERE WILL BE A BREAK
IN THE RAIN LATER THIS AFTERNOON INTO THE EARLY EVENING, BEFORE
ANOTHER BATCH OF RAIN/SHOWERS WILL SHIFT INTO THE AREA. CEILINGS
WILL LIKELY DROP BACK TO MVFR, WITH A 50% CHANCE OF IFR.
CONFIDENCE ON HOW LONG IFR WILL LAST IS LOW. RAIN WILL TAPER OFF
NORTH TO SOUTH OVERNIGHT. WINDS WILL INCREASE OUT OF THE
NORTHEAST, ESPECIALLY TONIGHT. GUSTS TO 25 KT APPEAR LIKELY AT
TIMES TONIGHT INTO THURSDAY.
KMD
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR ILZ003-ILZ004-
ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-ILZ104-
ILZ105-ILZ106-ILZ107-ILZ108.
BEACH HAZARDS STATEMENT THROUGH FRIDAY AFTERNOON FOR ILZ006-
ILZ103-ILZ104.
IN...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR INZ001-INZ002-
INZ010-INZ011-INZ019.
BEACH HAZARDS STATEMENT THROUGH FRIDAY AFTERNOON FOR INZ001-
INZ002.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CDT FRIDAY FOR THE IL AND IN
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page