134
FXUS63 KLOT 190840
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
340 AM CDT TUE AUG 19 2025
KEY MESSAGES
- THE LONG AWAITED PATTERN CHANGE TO QUIETER AND DRIER IS ON OUR
DOORSTEP AND WILL PERSIST THROUGH EARLY NEXT WEEK, ALONG WITH
NOTICEABLY LESS HUMID CONDITIONS WEDNESDAY ONWARD.
- TEMPERATURES EARLY TO MID NEXT WEEK WILL LIKELY BE AN EARLY
FALL PREVIEW!
- DANGEROUS SWIMMING CONDITIONS WILL DEVELOP AT SOUTHERN LAKE
MICHIGAN BEACHES LATE THIS AFTERNOON INTO THIS EVENING AND
PERSIST INTO THURSDAY MORNING.
DISCUSSION
ISSUED AT 340 AM CDT TUE AUG 19 2025
TODAY THROUGH THURSDAY NIGHT:
THE CONVECTIVELY AUGMENTED SYNOPTIC SHORT-WAVE THAT HAS KEPT THE
"PARADE OF STORMS" GOING NEAR/SOUTH OF I-88 EARLY THIS MORNING
IS PEELING OFF TO THE EAST. A PRIMARILY DRY AND COOLER DAY,
ALBEIT WITH HUMIDITY LEVELS STILL ON THE UNCOMFORTABLE SIDE
(ESPECIALLY I-80 AND SOUTH), IS ON THE WAY TODAY.
WITH THE FOOTPRINT OF DEEP CONVECTION MUCH LESS THAN EARLIER AND
EXPECTED TO DIMINISH INTO THE MORNING, WE WENT AHEAD AND
CANCELED THE AREAL FLOOD WATCH THAT WAS IN EFFECT. PLEASE REFER
TO ANY FLOOD WARNING OR ADVISORY PRODUCTS THAT REMAIN IN EFFECT
FOR YOUR AREA. IN THE NEAR-TERM THROUGH ABOUT 8-9AM THIS MORNING,
WE'LL HAVE TO KEEP AN EYE ON THE POSSIBLE DEVELOPMENT OF PATCHY
FOG ACROSS PORTIONS OF INTERIOR FAR NORTHERN ILLINOIS.
A COLD FRONT WILL MOVE SOUTH ACROSS THE AREA THIS MORNING,
CLEARING OUR FAR SOUTHERN CWA LOCALES BY EARLY AFTERNOON. THE
COMBINATION OF THE ENVIRONMENT BEING THOROUGHLY WORKED OVER AND
CLOUD COVER SHOULD LIMIT THE POTENTIAL FOR THE REDEVELOPMENT OF
ANY THUNDERSTORMS AFTER ANY ACTIVITY LINGERING PAST SUNRISE THIS
MORNING COMES TO AN END. HELD ONTO A SLIGHT CHANCE OF STORMS IN
CLOSER PROXIMITY TO THE FRONT (IE. NEAR/SOUTH OF US-24) TO BE
SAFE THROUGH ABOUT 2-3PM CDT.
MORE NOTABLY, THE FRONT WILL SHIFT WINDS TO BRISK NORTHERLY DOWN
THE FULL FETCH OF LAKE MICHIGAN, WITH SPEEDS PEAKING TONIGHT
THROUGH WEDNESDAY. THIS WILL RESULT IN LARGE WAVES AND STRONG
CURRENTS AT THE BEACHES, WITH BEACH HAZARDS STATEMENTS HOISTED
THIS MORNING (EARLIEST START LATE THIS AFTERNOON FOR NORTHWEST
INDIANA).
TONIGHT INTO WEDNESDAY MORNING WILL BE MOSTLY DRY WITH THE
POSSIBLE SMALL EXCEPTION OF DOWNWIND OF LAKE MICHIGAN, AS 850 MB
TEMPS DOWN INTO THE LOWER TEENS CELSIUS GENERATE SOME MODEST
LAKE INDUCED INSTABILITY. INVERSION HEIGHTS LOOK TOO MARGINAL
FOR ANY BONAFIDE SHOWERS, BUT CAN'T RULE OUT SOME SPOTTY
LAKE EFFECT SPRINKLES INTO PORTIONS OF NORTHEAST ILLINOIS AND
NORTHWEST INDIANA. HIGHS ON WEDNESDAY WILL BE IN THE UPPER 70S
TO LOWER 80S INLAND, AND MID 70S NEAR THE LAKE. FOLLOWING A
SEASONABLY COOL WEDNESDAY NIGHT (UPPER 50S TO LOWER 60S WELL
INLAND OF THE LAKE) AS SKIES CLEAR OUT, THURSDAY WILL BE ONE OF
THE NICEST DAYS IN QUITE SOME TIME FOR THE AREA. EXPECT MOSTLY
SUNNY SKIES, MUCH MORE COMFORTABLE HUMIDITY LEVELS, AND HIGHS
SIMILAR TO THOSE OF WEDNESDAY. THURSDAY NIGHT WILL BE SIMILARLY
COMFORTABLY COOL OUTSIDE OF CHICAGO TO WEDNESDAY NIGHT.
FRIDAY THROUGH MONDAY:
FRIDAY WILL FEATURE A BRIEF WARM-UP BACK TO THE LOWER-MID 80S
AWAY FROM THE LAKE AHEAD OF THE NEXT APPROACHING COLD FRONT.
THIS FRONT WILL COME THROUGH AT AN UNFAVORABLE TIME FRIDAY NIGHT
WITH MUCH LESS MOISTURE TO WORK WITH, SO EXPECT A DRY FRO-PA FOR
MOST OF THE AREA. SATURDAY WILL BE NEAR TO SLIGHTLY BELOW
SEASONABLE WITH COMFORTABLE HUMIDITY LEVELS. SEASONABLY DEEP
MID-UPER TROUGHING WILL SET UP OVER FROM ONTARIO TO HUDSON BAY
SUNDAY THROUGH EARLY NEXT WORK WEEK. 850 MB TEMPS BELOW +10C
THROUGH THIS TIME WILL SET THE STAGE FOR HIGHS IN THE LOWER TO
MID 70S, DEW POINTS IN THE 40S AND 50S, AND OVERNIGHT LOWS IN
THE UPPER 40S TO LOWER 50S OUTSIDE OF CHICAGO! THE BELOW NORMAL
TEMPERATURES SHOULD PERSIST THROUGH MID NEXT WEEK BEFORE
RETURNING BACK TO NEAR OR ABOVE SEASONAL NORMS HEADING INTO
LABOR DAY WEEKEND.
CASTRO
AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 1250 AM CDT TUE AUG 19 2025
FORECAST CONCERNS INCLUDE...
SCATTERED THUNDERSTORMS EARLY THIS MORNING.
IFR, POSSIBLE LIFR CIGS THROUGH MID MORNING.
FOG POTENTIAL AROUND SUNRISE.
WIND SHIFT TO NORTHERLY TUESDAY MORNING.
SCATTERED THUNDERSTORMS HAVE REDEVELOPED OVER THE CHICAGO
TERMINALS AND WILL CONTINUE FOR THE NEXT FEW HOURS, SLOWLY
MOVING EAST. ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE
THROUGH DAYBREAK AHEAD OF A COLD FRONT THAT WILL MOVE ACROSS THE
AREA. CONFIDENCE IS LOW FOR POSSIBLE COVERAGE WITH ANY
ADDITIONAL CONVECTION IN THE PREDAWN HOURS AND NEAR DAYBREAK.
PROB THUNDER MENTION STILL SEEMS REASONABLE AT THIS TIME.
PREVAILING WINDS WILL START LIGHT SOUTHERLY BUT ARE EXPECTED TO
SHIFT SOUTH/SOUTHWEST OVER THE NEXT FEW HOURS THEN TO THE WEST/
SOUTHWEST PRIOR TO DAYBREAK. AS THE COLD FRONT MOVES ACROSS THE
AREA, WINDS WILL SHIFT NORTHWEST AND THEN ARE EXPECTED TO BECOME
MAINLY NORTHERLY, WITH SPEEDS POTENTIALLY INTO THE 10-15KT
RANGE. EVENTUALLY, WINDS WILL BECOME NORTH/NORTHEAST FOR ORD/MDW
AND ONLY MEDIUM CONFIDENCE FOR THIS TIMING. WINDS WILL LIKELY
BECOME NORTH/NORTHEAST AT MDW BEFORE ORD AND TRENDS WILL NEED TO
BE MONITORED.
PATCHES OF LIFR CIGS BEGAN TO DEVELOP A FEW HOURS AGO, PRIOR TO
THIS LATEST ROUND OF THUNDERSTORMS. GUIDANCE IS IN VERY GOOD
AGREEMENT WITH LOW CLOUDS DEVELOPING AHEAD OF THE COLD FRONT AND
THEN SLOWLY LIFTING TUESDAY MORNING. PREVAILING IFR CIGS SEEM ON
TRACK BASED ON CURRENT MODEL TRENDS, WHICH WILL THEN LIFT
THROUGH MVFR AND LIKELY SCATTER OUT LATE TUESDAY AFTERNOON OR
TUESDAY EVENING.
FOG IS ALSO POSSIBLE AROUND DAYBREAK, MOST LIKELY NORTHWEST OF
THE CHICAGO TERMINALS AND MAY BE BRIEF, ASSOCIATED WITH THE COLD
FRONT. CONFIDENCE FOR FOG IS LOW, BUT TRENDS SUGGEST IFR VIS AT
RFD/DPA AND HAVE INCLUDED TEMPO MENTION WITH THIS FORECAST.
THERE IS A SMALL CHANCE THAT DENSE FOG MAY DEVELOP BUT THAT
SEEMS UNLIKELY, IF WIDESPREAD IFR CIGS DEVELOP. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH UNTIL 4 AM CDT EARLY THIS MORNING FOR ILZ003-
ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
ILZ019-ILZ020-ILZ021-ILZ023-ILZ103-ILZ104-ILZ105-ILZ106-
ILZ107-ILZ108.
IN...FLOOD WATCH UNTIL 4 AM CDT EARLY THIS MORNING FOR INZ001-
INZ002.
LM...NONE.
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