456
FXUS63 KLOT 191051
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
551 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. HOWEVER,
AREAS OF PONDING WATER IN FIELDS, LOW-LYING SPOTS, AND ROADWAYS
LIKELY CONTINUES WHERE THE HEAVIEST RAIN FELL IN THE PAST 24
HOURS. 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 /12Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 551 AM CDT TUE AUG 19 2025
A COLD FRONT WILL CONTINUE SLOWLY MOVING SOUTHWARD ACROSS THE
AIRSPACE THIS MORNING. AS THE FRONT PASSES OVERHEAD, WINDS WILL
VEER NORTHWESTERLY AND IFR TO MVFR CIGS WILL SPREAD OVERHEAD. A
FEW POCKETS OF MIST AND DRIZZLE WITH 4-6SM VISIBILITY REDUCTIONS
MAY OCCUR ALONG THE LEADING EDGE OF THE FRONT, AS WELL. BY MID-
MORNING, CIGS SHOULD BEGIN TO RISE EVER-SO-GRADUALLY AS WINDS
SETTLE ON A NEAR DUE NORTHERLY DIRECTION.
AS 850MB TEMPERATURES COOL THIS EVENING AND OVERNIGHT, LAKE-
INDUCED STRATUS SHOULD DEVELOP AND STREAM INLAND GUIDED BY
NORTHEASTERLY WINDS. MVFR STRATUS WILL THUS BE MAINTAINED AT ALL
TERMINALS THROUGH THE OVERNIGHT HOURS AT ALL SITES BUT RFD,
WHERE THE OUTER EDGE OF STRATUS MAY BE MORE PRONE TO BEING SCT
THAN BKN. A FEW SPRINKLES MAY FALL FROM TIME TO TIME DURING THE
OVERNIGHT HOURS WHERE THE STRATUS DECK IS THICKEST, THOUGH LOW
INVERSION HEIGHTS SHOULD TEND TO LIMIT MORE ROBUST PRECIPITATION
GENERATION.
BORCHARDT
LOT WATCHES/WARNINGS/ADVISORIES
IL...BEACH HAZARDS STATEMENT FROM THIS EVENING THROUGH THURSDAY
MORNING FOR ILZ006-ILZ103-ILZ104.
IN...BEACH HAZARDS STATEMENT FROM 4 PM CDT THIS AFTERNOON THROUGH
THURSDAY MORNING FOR INZ001-INZ002.
LM...SMALL CRAFT ADVISORY FROM 1 AM WEDNESDAY TO 4 AM CDT THURSDAY
FOR THE IL AND IN NEARSHORE WATERS.
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