816
FXUS63 KLOT 230521
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1221 AM CDT SAT AUG 23 2025
KEY MESSAGES
- SLIGHT CHANCE (20%) FOR A FEW THUNDERSTORMS SATURDAY
AFTERNOON.
- FALL-LIKE TEMPERATURES EARLY/MID NEXT WEEK.
DISCUSSION
ISSUED AT 206 PM CDT FRI AUG 22 2025
A STRONG UPPER LOW AND AN ASSOCIATED SURFACE LOW OVER MANITOBA
WILL SHIFT EASTWARD INTO ONTARIO TONIGHT INTO SATURDAY. WHILE THIS
LOW WILL STAY WELL NORTH-NORTHEAST OF OUR AREA, AN ASSOCIATED
COLD FRONT SHIFTING SOUTHWARD ACROSS THE UPPER MIDWEST THIS
EVENING WILL SHIFT ACROSS OUR AREA DURING THE DAY ON SATURDAY. A
LOW POTENTIAL (~20%) FOR A PERIOD OF WIDELY SCATTERED SHOWERS (AND
MAYBE A THUNDERSTORM) WILL EXIST WITH THIS FRONTAL BOUNDARY
BEGINNING LATE TONIGHT (AFTER 2 AM) ACROSS FAR NORTHWESTERN IL,
THEN DURING THE EARLY TO MID MORNING HOURS OF SATURDAY ACROSS THE
MUCH OF NORTHERN IL NORTH OF I-80. MOST AREAS ARE LIKELY TO REMAIN
DRY, AND IN THE AREAS IT DOES RAIN AMOUNTS WILL REMAIN LIGHT
(UNDER A TENTH OF AN INCH). A FEW ADDITIONAL ISOLATED TO WIDELY
SCATTERED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE (~20% CHANCE)
WITH THE FRONTAL BOUNDARY SATURDAY AFTERNOON, PRIMARILY TO TO
SOUTHEAST OF I-55.
THE CANADIAN UPPER LOW WILL CARVE OUT DEEP MID-UPPER LEVEL TROUGH
ACROSS THE GREAT LAKES SUNDAY INTO THE FIRST HALF OF NEXT WEEK.
THIS WILL FAVOR A PERIOD OF BELOW AVERAGE AND RATHER PLEASANT
TEMPERATURES NEXT WEEK AS A MUCH COOLER AUTUMN-LIKE AIRMASS SHIFTS
INTO THE AREA ON BREEZY WEST-NORTHWESTERLY WINDS IN THE WAKE OF
SATURDAY'S COLD FRONT. HIGH TEMPERATURES IN THIS AIRMASS WILL BE
FAVORED TO ONLY BE IN THE LOW TO MID 70S SUNDAY THROUGH THE MIDDLE
OF NEXT WEEK. COOL OVERNIGHT LOWS ARE ALSO EXPECTED, WITH
READINGS LIKELY TO DROP INTO THE 40S TO LOWER 50S OUTSIDE OF
CHICAGO! LATE IN THE WEEK, TEMPERATURES SHOULD BEGIN TO SLOWLY
MODERATE BACK CLOSE TO THE 80 DEGREE MARK.
OUTSIDE OF SOME POSSIBLE LAKE EFFECT SHOWERS EARLY NEXT WEEK
ACROSS PARTS OF NORTHWESTERN IN, AN EXTENDED PERIOD OF QUIET AND
DRY WEATHER IS EXPECTED NEXT WEEK.
KJB
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1220 PM CDT FRI AUG 22 2025
CONCERNS:
- BRIEF PERIOD OF VFR SHRA POSSIBLE SATURDAY MORNING ALONG A
COLD FRONT NEAR RFD AND NW OF THE CHICAGO TERMINALS, AND
AGAIN NEAR GYY IN THE AFTERNOON.
- BREEZY WNW WINDS WITH GUSTS 20-25 KT THIS AFTERNOON.
A SERIES OF COLD FRONTS WILL SHIFT THROUGH THE TERMINALS TODAY.
THE FIRST WILL TRACK THROUGH MAINLY BEFORE DAYBREAK. EXPECT SOME
LOWER VFR CEILINGS WITH THIS. A FEW SHOWERS WILL OCCUR WITH THE
FIRST WAVE, MAINLY NEAR RFD AND TO THE NW OF THE CHICAGO
TERMINALS IN THE 9Z-12 PERIOD BEFORE DECAYING TO A JUST A CLOUD
DECK.
MOISTURE WILL POOL AHEAD OF THE MAIN COLD FRONT THAT WILL SHIFT
THROUGH LATE MORNING INTO THE AFTERNOON. DEPENDING ON HOW QUICK
THE FRONT WILL GET THROUGH WILL DETERMINE WHETHER ENOUGH
INSTABILITY WILL BUILD ACROSS THE CHICAGO TERMINALS TO TRIGGER A
FEW SHOWERS. CURRENT GUIDANCE WOULD SUGGEST DEVELOPMENT FROM
KMDW SOUTHEASTWARD. HAVE INTRODUCED A PROB30 FOR KGYY GIVEN THE
SIGNAL FOR POSSIBLY A SLIGHTLY FARTHER NW DEVELOPMENT -- AS
EARLIER GUIDANCE SUGGESTED (AND MOST STILL DO) THAT THE CHICAGO
TERMINALS REMAIN DRY GIVEN THAT THE MOISTURE LAYER WILL BE
SOMEWHAT SHALLOW. HOWEVER, A FEW THUNDERSTORMS MAY DEVELOP
ALONG THE ORD SOUTHEAST ARRIVAL TRACK MID TO LATE AFTERNOON.
BREEZY NW WINDS WILL BUILD IN LATE MORNING INTO THE AFTERNOON
WITH GUSTS IN THE LOWER 20S. EXPECT CLEARING TONIGHT AND LIGHTER
NW WINDS.
KMD
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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