913
FXUS63 KLOT 090756
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
256 AM CDT TUE SEP 9 2025
KEY MESSAGES
- MOSTLY DRY WEATHER EXPECTED THE REMAINDER OF THE WORK WEEK
WITH GRADUALLY WARMING TEMPERATURES.
- UNSEASONABLY WARM WITH A (LESS THAN 30 PERCENT) CHANCE OF
SCATTERED SHOWERS AND SOME THUNDERSTORMS THIS WEEKEND.
DISCUSSION
ISSUED AT 256 AM CDT TUE SEP 9 2025
THROUGH WEDNESDAY:
GRADUAL WARMING TREND WILL CONTINUE TODAY INTO WEDNESDAY, WITH
MAINLY DRY CONDITIONS EXPECTED. THERE IS A LOW-CHANCE (<20%) OF
SHOWERS OR SPRINKLES AFTER MIDNIGHT TONIGHT OVER NORTHWEST IL
(WEST OF THE I-39 CORRIDOR), WHICH COULD PERSIST IN SPOTTY
FASHION INTO EARLY WEDNESDAY.
AS HAS BEEN ADVERTISED OVER THE PAST SEVERAL DAYS, EARLY
MORNING GOES WATER VAPOR IMAGERY INDICATES SEVERAL INDIVIDUAL
SHORT WAVE DISTURBANCES PROPAGATING TO THE EAST-SOUTHEAST
UPSTREAM OF THE FORECAST AREA. OF THESE, A WAVE CURRENTLY OVER
EASTERN SD/NE IS PROGGED TO GRADUALLY PHASE WITH A SLOWER-MOVING
DISTURBANCE OVER MO, AND EVENTUALLY MOVE ACROSS THE AREA
TONIGHT. THE MAIN AXIS OF STRONGER WARM/MOIST ADVECTION
CONTINUES TO BE FOCUSED WEST AND NORTHWEST OF THE CWA HOWEVER,
WITH LOW-LEVEL SOUTHEASTERLY FLOW AROUND SURFACE HIGH PRESSURE
TO OUR EAST MAINTAINING DRY CONDITIONS ACROSS IN/IL. THUS THE
MAIN IMPACTS OF THE PHASING MID-LEVEL SHORT WAVE TROUGH WILL BE
MAINLY A CONTINUED INCREASE IN HIGH LEVEL CLOUD COVER FROM THE
WEST THROUGH THIS EVENING.
WHILE WARM ADVECTION ALOFT STRENGTHENS SOMEWHAT AHEAD OF THE
TROUGH THIS EVENING, DEEPER MOISTURE CONTINUES TO LAG THE BETTER
FORCING ASSOCIATED WITH THE TROUGH. ANOTHER POSITIVE-TILT SHORT
WAVE CURRENTLY DROPPING SOUTHEAST TOWARD THE UPPER MIDWEST WILL
APPROACH THE REGION TOWARD MORNING, AND LOOKS TO HAVE THE
GREATEST POTENTIAL FOR PRODUCING SOME SCATTERED SHOWERS INTO AT
LEAST OUR WEST/NORTHWESTERN CWA AS SOMEWHAT BETTER MID- LEVEL
MOISTURE IS ADVECTED INTO THE AREA. GUIDANCE DEPICTS A WEAK
SURFACE LOW PRESSURE WAVE DEVELOPING WITH THIS WAVE HOWEVER,
WHICH TRACKS FROM MN INTO EASTERN IA/WESTERN IL INTO WEDNESDAY
WHICH ALLOWS SURFACE WINDS TO TURN MORE EAST- SOUTHEASTERLY AND
MAINTAIN DRY LOW-LEVEL ADVECTION. THEREFORE, THE "GREATEST"
SHOWER POTENTIAL (LESS THAN 20% OR SO) APPEARS TO BE LATE
TONIGHT THROUGH SUNRISE OR SO. CAN'T COMPLETELY RULE OUT SOME
SPOTTY SHOWERS OR SPRINKLES LINGERING INTO WEDNESDAY MORNING,
THOUGH CONFIDENCE IN THAT IS FAIRLY LOW GIVEN THE DRY LOW
LEVELS.
DESPITE INCREASING HIGH CLOUD COVER TODAY, AFTERNOON HIGHS ARE
EXPECTED TO REACH THE MID-70S IN MOST AREAS, WITH A FEW UPPER
70S POSSIBLE. A WEAK EAST-SOUTHEASTERLY LAKE BREEZE SHOULD
DEVELOP AGAIN THIS AFTERNOON, WITH SOME MODEST COOLING ALONG
PRIMARILY THE IL SHORE. WARMER THERMAL PROFILES WEDNESDAY SHOULD
SUPPORT TEMPS IN THE UPPER 70S TO LOWER 80S INLAND OF LAKE
MICHIGAN, WHERE A LARGER LAKE-COOLING FOOTPRINT WILL KEEP AREAS
ALONG THE LAKE IN THE LOW-MID 70S. A WEAK COLD FRONT WILL SAG
SOUTH OF THE AREA LATE.
RATZER
WEDNESDAY NIGHT THROUGH MONDAY:
A MID-LEVEL TROUGH CENTERED OVER THE GREAT LAKES REGION
WEDNESDAY EVENING WILL BRING PLENTY OF MID-LEVEL CLOUDS AND
PERHAPS SOME SPRINKLES OR ISOLATED SHOWERS BEFORE EXITING TO
THE EAST OVERNIGHT.
NO SUBSTANTIAL CHANGES IN FORECAST TRENDS LATE THIS WEEK INTO
EARLY NEXT WEEK WITH A HYBRID OMEGA/REX BLOCKING PATTERN
ANCHORED BY A STRONG MID-LEVEL RIDGE CENTERED SOUTHWEST OF
HUDSON BAY. ENSEMBLE GUIDANCE NO LONGER FAVORS A HIGH-LATITUDE
WAVE ROUNDING THE RIDGE AND TRACKING OVER THE WESTERN GREAT
LAKES REGION THIS WEEKEND. INSTEAD, THIS WAVE IS PROGGED TO
REMAIN WELL TO THE NORTHEAST WHILE PUSHING A COLD FRONT
SOUTHWESTWARD TOWARD OUR AREA. HOWEVER, WITH THE STRONG RIDGE
CENTERED SO FAR TO THE NORTHWEST, A RELATIVE WEAKNESS IN MID-
LEVEL HEIGHTS REMAINS FAVORABLE FOR SOME ENERGY FROM A WESTERN
UPPER-LOW (AND OTHER BLOCKING FEATURE) TO MEANDER TOWARD THE
WESTERN GREAT LAKES AS THE BACKDOOR COLD FRONT STALLS NEAR OR
OVER THE FORECAST AREA LATE IN THE WEEKEND INTO EARLY NEXT WEEK.
WHILE THIS SUPPORTS SCATTERED SHOWERS AND SOME STORMS, A LOW-
LEVEL THERMAL RIDGE NOSING NORTHEASTWARD TOWARD THE AREA MAY
PROVIDE SOME CAPPING AND REDUCE PRECIP CHANCES. THIS SET-UP
WOULD ALSO YIELD A WARM WEEKEND WITH HIGHS WELL INTO THE 80S TO
PERHAPS TOUCHING 90 IN SOME LOCATIONS. THE REGIONAL DRY SPELL
OVER THE PAST FEW WEEKS AND SEASONAL DECLINE IN
EVAPOTRANSPIRATION SHOULD PRECLUDE MORE OPPRESSIVE HUMIDITY AS
DEW POINTS LIKELY REMAIN BELOW 70.
KLUBER
AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 1217 AM CDT TUE SEP 9 2025
EXPECT VFR CONDITIONS THROUGH THE PERIOD WITH UPPER-LEVEL
CIRRUS GRADUALLY LOWERING INTO A MID-LEVEL CLOUD DECK. DRY
CONDITIONS ARE ALSO FAVORED, BUT A SLOW-MOVING WAVE CROSSING
SOUTHERN WISCONSIN MAY PRODUCE ISOLATED SPRINKLES OR VFR -SHRA
PRIOR TO SUNRISE WEDNESDAY AT RFD.
SE WINDS 5-10 KNOTS EARLY THIS MORNING WILL SHIFT SSW AROUND 10
KNOTS SHORTLY AFTER SUNRISE. WINDS WILL THEN SETTLE SSE AROUND
5 KNOTS THIS EVENING BEFORE VEERING BACK SSW/SW LATE TONIGHT.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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