272
FXUS63 KLOT 300528
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1228 AM CDT SUN AUG 30 2026
KEY MESSAGES
- HEAT AND HUMIDITY WILL RETURN ON SUNDAY AND PERSIST THROUGH
MUCH OF THE WORKWEEK.
- THERE MAY BE A OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS AT
TIMES AMIDST PLENTY OF DRY HOURS.
DISCUSSION
ISSUED AT 231 PM CDT SAT AUG 29 2026
REST OF TODAY:
DESPITE THE OMINOUS UPSTREAM RADAR EARLIER TODAY, DRIER AIR AT
THE LOWER LEVELS HAS SUBSTANTIALLY ERODED THE RAINFALL FOOTPRINT
THIS AFTERNOON (AS EXPECTED). THUS EXPECT OCCASIONAL SPRINKLES
AND PERHAPS LIGHT SHOWERS SUFFICIENT TO WET THE GROUND IN A FEW
SPOTS, FAVORING NEAR AND NORTH OF I-80 UNTIL SUNSET. MOSTLY
CLOUDY SKIES WILL KEEP TEMPERATURES IN THE MID 70S TO AROUND
80F, COOLEST NORTHWEST.
TONIGHT THROUGH SUNDAY NIGHT:
FOLLOWING A MOSTLY QUIET EVENING, ISOLATED TO SCATTERED SHOWERS
WILL LIKELY BLOSSOM OVERNIGHT (FAVORING NEAR/NORTH OF THE IL AND
KANKAKEE RIVERS) INTO SUNDAY MORNING. FORECAST SOUNDINGS ARE
UNFAVORABLE FOR ANYTHING MORE THAN ISOLATED EMBEDDED
THUNDERSTORMS (SLIGHT CHANCE/20% MENTION). LOWS WILL BE IN THE
MID 60S TO AROUND 70F.
SUNDAY WILL MARK THE START OF THE ADVERTISED VERY WARM TO HOT
AND HUMID PATTERN IN STORE FOR MUCH OF THE WEEK. HOWEVER,
RELATIVELY EXTENSIVE CLOUD COVER AND A SHARP LOWER LEVEL
INVERSION WILL KEEP TEMPERATURES IN CHECK SOMEWHAT (MID TO
LOCALLY UPPER 80S). BREEZY SOUTHWESTERLY FLOW BELOW THE
INVERSION WILL YIELD GUSTS UP TO 30 MPH. A MID-LEVEL SHORT-WAVE
WILL CROSS THE MID-UPPER MS VALLEY IN THE AFTERNOON, WHICH WILL
BRING ANOTHER CHANCE (20-30%) FOR ELEVATED CONVECTION (WIDELY
SCATTERED SHOWERS AND A FEW STORMS) TO AREAS PRIMARILY NORTH OF
I-80. FAIRLY MEAGER, SKINNY CAPE DUE TO MARGINAL MID-LEVEL
LAPSE RATES ROOTED ABOVE THE STRONG INVERSION DOWN AROUND 850
MB, AND OVERALL MODEST FORCING WILL LIKELY AGAIN SERVE TO KEEP
THUNDERSTORMS ISOLATED AT MOST.
ADDITIONAL ISOLATED TO SCATTERED SHOWERS (20-30% CHANCE) AND A
FEW STORMS MAY THEN MOVE ACROSS PORTIONS OF FAR NORTHERN
ILLINOIS LATE SUNDAY NIGHT/EARLY SUNDAY.
MONDAY ONWARD:
STRONG MID AND UPPER LEVEL RIDGING WILL AMPLIFY NORTHEASTWARD
FROM THE SOUTHERN PLAINS AND CENTER OVER THE OHIO VALLEY NEXT
WEEK. WHILE WE'RE PAST PEAK CROP EVAPOTRANSPIRATION, IT WILL BE
A VERY WARM TO HOT AND GENERALLY UNCOMFORTABLY HUMID WEEK.
MONDAY STILL LOOKS TO HAVE A GOOD CHANCE TO BE THE FIRST 90F
READING OF AUGUST AT CHICAGO AND ROCKFORD, ON THE LAST DAY OF
THE MONTH! SEPTEMBER AND THUS METEOROLOGICAL FALL (ALREADY?!)
WILL GET OFF TO A SUMMER-LIKE START WITH ADDITIONAL 90+ TEMPS
AND DAYTIME HEAT INDICES FLIRTING WITH 100F IN SPOTS PROBABLE ON
TUESDAY AND WEDNESDAY. IF THE RIDGE FLATTENS OUT SUFFICIENTLY
LATER IN THE WEEK, WEAK SURFACE HIGH PRESSURE MAY ENABLE A
BACKDOOR COLD FRONT TO SAG SOUTH AND BRING SOME COOLING,
PARTICULARLY CLOSER TO THE LAKE.
THE RIDGING CURRENTLY LOOKS AMPLIFIED ENOUGH TO RESULT IN MORE
PRONOUNCED CAPPING AND A BETTER CHANCE FOR "RING OF FIRE" TYPE
CONVECTIVE ACTIVITY TO REMAIN PRIMARILY NORTH OF THE AREA UNTIL
PERHAPS LATER IN THE WEEK, WHEN THE RIDGE MAY FLATTEN OUT SOME,
AS ALLUDED TO ABOVE. NORTHERN ILLINOIS (ESPECIALLY WITH
NORTHWARD EXTENT) IS CLOSE ENOUGH TO THE PRECARIOUS NORTHERN
PERIPHERY OF THE RIDGE TO WARRANT OCCASIONAL LOWER END (20-30%)
THUNDERSTORM CHANCES (FOCUSED AT NIGHT) THROUGH MIDWEEK.
ENSEMBLE GUIDANCE VARIANCE, EVEN LATER IN THE WEEK, IS SUCH THAT
PERIODIC POPS ARE STILL ONLY IN THE 20-30% RANGE.
LOOKING AHEAD TO LABOR DAY WEEKEND, CENTRAL CONUS RIDGING WILL
LIKELY REMAIN IN CONTROL, RESULTING IN CONTINUED WELL ABOVE
NORMAL TEMPS. THE EXACT POSITION AND ORIENTATION OF THE RIDGING
WILL MODULATE HOW WARM TEMPERATURES WILL GET, ALONG WITH
CONVECTIVE CHANCES.
CASTRO
AVIATION /06Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 1228 AM CDT SUN AUG 30 2026
SPOTTY SHOWERS ARE ONGOING ACROSS THE CENTRAL ZAU AIRSPACE AT
PRESS TIME ASSOCIATED WITH ISENTROPIC ASCENT BEING FORCED BY A
SOUTHWESTERLY 35-40 KT LOW-LEVEL JET ORIENTED TOWARD THE GREAT
LAKES. AS THE ORIENTATION OF THE LOW-LEVEL JET TURNS MORE
WESTERLY TOWARD DAYBREAK, THE EXPECTATION IS FOR COVERAGE OF
SHOWERS TO INCREASE AND PEAK GENERALLY IN THE 11 TO 15Z
TIMEFRAME, GIVE OR TAKE AN HOUR. WITH MID-LEVEL LAPSE RATES
GRADUALLY STEEPENING THROUGH THE NIGHT, OPTED TO CONVERT THE
INHERITED PROB30 GROUPS TO TEMPOS FOR -TSRA THIS MORNING (WILL
NOTE THERE HAS ALREADY BEEN LIGHTNING IN ACTIVITY ACROSS
SOUTHERN WISCONSIN EARLY THIS MORNING). WINDS OVERNIGHT THROUGH
MID SUNDAY MORNING SHOULD REMAIN GENERALLY WHERE THEY ARE RIGHT
NOW OUT OF THE SOUTHWEST AT 10 TO 15 KT (SOUTHEAST AT RURAL
TERMINALS).
AS THE LOW-LEVEL JET STARTS TO WEAKEN BY MID-MORNING, COVERAGE
OF SHOWERS SHOULD CORRESPONDINGLY DECREASE. UPWARD MIXING INTO
THE BASE OF THE DECAYING LOW-LEVEL JET SHOULD STILL PROMOTE
SOUTHWESTERLY GUSTS INCREASING TO 25 KT OR SO FROM MID-MORNING
TO EARLY AFTERNOON. A SHOWER OR TWO MAY REMAIN IN THE AREA
THROUGH EARLY AFTERNOON.
TOWARD MID-AFTERNOON A REMNANT MCV ORIGINATING OUT OF ONGOING
CONVECTION IN SOUTHERN NEBRASKA WILL MOVE INTO THE LOWER GREAT
LAKES. SUSPECT THERE WILL BE ANOTHER PERIOD OF SHOWERS ACROSS
THE REGION AS THE MCV MOVES THROUGH, THOUGH AM NOT CONFIDENT THE
HIGHEST COVERAGE WILL BE OVER THE TERMINALS OR OVER SOUTHERN
WISCONSIN. FOR NOW, WILL SIMPLY COVER THE THREAT WITH A
PROLONGED VCSH THROUGH EARLY EVENING.
TONIGHT, CURRENTLY EXPECT DRY CONDITIONS WITH A SOUTHWESTERLY
BREEZE AROUND 10 KT (SOUTHEASTERLY DIRECTLY AT RURAL TERMINALS).
A FEW SHOWERS MAY DEVELOP TOWARD DAYBREAK MONDAY AT THE NOSE OF
ANOTHER LOW-LEVEL JET. WILL TACKLE THAT WINDOW IN A LATER TAF
PACKAGE.
BORCHARDT
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page