035
FXUS63 KLOT 292346
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
646 PM CDT SAT AUG 29 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 /00Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 646 PM CDT SAT AUG 29 2026
AVIATION FORECAST CONCERNS FOR THIS TAF PERIOD INCLUDE TIMING
PERIODS OF SHOWERS, A RELATIVELY LOW POTENTIAL FOR MINIMAL LLWS
TONIGHT MAINLY FOR KRFD, AND BREEZY SOUTHWEST WINDS ON SUNDAY.
ONE BAND OF LIGHT SHOWERS IS OVER KMDW/KGYY AT ISSUANCE TIME,
BUT WILL MOVE EAST OF THE TERMINALS BY 00Z. THE FORECAST AREA
WILL REMAIN WITHIN A REGION OF BROAD WARM/MOIST ADVECTION
THROUGH THE PERIOD, THUS ISOLATED SPRINKLES OR LIGHT SHOWERS
CAN'T BE COMPLETELY RULED OUT THROUGH SUNDAY. HOWEVER, THE
PERIOD FROM LATE TONIGHT INTO SUNDAY MORNING APPEARS TO HAVE THE
GREATEST POTENTIAL FOR MORE ORGANIZED SHRA POTENTIAL AS A
35-40 KT SOUTHWEST LOW LEVEL JET DEVELOPS. HREF ENSEMBLE
GUIDANCE SUPPORTS A ROUGHLY 09Z-16Z WINDOW (KRFD EARLIEST AND
KGYY LATEST) FOR A FEW HOUR PERIOD OF SHRA. ISOLATED TS ARE NOT
OUT OF THE QUESTION, THOUGH POTENTIAL APPEARS TOO LOW FOR TAF
MENTION. MAY NEED TO GO WITH A TEMPO FOR THESE SHRA WITH LATER
UPDATES IF GUIDANCE TRENDS CONVERGE ON TIMING/COVERAGE. MAY ALSO
NEED ANOTHER PROB30 MENTION SUNDAY AFTERNOON, THOUGH THERE IS
MORE GUIDANCE SPREAD AND LOWER CONFIDENCE DURING THAT TIME.
OTHERWISE, VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD,
WITH SHOWERS MAINLY FROM MID-LEVEL (8-10 KFT) CLOUD BASES.
WIND-WISE, SURFACE WINDS ARE CURRENTLY BACKING SSE IN THE 10-15
KT RANGE EARLY THIS EVENING, THOUGH SHOULD EVENTUALLY SETTLE
BACK SSW AFTER MIDNIGHT. WITH THE LOW-LEVEL JET INCREASING,
EXPECT THERE WILL BE SOME SPORADIC GUSTS FOR KORD/KMDW WHICH
TYPICALLY REMAIN WARMER/MORE MIXED. LLWS APPEARS MARGINAL FROM A
TAF STANDPOINT EVEN FARTHER WEST AT KRFD WHERE SURFACE GUSTS
WILL LIKELY BE LESS FREQUENT, AND THEREFORE HAVE NOT INCLUDED IN
TAFS. IT DOES APPEAR THAT SURFACE WINDS WILL BECOME GUSTY TO
AROUND 25 KT LATER SUNDAY MORNING AS WE MIX INTO THE WEAKENING
JET AFTER SUNRISE.
RATZER
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