033
FXUS63 KLOT 281447
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
947 AM CDT SUN JUN 28 2026
KEY MESSAGES
- A DECAYING CLUSTER OF THUNDERSTORMS MAY AFFECT PORTIONS OF
NORTHERN ILLINOIS THIS AFTERNOON.
- DANGEROUS HEAT IS EXPECTED ACROSS THE AREA THIS WEEK.
- AFTERNOON HEAT INDEX VALUES FORECASTED OVER 100 DEGREES EACH
DAY NEXT WEEK, WITH LITTLE TO NO RELIEF AT THE LAKESHORE AND
AT NIGHT.
UPDATE
ISSUED AT 947 AM CDT SUN JUN 28 2026
ATTENTION IS BEING PAID TO THE MESOSCALE CONVECTIVE COMPLEX IN
NORTH CENTRAL IOWA AT THE MOMENT. THE CORE OF THE EMBEDDED MCV
LOOKS TO HAVE A DUE EAST MOVEMENT TO IT, AND YET THE TRAILING
SOUTHERN CLUSTER OF STORMS HAS A RECENT SOUTHEASTWARD DRIFT TO
IT. WHEN ANALYZING CURRENT SURFACE OBSERVATIONS, IT APPEARS THE
WARM FRONT IS DRAPED JUST SOUTH OF THE COMPLEX IN SOUTHERN IOWA
AND STRETCHES SOUTH INTO NORTHEAST MISSOURI AND ACROSS CENTRAL
ILLINOIS, JUST SOUTH OF THE FORECAST AREA. THE SPC MESOANALYSIS
HAS BROAD INSTABILITY AXIS STRETCHING SOUTHEASTWARD FROM OSAGE,
IOWA TO BLOOMINGTON, ILLINOIS. AS THE COMPLEX MOVES EASTWARD,
THE ESTIMATED TIME ARRIVING AT THE MISSISSIPPI RIVER WOULD BE
AROUND NOON, WHICH WOULD PLACE THE INSTABILITY GRADIENT ALONG A
DUBUQUE, IA TO PAXTON, IL LINE, WHICH WOULD BECOME THE FAVORED
LANE THAT THE CLUSTER OF STORMS WOULD WANT TO TRAVEL ON. GIVEN
THE STEEP LAPSE RATES AND STRONG SHEAR AVAILABLE IN THE
ENVIRONMENT, IT IS POSSIBLE THAT ISOLATED STRONGER EMBEDDED
STORMS COULD PRODUCE LOCALIZED DAMAGING WIND OR HAIL UP TO THE
SIZE OF A QUARTER. GUIDANCE CONTINUES TO SUGGEST THAT THIS
COMPLEX SHOULD BE IN A DECAYING STATE AS IT ENTERS, BUT EVEN
JUST THREE HOURS OUT, THERE IS UNCERTAINTY ON THE EXACT TRACK IT
TAKES AND WHETHER OR NOT IT CAN MAINTAIN ITS STRENGTH. THE BEST
CHANCES REMAIN IN THE NORTHWESTERN PORTION OF THE CWA, SO POPS
HAVE BEEN BOOSTED A BIT IN THAT AREA. LASTLY, THERE IS THE
POTENTIAL FOR ANOTHER WAKE LOW TO DEVELOP BEHIND THE SYSTEM.
GIVEN THE EXPECTED DECAYING NATURE OF THE SYSTEM, IT MIGHT NOT
BE AS STRONG OF A WAKE LOW AS PREVIOUSLY OCCURRED EARLIER THIS
YEAR, THERE IS THE POTENTIAL FOR SOUTHEAST WIND GUSTS TO 40 MPH
LATE THIS AFTERNOON AND THIS EVENING.
DK
DISCUSSION
ISSUED AT 252 AM CDT SUN JUN 28 2026
A WEAK 925-850 HPA WARM FRONT STRETCHING WNW TO ESE FROM AROUND
LEE COUNTY TO JUST SOUTH OF THE KANKAKEE RIVER VALLEY IN
NORTHWEST INDIANA CONTINUES TO PROVIDE A FOCUS FOR SPOTTY LIGHT
SHOWERS EARLY THIS MORNING. MEANWHILE, A DEVELOPING SURFACE
THETA-E GRADIENT ASSOCIATED WITH NOTABLY HIGHER MOISTURE JUST
SOUTHWEST OF THE CWA WILL LIFT NORTHWARD THROUGH THE DAY. WEAK
LOW-LEVEL ISENTROPIC ASCENT ASSOCIATED WITH THESE FEATURES
SHOULD ALLOW FOR AN AXIS OF INCREASED CLOUD COVER AND PERHAPS A
FEW LIGHT SHOWERS/SPRINKLES LATE THIS MORNING INTO THIS
AFTERNOON.
SEVERE CONVECTION TRACKING ALONG AND NORTH OF THE SD/NE LINE
EARLY THIS MORNING WILL REMAIN THE PRIMARY FOCUS FOR THE
FORECAST AREA THIS AFTERNOON. THIS CLUSTER OF CONVECTION HAS
REMAINED FAIRLY STRONG THROUGH MUCH OF THE NIGHT, WITH AN
ASSOCIATED MCV NOW EVIDENT. RENEWED CONVECTIVE CELLS OVER
NORTHEAST NEBRASKA AHEAD OF THIS COMPLEX INDICATE THAT THE
ENVIRONMENT IS NOT ENTIRELY CAPPED FARTHER SOUTH. THE CONVECTION
WILL BEGIN TO ENCOUNTER SUBSTANTIAL LOW TO MID-LEVEL WARMING
WITH AN INCOMING EML LIFTING NORTHEAST ACROSS THE MISSISSIPPI
RIVER VALLEY LATE THIS MORNING INTO THE AFTERNOON. HOWEVER, THE
COMBINATION OF STEEPENING MID-LEVEL LAPSE RATES, LOW-LEVEL
MOISTURE ADVECTION, AND LOCAL WEAKENING OF CAPPING NEAR ANY
MATURE MCV DOES WARRANT SOME CONCERN FOR CONVECTION TO PERSIST
ACROSS THE MISSISSIPPI RIVER AND INTO THE CWA. WITH MODESTLY
STRONG MID-LEVEL FLOW ACROSS SOUTHERN WISCONSIN AND A STRONG
INSTABILITY GRADIENT BIFURCATING THE CWA, THERE IS A SWEET SPOT
WHERE CONVECTION, POSSIBLY SEVERE, COULD EVENT REMAIN WELL
FORMED AND TRACK WELL INTO (OR EVEN ACROSS) THE CWA. HAVE
INTRODUCED CHANCE POPS FOR SHOWERS AND STORMS WEST OF THE
CHICAGO METRO, AND SLIGHT CHANCE POPS ELSEWHERE, FOR THE
AFTERNOON. ADDITIONALLY, SOME CAMS INDICATE THAT ANY DECAYING
MCV COULD PRODUCE A WAKE LOW AND RESULTANT STRONGER SOUTHEAST
WINDS OVER PORTIONS OF THE AREA THIS AFTERNOON.
REGARDLESS OF POTENTIAL CONVECTION, HEAT AND HUMIDITY WILL
BEGIN TO BUILD TODAY WITH HEAT INDEX VALUES RISING TO AROUND 90
INLAND DURING THE AFTERNOON AND PERSISTENT ONSHORE FLOW
MAINTAINING COOLER CONDITIONS ALONG THE SHORE.
THE WELL-ADVERTISED PERIOD OF HEAT THIS WEEK REMAINS ON TRACK,
PARTICULARLY MONDAY THROUGH WEDNESDAY. AN ANOMALOUSLY STRONG
MID-LEVEL RIDGE (HEIGHTS VERY NEAR 600DAM) DRIFTING ALONG THE
OHIO RIVER VALLEY AND H850/H700 TEMPS OF OVER 25C/12C MONDAY
THROUGH WEDNESDAY WILL YIELD UNSEASONABLY WARM CONDITIONS WITH
DAYTIME HIGHS WELL INTO THE 90S WHILE BUILDING AN INCREDIBLY
STRONG CAP OVER THE LOCAL AREA. COMBINED WITH PERSISTENT
SOUTHWEST LOW-LEVEL FLOW, THERE LOOKS TO BE NO RELIEF FROM LAKE
BREEZES OR UPSTREAM CONVECTIVE OUTFLOW BOUNDARIES DURING THIS
TIME. THOUGH CAPPING WILL BE QUITE STRONG FOR MONDAY AND TUESDAY
(AND POSSIBLY INTO WEDNESDAY), PERSISTENT STRONG SOUTHWESTERLY
GRADIENT FLOW WILL LIKELY ALLOW FOR MODEST MIXING INTO
INCREDIBLY DRY AIR ACROSS THE BASE OF THE EML. THOUGH THIS MAY
LOWER DEW POINTS BY JUST A COUPLE DEGREES (E.G. MID 70S VS UPPER
70S), THE DIFFERENCE MAY BE ENOUGH TO KEEP HEAT INDEX VALUES IN
CHECK.
HAVE MAINTAINED THE EXTREME HEAT WATCH FOR COOK COUNTY FROM
MONDAY THROUGH WEDNESDAY, AND ISSUED A HEAT ADVISORY FOR THE
REMAINDER OF THE FORECAST AREA FOR THE SAME PERIOD. EXPECTATIONS
ARE THAT COOK COUNTY WILL NEED TO BE UPGRADED TO AN EXTREME
HEAT WARNING (CRITERIA OF HEAT INDEX VALUES OF 100 OR HIGHER FOR
THREE DAYS). OUTSIDE OF COOK COUNTY, THIS LOOKS LIKE A SOLID
LONG DURATION ADVISORY EVENT WITH AFTERNOON HEAT INDEX VALUES
HOVERING AROUND 105 DEGREES (HEAT ADVISORY CRITERIA). A CASE CAN
BE MADE THAT THE LONGEVITY OF THE HEAT MAY REQUIRE AN EVENTUAL
UPGRADE TO AN EXTREME HEAT WARNING FOR AREAS OUTSIDE OF COOK
COUNTY IF CONVECTION REMAINS NORTH OF THE AREA ON THURSDAY AND
FRIDAY.
REGARDING THE POTENTIAL FOR CONVECTION THIS WEEK, THE STRONG
CAP EARLY IN THE WEEK SHOULD DEFLECT CONVECTION WELL TO THE
NORTHWEST (MINNESOTA THROUGH UPPER MICHIGAN) THROUGH AT LEAST
WEDNESDAY. AN EXPECTED FLATTENING OF THE RIDGE AND EVENTUAL SW
TO NE ORIENTATION OF THE RIDGE AXIS TOWARD THE WESTERN GREAT
LAKES WOULD FAVOR INCREASING CHANCES FOR CONVECTIVE EPISODES TO
AFFECT SOME OR ALL OF THE FORECAST AREA AS EARLY AS WEDNESDAY
NIGHT. AND WITH GUIDANCE OFTEN TOO SLOW WITH BREAKING DOWN THE
PERIPHERY OF SUMMERTIME RIDGES IN THE GREAT LAKES, DIRECT OR
INDIRECT (OUTFLOW) IMPACTS FROM CONVECTION LOWERS CONFIDENCE ON
HEADLINES BEYOND WEDNESDAY. THE OVERALL MESSAGE IS FOR HEAT TO
POTENTIALLY PERSIST INTO THE INDEPENDENCE DAY HOLIDAY, BUT FOR
INCREASING CHANCE FOR CONVECTION WITH EACH DAY.
KLUBER
AVIATION /12Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 637 AM CDT SUN JUN 28 2026
- PERIOD OF MVFR CEILINGS LIKELY THROUGH MIDDAY.
- CHANCE (~30%) OF A PERIOD OF SHRA/TSRA THIS AFTERNOON WITH
HIGHEST CHANCES TS AT KRFD AFTER ~19Z.
DEEP SURFACE LOW PRESSURE WAS LOCATED OVER WESTERN NE EARLY THIS
MORNING. WITH A NORTHWARD-LIFTING WARM FRONT EXTENDING EAST AND
SOUTHEAST FROM THE LOW IN TO THE LOWER MO/OH VALLEYS. A MOIST
LOW-LEVEL AIR MASS IS IN PLACE NORTH OF THE WARM FRONT INTO
NORTHERN IL/IN, WHICH WILL LIKELY SUPPORT DEVELOPMENT OF AN MVFR
DECK EARLY THIS MORNING (ALONG WITH NORTHWARD ADVECTION OF AN
EXISTENT MVFR DECK CURRENTLY ALONG/SOUTH OF A KSQI-KJOT-KOXI
LINE). ONCE DEVELOPED, MVFR MAY PERSIST THROUGH MIDDAY BEFORE
EVENTUALLY RISING TO VFR.
FARTHER TO THE NORTHWEST, A WELL-DEVELOPED THUNDERSTORM COMPLEX
WAS EVIDENT IN RADAR IMAGERY ACROSS SOUTHWEST MN/NORTHWEST IA
THIS MORNING. HIGH-RES CAM GUIDANCE CONTINUES TO INDICATE THE
SOUTHERN PORTION OF THIS COMPLEX MAY SPREAD INTO NORTHERN IL
THIS AFTERNOON, AT LEAST IN A WEAKENING FASHION, ON THE NOSE
OF A LOW-LEVEL JET AND REGION OF STEEP MID-LEVEL LAPSE RATES.
MODELS CONTINUE TO INDICATE THE GREATEST POTENTIAL (~30%) FOR
TSRA AT KRFD AND HAVE MAINTAINED THE PROB30 THERE AFTER 19Z.
INDICATIONS OF WEAKENING AND A DECREASING FOOTPRINT REMAIN FOR
AREAS FARTHER EAST/SOUTHEAST INTO THE CHICAGO TERMINALS, THOUGH
SUPPORT REMAINS FOR AT LEAST A PROB30 MENTION FOR SHRA AFTER
20Z, AND POTENTIALLY MAY NEED TS INCLUDED IF TRENDS DICTATE WITH
LATER UPDATES.
AS FOR WINDS, LIGHT VARIABLE/NORTHEAST WINDS SHOULD TURN MORE
EAST-SOUTHEAST AS WE MIX THIS MORNING, AND LOOK TO GRADUALLY
INCREASE THIS AFTERNOON AS THE GRADIENT TIGHTENS IN RESPONSE TO
THE AFOREMENTIONED SURFACE LOW LIFTING SLOWLY NORTHEAST TOWARD
THE UPPER MIDWEST. THERE HAS ALSO BEEN A SIGNAL IN SOME CAM
GUIDANCE FOR A WEAKENING WAKE-LOW INDUCED WIND FIELD ASSOCIATED
WITH THE STORM COMPLEX TO SPREAD INTO SOUTHERN WI/NORTHERN IL
LATER THIS AFTERNOON. HAVE THUS BUMPED UP WINDS (INCLUDING IN
THE PROB30 GROUPS) FOR POTENTIALLY BREEZIER CONDITIONS. WINDS
SHOULD SETTLE INTO A SOUTHEAST DIRECTION LATER TODAY/TONIGHT AND
MAY BECOME BREEZY AGAIN OVERNIGHT IN RESPONSE TO A DEVELOPING 30
KT LOW LEVEL JET, WHILE VEERING SOUTH WITH THE APPROACH OF THE
SURFACE WARM FRONT. WINDS SHOULD THEN SHIFT SOUTHWEST AND REMAIN
SOMEWHAT BREEZY AFTER DAYBREAK MONDAY AS THE WARM FRONT LIFTS
NORTH OF THE TERMINALS.
RATZER
CLIMATE
ISSUED AT 252 AM CDT SUN JUN 28 2026
.DAILY RECORDS FOR THE UPCOMING WEEK........
CHICAGO (KORD)
RECORD HIGH RECORD WARM MINIMUM
JUNE 29 97 (1954) 80 (1931)
JUNE 30 99 (1953) 80 (2018)
JULY 1 103 (1956) 78 (1931)
JULY 2 99 (1970) 79 (1911)
JULY 3 102 (1949) 78 (1911)
JULY 4 102 (2012) 80 (1921)
ROCKFORD (KRFD)
RECORD HIGH RECORD WARM MINIMUM
JUNE 29 103 (1931) 75 (1931)
JUNE 30 102 (1931) 76 (2018)
JULY 1 101 (1931) 76 (1970)
JULY 2 99 (1910) 74 (1970)
JULY 3 99 (1925) 75 (2012)
JULY 4 102 (2012) 77 (1977)
NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...HEAT ADVISORY FROM NOON MONDAY TO 10 PM CDT WEDNESDAY FOR
ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
ILZ106-ILZ107-ILZ108.
EXTREME HEAT WATCH FROM MONDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR ILZ103-ILZ104-ILZ105.
IN...HEAT ADVISORY FROM NOON CDT /1 PM EDT/ MONDAY TO 10 PM CDT /11
PM EDT/ WEDNESDAY FOR INZ001-INZ002-INZ010-INZ011-INZ019.
LM...NONE.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page