793
FXUS63 KLOT 192340
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
640 PM CDT SUN JUL 19 2026
KEY MESSAGES
- SEVERE THUNDERSTORMS WITH THE POTENTIAL FOR DAMAGING WINDS AND
LOCALLY HEAVY RAINFALL/LOCALIZED FLASH FLOODING POSSIBLE
MONDAY NIGHT.
- EARLY AUTUMN LIKE COLD FRONT WILL BRING MUCH COOLER
TEMPERATURES, GUSTY WINDS, HAZARDOUS WINDS/WAVE ON THE LAKE,
AND REFRESHINGLY LOW HUMIDITY BY MIDWEEK.
DISCUSSION
ISSUED AT 222 CDT SUN JUL 19 2026
SATELLITE IMAGERY DOES SHOW SMOKE LINGERING ACROSS MUCH OF THE
WESTERN GREAT LAKES AND MID-MISSISSIPPI VALLEY EARLY THIS
AFTERNOON. SURFACE VISIBILITIES ACROSS OUR CWA HAVE BEEN LARGELY
IN THE 4-7SM RANGE TODAY WITH LOWER VISIBILITIES AND DENSER NEAR
SURFACE SMOKE ACROSS WISCONSIN. SATELLITE IMAGERY DOES SHOW WHAT
APPEARS TO BE AN AREA OF SOMEWHAT DENSE SMOKE UPSTREAM ACROSS
CENTRAL LAKE MICHIGAN AND WESTERN LOWER MICHIGAN WHICH COULD
ADVECT INTO PORTIONS OF OUR AREA THIS EVENING. WHILE NO WHERE
NEAR AS DENSE AS THE EPISODE LATE LAST WEEK, WIDESPREAD SMOKE
(WITH SOME VARIANCE IN DENSITY) COVERS THE REGION AND WILL
LIKELY CONTINUE TO DO SO LOCALLY TONIGHT AND INTO MONDAY
MORNING. GRADUALLY INCREASING SOUTHWEST WINDS SHOULD PUSH THE
BRUNT OF THE SMOKE NORTHEAST OUT OVER THE LAKE AND INTO MICHIGAN
MONDAY.
HIGH PRESSURE IN THE WAKE OF SATURDAY'S COLD FRONT HAS PUSHED
THE DEEP, TROPICAL MOISTURE SOUTH INTO SOUTHERN ILLINOIS, WITH A
DRIER AND STABLE AIR MASS ACROSS THE WESTERN GREAT LAKES AND
UPPER MIDWEST. WATER VAPOR IMAGERY EARLY THIS AFTERNOON DEPICT A
VIGOROUS SHORTWAVE TROUGH AND ASSOCIATED CLOSED MID-UPPER LEVEL
LOW MOVING EAST INTO SASKATCHEWAN. SURFACE CYCLOGENESIS
ASSOCIATED WITH TROUGH AND RESULTANT TIGHTENING SOUTHERLY
GRADIENT AND PRESSURE FALLS IS RESULTING IN A RAPID NORTHWARD
TRANSPORT OF LOW LEVEL MOISTURE ACROSS THE CENTRAL AND NORTHERN
PLAINS.
GUIDANCE IS IN GOOD AGREEMENT WITH RESPECT TO SYNOPTIC FEATURES
OVER THE NEXT 36 HOURS WITH A DEEPENING SURFACE LOW TRACKING
EAST ACROSS CANADA. BY EARLY MONDAY EVENING, AN UNSEASONABLY
STRONG 992MB SURFACE LOW IS PROGGED TO BE OVER WESTERN ONTARIO
WITH A DRYLINE EXTENDING SOUTH-SOUTHWEST FROM THIS LOW ACROSS
WESTERN WISCONSIN. THIS BOUNDARY IS THEN PROGGED TO LAY OUT MORE
WEST TO EAST ACROSS NORTHERN IOWA TAKING MORE OF A COLD FRONTAL
STRUCTURE WITH GREATER THERMAL DIFFERENCE ACROSS THE BOUNDARY.
STRONG MASS RESPONSE TO THIS DEEP LOW WILL RAPIDLY DRAW THE VERY
WARM AND MOIST AIR MASS NORTHWARD MONDAY, INITIALLY TO OUR
WEST, BUT EVENTUALLY SPREADING EAST ACROSS OUR CWA LATE IN THE
AFTERNOON INTO THE EARLY EVENING. SEASONABLY COOL MID LEVEL
TEMPS AND MODERATELY STEEP MID LEVEL LAPSE RATES ABOVE THIS
QUICKLY MOISTURE BOUNDARY LAYER SHOULD RESULT IN AN AXIS OF
STRONG TO EXTREME SURFACE BASED INSTABILITY IN ADVANCE OF THE WI
DRYLINE AND ACROSS NORTHWEST IL UP TO AND EVEN A BIT NORTH OF
THE BOUNDARY ACROSS NORTHERN IOWA. THE UNSEASONABLY STRONG
UPPER TROUGH WILL BE ACCOMPANIED BY EQUALLY STRONG KINEMATIC
FIELDS, RESULTING IN A LARGE AREA WITH STRONG DEEP LAYER SHEAR,
LIKELY CO-LOCATED WITH THE EXTREME INSTABILITY.
SYNOPTICALLY, THIS SET-UP LOOKS QUITE CONCERNING FOR A POTENTIAL
OUTBREAK OF SEVERE THUNDERSTORMS ACROSS THE REGION. CURIOUSLY,
THE SIGNAL IN MODEL GUIDANCE WITH RESPECT TO CONVECTION
TOMORROW AFTERNOON IS MIXED AND NOT ENTIRELY CLEAR.
STRENGTHENING LOW LEVEL JET AND RESULTING STRONG LOW LEVEL
THETA-E ADVECTION LOOKS LIKELY TO SUPPORT THE DEVELOPMENT OF A
NOCTURNAL MCS OVERNIGHT SOMEWHERE FROM NORTHERN IA NORTH INTO
CENTRAL MN. HREF AND RREFS SUGGEST THIS ACTIVITY WILL PUSH EAST
INTO WI MONDAY MORNING, AND LIKELY WEAKENING/DISSIPATING AS IT
ENCOUNTERS AN INITIALLY MORE STABLE AIR MASS AND AS WELL AS
DIURNAL WEAKENING OF THE LOW LEVEL JET. THE SIGNAL IN THE CAMS
IS NOT OVERLY SUGGESTIVE OF THIS MCS DEVELOPING A LARGE COLD
POOL OR LEAVING A SIGNIFICANT FOOTPRINT IN ITS WAKE MONDAY.
IF IT WERE TO LEAVE A STRONGER COLD POOL, THAT COULD LEAVE AN
EFFECTIVE BOUNDARY LAID OUT EAST-WEST-ISH TO OUR NORTH AND THAT
COULD BECOME A FOCUS FOR CONVECTIVE DEVELOPMENT. THAT SCENARIO
ISN'T REALLY DEPICTED IN GUIDANCE AND SEEMS LIKE IT IS ON THE
LOWER END OF THE SPECTRUM OF PROBABILITY. THE MORE LIKELY
SCENARIO SEEMS TO BE INTENSE CONVECTION DEVELOPING ALONG THE DRY
LINE ACROSS WESTERN WI MONDAY AFTERNOON, THOUGH GIVEN THE
STRONG CROSS-BOUNDARY SHEAR, STORMS WOULD LIKELY BE
SUPERCELLULAR AND PRONE TO BREAKING OFF THE DRYLINE. THIS COULD
LESSEN THE THREAT OF DEVELOPING A COULD POOL AND QLCS FROM THIS
ACTIVITY, THOUGH SHOULD CONVECTION CONGEAL, THE SOUTHERN FLANKS
OF IT WOULD HAVE A TENDENCY TO PROPAGATE/BOW SOUTHEASTWARD INTO
OUR CWA EARLY MONDAY EVENING.
SECONDARY CONCERN IS FOR THE PRETTY CONSISTENT SIGNAL AMONG THE
VARIOUS MODELS IN DEPICTING A NOTABLE INCREASE IN CONVECTIVE QPF
ACROSS NORTHERN IA EAST INTO NORTHERN IL MONDAY EVENING. THIS
SEEMS TO BE THE RESULT OF STRENGTHENING SYNOPTIC ASCENT/UPPER
LEVEL DIVERGENCE IN RESPONSE TO A 130KT+ 250MB JET TRANSLATING
EAST INTO THE REGION. MOST GUIDANCE SUGGESTS MUCAPE OF AT LEAST
1500-2000 J/KG ACROSS OUR AREA MONDAY NIGHT, WHICH GIVEN THE
STRONG SHEAR PROFILE WOULD CERTAINLY SUPPORT A THREAT FOR SEVERE
THUNDERSTORMS CAPABLE OF DAMAGING WINDS. THERE IS STILL SOME
SPREAD IN THE GUIDANCE IN HOW EXACTLY THIS PLAYS OUT, WITH SOME
TYPICALLY RELIABLE MODELS NOTABLY MUTED WITH CONVECTIVE COVERAGE
OVER NORTHERN IL MONDAY NIGHT. CERTAINLY CANNOT TOTALLY DISCOUNT
SOLUTIONS LIKE THIS, SO WHILE THE CEILING FOR POTENTIAL IMPACTS
IS FAIRLY HIGH, CONFIDENCE IS STILL SOMEWHAT ON THE LOWER END OF
THE SPECTRUM AT THIS TIME.
THE AIR MASS OVER OUR CWA MONDAY NIGHT WILL BE QUITE MOIST WITH
PWATS NEARING 2 INCHES. ALSO CONCERNING IS THE POTENTIAL FOR
CONVECTION TO LAY OUT WEST-EAST ACROSS THE AREA WITH FAIRLY
UNIDIRECTIONAL FLOW ORIENTED LARGELY PARALLEL TO THE SYNOPTIC
BOUNDARY. SO IF THIS SECONDARY AREA OF CONVECTION DOES DEVELOP
MONDAY EVENING INTO MONDAY NIGHT, THEN THE POTENTIAL WOULD EXIST
FOR SOME AREAS TO PICK UP VERY HEAVY RAINFALL RESULTING IN
LOCALIZED FLASH FLOODING.
FRONT WILL PUSH OUT OF THE CWA EARLY TUESDAY MORNING WITH STRONG
AND GUSTY WEST-NORTHWEST WINDS IN THE WAKE OF THE FRONT TUESDAY.
AIR MASS TUESDAY WILL BE SOMEWHAT LESS HUMID, BUT STILL WARM
WITH DEWPOINTS IN THE 60S. A SECONDARY COLD FRONT IS EXPECTED TO
DROP SOUTH OUT ACROSS WI AND EVENTUALLY INTO NORTHERN IL BY
EARLY TUESDAY EVENING. GIVEN THE LINGERING LOW LEVEL MOISTURE
AND COOLING MID-LEVEL TEMPS, SUFFICIENT INSTABILITY COULD
DEVELOP TO SUPPORT SCATTERED CONVECTION WITH THIS SECONDARY
FRONT. THE GREATEST COVERAGE LOOKS TO BE JUST TO OUR NORTH IN
WI TUESDAY AFTERNOON, BUT SOME THREAT OF CONVECTION COULD GET
SNEAK INTO NORTHERN (ESPECIALLY NORTHEAST) IL BY EARLY TUESDAY
EVENING.
GUIDANCE SUGGESTS THAT THIS SECONDARY FRONT WILL PACK QUITE A
PUNCH FOR JULY WITH SOME EARLY FALL LIKE CHARACTERISTIC. STRONG
AND GUSTY NORTHERLY WINDS ARE EXPECTED TUESDAY NIGHT INTO
WEDNESDAY BEHIND THIS FRONT, PARTICULARLY NEAR THE LAKE WHERE
GUSTS OVER 30 MPH APPEAR LIKELY. COOLER AIR FLOWING OVER THE NOW
QUITE WARM LAKE WATERS WILL RESULT IN AN UNSTABLE MARINE
BOUNDARY LAYER AND STRONG (FOR JULY) NORTHERLY WINDS DOWN THE
FULL-FETCH OF THE LAKE. THIS WILL LIKELY RESULT IN UNUSUALLY
LARGE AND DANGEROUS WAVES AT SOUTHERN LAKE MICHIGAN BEACHES
TUESDAY NIGHT THROUGH AT LEAST WEDNESDAY NIGHT. BEACH HAZARD
STATEMENTS APPEAR TO BE AN ALMOST CERTAINTY FOR THAT TIME
PERIOD.
- IZZI
AVIATION /00Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 640 PM CDT SUN JUL 19 2026
FORECAST CONCERNS INCLUDE...
SCATTERED THUNDERSTORMS MONDAY EVENING/MONDAY NIGHT.
GUSTY SOUTHWEST WINDS MONDAY AFTERNOON/EVENING.
WILDFIRE SMOKE THROUGH MONDAY MORNING.
NORTHEAST WINDS MAINLY UNDER 10KTS WILL SLOWLY TURN SOUTHEAST
LATER THIS EVENING AND SOUTHERLY OVERNIGHT WITH SOME AREAS
LIKELY BECOMING LIGHT AND VARIABLE. SOUTHWEST WINDS WILL
INCREASE INTO THE 10KT RANGE BY MID/LATE MONDAY MORNING AND THEN
STEADILY INCREASE MONDAY AFTERNOON WITH GUSTS INTO THE LOWER/MID
20KT RANGE LATE MONDAY AFTERNOON THROUGH EARLY/MID MONDAY
EVENING.
AS THE WINDS TURN BACK SOUTHERLY AND SOUTHWESTERLY MONDAY
MORNING, THAT SHOULD HELP PUSH THE WILDFIRE SMOKE BACK NORTHEAST
OF THE AREA. UNTIL THEN, MINOR VIS REDUCTIONS INTO THE 4-6SM
RANGE CAN BE EXPECTED.
THUNDERSTORM TRENDS FOR LATE MONDAY AFTERNOON THROUGH EARLY
TUESDAY MORNING REMAIN VERY UNCERTAIN. SCATTERED THUNDERSTORMS
ARE EXPECTED TO DEVELOP ACROSS PARTS OF WI MONDAY AFTERNOON.
WHETHER THESE MOVE EAST INTO MI OR EVOLVE INTO A LINE OF STORMS
WHICH THEN MOVES SOUTHEAST INTO NORTHERN IL IS UNCLEAR. IF THIS
WERE TO OCCUR, STORMS COULD BE APPROACHING THE TERMINALS BY
01Z-02Z. ANOTHER POSSIBILITY IS FOR ADDITIONAL THUNDERSTORMS TO
DEVELOP ACROSS EASTERN IA AND NORTHWEST IL DURING THE EVENING,
AND MOVE EAST/SOUTHEAST THROUGH EARLY TUESDAY MORNING. DESPITE
THE LOW CONFIDENCE, PROB THUNDER MENTION IS WARRANTED FOR
ORD/MDW FOR MONDAY EVENING WITH THE NEW 30 HOUR TAF PERIOD. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...AIR QUALITY ALERT UNTIL MIDNIGHT CDT MONDAY NIGHT FOR ILZ003-
ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-
ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...AIR QUALITY ALERT UNTIL MIDNIGHT CDT /1 AM EDT/ MONDAY NIGHT
FOR INZ001-INZ002-INZ010-INZ011-INZ019.
LM...NONE.
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