112
FXUS63 KLOT 071831
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
131 PM CDT TUE JUL 7 2026
KEY MESSAGES
- DRY AND SEASONABLY WARM WEATHER THROUGH WEDNESDAY, THEN SHOWER
AND THUNDERSTORM CHANCES RETURN THURSDAY.
- A CORRIDOR OF HEAVY RAINFALL MAY OCCUR SOMEWHERE IN THE REGION
THURSDAY-FRIDAY, THOUGH CONFIDENCE IN LOCAL IMPACTS REMAINS
LOW.
- MAINLY DRY, WARMER WEATHER EXPECTED THIS WEEKEND.
DISCUSSION
ISSUED AT 131 PM CDT TUE JUL 7 2026
12Z UPPER AIR ANALYSIS DEPICTS A SHORT-WAVE UPPER LEVEL RIDGE
AXIS ACROSS NORTHERN IL, BETWEEN A LINGERING MID-LEVEL TROUGH
OVER THE LOWER MISSOURI/OHIO VALLEYS TO THE SOUTH OF MORE ZONAL
WESTERLY FLOW ACROSS THE NORTHERN TIER OF THE CONUS. A LOW-
AMPLITUDE SHORT WAVE WITHIN THIS ZONAL FLOW WAS EVIDENT IN GOES
VAPOR IMAGERY ACROSS THE UPPER MIDWEST, BUT IS
WEAKENING/SHEARING AS IT ENCOUNTERS THE AFOREMENTIONED RIDGE. AT
THE SURFACE, WEAK HIGH PRESSURE WAS CENTERED OVER OUR
NORTHWESTERN CWA EARLY THIS AFTERNOON, WITH PLENTY OF SUNSHINE
ALLOWING SEASONABLE TEMPERATURES (LOW-80S WARMING TOWARD THE
MID-80S), RELATIVELY MODEST HUMIDITY LEVELS AND LIGHT/VARIABLE
WINDS. FARTHER TO THE SOUTH, INTO CENTRAL IL, SURFACE DEW POINTS
REMAIN IN THE MID-UPPER 60S MAKING FOR SOMEWHAT MORE MUGGY
CONDITIONS AS WELL AS CONTRIBUTING TO A DEVELOPING DIURNAL
CUMULUS FIELD. DESPITE THE CU FIELD, RAP FORECAST SOUNDINGS
DEPICT AN INVERSION ~800 MB WHICH SHOULD PREVENT ANY CONVECTIVE
UPDRAFTS FROM GROWING DEEP ENOUGH TO SUPPORT ANY PRECIPITATION.
THE SURFACE HIGH IS FORECAST TO DRIFT SOUTHEAST ACROSS THE
REMAINDER OF THE FORECAST AREA TONIGHT INTO WEDNESDAY,
MAINTAINING DRY WEATHER CONDITIONS. SURFACE WINDS WILL TURN
SOUTHWESTERLY WEDNESDAY, ALLOWING SLIGHTLY WARMER TEMPERATURES
IN THE MID-UPPER 80S.
ANOTHER SLIGHTLY MORE VIGOROUS SHORT WAVE IS PROGGED TO TRACK
EAST-SOUTHEAST FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST
LATE WEDNESDAY AND WEDNESDAY NIGHT. HEIGHT FALLS ASSOCIATED WITH
THIS WAVE WILL ERODE THE NORTHEASTWARD EXTENT OF THE MID-LEVEL
RIDGE ACROSS OUR REGION, WITH FASTER WESTERLY FLOW TO SETTLE
ACROSS THE FORECAST AREA BY EARLY THURSDAY MORNING. MEANWHILE,
AN ASSOCIATED SURFACE LOW WILL TRACK ACROSS MN/WI INTO NORTHERN
LOWER MI DURING THAT TIME, TRAILING A COLD FRONT BACK ACROSS
WI/IA/NE. RETURN FLOW AHEAD OF THIS FRONT WILL SUPPLY RENEWED
WARM/MOIST ADVECTION INTO THE PLAINS AND UPPER MISSISSIPPI
VALLEY DURING THE PERIOD, WHICH IN TURN IS EXPECTED TO RESULT IN
DEVELOPING CONVECTION ALONG THE FRONT TO OUR WEST/NORTHWEST
WEDNESDAY NIGHT. CURRENT 12Z CAM GUIDANCE INDICATES THE BULK OF
THIS WILL OCCUR WELL NORTH/WEST OF THE CWA, THOUGH THERE IS SOME
POTENTIAL FOR DECAYING STORMS TO WORK INTO THE IL/WI BORDER
AREA BY SUNRISE THURSDAY MORNING ESPECIALLY IF A SIGNIFICANT
OUTFLOW BOUNDARY DEVELOPS.
GREATER SHOWER AND THUNDERSTORM CHANCES APPEAR TO BE THURSDAY
AFTERNOON INTO THURSDAY NIGHT HOWEVER, AS THE APPROACHING COLD
FRONT SLOWLY SAGS SOUTHEAST ACROSS THE FORECAST AREA. THERE
CONTINUES TO BE A SIGNAL IN VARIOUS GUIDANCE FOR A MORE
AMPLIFIED SHORT WAVE (POTENTIALLY CONVECTIVELY-ENHANCED FROM AN
MCS ACROSS THE PLAINS LATE WEDNESDAY) TO TRACK EAST ACROSS THE
AREA IN THIS THURSDAY-THURSDAY NIGHT PERIOD. GIVEN INCREASING
LOW-LEVEL MOISTURE (DEW POINTS PROGGED INTO THE LOW-70S) AND
ENHANCED MID-LEVEL WESTERLY FLOW (40-45 KTS DEPENDING ON MODEL -
AND THE POTENTIAL TO BE STRONGER IF AN UPSTREAM MCV DEVELOPS),
THE BALANCE OF INSTABILITY AND SHEAR WOULD LIKELY SUPPORT SOME
INCREASED RISK OF SEVERE STORMS. IN ADDITION, FORECAST
PRECIPITABLE WATER VALUES OF AROUND 2" WOULD ALSO SUPPORT THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL, WHICH WE CERTAINLY DON'T
NEED IN THE WAKE OF RECENT HEAVY RAINS. SPC AND WPC BOTH HAVE
PORTIONS OF OUR AREA IN MARGINAL (LEVEL 1 OF 5/4) OUTLOOKS FOR
SEVERE WEATHER AND FLOOD POTENTIAL RESPECTIVELY. AT THIS TIME,
THERE'S STILL QUITE A BIT OF SPREAD IN GUIDANCE WITH RESPECT TO
THE MESOSCALE FEATURES WHICH WILL ULTIMATELY AFFECT THE DETAILS,
SO WE'LL HAVE TO CONTINUE TO MONITOR THINGS.
BASED ON CURRENT TIMING IN GUIDANCE, THE SURFACE COLD FRONT IS
PROGGED TO GRADUALLY SHIFT SOUTH OF THE FORECAST AREA THROUGH
FRIDAY-FRIDAY NIGHT. THIS LOOKS TO SHIFT THUNDERSTORM POTENTIAL
OFF TO THE SOUTH, THOUGH PERHAPS STILL ACROSS THE SOUTHERN HALF
OF OUR FORECAST AREA. FROM THE WEEKEND INTO EARLY NEXT WEEK,
THERE IS DECENT GLOBAL ENSEMBLE GUIDANCE AGREEMENT IN REBUILDING
OF UPPER RIDGING ACROSS THE CENTRAL CONUS AND UPPER MIDWEST.
INITIALLY, THIS SUPPORTS SURFACE HIGH PRESSURE ACROSS THE GREAT
LAKES REGION, THOUGH WITH A RETURN OF SOME 90-DEGREE HEAT
(THOUGH LIKELY WITH SOME LAKE-COOLING). EVENTUALLY HOWEVER,
MODELS WEAKEN THE EASTERN EXTENT OF THE RIDGE IN THE MONDAY-
TUESDAY TIME FRAME AND INDICATE A TREND TOWARD A PATTERN OF
NORTHWEST FLOW ALOFT WHICH WE'LL HAVE TO WATCH FOR "RING OF
FIRE" MCS POTENTIAL BY THE END OF THE PERIOD.
RATZER
AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 1232 PM CDT TUE JUL 7 2026
EXPECT VFR CONDITIONS THROUGH THE PERIOD. A LAKE BREEZE
CURRENTLY CROSSING MDW WILL EDGE WESTWARD ACROSS ORD OVER THE
NEXT HOUR OR TWO, WITH A CHANCE THE BOUNDARY SLOWS OR EVEN
STALLS OVER THE AIRFIELD MID-AFTERNOON. WINDS WILL REMAIN VRB
BUT MAY FAVOR NW UNDER 10 KNOTS AHEAD OF THE LAKE BREEZE BEFORE
SHIFTING ENE/E UP TO 10 KNOTS WITH THE PASSAGE OF THE LAKE
BREEZE. FOR ORD/MDW/GYY, WINDS WILL STEADILY VEER SE AROUND 5
KNOTS THIS EVENING, S AROUND MIDNIGHT, AND SSW OVERNIGHT BEFORE
SETTLING SW AROUND 10 KNOTS ON WEDNESDAY. FOR DPA AND ESPECIALLY
RFD, THE LAKE BREEZE IS UNLIKELY TO CROSS THE TERMINALS,
LEADING TO W WINDS THOUGH SUNSET, VRB WINDS THIS EVENING, AND
SSW/SW WINDS OVERNIGHT THROUGH WEDNESDAY.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...AIR QUALITY ALERT FROM MIDNIGHT TONIGHT TO MIDNIGHT CDT
WEDNESDAY NIGHT FOR INZ001-INZ002-INZ010-INZ011.
LM...NONE.
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