181
FXUS63 KLOT 240744
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
244 AM CDT FRI JUL 24 2026
KEY MESSAGES
- HEAT AND HUMIDITY WILL RETURN TO THE REGION SUNDAY AND
CONTINUE INTO MONDAY, POTENTIALLY REQUIRING HEADLINES FOR AT
LEAST SOME AREAS.
- SOME POTENTIAL FOR THUNDERSTORMS LATE SUNDAY THROUGH MONDAY
NIGHT, BUT PREDICTABILITY IN TIMING, LOCATION, AND COVERAGE OF
STORMS IS VERY LOW THIS FAR OUT.
DISCUSSION
ISSUED AT 244 AM CDT FRI JUL 24 2026
OUR PREVIEW OF SEPTEMBER-LIKE WEATHER WILL CONTINUE TODAY,
THOUGH TEMPS WILL LIKELY BE A COUPLE DEGREES WARMER THAN
THURSDAY, BUT DEWPOINTS ARE LIKELY TO REMAIN UNUSUALLY LOW FOR
LATE JULY. ONE DIFFERENCE FOR TODAY IS THE EXPECTATION OF MORE
CLOUDINESS THIS MORNING AS A FAIRLY PRONOUNCED SHORTWAVE TROUGH
MOVES ACROSS THE REGION. MAJORITY OF THE ASSOCIATED ASCENT WITH
THIS FEATURE IS GOING TOWARD SATURATING THE PARCHED ATMOSPHERE,
THOUGH RATHER STRONG AND DEEP F-GEN CIRCULATION HAS BEEN
EFFECTIVE AT ALLOWING A BAND OF SOME SPRINKLES OR VERY LIGHT
RAIN SHOWERS TO ACTUALLY REACH THE GROUND ACROSS IOWA. THIS
F-GEN BAND IS PROGGED TO TRANSLATE EASTWARD INTO NORTHERN
ILLINOIS THIS MORNING AND CERTAINLY CAN'T RULE OUT SOME
SPRINKLES MAKING IT EASTWARD INTO OUR AREA. THE BEST CHANCE OF
SPRINKLES LOOKS TO BE ROUGHLY NEAR AND JUST SOUTH OF THE I-80
CORRIDOR.
IN THE WAKE OF THIS SHORTWAVE, SKIES SHOULD CLEAR OUT FROM
NORTHWEST TO SOUTHEAST THIS AFTERNOON, THOUGH SOME HIGH LEVEL
SMOKE NOTED UPSTREAM ON SATELLITE IMAGERY THURSDAY COULD MAKE IT
INTO THE AREA. THE HRRR SMOKE GUIDANCE DOES SHOW A BIT OF AN
INCREASE IN VERTICALLY INTEGRATED SMOKE THIS AFTERNOON, THOUGH
SMOKE LOOKS TO REMAIN ALOFT AND MUCH LESS THICK THAN LAST WEEK,
SO ONLY NUDGED SKY COVER UP A BIT TO ACCOUNT FOR THE SMOKE.
ANOTHER, CONVECTIVELY ENHANCED, SHORTWAVE TROUGH IS LIKELY TO
PASS SOUTH OF OUR AREA TONIGHT INTO SATURDAY MORNING. FAIRLY
DEEP (300-315K SURFACES) BUT MODEST ISENTROPIC ASCENT COULD
RESULT IN A FEW SHOWERS ACROSS MAINLY OUR SOUTHERN CWA LATE
TONIGHT INTO SATURDAY MORNING.
UPPER RIDGE IS PROGGED TO AMPLIFY OVER THE CENTRAL U.S. SUNDAY
INTO MONDAY, LIKELY ALLOWING FOR A QUICK SHOT OF HEAT AND
HUMIDITY. EVAPOTRANSPIRATIONALLY-SUPPLEMENTED DEWPOINTS APPEAR
LIKELY TO SURGE WELL INTO THE 70S AND PROBABLY LOWER 80S IN THE
DENSEST AGRICULTURAL AREAS SUNDAY INTO MONDAY WHILE NUDGING
TEMPERATURES DOWN A BIT FROM THE NBM. NET RESULT IS SUNDAY HEAT
INDICES PEAKING WELL INTO THE 90S TO SLIGHTLY OVER 100 DEGREES
IN SOME AREAS, WITH MORE WIDESPREAD 100 TO LOCALLY OVER 105
DEGREE HEAT INDICES POSSIBLE MONDAY.
THE CAVEAT TO THE HEAT SUNDAY AND MONDAY IS THE POTENTIAL FOR
CONVECTION. CONCEPTUALLY, A NORTHWEST FLOW PATTERN LIKE THE ONE
COMING SUNDAY INTO MONDAY CAN PRODUCE ROBUST MCS ACTIVITY.
HOWEVER, THE SEEDLING LOW AMPLITUDE SHORTWAVES THAT ULTIMATELY
GO ON TO SPAWN STRONG MCSS AND CONVECTIVELY ENHANCED VORTS TEND
TO BE MUCH TOO LOW AMPLITUDE TO RESOLVE AT THIS DISTANCE. OFTEN,
THOUGH NOT ALWAYS, GUIDANCE AT THIS DISTANCE WOULD HAVE A MORE
ROBUST CONVECTIVE SIGNAL, BUT THAT CERTAINLY DOESN'T PRECLUDE
SOMETHING MORE COHERENT COMING INTO SIGHT IN LATER RUNS.
BARRING ANY CONVECTIVELY ENHANCED SHORTWAVES/MCS ACTIVITY,
FORECAST SOUNDINGS SUNDAY AND MONDAY EXHIBIT A STRONG CAPPING
INVERSION, WHICH WOULD LIKELY KEEP THINGS DRY. OPTED TO MAINTAIN
SLIGHT CHANCES FOR THUNDERSTORMS SUNDAY AFTERNOON THROUGH
MONDAY, TO COVER THE POTENTIAL FOR AN UPSTREAM MCS DEVELOPING
AND RIPPING SOUTHEAST ACROSS OUR AREA. IF A WELL TIMED MCS OR
MCS DEBRIS MOVE ACROSS THE AREA DURING THIS TIME FRAME, THEN
THAT WOULD OBVIOUSLY HAVE BIG IMPLICATIONS ON TEMPERATURES AND
HEAT POTENTIAL.
COLD FRONT AND MORE OF SYNOPTIC SHORTWAVE TROUGH COULD RESULT IN
BETTER CHANCES FOR THUNDERSTORMS MONDAY NIGHT FOLLOWED BY
SOMEWHAT COOLER AND LESS HUMID WEATHER HEADING INTO THE MIDDLE
OF NEXT WEEK.
- IZZI
AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 1219 AM CDT FRI JUL 24 2026
MAIN ITEM OF NOTE:
- SOMEWHAT UNCERTAIN WIND DIRECTIONS AT ORD AND MDW, ESPECIALLY
THIS AFTERNOON.
WHILE IT WILL BE ANOTHER VFR PERIOD WITH NO SIGNIFICANT
CONCERNS, THE WIND FORECAST IS A BIT TRICKY AT THE NEAR LAKE
TERMINALS. FOLLOWING LIGHT/VRB TO CALM WINDS THROUGH THE PRE-
DAWN HOURS AREA-WIDE, WIND DIRECTION AT ORD AND MDW SHOULD
INITIALLY FAVOR SOUTHEAST BY THE MID TO LATE MORNING. AS A LAKE
BREEZE BOUNDARY SHARPENS UP THIS AFTERNOON, WINDS TO THE WEST OF
THE BOUNDARY SHOULD VEER TO SOUTH-SOUTHWEST. GIVEN TYPICALLY
WEAK LAKE BREEZES IN LATE JULY, CURRENT THINKING IS THAT THE
BOUNDARY WILL REMAIN EAST OF MDW AND ESPECIALLY ORD (HIGHER
CONFIDENCE THERE), WITH VRB WINDS AT GYY. ASIDE FROM THE
UNCERTAINTY NEAR THE LAKE, EXPECT LIGHT TO MODERATE SOUTH-
SOUTHWEST WINDS INLAND, DIMINISHING WITH SUNSET THIS EVENING.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...NONE.
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