930
FXUS63 KLOT 210522
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1222 AM CDT TUE JUL 21 2026
KEY MESSAGES
- THE THREAT FOR SEVERE WEATHER TONIGHT CONTINUES TO DIMINISH.
- A SERIES OF COLD FRONTS WILL LEAD TO COOLER TEMPERATURES BY
MIDWEEK.
MESOSCALE
ISSUED AT 817 PM CDT MON JUL 20 2026
THE BOTTOM LINE UP FRONT IS THAT THE THREAT FOR ANY NOTABLE
SEVERE WEATHER TONIGHT LOCALLY APPEARS TO HAVE DECREASED
CONSIDERABLY.
A SHARP WNW TO ESE ORIENTED INSTABILITY GRADIENT HAS RESIDED
FROM THE MID MISSISSIPPI VALLEY TO NEAR LAKE MICHIGAN SINCE THIS
MORNING. THIS HAS SERVED AS THE MCS PATH TODAY, BRINGING A PAIR
OF WEAKENING COMPLEXES (LATE AM- EARLY AFTERNOON AND NOW LATE
AFTERNOON-EARLY EVENING) SOUTHWARD ACROSS THE AREA, STUNTING
ATTEMPTED DESTABILIZATION.
THIS ABOVE EVOLUTION MADE THE PLAUSIBLE PLAY FOR ANY SEVERE
WEATHER TONIGHT LOCALLY TIED TO WHAT HAPPENS WITH STORMS ON THE
COLD FRONT FROM SOUTHEAST MINNESOTA TO NORTHERN WISCONSIN.
DESPITE THE PRESENCE OF UNSEASONABLY STRONG FORCING FOR ASCENT
OVERLAPPING THE COLD FRONTAL BOUNDARY, PLENTIFUL MID-LEVEL DRY
AIR ENTRAINMENT HAS RELEGATED CONVECTION TO SCATTERED LOW
PRECIPITATION (LP) SUPERCELLS TO THIS POINT. AN IMBALANCE
BETWEEN THE EXTREME SHEAR AND ENVIRONMENTAL DRY AIR, AND
ORTHOGONAL DEEP LAYER SHEAR VECTOR ORIENTATION TO THE COLD
FRONT FAVORING SUPERCELLULAR MODE BOTH POINT AGAINST THE
ACTIVITY QUICKLY CONGEALING INTO A QLCS. QLCS MODE WAS GOING TO
BE THE MOST LIKELY PATH TOWARDS OVERNIGHT SEVERE WEATHER IN OUR
AREA AND THIS DOES NOT LOOK LIKELY AT THE MOMENT. THE HIGHEST
COVERAGE OF STORMS IS MOST FAVORED TO PUSH ACROSS NORTHERN AND
CENTRAL LAKE MICHIGAN INTO NORTHERN AND CENTRAL LOWER MICHIGAN.
WITH THE COLD FRONT STILL SET TO MOVE ACROSS THE AREA TONIGHT
PAIRED WITH FAIRLY LARGE MUCAPE, CAN'T COMPLETELY RULE OUT A
FEW STORMS INTO THE CWA TOWARDS AND ESPECIALLY AFTER MIDNIGHT.
AS SUCH, WE HELD ONTO 20-40% POPS TO BE SAFE. THIS BEING SAID,
THERE IS A REALISTIC SCENARIO IN WHICH LITTLE TO NO CONVECTIVE
ACTIVITY OCCURS WITHIN OUR AREA TONIGHT. *IF* A STORM OR TWO ARE
ABLE TO OVERCOME LIKELY REMAINING MUCIN, THERE WILL CERTAINLY BE
ENOUGH DEEP LAYER SHEAR TO SUPPORT A LOCALIZED DAMAGING WIND AND
HAIL THREAT, BUT CHANCES FOR SEVERE WEATHER ARE PROBABLY LESS
THAN 15% THROUGH THE NIGHT.
CASTRO
DISCUSSION
ISSUED AT 236 PM CDT MON JUL 20 2026
TUESDAY...
RRFS AND HRRR BOTH HAVE A SIGNAL FOR ADDITIONAL SMOKE CONCENTRATIONS
BACK BEHIND THE LEADING COLD FRONT TONIGHT, BUT THERE IS A MUTED
SIGNAL FOR ANY VISIBILITY REDUCTIONS. OUTSIDE OF THIS, A
STRENGTHENING UPPER JET AND COLDER TEMPERATURES ALOFT WILL PROMOTE
CUMULUS DEVELOPMENT DURING THE AFTERNOON. A SECONDARY AND MORE
NOTEWORTHY FRONT WILL SWEEP SOUTHWARD ACROSS THE GREAT LAKES DURING
THE AFTERNOON HOURS POSSIBLY ACCOMPANIED BY LOW-TOPPED SHOWERS AND
SPRINKLES, BUT NOT BEFORE TEMPERATURES RECOVER BACK TO THE LOW TO
MID 80S. NORTHWESTERLY WINDS WILL INCREASE AND GUST IN THE 20 TO 25
MPH RANGE DURING THE AFTERNOON. THE SURFACE HIGH, QUITE STRONG FOR
MID JULY, WILL STRENGTHEN FURTHER TUESDAY NIGHT AND DIP SOUTH ACROSS
THE UPPER MIDWEST. A SHARP UPPER TROUGH WILL PASS OVER THE GREAT
LAKES AND PUSH A NOTABLY COOLER AND DRIER AIRMASS INTO THE LOWER
GREAT LAKES REGION OVERNIGHT INTO WEDNESDAY. THERE IS A LIMITED QPF
FOOTPRINT ON SEVERAL GUIDANCE SOURCES, AND CLOUD DEPTHS MAY GET JUST
TALL ENOUGH FOR SOME SPRINKLES OR LOW TOPPED SHOWERS LATER IN THE
DAY INTO THE EVENING, HIGHEST CONFIDENCE INTO NW INDIANA. THIS WILL
SET THE STAGE FOR SOME SEASONABLY COMFORTABLE OVERNIGHT LOWS (IN THE
50S) FOR MANY AREAS OUTSIDE THE URBAN CORE.
KMD
WEDNESDAY THROUGH SUNDAY...
WEDNESDAY ONWARD, DEEP CYCLONIC UPPER-LEVEL FLOW WILL ONLY GRADUALLY
SHIFT EASTWARD AS A SURFACE HIGH PRESSURE SYSTEM MEANDERS THROUGH
THE UPPER MISSISSIPPI RIVER VALLEY. THE NET RESULT SHOULD BE A
PERIOD OF PLEASANT CONDITIONS WITH NO PRECIPITATION, HIGHS IN THE
UPPER 70S TO AROUND 80, AND OVERNIGHT LOWS IN THE UPPER 50S TO
AROUND 60. CHOPPY WAVES WILL MAKE SWIMMING HAZARDOUS ON LAKE
MICHIGAN BEACHES WEDNESDAY AND PERHAPS INTO EARLY THURSDAY.
ENSEMBLE GUIDANCE DEPICTS THE REDEVELOPMENT OF AN EXPANSIVE UPPER-
LEVEL RIDGE ACROSS THE CENTRAL UNITED STATES TOWARD NEXT WEEKEND
WHICH WOULD ENCOURAGE TEMPERATURES LOCALLY TO CLIMB BACK INTO THE
UPPER 80S TO PERHAPS LOWER 90S. THERE IS ONE RIPPLE IN THE MONSOONAL
MOISTURE THAT SHOULD BE ABLE TO PROGRESS TOWARD THE OHIO VALLEY ON
FRIDAY, BUT MOST GUIDANCE SENDS ANY PRECIPITATION WITH THIS WAVE
WELL SOUTH OF THE LOCAL AREA. THERE IS STILL A SIGNAL FOR A
CONVECTIVE EVENT SOMETIME IN THE JULY 27-29 TIMEFRAME IN THE GENERAL
REGION WITH NORTHWEST FLOW IN PLACE ON THE NORTHEAST FRINGES OF THE
STRONG UPPER RIDGE. THIS WOULD POSE THE NEXT CHANCE OF MEANINGFUL
RAINFALL SHOULD THIS SYSTEM MOVE TOWARD OUR LATITUDE.
BORCHARDT/KMD
AVIATION /06Z TAFS THROUGH 12Z WEDNESDAY/
ISSUED AT 1222 AM CDT TUE JUL 21 2026
KEY MESSAGES FOR THE 06Z TAF PERIOD:
* STILL SEEING A CHANCE FOR THUNDERSTORMS AFTER 06Z INTO THE
PREDAWN HOURS.
* GUSTY NORTHERLY WINDS TUESDAY EVENING INTO WEDNESDAY.
THE POTENTIAL IS STILL ALIVE AND WELL FOR A PERIOD OF SCATTERED
THUNDERSTORMS OVERNIGHT INTO THE PREDAWN HOURS. A NEWLY-
DEVELOPED CLUSTER OF CONVECTIVE SHOWERS IS ALREADY MOVING ACROSS
NW IL AND CLOSING IN ON RFD VCY. RFD MAY SEE SHOWERS AND MAYBE
A STORM NEARBY PRIOR TO 06Z, WITH CHANCES BUILDING ALL AROUND
AFTER 06Z. STORMS COULD LINGER INTO THE PREDAWN HOURS OF
TUESDAY, POSSIBLY EVEN STRETCHING INTO DAYBREAK AT MDW AND
ESPECIALLY GYY. SOME STORMS COULD BE ON THE STRONGER SIDE WITH
HIGH WINDS AND HEAVY RAIN LEADING TO REDUCED VSBYS. GIVEN
CURRENT EXPECTATIONS, FELT HANGING ONTO PROB30S FOR STORMS WAS
APPROPRIATE. LOOK FOR TACTICAL AMDS AS CONFIDENCE BUILDS.
W WINDS WILL BUILD IN THE WAKE OF THIS WAVE, GOING NW DURING
THE MORNING AND GUSTING TO 20 TO 25 KT FOR THE LATE MORNING AND
AFTERNOON. WINDS WILL SUBSIDE SOME BUT REMAIN BREEZY FOR THE
EVENING AND NIGHT AS DIRECTION TURNS NORTHERLY. WINDS MAY TOGGLE
ON EITHER SIDE OF NORTHERLY FROM THIS EVENING THROUGH THE
BETTER PART OF WEDNESDAY. NNW IS FAVORED THROUGH THE EARLY
EVENING BEFORE FLOPPING TO NNE FOR THE NIGHT, THEN LIKELY BACK
TO NNW BY DAWN ON WEDNESDAY.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 AM CDT EARLY THIS MORNING FOR THE
IL AND IN NEARSHORE WATERS.
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