307
FXUS63 KDTX 210752
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
352 AM EDT SUN JUN 21 2026
KEY MESSAGES
- DRY WEATHER WITH INCREASING CLOUDS TODAY.
- SHOWERS AND THUNDERSTORMS INCREASE COVERAGE TONIGHT, ESPECIALLY
SOUTH OF I-69 WHERE RAINFALL TOTALS RANGE FROM 0.5 TO 1 INCH. THE
BEST CHANCE OF LOCALLY HIGHER AMOUNTS IS TOWARD THE OHIO BORDER.
- SHOWERS LINGER MONDAY MORNING THEN DRY WEATHER FOLLOWS IN THE
AFTERNOON AND EVENING.
- COOLER THAN NORMAL TEMPERATURES CONTINUE THROUGH AT LEAST THE
MIDDLE OF NEXT WEEK.
DISCUSSION
EARLY MORNING SATELLITE AND SURFACE ANALYSIS INDICATE PATCHY FOG AND
STRATUS LEADING UP TO SUNRISE, ESPECIALLY TOWARD THE TRI CITIES AND
THUMB WHERE WET GROUND AUGMENTS SURFACE BASED MOISTURE. THE FOG
COMPONENT CONTINUES TO EXPAND THROUGH SUNRISE AND THEN QUICKLY
DISSIPATES. OTHERWISE, THE DAY STARTS WITH FULL SUN AS BROAD BUT
WEAK HIGH PRESSURE BUILDS FROM THE MIDWEST INTO LOWER MI TO GOVERN
CONDITIONS THROUGH TODAY. CLOUDS ARE ON THE INCREASE THIS AFTERNOON
IN A COMBINATION OF HIGH BASED CUMULUS AND THICKENING CIRRUS OFF THE
CENTRAL PLAINS MCS DEBRIS SHIELD. THE SLIGHTLY BELOW NORMAL
TEMPERATURE THEME OF RECENT DAYS CONTINUES TODAY AS ABBREVIATED
AFTERNOON PEAK HEATING LEAVES HIGHS IN THE MID 70S.
THE INBOUND CIRRUS CLOUD SHIELD THIS AFTERNOON IS A PRELUDE TO
INCREASING COVERAGE OF SHOWERS AND A FEW THUNDERSTORMS ACROSS
SOUTHERN LOWER MI THIS EVENING WHICH CONTINUE THROUGH THE NIGHT AND
MONDAY MORNING. THIS PATTERN IS DRIVEN BY THE CENTRAL PLAINS LOW
PRESSURE/MCS COMBO IN PROGRESS AS THE SHORT WAVE AND MESOSCALE
FEATURES MIGRATE INTO THE MID MS AND OH VALLEYS TONIGHT. PRONOUNCED
MID/UPPER LEVEL CIRCULATION NOTED OVER SD/NE IN WV SATELLITE IMAGERY
EARLY THIS MORNING ADDS CONFIDENCE TO THE MOISTURE TRANSPORT SCENARIO
EXPECTED TO BE THE PRIMARY DRIVER OF SHOWERS/ELEVATED STORMS ACROSS
SOUTHERN LOWER MI TONIGHT. BACKED 850-700 MB FLOW AHEAD OF THIS SHORT
WAVE CARRIES MOISTURE AND ELEVATED INSTABILITY INTO LOWER MI TO FUEL
THE EXPANDING AREA OF SHOWERS/GENERAL STORMS. CONSENSUS OF
DETERMINISTIC MODEL QPF HOLDS TOTALS BELOW 1 INCH WHICH IS NOW
REFLECTED IN THE LATEST NBM RUN. ATTENTION IS ALSO GIVEN TO HREF PMM
QPF KEEPING HIGHER END TOTALS AROUND 1.5 INCHES IN PLAY, WHICH IS
PLAUSIBLE GIVEN THE POTENTIAL FOR STRONG MESOSCALE INTERACTIONS
BETWEEN THE NORTH FLANK OF THE MCV, THE SHORT WAVE, AND UPPER JET
ENTRANCE REGION DURING THE PEAK OF THE EVENT AROUND 06Z TONIGHT. THE
STRONGER FORCING GIVES SHOWERS A CHANCE TO REACH FARTHER NORTH TOWARD
THE TRI CITIES AND NORTHERN THUMB WHILE THE BULK OF GREATER RAINFALL
STILL OCCURS SOUTH OF I-69.
THE SCENARIO TRANSITIONS TO A SHEARING DEFORMATION PATTERN WHICH
KEEPS SHOWERS FOCUSED OVER SOUTHERN LOWER MI THROUGH MONDAY MORNING.
THIS ADDITIONAL RAINFALL IS ACCOUNTED FOR IN THE SYSTEM TOTAL BUT
PRODUCES GENERALLY LESS THAN AN ADDITIONAL 0.25 INCH UNTIL ENDING BY
EARLY AFTERNOON AS THE DEFORMATION AXIS MOVES EASTWARD. THE REST OF
MONDAY AND MONDAY NIGHT END UP WITH DRY WEATHER AS A SHORT WAVE
RIDGING MOVES FROM THE MIDWEST INTO THE GREAT LAKES ALONG WITH
ACCOMPANYING SURFACE HIGH PRESSURE. THE MID/UPPER LEVEL LONG WAVE
FLOW REMAINS LOW AMPLITUDE AND PROGRESSIVE THROUGH MID WEEK WITH THE
NEXT LOW PRESSURE SYSTEM CURRENTLY PROJECTED FOR WEDNESDAY.
MARINE
A DIFFUSE AREA OF HIGH PRESSURE WILL HOLD ACROSS THE GREAT LAKES
THROUGH TODAY, SUPPORTING A CONTINUATION OF LIGHTER WINDS. A COMPACT
LOW PRESSURE SYSTEM WILL THEN MOVE THROUGH THE OHIO VALLEY AND
SOUTHERN GREAT LAKES TONIGHT INTO MONDAY MORNING. RAIN SHOWERS ARE
EXPECTED TO BE MOST CONCENTRATED ACROSS LAKE ERIE UP TO LAKE ST.
CLAIR. ELEVATED NORTHEASTERLY WINDS WILL INCREASE AND PERSIST
THROUGH THE DAYLIGHT HOURS MONDAY. THE LONGER ONSHORE FETCH ON LAKE
ERIE WILL SUPPORT HIGHER WAVES BY DAYBREAK MONDAY. A SMALL CRAFT
ADVISORY IS IN EFFECT THERE FOR LATE TONIGHT AND MONDAY.
HYDROLOGY
SHOWERS AND THUNDERSTORMS EXPAND OVER SOUTHERN LOWER MI TONIGHT AS
AN UNSEASONABLY STRONG LOW PRESSURE SYSTEM MOVES FROM THE CENTRAL
PLAINS THROUGH THE MID MISSISSIPPI RIVER VALLEY LATE SUNDAY AND INTO
THE OHIO RIVER VALLEY SUNDAY NIGHT. WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY DEVELOPS ALONG THE NORTHERN PERIPHERY OF THE
LOW PRESSURE SYSTEM AND MAY BRING LOCALLY HEAVY RAINFALL TO SOUTHERN
PORTIONS OF SE MICHIGAN. WHILE UNCERTAINTY EXISTS ON THE EXACT
PLACEMENT, THE POTENTIAL EXISTS FOR A LARGE AREA OF RAINFALL AMOUNTS
RANGING FROM 0.5 TO 1 INCH GENERALLY SOUTH OF THE I-69 CORRIDOR.
THERE IS ALSO A CHANCE FOR LOCALIZED TOTALS AROUND 1.5 INCHES FROM
ABOUT THE I-94 CORRIDOR TO THE OHIO BORDER. TRENDS WILL BE MONITORED
FOR SIGNS OF ANY NORTHWARD SHIFT ON THE TRACK OF THE LOW PRESSURE
SYSTEM THAT WOULD PRODUCE A CHANCE FOR A CORRESPONDING NORTHWARD
SHIFT TO HIGHER RAINFALL TOTALS AND THE POTENTIAL FOR URBAN
FLOODING. OTHERWISE, THE ABOVE MENTIONED TOTALS LIMIT FLOODING
POTENTIAL TO PONDING OF WATER ON ROADS AND SIMILAR PRONE AREAS UNTIL
THE RAIN MOVES OUT BY MONDAY AFTERNOON.
PREV DISCUSSION
ISSUED AT 126 AM EDT SUN JUN 21 2026
AVIATION...
GENERAL NOCTURNAL STABILITY OVERNIGHT WILL MAINTAIN MOSTLY CLEAR
SKIES. POTENTIAL EXISTS FOR A PERIOD OF FOG PRIOR TO DAYBREAK,
MAINLY ACROSS FNT AND MBS. OBSERVATIONAL TRENDS SUGGEST FOG COULD
BECOME MORE DENSE AT MBS OWING TO THE RECENT RAINFALL, LEADING
LIFR/IFR VISIBILITY RESTRICTIONS. DRY AND STABLE CONDITIONS WILL
MAINTAIN BENIGN CONDITIONS FOR THE DAYLIGHT PERIOD SUNDAY. STANDARD
HIGHER BASED DIURNAL CU TO EMERGE WITH DAYTIME HEATING. LOW PRESSURE
SYSTEM TRACKING THROUGH THE OHIO VALLEY WILL BRING THICKENING MID
CLOUD AND INCREASING RAIN CHANCES AROUND 00Z, WITH A STEADY DECLINE
IN CLOUD BASE LIKELY THEREAFTER HEADING INTO THE OVERNIGHT PERIOD
SUNDAY.
D21/DTW CONVECTION... NO THUNDERSTORMS EXPECTED THROUGH SUNDAY.
DTW THRESHOLD PROBABILITIES...
* LOW FOR CEILING AT OR BELOW 5000 FT SUNDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 4 AM TO 5 PM EDT MONDAY FOR LEZ444.
DISCUSSION...BT
MARINE.......AM
HYDROLOGY....BT
AVIATION.....MR
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