533  
FXUS63 KDTX 170757  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
357 AM EDT SUN AUG 17 2025  
   
KEY MESSAGES
 
 
- BREEZY NW TO NE WIND BRINGS COOLER AND LESS HUMID AIR INTO SE  
MICHIGAN THAT IS MORE NOTICEABLE BY TONIGHT.  
 
- DRY WEATHER MONDAY AND MONDAY EVENING, THEN ANOTHER ROUND OF  
SHOWERS AND STORMS IS POSSIBLE EARLY TUESDAY THROUGH TUESDAY NIGHT.  
LOCALLY HEAVY RAINFALL IS THE PRIMARY CONCERN WITH THIS ACTIVITY.  
 
- COOLER TEMPERATURES AND DRY WEATHER MOVE IN AND HOLD WEDNESDAY  
THROUGH FRIDAY.  
 

 
   
DISCUSSION
 
 
CLUSTERS OF SHOWERS AND THUNDERSTORMS HAVE EXITED INTO ONTARIO AT  
FORECAST ISSUANCE LEAVING JUST A SHORT TIME WINDOW FOR ANY NEW  
DEVELOPMENT TOWARD METRO DETROIT AND THE OHIO BORDER LEADING UP TO  
SUNRISE. A STRAY SHOWER IS ALSO POSSIBLE OFF THE WARM WATER OF  
SOUTHERN LAKE HURON WHILE LOW LEVEL MOISTURE DEPTH IS STILL ADEQUATE  
DURING THE MORNING. AN OVERALL DECREASING TREND IS PROMOTED BY THE  
LARGER SCALE ATMOSPHERIC ENVIRONMENT BECOMING INCREASINGLY SUBSIDENT  
AS THE ROBUST MCV AND SURFACE WAVE EXIT EASTWARD WHILE THE FRONT  
MOVES SOUTHWARD. SHOWERS END BUT CLOUDS LINGER WELL INTO THE  
AFTERNOON IN A TRAPPED BOUNDARY LAYER MOISTURE PROFILE THAT LIMITS  
TEMPERATURES TO HIGHS IN THE UPPER 70S TO LOWER 80S WITH A LINGERING  
HUMID FEEL THROUGH THE DAY. WIND DIRECTION THEN TURNS MORE FROM THE  
NE WITH GUSTS AROUND 25 MPH AS MARKER FOR THE ARRIVAL OF  
SUFFICIENTLY DRY AIR TO SUPPORT DECREASING CLOUDS INTO THIS EVENING  
AND LOWER HUMIDITY THROUGH TONIGHT.  
 
MONDAY STARTS OUT WITH A BROAD AREA OF HIGH PRESSURE CENTERED ALONG  
THE ONTARIO/QUEBEC BORDER REACHING DOWN INTO LOWER MI. IT IS  
REINFORCED BY A LARGER SCALE 500 MB RIDGE CENTERED OVER CENTRAL  
CANADA AND THE PLAINS STATES TO ENSURE DRY WEATHER IN SE MI INTO  
MONDAY NIGHT. THERE IS, HOWEVER, A SHORT WAVE/MCV HYBRID EMBEDDED IN  
THIS LARGER SCALE RIDGE PATTERN THAT IS FORECAST WITH GOOD MODEL  
AGREEMENT TO ROUND THE RIDGE AND MOVE INTO THE UPPER MIDWEST AND  
NORTHERN GREAT LAKES MONDAY NIGHT. THE ASSOCIATED SURFACE LOW IS  
WELL ORGANIZED AND CAPABLE OF PULLING THE OHIO VALLEY FRONT BACK  
NORTHWARD AS A FOCUS FOR A NEW ROUND OF SHOWERS/STORMS. MORE  
IMPORTANT, THE SYSTEM IS STRONG ENOUGH TO SUPPORT A LOW LEVEL JET  
CAPABLE OF MEANINGFUL MOISTURE/INSTABILITY TRANSPORT FROM THE UPPER  
MIDWEST INTO LOWER MI LATE MONDAY NIGHT INTO TUESDAY. IT IS A  
FAVORABLE ENVIRONMENT TO SUSTAIN A CONVECTIVE SYSTEM, HOWEVER THERE  
IS A WIDE RANGE OF TRACK OUTCOMES SUGGESTED BY MODEL QPF AT THESE  
LONGER FORECAST TIME RANGES. IT DOES LOOK LIKE EARLY DAY TIMING IS A  
LIMITING FACTOR FOR SEVERE POTENTIAL WHILE SPEED OF THE SYSTEM EASES  
HEAVY RAINFALL CONCERN.  
 
A CHANCE OF SHOWERS/STORMS CONTINUES INTO TUESDAY NIGHT AS THE LOW  
PRESSURE SYSTEM AND COLD FRONT SWEEP THROUGH THE GREAT LAKES. IT'S A  
SHORT TIME WINDOW ENDING BEFORE MIDNIGHT AS THE 500 MB WAVE AND  
SURFACE LOW EXIT EASTWARD. PASSAGE OF THE COLD FRONT BRINGS ANOTHER  
ROUND OF COOLER AND LESS HUMID AIR WITH GREATER STAYING POWER DURING  
THE LATE WEEK. THE LONG WAVE RIDGE CENTERED OVER THE 4 CORNERS  
REACHES UP INTO THE GREAT LAKES TO HELP MAINTAIN DRY WEATHER  
WEDNESDAY THROUGH FRIDAY.  
 

 
   
MARINE
 
 
A COLD FRONT IS CLEARING THE SOUTHERN MICHIGAN BORDER THIS MORNING.  
STRONG HIGH PRESSURE BUILDING OVER NORTHWEST ONTARIO AND SOLID COLD  
ADVECTION (850 MB TEMPS LOWERING INTO LOWER TEENS) OVER LAKE HURON  
WILL ALLOW NORTHEAST WINDS TO REACH 20-25 KNOTS, WITH BRIEF GUSTS TO  
AROUND 30 KNOTS THIS AFTERNOON. SMALL CRAFT ADVISORIES ALREADY  
ISSUED FOR ALL OF SOUTHERN LAKE HURON NEARSHORE WATERS AS WAVES  
BUILD IN EXCESS OF 4 FEET.  
 
WINDS BECOME EASTERLY ON MONDAY AS HIGH PRESSURE RETREATS AND A WARM  
FRONT LIFTS IN FROM THE WESTERN GREAT LAKES. CHANNELING OF THE WINDS  
OVER NORTHERN THIRD OF LAKE HURON/NEAR THE STRAIGHTS LOOKS TO  
SUPPORT WIND GUSTS OF 20 TO 30 KNOTS.  
 
PERIODS OF SHOWERS AND THUNDERSTORMS MONDAY-WEDNESDAY, PARTICULARLY  
ON TUESDAY AS SURFACE LOW PRESSURE TRACKS THROUGH THE CENTRAL GREAT  
LAKES. WIND SPEEDS MOSTLY IN THE 15 TO 25 KNOT RANGE AROUND THE  
CIRCULATION.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 1227 AM EDT SUN AUG 17 2025  
 
AVIATION...  
 
THE THUNDER POTENTIAL APPEARS TO BE DECREASING GIVEN THE RECENT  
OBSERVATIONAL TRENDS, EXPECT FOR POSSIBLY KMBS. CONFIDENCE IS NOT  
HIGH ENOUGH TO CARRY TEMPO TSRA AT ANY OF THE TAF SITES WITH THIS  
ISSUANCE. WILL MONITOR TRENDS OVERNIGHT AND AMEND THEM BACK IN IF  
NEEDED. WILL CARRY TEMPO VFR SHOWERS INSTEAD AS THE FRONT WORKS SOUTH  
AND DOES BRING POTENTIAL FOR SCATTERED SHOWERS DURING THE EARLY  
MORNING. BEST COVERAGE DOES LOOK TO BE ACROSS THE THUMB THOUGH.  
FRONTAL PASSAGE WILL COME WITH A VEERING WIND TO THE NORTHWEST  
THROUGH THE EARLY-MID MORNING HOURS AS CEILINGS LOWER TO MVFR AND  
POSSIBLY IFR AT TIMES. PATCHY MVFR WILL ALSO BE POSSIBLE IN THE WAKE  
OF THE FRONT AS WELL. WINDS BECOME MORE NORTH TO NORTHEAST TOWARDS  
MID MORNING AND INTO THE AFTERNOON WHILE BECOMING GUSTY TO 20-25  
KNOTS. CEILINGS BEGIN TO IMPROVE TOWARDS 00Z THIS EVENING.  
 
FOR DTW/D21 CONVECTION...THUNDERSTORM POTENTIAL HAS DECREASED BASED  
ON EARLY NIGHT OBSERVATIONAL TRENDS. BEST POTENTIAL, IF THERE IS AN  
ISOLATED THUNDERSTORM TO POP UP, WOULD BE BETWEEN 08Z AND 10Z BASED  
ON FRONTAL TIMING. CONFIDENCE NOT HIGH ENOUGH NOW TO INCLUDE TEMPO  
TSRA GROUP AT THIS TIME.  
 
THRESHOLD PROBABILITIES...  
 
* LOW FOR THUNDERSTORMS THROUGH ABOUT 10Z.  
 
* HIGH FOR CEILINGS AT OR BELOW 5 KFT BY AROUND 10-12Z AND THROUGH  
MUCH OF THE AFTERNOON.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...BEACH HAZARDS STATEMENT FROM 9 AM EDT THIS MORNING THROUGH THIS  
EVENING FOR MIZ048-049-055-063.  
 
LAKE HURON...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO NOON EDT MONDAY FOR  
LHZ421-441.  
 
SMALL CRAFT ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR  
LHZ422.  
 
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 8 AM EDT MONDAY FOR  
LHZ442-443.  
 
LAKE ST CLAIR...NONE.  
 
MICHIGAN WATERS OF LAKE ERIE...NONE.  
 

 
 

 
 
DISCUSSION...BT  
MARINE.......SF  
AVIATION.....AA  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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