442  
FXUS63 KDTX 180803  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
403 AM EDT MON AUG 18 2025  
   
KEY MESSAGES  
 
- DRY WEATHER TODAY AND MOST OF TONIGHT.  
 
- SCATTERED SHOWERS AND STORMS BECOME POSSIBLE LATE TONIGHT THROUGH  
TUESDAY EVENING. LOCALLY HEAVY RAINFALL IS THE PRIMARY CONCERN WITH  
THIS ACTIVITY.  
 
- SEASONABLE TEMPERATURES AND DRY WEATHER MOVE IN AND HOLD WEDNESDAY  
THROUGH FRIDAY.  
 
 
   
DISCUSSION  
 
COMFORTABLY COOL CONDITIONS ARE IN PLACE ACROSS ALL OF SE MI TO  
START THE DAY AS MOST LOCATIONS REPORT TEMPERATURE WELL DOWN INTO  
THE 50S OUTSIDE OF METRO DETROIT. SOME FAINT INDICATIONS OF LAKE  
CLOUDS OFF HURON AND SAGINAW BAY, AND NOT SO FAINT OFF ERIE, SINCE  
MIDNIGHT ALSO EMPHASIZE THE AIR MASS CONTRAST ACROSS THE WATER THAT  
IS AT PEAK SEASONAL WARMTH. TEMPERATURE ON LAND REBOUNDS ACCORDINGLY  
WITH FULL SUN OUTSIDE OF PATCHY STRATOCU EARLY AND CIRRUS THROUGHOUT  
THE DAY LEADING TO GUIDANCE HIGHS AROUND 80.  
 
UPSTREAM OBSERVATIONS REMIND US THAT THE NEXT ROUND OF SHOWERS AND  
STORMS IS NEARBY TO THE WEST AND DUE INTO LOWER MI LATE TONIGHT  
THROUGH TUESDAY. THE FRONT STALLED IN THE OHIO VALLEY EXTENDS INTO  
THE UPPER MIDWEST WHERE CLUSTERS OF CONVECTION ILLUSTRATE THE SHARP  
TEMPERATURE AND MOISTURE CONTRAST STILL PRESENT. THE FRONT IS  
READILY AVAILABLE TO LOW PRESSURE DEVELOPING IN THE NORTHERN PLAINS  
AND ITS LOW LEVEL JET SPREADING MOISTURE ALONG AND AHEAD OF THE  
FRONTAL ZONE. THE SHARPNESS OF THE 850-700 MB THETA-E RIDGE ALSO  
SUGGESTS ELEVATED CONVECTION IS LIKELY TO SURVIVE AND CONTINUE  
EASTWARD THROUGH THE TYPICALLY HOSTILE DAYLIGHT HOURS FOR ELEVATED  
CONVECTION. ANY LOSS OF COVERAGE AND INTENSITY IS REGAINED WITH A  
NEW ROUND OF NOCTURNAL MOISTURE TRANSPORT TONIGHT BEGINNING NEARBY  
IN NORTHERN AND WESTERN LOWER MI AND PROGRESSING ACROSS SE MI LATE  
TONIGHT AND EARLY TUESDAY. HEAVY RAINFALL POTENTIAL IS BEST DURING  
THIS PHASE OF THE SYSTEM IN THE GREAT LAKES BUT STILL MARGINAL DUE  
TO A RELATIVELY WEAK LOW LEVEL JET, THE POSSIBILITY OF MOISTURE  
DISRUPTION FROM MID MS VALLEY CONVECTION, AND STEADY PROGRESSION OF  
THE LARGER SCALE PATTERN. THERE IS ALSO A SURFACE BASED CONVECTIVE  
COMPONENT LIKELY BY TUESDAY AFTERNOON INTO THE EVENING AS THE LOW  
LEVEL MOISTURE AXIS MOVES ACROSS LOWER MI FOLLOWED BY THE COLD  
FRONT/OCCLUSION, HOWEVER STORM INTENSITY IS EXPECTED TO BE LIMITED  
BY MINIMAL RECOVERY OF INSTABILITY AFTER THE EARLIER DAY ACTIVITY.  
 
CONTINUED OCCLUSION OF THE SURFACE FRONTAL SYSTEM, AND A BOOST FROM  
THE 500 MB WAVE, RESULT IN SECONDARY LOW PRESSURE NEAR THE OHIO  
BORDER AND A LINGERING CHANCE OF SHOWERS IN SE MI TUESDAY EVENING.  
THE LOW PRESSURE SYSTEM MAKES A MORE AGGRESSIVE MOVE TO EXIT  
EASTWARD AS THE EFFECTIVE FRONTAL PASSAGE BY WEDNESDAY MORNING  
FOLLOWED BY INCREASING NORTH WIND ACROSS LOWER MI THAT BRINGS IN  
ANOTHER ROUND OF COOLER AND LESS HUMID AIR. THE 18/00Z MODEL RUN IS  
IN GOOD AGREEMENT ON SOLUTIONS THAT SHOW THE LONG WAVE RIDGE  
BUILDING BACK NORTH INTO CENTRAL CANADA AND THEN LEANING EASTWARD  
OVER THE GREAT LAKES DURING THE LATE WEEK. THIS IS FOLLOWED BY A  
LARGER/STRONGER CANADIAN LOW PRESSURE SYSTEM SET TO BRING THE NEXT  
COLD FRONT THROUGH LOWER MI TO START NEXT WEEKEND.  
 
 
   
MARINE  
 
EAST-NORTHEAST WINDS WILL BE MOSTLY WEAKER TODAY COMPARED TO  
YESTERDAY AS HIGH PRESSURE RETREATS AND A WARM FRONT LIFTS IN FROM  
THE WESTERN GREAT LAKES, ALLOWING WAVES TO DIMINISH FURTHER.  
HOWEVER, THE EXCEPTION WILL BE ACROSS THE NORTHERN THIRD OF LAKE  
HURON/NEAR THE STRAITS WHERE CHANNELING OF THE WINDS LOOKS TO  
SUPPORT GUSTS OF 25 KNOTS TO POSSIBLY BRIEFLY NEAR 30 KNOTS THIS  
AFTERNOON.  
 
SURFACE LOW PRESSURE TRACKING THROUGH NORTHERN LOWER MICHIGAN ON  
TUESDAY LOOKS TO BE TRIGGERING SHOWERS AND THUNDERSTORMS, ESPECIALLY  
OVER NORTHERN LAKE HURON WHERE SOUTHEAST WINDS LOOK TO BE AT LEAST  
25 KNOTS, WITH THE POTENTIAL TO REACH AROUND 30 KNOTS.  
 
NORTHEAST WINDS REDEVELOP OVER ALL OF LAKE HURON TUESDAY NIGHT AS  
THE LOW TRACKS TO THE EAST, AND ANOTHER ROUND OF SMALL CRAFT  
ADVISORIES ARE LIKELY AS WINDS LOOK TO GUST AROUND 25 KNOTS ONCE  
AGAIN ON WEDNESDAY OVER SOUTHERN LAKE HURON. SURFACE RIDGE TRACKING  
THROUGH THE CENTRAL GREAT LAKES WILL ALLOW FOR LIGHT WINDS ON  
THURSDAY AND FRIDAY HOWEVER.  
 
 
   
PREV DISCUSSION  
 
ISSUED AT 1220 AM EDT MON AUG 18 2025  
 
AVIATION...  
 
HIGH PRESSURE BRINGS QUIET AVIATION CONDITIONS THROUGH TODAY WITH  
PREVAILING VFR SKIES. NORTHEASTERLY WINDS WILL VEER TOWARDS THE  
SOUTHEAST THROUGHOUT THE MORNING INTO THE EARLY AFTERNOON. WEAK  
LOWER LEVEL WIND FIELDS WILL LIMIT GUST POTENTIAL AND KEEP WINDS  
MOSTLY BELOW 10 KNOTS. SOUTHEAST WINDS WILL ADD A SLIGHT BOOST IN  
LAKE MOISTURE AND AIDE IN VFR DAYTIME CUMULUS DEVELOPING BY LATE  
MORNING/AFTERNOON.  
 
FOR DTW/D21 CONVECTION...THUNDERSTORM ACTIVITY IS NOT ANTICIPATED  
THIS PERIOD.  
 
THRESHOLD PROBABILITIES...  
 
* LOW FOR CEILINGS AT OR BELOW 5000 FEET THIS EVENING AND TOMORROW.  
 
 
   
DTX WATCHES/WARNINGS/ADVISORIES  
 
MI...NONE.  
 
LAKE HURON...SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR LHZ421-441.  
 
SMALL CRAFT ADVISORY UNTIL 8 AM EDT THIS MORNING FOR LHZ442-443.  
 
LAKE ST CLAIR...NONE.  
 
MICHIGAN WATERS OF LAKE ERIE...NONE.  
 
 
 
 
 
DISCUSSION...BT  
MARINE.......SF  
AVIATION.....AA  
 
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