669  
FXUS63 KDTX 191914  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
314 PM EDT TUE AUG 19 2025  
   
KEY MESSAGES
 
 
- SEASONABLE TEMPERATURES AND DRY WEATHER MOVE IN AND HOLD WEDNESDAY  
THROUGH FRIDAY.  
 

 
   
DISCUSSION
 
 
STRONG UPPER LEVEL ANTICYCLONIC WAVE BREAK OVER THE CANADIAN PRAIRIE  
PROVINCES COMBINED WITH WEAK ENTRANCE REGION DYNAMICS OVER  
ONTARIO/QUEBEC IS RESULTING IN THE AMPLIFICATION AND DIGGING OF A  
TROUGH OVER THE GREAT LAKES REGION TODAY. THE GREATEST AREA OF THE  
HEIGHT FALLS AND SYNOPTIC SCALE ASCENT HAS NOW BEEN SQUEEZED  
IMMEDIATELY SOUTH AND EAST OF THE CWA. WILL STILL HAVE TO WORK  
THROUGH AN AXIS OF SHOWERS AND CONVERGENCE THAT IS NOW PUSHING INTO  
NORTHERN METRO DETROIT. RADAR DATA SUPPORTS WARM CLOUD/SMALL DROPLET  
DISTRIBUTION IN THE SHOWERS. NO THUNDERSTORMS ARE EXPECTED, BUT  
RAINFALL RATES COULD PROVE TO BE SUPRISINGLY EFFICIENT THE COUPLE OF  
HOURS. MODEL DATA THE PAST 24 HOURS OR SO HAS STEADILY CONVERGED ON  
A SOLUTION THAT IS MUCH DRIER FOR THE EVENING HOURS. WILL CONTINUE  
CHANCE POPS.  
 
THE MIDLEVEL TROUGH IS FORECASTED TO BE PROGRESSIVE, OPENING THE  
DOORS TO DIFFERENTIAL GEOPOTENTIAL HEIGHT RISES TONIGHT. WHILE THE  
LARGE SCALE UPPER LEVEL PATTERN SUPPORTS BLOCKING OVER THE SOUTHWEST  
UNITED STATES, TILTING OF THE UPPER LEVEL RIDGE INTO THE GREAT  
LAKES IS ANTICIPATED. THE NET RESULT WILL BE A UNIFORM EXPANSION OF  
SURFACE HIGH PRESSURE INTO SOUTHEAST MICHIGAN WITH THE ANTICYCLONE  
THEN PERSISTING THROUGH THE EARLY PORTION OF SATURDAY. MORE  
COMFORTABLE WEATHER IS EXPECTED WITH HIGHS GENERALLY IN THE LOWER  
80S (AROUND NORMAL) WITH SURFACE DEWPOINTS IN THE 50/60S.  
 
THE NEXT CHANCE OF RAINFALL IS EXPECTED TO BE LATE SATURDAY AND  
SUNDAY. THERE HAS BEEN A STRONG CONSENSUS AMONGST THE GLOBAL MODELS  
IN AMPLIFYING A LARGE WAVELENGTH UPPER LEVEL LOW PRESSURE SYSTEM AS  
IT PUSHES EAST OF HE ROCKY MOUNTAINS. CURRENT FORECAST SUGGESTS  
DAYTIME HIGH TEMPERATURES IN THE LOW 70S NEXT MONDAY AND TUESDAY,  
APPROXIMATELY 8 TO 10 DEGREES BELOW NORMAL.  
 

 
   
MARINE
 
 
LOW PRESSURE REACHES WESTERN LAKE ERIE LATE THIS AFTERNOON AND  
CONTINUES TO TRACK EAST TOWARD LAKE ONTARIO TONIGHT. SHOWERS WITH  
EMBEDDED THUNDERSTORMS WILL WANE IN COVERAGE THROUGH THE EVENING  
WHILE WIND OVER LAKE HURON BACKS FROM EAST TO NORTHEAST, INCREASING  
TO AROUND 15 TO 20 KNOTS WITH GUSTS TO 25 KNOTS ON WEDNESDAY. SMALL  
CRAFT ADVISORIES ARE IN EFFECT FOR ALL SOUTHERN LAKE HURON NEARSHORE  
ZONES THROUGH WEDNESDAY EVENING. HIGH PRESSURE BUILDS IN FROM THE  
NORTHERN GREAT LAKES THROUGH THURSDAY CAUSING NORTHEAST WIND TO  
BECOME LIGHT. WIND THEN SHIFTS TO SOUTHWEST ON FRIDAY AHEAD OF THE  
NEXT COLD FRONT SET TO ARRIVE ON SATURDAY.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 138 PM EDT TUE AUG 19 2025  
 
AVIATION...  
 
LOW PRESSURE NOW CENTERED OVER SE MI WILL CONTINUE TO PROGRESS EAST  
INTO SOUTHERN LAKE HURON AND ONTARIO LATE TONIGHT AND OVERNIGHT.  
COPIOUS LOW LEVEL MOISTURE HAS REINFORCED IFR CIGS AND SPOTTY  
SHOWERS LEADING INTO THE AFTERNOON HOURS. WHILE SOME MINOR  
IMPROVEMENTS TO CEILING HEIGHTS INTO MVFR WILL BE POSSIBLE IN THE  
AFTERNOON WITH DAYTIME HEATING, MOST FAVORABLE FOR THE METRO  
TERMINALS, THE EXPECTATION IS THAT WRAP AROUND MOISTURE FROM THE  
DEPARTING LOW IN CONJUNCTION WITH LAKE ENHANCED MOISTURE WILL  
REINFORCE IFR CIGS LATE TONIGHT AND OVERNIGHT. SOME PERIODS OF LIFR  
CANNOT BE RULED OUT OVERNIGHT, MOST FAVORABLE ACROSS KPTK TO KFNT  
WITH THE HIGHER TERRAIN.  
 
ADDITIONALLY, SOME SPOTTY SHOWERS WILL BE POSSIBLE THROUGH THE  
AFTERNOON. A STRENGTHENING LOW LEVEL INVERSION WILL MAINTAIN LOW  
LYING STRATUS LEADING INTO THE EARLY AFTERNOON HOURS TOMORROW.  
OTHERWISE, PASSAGE OF THE LOW WILL RAPIDLY CHANGE WIND DIRECTION  
FROM SOUTHWEST TO NORTHWEST THROUGH THE AFTERNOON AND EARLY EVENING  
HOURS.  
 
FOR DTW/D21 CONVECTION...THERE WILL BE A 10% CHANCE FOR AN ISOLATED  
THUNDERSTORM THROUGH 22Z. BUT OVERALL, THUNDERSTORM CHANCES HAVE  
BEEN TRENDING DOWNWARDS GIVEN THE COPIOUS CLOUD COVER AND LACK OF  
INSTABILITY. HAVE REMOVED MENTIONS OF THUNDERSTORMS GIVEN THE LOW-  
END PROBABILITIES.  
 
THRESHOLD PROBABILITIES...  
 
* HIGH FOR CEILINGS AOB 5000 FEET THROUGH THE TAF PERIOD.  
 
* LOW FOR THUNDERSTORMS THROUGH 22Z.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...BEACH HAZARDS STATEMENT FROM WEDNESDAY MORNING THROUGH WEDNESDAY  
EVENING FOR MIZ049-055-063.  
 
LAKE HURON...SMALL CRAFT ADVISORY FROM 8 AM TO 10 PM EDT WEDNESDAY FOR LHZ421-  
422-441>443.  
 
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
DISCUSSION...CB  
MARINE.......TF  
AVIATION.....AM  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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