273  
FXUS63 KDTX 121009  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
609 AM EDT TUE AUG 12 2025  
   
KEY MESSAGES  
 
- HOT AND MUGGY CONDITIONS AGAIN TODAY WITH HEATING INDICES IN THE  
LOW TO MID-90S.  
 
- POTENTIAL EXISTS FOR SHOWERS AND THUNDERSTORMS TO DEVELOP THROUGH  
TONIGHT.  
 
- THE STRONGEST STORMS WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY  
RAINFALL. IN ADDITION, ISOLATED WIND GUSTS OF 50 TO 60 MPH WILL BE  
POSSIBLE THIS AFTERNOON AND EVENING.  
 
- HIGH PRESSURE BRINGS NEAR NORMAL TEMPERATURES AND LESS HUMID  
CONDITIONS TO CLOSE OUT THE WORK WEEK.  
 
 
   
AVIATION  
 
AXIS OF SHOWERS AND STORMS THAT HAS BEEN DRAPED ACROSS NORTHERN MI  
AND WI THE LAST COUPLE DAYS WILL SHIFT OVER SOUTHERN MI TODAY.  
SHOWERS AND STORMS WILL BE POSSIBLE THROUGHOUT THE DAY AND INTO THE  
OVERNIGHT AS THE ATMOSPHERE BECOMES UNCAPPED AND STORMS COULD GO UP  
ANYWHERE. WE ARE WATCHING THE UPSTREAM COMPLEX OVER SOUTHERN WI  
WHICH IS FORECAST TO TRACK THROUGH CENTRAL MI POSSIBLY AFFECTING FNT  
AND MBS THIS AFTERNOON. OTHERWISE WE'LL BE KEYING IN ON PREFRONTAL  
ACTIVITY INCREASING IN COVERAGE LATE THIS AFTERNOON INTO THE  
EVENING. HIRES MODELS ARE SHOWING POTENTIAL FOR DTW TO STAY DRY FOR  
A GOOD CHUCK OF THE DAY, POSSIBLY TIL AROUND 00Z WHEN A MORE  
DEVELOPED LINE PUSHED THROUGH. BUT CONFIDENCE IS LOW WITH ANY  
SINGULAR MODEL. SO WILL TEMPO/PROB30 IN A WINDOW OF BEST CHANCE  
TIMING AND ADJUST AS NEEDED.  
 
FOR DTW/D21 CONVECTION... A STRAY THUNDERSTORM REMAINS POSSIBLE LATE  
THIS MORNING, MAINLY NORTH OF DTW. STORM COVERAGE INCREASES  
CONSIDERABLY THROUGH THE AFTERNOON INTO TUESDAY EVENING. BEST CHANCE  
FOR CONVECTION LOOKS TO BE AROUND 8P-12A, BUT STORMS COULD GO UP  
BEFORE THAT.  
 
THRESHOLD PROBABILITIES...  
 
* LOW FOR THUNDERSTORMS THIS AFTERNOON. MODERATE FOR THIS EVENING.  
 
 
   
PREV DISCUSSION  
 
ISSUED AT 324 AM EDT TUE AUG 12 2025  
 
DISCUSSION...  
 
RENEWED LOW-MID LEVEL THETA-E ADVECTION UNDERWAY LOCALLY EARLY THIS  
MORNING, SOLIDIFIED BY INCREASING DEPTH TO SOUTH TO SOUTHWEST FLOW  
WITHIN THE IMMEDIATE DOWNSTREAM FLANK OF BROADER UPPER MIDWEST  
TROUGHING. THIS PROCESS IN COMBINATION WITH LOW LEVEL JET SUPPORT  
SUSTAINING A SMALL CORRIDOR OF CONVECTION ACROSS SOUTHWEST LOWER MI.  
THIS ACTIVITY MAY CONTINUE TO CAPITALIZE ON THE UNDERLYING MOIST AND  
WEAKLY UNSTABLE ENVIRONMENT, WITH CURRENT TRAJECTORY OFFERING SOME  
POTENTIAL FOR A PERIOD OF ELEVATED CONVECTION OVER MAINLY AREAS  
NORTH OF I-69 YET THIS MORNING. LITTLE EVIDENCE PER RADAR/SATELLITE  
TRENDS TO SUGGEST A GREATER NOCTURNAL RESPONSE WILL MATERIALIZE TO  
THE SOUTH THIS MORNING, WITH THE ADVECTIVE PROCESS ALONE PROVING  
INADEQUATE.  
 
RESIDENT MOIST AND DIURNALLY DESTABILIZING ENVIRONMENT WILL REMAIN  
CONDUCIVE TO SOME DEGREE OF CONVECTIVE DEVELOPMENT ACROSS THE  
AFTERNOON AND EVENING PERIODS FROM A THERMODYNAMIC PERSPECTIVE, BUT  
STILL CARRIES CONSIDERABLE UNCERTAINTY ON POTENTIAL SCALE AND TIMING  
OWING TO LESS DEFINED SOURCES OF GREATER FORCED ASCENT. A SUBSET OF  
THE HI RES SOLUTION SPACE KEY ON ONGOING ACTIVITY NOW SPILLING INTO  
WESTERN ILLINOIS, WITH THE POSSIBILITY FOR THE GOVERNING  
CONVECTIVELY ENHANCED VORT MAX TO MAINTAIN AN NE/ENE TRAJECTORY AND  
ARRIVE LOCALLY BY EARLY-MID AFTERNOON. AREAS GENERALLY NORTH OF M-59  
POSITIONED MORE FAVORABLY IN THIS INSTANCE. FROM THERE INTO THE  
EVENING, CONVECTIVE INITIATION REMAINS PLAUSIBLE ESSENTIALLY  
ANYWHERE THROUGHOUT LOWER MICHIGAN STRETCHING BACK INTO SOUTHERN  
LAKE MI/CHICAGO AREA AS POCKETS OF CONVERGENCE ENGAGE THE EXISTING  
INSTABILITY GRADIENT. HEAVY RAINFALL RISK CERTAINLY EXISTS GIVEN  
EFFICIENT RAIN RATE POTENTIAL WITHIN A DEEP MOIST LAYER, BUT PERHAPS  
WITH THE OVERALL RAIN DURATION AT ANY ONE LOCATION MORE LIMITED WITH  
JUST ENOUGH STEERING FLOW IN THE COLUMN TO KEEP CONVECTIVE CLUSTERS  
MORE PROGRESSIVE. AREAS NORTH OF M-59 APPEAR MORE SUSCEPTIBLE TO  
MULTIPLE ROUNDS OF ACTIVITY UNDER THE CURRENT SETUP, HIGHLIGHTING A  
HIGHER PROBABILITY FOR A LOCALIZED HIGHER QPF STRIP IN EXCESS OF  
0.75-1" SOMEWHERE WITHIN THIS CORRIDOR. ISOLATED OCCURRENCES OF  
STRONG WIND GUSTS ALSO PLAUSIBLE WITHIN ANY DEEPER PRECIPITATION  
LOADED CORES. ENOUGH POTENTIAL EXISTS TO WARRANT AN UPGRADE IN THE  
DAY 1 SPC OUTLOOK TO A MARGINAL RISK. FORECAST WILL OFFER A SLIGHT  
INCREASE IN PROJECTED HIGHS ACROSS THE SOUTH, ACKNOWLEDGING A  
GREATER LIKELIHOOD FOR LIMITED TO NO CONVECTIVE DISRUPTION TO THE  
HEATING CYCLE, AFFORDING ANOTHER DAY PUSHING TO/ABOVE 90 DEGREES.  
THIS PLACES PEAK HEAT INDEX VALUES AGAIN IN THE MID 90S FOR METRO  
DETROIT.  
 
GREATER HEIGHT FALLS COMMENCING ACROSS THE NORTHERN GREAT LAKES WILL  
DRAW A COLD FRONT ACROSS LOWER MICHIGAN OVERNIGHT INTO EARLY  
WEDNESDAY. INHERENT FRONTAL CONVERGENCE MAINTAINS LOWER END PRECIP  
CHANCES THROUGH THIS PERIOD, WITH PACE OF THE FRONTAL PASSAGE AND  
TRAILING DRY AIR ADVECTION DICTATING WHETHER THIS POTENTIAL LAGS  
INTO THE DAYLIGHT PERIOD WEDNESDAY FOR SOUTHERN SECTIONS. OTHERWISE,  
TEMPERATURES TRENDING COOLER RELATIVE TO RECENT DAYS, WITH A MORE  
NOTEWORTHY DOWNTURN IN HUMIDITY FOR THE LATE WEEK PERIOD AS HIGH  
PRESSURE TAKES CONTROL. HEAT AND HUMIDITY WILL RETURN NEXT WEEKEND  
WITH UPPER RIDGING GAINING INFLUENCE.  
 
MARINE...  
 
STRONG LOW PRESSURE TRACKS ACROSS NORTHERN ONTARIO TODAY AND  
TONIGHT, DRAGGING A COLD FRONT ACROSS THE GREAT LAKES LATE THIS  
AFTERNOON-EVENING. SHOWER AND THUNDERSTORM CHANCES EXIST THROUGHOUT  
THE DAY AS THE FRONT APPROACHES AND THE AIRMASS REMAINS  
WARM/UNSTABLE, BUT NOTABLY SHIFTS TO A MORE LINEAR STORM MODE AS THE  
FRONT DRAWS CLOSER IN THE EVENING. GUSTY WINDS IN EXCESS OF 40 KNOTS  
WILL BE POSSIBLE IN ADDITION TO HEAVY RAINFALL AND FREQUENT  
LIGHTNING. SHOWERS AND ELEVATED STORMS LINGER THROUGH WEDNESDAY  
MORNING BEFORE THE FRONT FULLY CLEARS EAST AND WINDS SHIFT TO THE  
NORTHWEST. BY THIS POINT, UPPER LEVEL TROUGHING AND HIGH PRESSURE  
BUILD IN WHICH ALLOWS COOLER AND DRIER CONDITIONS TO DEVELOP FOR THE  
BACK HALF OF THE WORK WEEK. FLOW SHIFTS ONSHORE LATE IN THE WEEK AS  
WINDS VEER AROUND THE HIGH PRESSURE SYSTEM, WHICH WILL ELEVATED WAVE  
HEIGHTS ESPECIALLY FOR SAGINAW BAY AND THE THUMB REGION.  
 
HYDROLOGY...  
 
A HIGH LIKELIHOOD EXISTS FOR SHOWERS AND THUNDERSTORMS TO DEVELOP  
THROUGH TONIGHT WITHIN A HOT AND HUMID ENVIRONMENT. A VERY MOIST  
ENVIRONMENT WILL CREATE FAVORABLE CONDITIONS FOR LOCALLY HEAVY  
RAINFALL, WITH RAINFALL RATES POTENTIALLY IN EXCESS OF 2"/HR UNDER  
THE STRONGEST STORMS. BASIN AVERAGE RAINFALL RATES BETWEEN ONE HALF  
AND ONE INCH ARE POSSIBLE, WITH LOCALLY HIGHER AMOUNTS IN EXCESS OF  
ONE INCH WHERE SLOW MOVING OR TRAINING CELLS DEVELOP. LOCALIZED  
FLOODING OF URBAN, LOW-LYING AND POOR DRAINAGE AREAS ALONG WITH  
RISES IN AREA RIVERS WILL BE POSSIBLE.  
 
 
   
DTX WATCHES/WARNINGS/ADVISORIES  
 
MI...NONE.  
LAKE HURON...NONE.  
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  
 
 
 
 
AVIATION.....DRK  
DISCUSSION...MR  
MARINE.......MV  
HYDROLOGY....MR  
 
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AT WWW.WEATHER.GOV/DETROIT.  
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