832  
FXUS63 KDTX 151727  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
127 PM EDT FRI AUG 15 2025  
   
KEY MESSAGES
 
 
- WARMER AND DRY TODAY WITH HIGHS IN THE UPPER 80S.  
 
- HEAT AND HUMIDITY RETURN THIS WEEKEND AS HEAT INDICES PEAK IN THE  
UPPER 90S SATURDAY AFTERNOON.  
 
- CHANCE OF THUNDERSTORMS SATURDAY THROUGH SUNDAY MORNING WITH AN  
ISOLATED SEVERE STORM POSSIBLE SATURDAY AFTERNOON-EVENING.  
 
- COOLER AND LESS HUMID EARLY NEXT WEEK.  
 

 
   
AVIATION
 
 
STRONG H5-H3 GEOPOTENTIAL HEIGHT RISES IS FORECASTED TODAY AND  
TONIGHT AS AN EXTENSION TO UPPER LEVEL RIDGING BUILDS INTO  
SOUTHEAST MICHIGAN AND THE CENTRAL GREAT LAKES. THERE IS A VERY GOOD  
SIGNAL FOR WARMING ALOFT WITH ACTIVE SUBSIDENCE IN THE 5.0 TO 13.0  
KFT AGL LAYER. MODELS SUGGEST CONVECTIVE REMNANTS WITH ASSOCIATED  
MOISTURE WILL ARRIVE OVER THE AREA AFTER 15Z SATURDAY. THERE MAY BE  
ENOUGH MIDLEVEL MOISTURE AND COOLING TO ERODE STABILITY OVER THE  
REGION TO RESULT IN SOME SPORADIC SHOWERS OR THUNDERSTORM ACTIVITY.  
UNCERTAINTY IS HIGH AND CONFIDENCE IS LOW, BUT DID INTRODUCE A  
PROB30 GROUP FOR -TSRA AT DTW.  
 
FOR DTW/D21 CONVECTION...LOW CHANCE FOR A THUNDERSTORM BETWEEN 19-  
22Z SATURDAY.  
 
THRESHOLD PROBABILITIES...  
 
* LOW FOR CEILING AT OR BELOW 5 KFT DURING THE AFTERNOON.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 406 AM EDT FRI AUG 15 2025  
 
DISCUSSION...  
 
PATCHY FOG IS OBSERVED THIS MORNING ACROSS THE SAGINAW VALLEY AND  
THUMB REGIONS WHERE EASTERLY FLOW OFF OF LAKE HURON HAS LOCALLY  
ENHANCED BOUNDARY LAYER MOISTURE. SHOULD HAVE NO PROBLEM MIXING THIS  
OUT ONCE SOLAR HEATING RAMPS UP. LOW AMPLITUDE SHORTWAVE IS NOTED  
OVER WISCONSIN AT ISSUANCE, AND WILL SLOWLY SHIFT EAST THROUGHOUT  
THE DAY BRINGING AN INCREASE IN MID CLOUD ACROSS CENTRAL LOWER  
MICHIGAN THROUGHOUT THE DAY. AIRMASS MODIFICATION AND EMERGING  
SOUTHERLY FLOW PUSH HIGHS INTO THE UPPER 80S TODAY.  
 
LOW PREDICTABILITY HEADING INTO THE SATURDAY FORECAST, WITH SEVERAL  
WINDOWS OF OPPORTUNITY FOR CONVECTION, BUT LOW CONFIDENCE IN EACH.  
THE FIRST OF THESE BEGINS LATE TONIGHT AS A NOCTURNAL MCS DEVELOPS  
ALONG A COLD FRONT THAT IS SET TO DROP THROUGH THE GREAT LAKES LATER  
THIS WEEKEND. FAMILIAR SETUP EXISTS WHERE THE MCS WILL RIDE THE  
INSTABILITY GRADIENT AND EITHER CLIP SE MICHIGAN SATURDAY MORNING,  
OR GENERATES SUBSIDENCE AND EATS INTO THE INSTABILITY THAT WE RELY  
ON FOR LATER DAY CONVECTION. SHOULD INSTABILITY BE ABLE TO REBOUND  
SUFFICIENTLY BY THE AFTERNOON-EVENING TIMEFRAME, A COUPLE OF DEFINED  
PERTURBATIONS ALOFT COMBINE WITH DIFFERENTIAL HEATING AT THE SURFACE  
TO SUPPORT A SECOND WINDOW OF THUNDERSTORM POTENTIAL. SWODY2 KEEPS  
THE MARGINAL RISK WEST OF OUR FORECAST AREA, BUT THERE ARE SOME  
ENVIRONMENTAL SIGNATURES FOR STRONG DOWNDRAFT POTENTIAL. FOR  
EXAMPLE, HRRR/RAP SOUNDINGS SHOW INVERTED-V SOUNDINGS WITH SFC-3KM  
AGL LAPSE RATES OF 8.5-9.0 C/KM WHILE INCREASING MID-LEVEL WINDS  
LATE IN THE DAY COULD SUPPORT ORGANIZED CELLS.  
 
THE OTHER FORECAST POINT FOR SATURDAY IS THE RETURN OF WARM AND  
MUGGY CONDITIONS. FORECAST HIGHS ON SATURDAY AROUND 90 DEGREES BRING  
HEAT INDICES INTO THE MID-90S, ALTHOUGH CONVECTIVE CLOUD DEBRIS  
AND/OR DISRUPTION TO MOISTURE TRANSPORT COULD SUPPRESS WARMING  
SIGNIFICANTLY.  
 
BY SATURDAY EVENING, THE COLD FRONT WILL BEGIN SETTLING ACROSS LOWER  
MICHIGAN. THE DETERMINISTIC RUNS ARE FAIRLY LEAN ON PRECIPITATION  
COVERAGE OVERNIGHT-SUNDAY MORNING, BUT GIVEN THE DEFINED FORCING AND  
PLENTIFUL MOISTURE (PWATS NEAR 1.8"), THOUGHTS ARE MUCH MORE IN LINE  
WITH THE BULK OF ENSEMBLE MEMBERS FROM THE EPS/GEFS/CMCE WHICH KEEPS  
SHOWER/THUNDERSTORM CHANCES GOING THROUGH AT LEAST SUNDAY MORNING.  
MODELS DISAGREE ON THE PACE OF THE FRONT, WITH SOME STALLING THE  
BOUNDARY OVERHEAD ON SUNDAY TO KEEP RAIN CHANCES AROUND FOR THE  
DAYTIME HOURS AS WELL. THE FORECAST FROM SUNDAY THROUGH EARLY NEXT  
WEEK WILL BE HIGHLY SENSITIVE TO THE POSITIONING OF THIS FRONTAL  
BOUNDARY, AND WILL LIKELY SEE A GRADIENT IN BOTH TEMPERATURE AND  
PRECIPITATION CHANCES ACROSS THE CWA. PRECIPITATION IS LIKELY TO  
FLARE UP AT TIMES ALONG THE FRONTAL ZONE, LEADING TO UNSETTLED  
CONDITIONS AND POTENTIAL FOR HEAVY RAINFALL TO START THE WORK WEEK.  
THE WPC EXCESSIVE RAINFALL OUTLOOK HIGHLIGHTS ALL OF SE MICHIGAN IN A  
BROAD MARGINAL RISK FOR MONDAY-TUESDAY. OTHERWISE, COOLER CONDITIONS  
ARE EXPECTED NEXT WEEK.  
 
MARINE...  
 
HIGH PRESSURE OVER EASTERN QUEBEC THIS MORNING, LEADING TO LIGHT  
SOUTHERLY FLOW (MOSTLY UNDER 20 KNOTS) TODAY. CONTINUED LOW LEVEL  
WARMING INTO SATURDAY AHEAD OF A COLD FRONT SHOULD CAP WIND SPEEDS  
IN THE 15 TO 20 KNOT RANGE. INCREASING CHANCE OF SHOWERS AND  
THUNDERSTORMS SATURDAY EVENING AS COLD FRONT ENTERS THE REGION.  
SCATTERED-NUMEROUS SHOWERS AND THUNDERSTORMS SHOULD BE AROUND  
SATURDAY NIGHT INTO SUNDAY AS THE FRONT DRIVES SOUTH. SOLID COLD  
ADVECTION (850 MB TEMPS LOWERING INTO LOWER TEENS/AROUND 10 C) OVER  
LAKE HURON ON SUNDAY WILL ALLOW NORTHEAST WINDS TO REACH 20-25  
KNOTS, WITH THE POTENTIAL FOR WINDS TO BRIEFLY GUST TO AROUND 30  
KNOTS. EVEN IF WINDS COME UP A BIT SHORT, THE PROLONG NORTHEAST  
WINDS WILL LIKELY ALLOW WAVES TO BUILD AROUND 4 FEET ACROSS THE  
NEARSHORE WATERS, AS EASTERLY WINDS PERSIST INTO EARLY NEXT WEEK  
WITH ANOTHER STRONG HIGH PRESSURE SYSTEM DEVELOPING OVER EASTERN  
CANADA.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...NONE.  
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

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