815
FXUS63 KDTX 190359
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1159 PM EDT MON AUG 18 2025
KEY MESSAGES
- SCATTERED SHOWERS AND STORMS BECOME POSSIBLE EARLY THIS MORNING
THROUGH THIS EVENING. LOCALLY HEAVY RAINFALL IS THE PRIMARY
CONCERN WITH THIS ACTIVITY.
- THERE IS A MARGINAL RISK OF SEVERE STORMS FOR FAR SOUTHEASTERN
MICHIGAN TUESDAY AFTERNOON EAST OF A LINE FROM PORT HURON TO
ADRIAN.
- SEASONABLE TEMPERATURES AND DRY WEATHER MOVE IN AND HOLD WEDNESDAY
THROUGH FRIDAY.
AVIATION
INCREASING MOISTURE ADVECTION BRINGS INCREASING CHANCES FOR SHOWERS
AND THUNDERSTORMS ACROSS THE TERMINALS THROUGH THE MORNING HOURS.
BEST THUNDERSTORM POTENTIAL ACROSS SOUTHEAST MICHIGAN LIES WITHIN
THE 12Z TO 16Z TIME FRAME THIS MORNING, WITH THE STRONGER
THUNDERSTORM POTENTIAL FOCUSED ACROSS THE SOUTHERN METRO TERMINALS.
BRIEF IFR TO LIFR CONDITIONS WILL ACCOMPANY THE THUNDERSTORMS
BRINGING POTENTIAL FOR HEAVY RAINFALL. A MORE SOLID LOW MVFR/IFR
CEILING WITH SCATTERED LIFR CEILINGS SETTLE IN TOWARDS THE AFTERNOON
WITH CONTINUED RAIN CHANCES. LOW CLOUDS HOLD INTO THE EVENING AND
TONIGHT ALONG WITH A FEW STRAY SHOWERS IN THE NORTHERLY TO NORTHEAST
WIND OFF LAKE HURON, THOUGH FOCUS MAY HOLD EAST OF TERMINAL
CORRIDOR.
FOR DTW/D21 CONVECTION...THUNDERSTORM ACTIVITY IS POSSIBLE BETWEEN
12Z AND 16Z TODAY. GUSTY WINDS AND HEAVY RAINFALL WILL BE POSSIBLE
WITH STRONGEST THUNDERSTORMS.
THRESHOLD PROBABILITIES...
* MEDIUM FOR THUNDERSTORMS BETWEEN 12Z TO 16Z TODAY.
PREV DISCUSSION
ISSUED AT 338 PM EDT MON AUG 18 2025
DISCUSSION...
REGIONAL SATELLITE IMAGERY SHOWS THE EXTENSIVE CLOUD FIELD
ASSOCIATED WITH THE LOW PRESSURE SYSTEM OVER MN/WI THIS AFTERNOON
THAT WE WILL BE FOCUSING ON FOR CONVECTIVE CHANCES THROUGH LATE
TUESDAY. WITH LOW AMPLITUDE RIDGE AXIS FOLDING OVER THE REGION IN
THE MID LEVELS, THE LOW WILL DRIFT EASTERLY FROM SOUTHERN WI TONIGHT
INTO CENTRAL LOWER MI BY TUESDAY MORNING. IN ADVANCE OF THIS, THE
850MB THETA E GRADIENT WILL LIFT NORTHEAST THROUGH LOWER MI TONIGHT
ON THE NOSE OF THE LOW LEVEL JET, HELPING TO FUEL A ROUND OF SHOWERS
AND ELEVATED THUNDERSTORMS. THIS ACTIVITY WOULD BE MOSTLY NORTH OF
I69. MORE WIDESPREAD ACTIVITY WILL MOVE IN FROM WEST TO EAST AROUND
10-14Z AS THE LOW LEVEL JET AND DRAPING WARM FRONT PUSH THROUGH THE
AREA. LOW RISK OF SEVERE WEATHER WITH THE EARLY ROUND OF MOSTLY
ELEVATED STORMS, LOW SHEAR AND JUST A FEW HUNDRED J/KG OF MUCAPE.
A NARROW WARM SECTOR WILL TRAVERSE THE AREA THROUGH THE AFTERNOON
PROVIDING ANOTHER ROUND OF MORE WIDESPREAD SHOWERS AND STORMS.
CURRENTLY THE LOW LOOKS TO PASS THROUGH THE THUMB WHICH WILL BRING
THE WARM SECTOR THROUGH DURING PEAK HEATING, ALBEIT MUTED DUE TO
LIKELIHOOD OF CLOUDY SKIES. CAMS SUGGEST THERE COULD STILL BE AROUND
1000 J/KG OF SURFACE BASED CAPE WITH >20 KNOTS OF SHEAR WHILE THE
WEAKENING LOW LEVEL JET PASSES OVER JUST AHEAD OF THE COLD FRONT.
ADDING TO THE SYNOPTIC SUPPORT WILL BE A 500MB SHORTWAVE ADVANCING
OVER THE REGION. SPC CLIPPED A SMALL PORTION OF SE MI WITH A
MARGINAL RISK FROM ABOUT PORT HURON TO ADRIAN AND EASTWARD. THIS
WILL ALL BE DEPENDENT ON WHERE THE SURFACE LOW ACTUALLY TRACKS. SOME
EARLIER GUIDANCE HAD THE LOW A BIT FURTHER SOUTH.
MAIN RISK WITH THE STORMS TONIGHT AND TUESDAY WILL BE HEAVY RAIN AND
LOCALIZED FLOODING. THE OVERNIGHT STORMS APPEAR TO BE FAIRLY
PROGRESSING, BUT AS THE LOW DRIFTS ACROSS THE AREA, THERE IS
POTENTIAL FOR SLOWER MOVING STORMS AROUND THE LOW CENTER WITH AMPLE
MOISTURE AS PWATS RISE TO JUST OVER 2 INCHES (WITH SURFACE DEWPOINTS
ONCE AGAIN AT OR ABOVE 70) WITH STRONG MOISTURE ADVECTION. STRONG TO
SEVERE WIND GUSTS WILL BE ANOTHER CONCERN WITH THESE STRONGER
STORMS.
THE BULK OF THE ACTIVITY WILL BE DONE IN THE EVENING BUT THERE IS A
CHANCE THAT THE WRAP AROUND MOISTURE AND DEFORMATION BAND COULD KEEP
SOME SHOWERS AROUND AFTER 00Z FOR A FEW HOURS. OTHERWISE, HIGH
PRESSURE WILL RETURN TO THE GREAT LAKES OUT OF CANADA WITH
NORTHEASTERLY WINDS ACROSS THE REGION. THIS WHILE THE UPPER LEVEL
RIDGE BUILDS BACK OVER THE WESTERN/CENTRAL CONUS AND BEGINS PUSHING
INTO LOWER MI.
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. TEMPERATURES WILL
HOVER AROUND 80 MID WEEK BEFORE SLOWLY CLIMB THROUGH THE END OF THE
WEEK WITH A CHANCE OF THE RIDGE AXIS FOLDING OVER THROUGH THE REGION
ON FRIDAY BRINGING MID 80S BACK FOR A DAY.
MARINE...
HIGH PRESSURE CENTERED OVER SOUTHERN QUEBEC MAINTAINS EAST TO EAST-
SOUTHEAST WIND THIS AFTERNOON THAT GRADUALLY SHIFTS SOUTHEAST AND
STRENGTHENS TONIGHT AS A LOW PRESSURE SYSTEM TRACKS IN FROM THE
MIDWEST. GUSTS TO AROUND 25 KNOTS WILL BE LOCALIZED ACROSS NORTHERN
LAKE HURON GIVEN FAVORABLE FETCH AND CHANNELING EFFECTS. SCATTERED
TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE LOW
PRESSURE THROUGH THE CENTRAL GREAT LAKES OVERNIGHT AND THROUGH THE
DAY TUESDAY. GUSTY SOUTHEAST WINDS TO AROUND 15 TO 20 KNOTS WILL
PERSIST ACROSS LAKE HURON DURING THIS PERIOD. THE LOW PASSES EAST
CAUSING WIND TO SHIFT TO NORTHEAST LATE TUESDAY NIGHT INTO
WEDNESDAY, REACHING A PEAK OF 20 TO 25 KNOTS WEDNESDAY AFTERNOON
WITH SOME GUSTS UP TO 30 KNOTS POSSIBLE ALONG THE SOUTHERN LAKE
HURON SHORELINE. SMALL CRAFT ADVISORIES ARE LIKELY THROUGH WEDNESDAY
EVENING AS WAVES BUILD TO 4+ FEET. HIGH PRESSURE THEN BUILDS IN FROM
THE NORTHERN GREAT LAKES THROUGH THE LATE WEEK WITH NORTHEAST WIND
BECOMING LIGHT.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....AA
DISCUSSION...DRK
MARINE.......TF
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