722
FXUS63 KDTX 010834
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
434 AM EDT THU OCT 1 2026
KEY MESSAGES
- WARMER AND MUCH MORE HUMID TODAY WITH PERIODS OF SHOWERS.
- COVERAGE AND INTENSITY OF RAINFALL INCREASES LATER TODAY WITH A
CHANCE FOR LOCALLY HEAVY RAIN THIS EVENING AND EARLY TONIGHT.
- COOLER TEMPERATURES AND DRIER WEATHER ARRIVES MIDDAY FRIDAY,
CONTINUING THROUGH THE WEEKEND AND INTO NEXT WEEK.
DISCUSSION
SIGNIFICANT TROPOSPHERIC MOISTENING WAS SAMPLED VIA THE 01.00Z KDTX
RAOB, MARKED BY VERTICAL CONTINUITY IN SATURATION AND A MEASURED
PWAT OF 1.70 INCHES. THIS MODIFIED TROPICALLY SOURCED AIR MASS HAS
ALLOWED OVERNIGHT SHOWERS TO PERCOLATE WITH EASE BENEATH SUSTAINED
PERTURBED FLOW ALOFT. THE LATEST FORCING MECHANISM HAS BEEN
ATTRIBUTED TO A SERIES OF SHORTWAVE IMPULSES POSITIONED AHEAD OF AN
INBOUND LONGWAVE TROUGH MOVING EASTWARD OVER SOUTHERN CANADA, AND
DOWNSTREAM OF A SOUTHERN CONUS CLOSED LOW. THE SOUTHERN WAVE HAS
BEEN RESPONSIBLE FOR THE INFLUX OF EASTERN PACIFIC AND GULF
MOISTURE, UPHOLDING THE APPROPRIATE ENVIRONMENT FOR THIS EXTENDED
PERIOD OF RAINFALL.
THE LOW-LEVEL JET MOISTURE CONNECTION IS FULLY ENGAGED EARLY THIS
MORNING, WITH BOTH INCREASING MAGNITUDE (30+ KNOTS) AND TRAJECTORY
CONTINUITY. LATEST PROGS INDICATE THE CONFLUENT STREAM ARCS BACK TO
TEXAS WHERE THE REMNANTS OF HURRICANE POLO MERGE WITH GULF-WIDE
THETA-E ADVECTION. ADDITIONALLY, THE TWO SYNOPTIC WAVES WILL BEGIN
TO PHASE DURING THE PM HOURS, LEADING TO A RISE IN UPPER-LEVEL
DIVERGENCE AND LOCAL THETA-E CONVERGENCE. THIS LENDS CONTINUED
CONCERN FOR THE LOCALIZED RISK OF HEAVY RAINFALL LATER TODAY,
ESPECIALLY AS A COLD FRONT EXTENDING FROM THE NORTHERN SYSTEM TRACKS
SOUTHEASTWARD ACROSS LOWER MICHIGAN. THE PERIOD OF GREATEST CONCERN
WILL BE AS THE FRONTAL SLOPE ENGAGES THE PEAK IN LOW-LEVEL MOISTURE
TRANSPORT LATE THIS AFTERNOON INTO THE EVENING TIMEFRAME, WHILE THE
SYSTEM'S DEFORMATION AXIS CENTERS OVERHEAD. SEE THE HYDROLOGY
SECTION FOR ADDITIONAL DETAILS.
LATEST NWP SUITE INDICATES PEAK 3-HOURLY RAINFALL RATES BETWEEN 00Z
AND 06Z TONIGHT AS THE FRONT PUSHES THROUGH. WINDS FLIP
NORTHWESTERLY IMMEDIATELY BEHIND THE SURFACE FRONT TONIGHT, ALTHOUGH
SHOWERS WILL BE SLOWER TO CLEAR. ONCE AGGRESSIVE POST-FRONTAL SYSTEM-
RELATIVE ISENTROPIC DOWNGLIDE BUILDS IN, RAINFALL WILL QUICKLY
CONCLUDE. DRY WEATHER IS THEN FORECAST BY MID-MORNING FRIDAY AS THE
GREAT LAKES RESIDE DOWNSTREAM OF BUILDING 1028 MB HIGH PRESSURE
MOVING INTO THE UPPER MIDWEST. SEASONABLY COOL AND DRY AS THE RIDGE
DOMINATES. A CLIPPER SYSTEM COULD BRING A FEW SPRINKLES THROUGH
SUNDAY MORNING, WHILE THERMAL TROUGHING PERSISTS. 850 MB
TEMPERATURES CRATER EARLY NEXT WEEK, WITH SUB-0C VALUES POSSIBLE.
MORNING FROST CONCERNS MAY ARISE SHOULD LOWS DROP INTO THE UPPER 30S.
MARINE
SOUTHWESTERLY WINDS WILL CONTINUE OUT AHEAD OF AN APPROACHING COLD
FRONT, WHICH ARRIVES AND STALLS OVER SOUTHERN LOWER MICHIGAN TODAY.
WITH WARM ADVECTION LEADING TO MORE STABLE PROFILES AND SHOWERS
MOVING THROUGH DURING THIS TIMEFRAME, WIND GUSTS ARE EXPECTED TO TOP
OUT ONLY AROUND 25 KNOTS. WITH THE FRONT HUNG UP UNTIL NIGHT, THE
POST FRONTAL COLD ADVECTION NOW LOOKS SLOWER; THUS, THE POTENTIAL FOR
NORTHWEST WIND GUSTS REACHING OR EXCEEDING 25 KNOTS LOOKS TO BE LATE
IN THE DAY ON FRIDAY AS 850 MB TEMPS LOWER INTO THE MID SINGLE
DIGITS BY FRIDAY.
A LARGE AREA OF HIGH PRESSURE THEN BUILDS IN BEHIND THE DEPARTING
COLD FRONT ON FRIDAY INTO SATURDAY. THIS WILL BRING LIGHTER WINDS
FOR THE FIRST HALF OF THE WEEKEND. A STRONGER LOW TRACKING THROUGH
THE NORTHERN GREAT LAKES FOR THE SECOND HALF OF THE WEEKEND BRINGS
ANOTHER OPPORTUNITY FOR WINDS TO REACH OR EXCEED 25 KNOTS OVER LAKE
HURON.
HYDROLOGY
A MID TO LATE WEEK RAINFALL EPISODE CONTINUES TODAY, PEAKING THIS
EVENING AND EARLY TONIGHT. IT OCCURS AS TROPICAL MOISTURE STREAMS
INTO LOWER MICHIGAN, ALONG AND AHEAD OF AN APPROACHING MIDWEST COLD
FRONT. A MORE PERSISTENT BAND OF RAIN IS ESTABLISHED ACROSS THE AREA
THIS AFTERNOON AS THE COLD FRONT MOVES THROUGH THE REGION BY
TONIGHT, WHEN MOISTURE PARAMETERS PEAK. HIGH CONFIDENCE IN RAINFALL
TOTALS UP TO 1 INCH AND MEDIUM CONFIDENCE IN TOTALS OVER AN INCH.
THE LOW-END CHANCE FOR SYSTEM RAINFALL TOTALS TO REACH 2 INCHES
REQUIRES A SLOWER FRONTAL PASSAGE, LEADING TO A LONGER WINDOW FOR
PERSISTENT RAINFALL. THE CHANCE EXISTS FOR MINOR FLOODING OF LOW-
LYING AREAS AND PONDING ON ROADS ACROSS THE REGION UNTIL THE RAIN
QUICKLY ENDS POST-FRONT FRIDAY MORNING.
PREV DISCUSSION
ISSUED AT 1225 AM EDT THU OCT 1 2026
AVIATION...
DEEP GULF MOISTURE STREAMING INTO THE REGION WILL CONTINUE TO
SUPPORT EXTENSIVE CLOUD COVER AND SCATTERED RAIN SHOWERS THROUGH THE
EARLY MORNING HOURS. VARIETY OF CEILINGS AND VISIBILITY ACROSS THE
TERMINAL CORRIDOR FROM NORTH TO SOUTH WITH IFR TO MVFR CONDITIONS
FOCUSED ACROSS MBS AND WITH MVFR TO VFR DOWN TOWARDS THE METRO
TERMINALS. A BREAK FROM PRECIPITATION AND IMPROVED CEILINGS WILL
OCCUR ACROSS THE METRO TERMINALS MID-LATE TOMORROW MORNING AS WE GET
BACKING FLOW AHEAD OF AN APPROACHING COLD FRONT. THOUGH, CHANCES FOR
RAIN WILL CONTINUE FOR KMBS/KFNT. COLD FRONT MOVES THROUGH TONIGHT
AS WINDS TURN NORTHWESTERLY AND EVENTUALLY OUT OF THE NORTH
STARTING FIRST ACROSS KMBS AROUND 00Z AND SPREADING SOUTHWARD OVER
THE NEXT SEVERAL HOURS. THE FRONT WILL RESULT IN DECREASING CEILINGS
AND THE NEXT ROUND OF RAIN TO THE REACH THE SOUTH TERMINALS. CANNOT
RULE OUT AN ISOLATED THUNDERSTORM WITH THE FRONT, BUT LIMITED
INSTABILITY PRECLUDES MENTION.
D21/DTW CONVECTION...LOW POTENTIAL FOR THUNDERSTORMS THROUGH THIS
FORECAST PERIOD.
DTW THRESHOLD PROBABILITIES...
* MEDIUM FOR CEILINGS AT OR BELOW 5,000 FEET THROUGH THE TAF THIS
MORNING AND AFTERNOON THEN HIGH AFTER 00Z THIS EVENING.
* LOW FOR THUNDERSTORMS TONIGHT.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KGK
MARINE.......SF/SS/KGK
HYDROLOGY....KGK
AVIATION.....AA
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