539
FXUS63 KDTX 300717
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
317 AM EDT SUN AUG 30 2026
KEY MESSAGES
- WIDESPREAD SHOWERS AND THUNDERSTORMS THIS MORNING THROUGH TOMORROW
MORNING. ADDITIONAL CHANCES MONDAY AFTERNOON INTO TUESDAY.
- SEVERE STORMS ARE NOT EXPECTED, BUT THERE IS POTENTIAL FOR A SWATH
OF LOCALLY HEAVY RAINFALL MAINLY FOCUSED ACROSS THE THUMB THAT MAY
BRING LOCALIZED FLOODING CONCERNS THROUGH MONDAY MORNING.
- SLIGHTLY WARMER TEMPERATURES AND INCREASED HUMIDITY DURING THE
EARLY TO MID WEEK WITH UNSETTLED WEATHER PATTERN REMAINING.
DISCUSSION
BRIEF PERIOD OF INCREASING SUBSIDENCE WILL MARK THIS EARLY MORNING
PERIOD AS HIGH BASED SCATTERED SHOWER ACTIVITY FROM DECAYING MCS
CONTINUES TO DECREASE IN COVERAGE. ATTENTION QUICKLY TURNS TO AN
EXPANDING AREA OF PRECIPITATION THIS MORNING THAT WILL CONTINUE
THROUGH TODAY. WIDESPREAD/NUMEROUS SHOWERS AND SCATTERED
THUNDERSTORMS WILL BE FORCED ALONG A WARM FRONTAL ZONE AND THETA-E
RIDGE WITH ADDITIONAL SUPPORT FROM THE LOW LEVEL JET, THOUGH
STRONGEST LLJ WINDS HOLD TO THE WEST. THE WARM FRONT SETS UP OVER
LOWER MICHIGAN THIS MORNING THEN LIFTS NORTHWARD TOWARDS THE I-69
CORRIDOR LATER TODAY FOCUSING THE HIGHER COVERAGE OF SHOWERS WITH
TIME ACROSS NORTHERN LOWER MICHIGAN AND SOUTHEAST THROUGH THE THUMB.
THE OVERALL AIRMASS WILL BE QUITE MOIST AS DEWPOINTS CLIMB INTO THE
60S AND PWATS VALUES INCREASE TO 1.75 INCHES OR GREATER ACROSS
SOUTHEAST MICHIGAN WHILE APPROACHING 2 INCHES OVER THE THUMB.
OVERALL SEVERE THREAT WILL BE VERY LIMITED WITH THE LACK OF SURFACE
INSTABILITY AND MEAN MUCAPE VALUES GENERALLY AROUND 500 J/KG OR
LESS, PEAKING LATER THIS AFTERNOON AND EVENING. MAIN CONCERN WILL BE
FOR REPEATED ROUNDS OF SHOWERS AND THUNDERSTORMS THAT COULD BRING
LOCALLY HEAVY RAINFALL. AFTER A BRIEF PERIOD OF LOWER QPF POTENTIAL
LATER THIS EVENING, AN ADDITIONAL UPTICK IN CONVECTIVE POTENTIAL
OCCURS LATE THIS EVENING THROUGH MONDAY MORNING AS A COLD FRONT THEN
DROPS INTO NORTHERN LOWER MICHIGAN SUPPORT A CORRIDOR OF MORE FOCUSED
FORCING. WHILE SHEAR WILL REMAIN FAVORABLE, SEVERE POTENTIAL AGAIN
LOOKS LIMITED GIVEN THE WEAKER INSTABILITY. LOCALLY HEAVY RAINFALL
WILL CONTINUE TO BE THE MAIN CONCERN.
MODEL CONSENSUS PUTS THE AXIS OF HEAVIER PRECIPITATION FOCUSED ALONG
AND NORTH OF A LINE FROM MIDLAND TO PORT HURON. AVERAGE TOTAL
RAINFALL AMOUNTS TO AROUND AN INCH ARE FORECAST IN THIS AXIS
STARTING THIS MORNING (12Z) TO EARLY MONDAY AFTERNOON (18Z).
A LOCALIZED SWATH OF 2 TO NEAR 4 INCHES OF TOTAL RAINFALL WILL BE
POSSIBLE ACROSS PARTS OF THE THUMB, WHICH IS HIGHLIGHTED WELL IN THE
HREF 24-HR QPF ENSEMBLE LOCALIZED PROBABILITY-MATCHED MEAN. AMOUNTS
TO HALF AN INCH ARE FORECAST DOWN TO ROUGHLY THE M-59 CORRIDOR AND A
QUARTER INCH OR LESS SOUTH OF M-59 DOWN TO THE SOUTHERN BORDER.
SOUTHEAST MICHIGAN WILL RESIDE ON THE NORTHERN END OF A RIDGE DURING
THE EARLY TO MID-WEEK PERIOD. SLIGHT INCREASE IN HEAT AND HUMIDITY
WILL ARRIVE WITH THE PERSISTENT WEST-SOUTHWEST LOW TO MID LEVEL
FLOW. EMBEDDED SHORTWAVES WITHIN THIS FLOW AROUND THE RIDGE WILL
CONTINUE TO OFFER CHANCES OF PRECIPITATION INTO MID-WEEK. GIVEN THE
PATTERN AND POTENTIAL FOR CONTINUED CHANCES OF RAINFALL AND
INCREASED CLOUD COVER, CURRENT NBM FORECAST TEMPERATURES ARE
PROBABLY ON THE HIGH SIDE MID-WEEK IF THAT PANS OUT. MICHIGAN WILL
REMAIN IN A CORRIDOR OF HIGHER PWATS, WHICH KEEP THE POTENTIAL FOR
LOCALIZED HEAVY RAINFALL AS A CONCERN DURING THIS STRETCH AND DAILY
ORGANIZED CONVECTIVE CHANCES WILL DEPEND ON THE DEGREE OF
INSTABILITY THAT IS ABLE TO DEVELOP EACH DAY.
MARINE
WE CONTINUE THE TRANSITION OUT OF HIGH PRESSURE TODAY WITH AS A
DEVELOPING LOW PRESSURE SYSTEM OVER THE NORTHERN PLAINS BEGINS TO
IMPACT THE AREA. THE LEADING WARM FRONT HAS LIFTED INTO SOUTHERN
MICHIGAN AND WILL KEEP OVERCAST SKIES AND RAIN CHANCES THROUGH THE
DAY. IN ADDITION, A COLD FRONT WILL BE DRIFTING SOUTHWARD TOWARD THE
NORTHERN GREAT LAKES ADDING TO THE FORCING WHICH WILL DRIVE
PRECIPITATION CHANCES. WINDS WILL LARGELY BE FROM THE SOUTH TODAY
WITH MAX GUSTS AROUND 20 KNOTS. WINDS TURN MORE SOUTHEASTERLY ON
MONDAY WHILE REMAINING MOSTLY BELOW 20 KNOTS BEFORE TURNING WESTERLY
ON TUESDAY.
PREV DISCUSSION
ISSUED AT 1138 PM EDT SAT AUG 29 2026
AVIATION...
AN ELEVATED WARM FRONT WITHIN A REGION OF AMPLE MID LEVEL MOISTURE
HAS PRODUCED SOME HIGH BASED SHOWERS ACROSS THE AREA. THESE SHOWERS
WILL DEPART TO THE EAST BY 06Z. AVAILABLE GUIDANCE AND REGIONAL
OBSERVATIONS ARE SUPPORTIVE OF VFR CONDITIONS PREVAILING THROUGH THE
NIGHTTIME HOURS. AN INFLUX OF MOISTURE ARRIVING LATE TONIGHT WITHIN
A DEVELOPING WARM FRONT WILL RESULT IN INCREASING
SHOWER/THUNDERSTORM CHANCES DURING THE MORNING. SHOWER CHANCES WILL
BE GREATEST ACROSS FNT AND MBS, WITH LOWER CHANCES SOUTH. POTENTIAL
INCREASE IN AFTERNOON INSTABILITY WILL SUPPORT A CHANCE OF
CONVECTION SUNDAY AFTERNOON. CURRENT INDICATIONS SUGGEST THE HIGHER
PROBABILITIES NEAR THE WARM FRONT, TARGETING KFNT AND KMBS.
D21/DTW CONVECTION...OVERALL THUNDERSTORM CHANCES THROUGH THE DAY
SUNDAY WILL BE UNDER 30 PERCENT.
DTW THRESHOLD PROBABILITIES...
* LOW IN THUNDERSTORMS SUNDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...AA
MARINE.......DRK
AVIATION.....SC
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