303
FXUS63 KDTX 170427
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1227 AM EDT SUN AUG 17 2025
KEY MESSAGES
- ADDITIONAL SHOWER AND THUNDERSTORM CHANCES EXIST THROUGH THE EARLY
MORNING AND AGAIN MONDAY-TUESDAY. LOCALLY HEAVY RAINFALL IS
POSSIBLE.
- COOLER AND DRIER CONDITIONS EXPECTED WEDNESDAY THROUGH FRIDAY.
AVIATION
THE THUNDER POTENTIAL APPEARS TO BE DECREASING GIVEN THE RECENT
OBSERVATIONAL TRENDS, EXPECT FOR POSSIBLY KMBS. CONFIDENCE IS NOT
HIGH ENOUGH TO CARRY TEMPO TSRA AT ANY OF THE TAF SITES WITH THIS
ISSUANCE. WILL MONITOR TRENDS OVERNIGHT AND AMEND THEM BACK IN IF
NEEDED. WILL CARRY TEMPO VFR SHOWERS INSTEAD AS THE FRONT WORKS SOUTH
AND DOES BRING POTENTIAL FOR SCATTERED SHOWERS DURING THE EARLY
MORNING. BEST COVERAGE DOES LOOK TO BE ACROSS THE THUMB THOUGH.
FRONTAL PASSAGE WILL COME WITH A VEERING WIND TO THE NORTHWEST
THROUGH THE EARLY-MID MORNING HOURS AS CEILINGS LOWER TO MVFR AND
POSSIBLY IFR AT TIMES. PATCHY MVFR WILL ALSO BE POSSIBLE IN THE WAKE
OF THE FRONT AS WELL. WINDS BECOME MORE NORTH TO NORTHEAST TOWARDS
MID MORNING AND INTO THE AFTERNOON WHILE BECOMING GUSTY TO 20-25
KNOTS. CEILINGS BEGIN TO IMPROVE TOWARDS 00Z THIS EVENING.
FOR DTW/D21 CONVECTION...THUNDERSTORM POTENTIAL HAS DECREASED BASED
ON EARLY NIGHT OBSERVATIONAL TRENDS. BEST POTENTIAL, IF THERE IS AN
ISOLATED THUNDERSTORM TO POP UP, WOULD BE BETWEEN 08Z AND 10Z BASED
ON FRONTAL TIMING. CONFIDENCE NOT HIGH ENOUGH NOW TO INCLUDE TEMPO
TSRA GROUP AT THIS TIME.
THRESHOLD PROBABILITIES...
* LOW FOR THUNDERSTORMS THROUGH ABOUT 10Z.
* HIGH FOR CEILINGS AT OR BELOW 5 KFT BY AROUND 10-12Z AND THROUGH
MUCH OF THE AFTERNOON.
PREV DISCUSSION
ISSUED AT 359 PM EDT SAT AUG 16 2025
DISCUSSION...
TAIL OF CONVECTION FLANKING TO THE SOUTHWEST OF AN OLD MCV FEATURE
HAS RESULTED IN ELEVATED SHOWER AND THUNDERSTORM ACTIVITY OVER
EASTERN PORTIONS OF THE THUMB THIS AFTERNOON. SURFACE OBSERVATIONS
PICKED UP ON RELATIVELY STRONGER NORTHEAST FLOW, UP TO 25 KNOTS, IN
ADVANCE OF THE MCV SIGNIFYING THE ORGANIZATION OF THE SYSTEM.
THUNDERSTORM ACTIVITY WILL LIKELY CONTINUE TO FIRE AND ZIPPER OPEN
FOR A TIME AS THE CONVERGENCE AXIS TRIES TO WORK OUT OF THE STATE.
UPSTREAM OVER WISCONSIN, THE DEEPEST OF CONVECTION IS SETTING UP ON
THE SOUTHERN PERIPHERY OF THE NEXT MCS/MCV. TOUCHED ON THE
EXPECTATIONS FOR TIMING OF THUNDERSTORMS AND THE POTENTIAL OF SEVERE
WEATHER IN THE UPDATE DISCUSSION ISSUED EARLIER. MUCH OF THIS
PREVIOUS THINKING REMAINS VALID.
STORM SCALE SUBSIDENCE IS FORECASTED TO COMBINE WITH STRENGTHENING
NORTHERLY FLOW LATE TONIGHT IN SHAPING UP A NEAR SURFACE COLD FRONT
OVER THE STATE. LATEST PLAN VIEW PROGS OF THETAE SUPPORT THIS COLD
FRONT PUSHING SOUTHWARD INTO THE NORTHERN OHIO RIVER VALLEY BETWEEN
12-15Z SUNDAY. FORECAST SOUNDINGS SIGNAL ACTIVE SUBSIDENCE
DEVELOPING BETWEEN 6.0 AND 12.0 KFT EARLY IN THE DAY, THEN DEEPENING
AND LOWERING TOWARD THE SURFACE DURING THE COURSE OF THE AFTERNOON.
OUTSIDE OF A ROGUE SHOWER OR SPRINKLE DOWNWIND OF THE GREAT LAKES,
RELATIVELY HIGH CONFIDENCE IN DRY CONDITIONS FOR MUCH OF THE AREA
SUNDAY. GUSTY NORTH WINDS 10 TO 20 MPH WITH DECREASING HUMIDITY LATE
IN THE DAY.
SURFACE HIGH PRESSURE IS FORECASTED TO BUILD AGGRESSIVELY INTO THE
STATE FOR MONDAY WITH DEEP COLUMN RIDGING. FORECAST SOUNDINGS
SUPPORT EXTREMELY STRONG STABILITY DEVELOPING IN THE 4.0 TO 16.0 KFT
AGL. MODESTLY LESS HUMID CONDITIONS ESPECIALLY AS DEEPER MIXING
OCCURS DURING THE AFTERNOON. HIGHS ARE EXPECTED TO RANGE IN THE
LOWER 80S.
FORECAST MODELS SUPPORT THE BROAD LONGWAVE RIDGE AMPLIFYING OVER
MUCH OF NORTH AMERICA QUICKLY LATE MONDAY AND TUESDAY. SIGNS POINT
TO A WEAKNESS IN THE RIDGE CORRESPONDING TO A VERY WEAK JET AXIS
DIRECTED AT THE WESTERN AND CENTRAL GREAT LAKES TUESDAY. RELATIVELY
HIGHER PREDICTABILITY APPEARS TO EXIST WITH A MCS AND LARGER LOW
PRESSURE CIRCULATION TRACKING IN VICINITY OF SOUTHEAST MICHIGAN. THE
MOST EYE CATCHING ITEM OF THIS MIDWEEK SYSTEM IS THE SHARPNESS AND
STRENGTH OF THETAE GRADIENT THAT WILL PUSH INTO THE AREA LATE MONDAY
NIGHT. OVERALL, THE SPECIFICS OF THIS TUESDAY SYSTEM WILL COME DOWN
TO TIMING OF THE COLD FRONT AND WHETHER OR NOT AN UPSTREAM
CONVECTIVE SYSTEM TRACKS THROUGH THE AREA. COULD LOOK AT AN EARLY
TUESDAY MORNING TIMING THAT SHORT CIRCUITS AIRMASS RECOVERY ON
TUESDAY. WILL BE MONITORING TRENDS FOR A HEAVY RAINFALL THREAT.
UPPER LEVEL RIDGING IS EXPECTED TO BRING AN EXTENDED RUN OF DRY
WEATHER FOR THE END OF THE WEEK. CURRENT FORECAST DATA SUGGESTS MUCH
LESS HUMID WEATHER LATE WEDNESDAY THROUGH FRIDAY.
MARINE...
CONTINUED LOW LEVEL WARMING TODAY AHEAD OF A COLD FRONT SHOULD CAP
SOUTHERLY WIND SPEEDS IN THE 15 TO 20 KNOT RANGE. NUMEROUS SHOWERS
AND THUNDERSTORMS DEVELOPING BY THIS EVENING AS THE COLD FRONT
ENTERS THE REGION. ALTHOUGH THE FRONT QUICKLY DROPS SOUTH OF THE
STATE SUNDAY MORNING, STILL A LINGERING CHANCE OF SHOWERS AND
THUNDERSTORMS FOR GOOD PORTION OF THE DAY. STRONG HIGH PRESSURE
BUILDING OVER NORTHWEST ONTARIO AND SOLID COLD ADVECTION (850 MB
TEMPS LOWERING INTO LOWER TEENS) OVER LAKE HURON ON SUNDAY WILL
ALLOW NORTHEAST WINDS TO REACH 20-25 KNOTS, WITH STILL THE POTENTIAL
FOR WINDS TO BRIEFLY GUST TO AROUND 30 KNOTS. EVEN IF WINDS COME UP
A BIT SHORT, THE PROLONG NORTHEAST WINDS WILL ALLOW WAVES TO BUILD
IN EXCESS OF 4 FEET ACROSS THE NEARSHORE WATERS OF LAKE HURON, AS
EASTERLY WINDS PERSIST INTO EARLY NEXT WEEK WITH ANOTHER STRONG HIGH
PRESSURE SYSTEM DEVELOPING OVER EASTERN CANADA.
DTX WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT FROM 9 AM EDT THIS MORNING THROUGH THIS
EVENING FOR MIZ048-049-055-063.
LAKE HURON...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO NOON EDT MONDAY FOR
LHZ421-441.
SMALL CRAFT ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT FOR
LHZ422.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 8 AM EDT MONDAY FOR
LHZ442-443.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....AA
DISCUSSION...CB
MARINE.......SF
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