808
FXUS63 KDTX 201945
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
345 PM EDT MON OCT 20 2025
KEY MESSAGES
- DRY AND SEASONABLE THROUGH THIS EVENING.
- A BRIEF LINE OF SHOWERS IS EXPECTED LATE TONIGHT INTO EARLY
TUESDAY MORNING.
- NUMEROUS SHOWERS ON TUESDAY AFTERNOON AND EVENING. ISOLATED
STRONGER SHOWERS WILL BE CAPABLE OF PRODUCING GUSTY WINDS TO 40 MPH,
SMALL HAIL, AND THUNDER.
- OCCASIONAL SHOWERS TUESDAY NIGHT AND WEDNESDAY WITH MUCH COOLER
CONDITIONS LASTING THROUGH THURSDAY.
DISCUSSION
CONDITIONS TODAY OFFER A BRIEF RESPITE FROM AN OTHERWISE ACTIVE
PATTERN THAT WILL PERSIST THROUGH THE MIDDLE PART OF THE WEEK. THE
SUNNY AND SEASONABLE WEATHER IS DRIVEN BY STABLE CONDITIONS BENEATH
A COMPACT MID-LEVEL RIDGE SQUEEZED BETWEEN THE DEPARTING AMPLIFIED
TROUGH OVER NEW ENGLAND AND THE NEXT INBOUND WAVE APPROACHING THE
WESTERN GREAT LAKES. DRY AND PLEASANT WEATHER CARRIES THROUGH THE
EVENING WITH TEMPS FALLING INTO THE 40S TONIGHT.
A SHORTWAVE DROPPING OUT OF SOUTHERN MANITOBA IS BEGINNING A MERGER
WITH THE MEAN TROUGHING TRACKING ACROSS THE UPPER MIDWEST THIS
AFTERNOON. THIS WILL CAUSE THE ELONGATED ZONE OF LOWER MSLP IN THE
VICINITY TO COALESCE INTO A DEEPENING LOW THAT REACHES WESTERN LAKE
SUPERIOR AFTER MIDNIGHT. A PERIOD OF RELATIVELY BRIEF BUT FOCUSED
ASCENT THEN SPREADS IN ACROSS THE LOWER PENINSULA ALONG THE CORRIDOR
OF HEIGHT FALLS AND JET EXIT REGION DYNAMICS. THE WARM FRONT IS
QUICKLY FOLLOWED BY THE COLD FRONT TUESDAY MORNING AS THE SYSTEM
BEGINS OCCLUDING AND STALLS ACROSS THE NORTHERN GREAT LAKES. TIMING
OF THE RESULTANT ARC OF SHOWERS HAS REMAINED STABLE IN THE PAST FEW
MODEL CYCLES, ARRIVING IN WESTERN COUNTIES AROUND 3 AM AND DEPARTING
THE THUMB AROUND 9 AM. BREEZY CONDITIONS TO AROUND 20 TO 25 MPH ARE
POSSIBLE OVERNIGHT, BUT MOST OF THE MOMENTUM FROM THE 40+ KT LLJ
WILL BE INACCESSIBLE TO THE SURFACE LAYER DUE TO STRONG STABILITY
WITHIN THE WARM ADVECTION.
POST-FRONTAL COLD ADVECTION ENSUES ACROSS THE AREA TUESDAY MORNING
AS THE SHOWERS DEPART. THIS TAPS INTO STILL ENERGETIC FLOW (25 TO 30
KT AT 850MB) TO PRODUCE 25 TO 30 MPH GUSTS DURING THE DAYTIME
TUESDAY. SOME AREAS OF THE THUMB COULD SEE HIGHER GUSTS CLOSER TO 35
MPH. SUBSIDENCE BEHIND THE COLD FRONT INITIALLY KEEPS THE AREA DRY
MIDDAY, BUT INCREASING MOISTURE FLUX AND INSTABILITY WITHIN BROAD
CYCLONIC FLOW AROUND THE LOW WILL RESULT IN AN INCREASING COVERAGE
OF SHOWERS THROUGH THE AFTERNOON AND EVENING. STEEP LAPSE RATES WILL
DEVELOP AS 500MB TEMP CRASHES TO BELOW -25C. THIS WITH FALLING
FREEZING LEVELS WILL BRING THE POTENTIAL FOR BRIEF BOUTS OF GRAUPEL,
LOCALLY HIGHER GUSTS TO 40+ MPH, AND/OR THUNDER WITHIN ANY STRONGER
CONVECTIVE ELEMENTS. COVERAGE OF CONVECTION PEAKS LATE AFTERNOON TO
EARLY EVENING COINCIDENT WITH A SHORTWAVE PASSING OVERHEAD, THEN
SHOWERS BECOME MORE SCATTERED LATE EVENING INTO THE OVERNIGHT.
MEANWHILE, TEMPS WILL PLUMMET FROM THE UPPER 50S INTO THE 40S WITH
THE LOSS OF DAYLIGHT.
THE STALLED LOW PRESSURE OVER LAKE SUPERIOR RELEASES SOUTH INTO
NORTHERN LOWER MI WEDNESDAY MORNING, DRAGGING IN A REINFORCING SHOT
OF COOL AIR AND DEEP-LAYER MOISTURE. THIS PAIRED WITH DIURNAL
INSTABILITY SUSTAINS SCATTERED TO NUMEROUS COVERAGE OF SHOWERS
THROUGH WEDNESDAY. THE DEGREE OF AMBIENT GUSTINESS CARRIES A BIT OF
UNCERTAINTY DEPENDENT ON THE STRENGTH AND PROXIMITY OF THE LOW, BUT
WILL CONTINUE TO ADVERTISE DAYTIME GUST OF 25 TO 30 MPH. WILL NOTE
THAT LAPSE RATES ARE CURRENTLY PROJECTED TO BE WEAKER THAN TUESDAY
WHICH OFFERS LOWER CONFIDENCE ON ANY MORE VIGOROUS CONVECTION.
BROAD UPPER LOW PRESSURE REMAINS STALLED OVER THE NORTHERN GREAT
LAKES INTO THURSDAY WITH ANOTHER LOBE OF VORTICITY OFFERING
ADDITIONAL SCATTERED LIGHT SHOWERS. THE 850MB THERMAL TROUGH BOTTOMS
OUT IN THE SINGLE DIGITS BELOW 0 C AND HOLDS TEMPS SOME 10 DEGREES
BELOW NORMAL ANOTHER DAY. THE BULK OF SOLUTIONS ACROSS THE ENSEMBLE
SPACE THEN ALLOW THE UPPER TROUGH TO RELEASE EAST BY THE END OF THE
WEEK TO FAVOR LOWER PRECIP CHANCES, BUT JET PLACEMENT OVERHEAD AND
SEVERAL SMALLER SCALE WAVES EVIDENT IN MEDIUM RANGE GUIDANCE
PRECLUDE A COMPLETELY DRY FORECAST AT THIS STAGE.
MARINE
INCREASING SOUTHWEST WINDS TONIGHT AS A LARGE LOW PRESSURE SYSTEM
CENTERED OVER MINNESOTA TRACKS INTO LAKE SUPERIOR TOMORROW. WIND
GUSTS TO 25 KNOTS APPEAR LIKELY FOR ALL NEARSHORE WATERS, AND HAVE
ISSUED SMALL CRAFT ADVISORIES FOR LAKE ST. CLAIR AND LAKE ERIE
TONIGHT THROUGH WEDNESDAY NIGHT. AS MUCH OLDER AIR FILTERS IN
TUESDAY AND WEDNESDAY, WIND GUSTS OVER LAKE ST. CLAIR AND LAKE ERIE
ACTUALLY LOOK STRONGER ON WEDNESDAY AS 850 MB TEMPS REACH AT OR
SLIGHTLY BELOW FREEZING. FORECASTED SOUNDINGS INDICATING THE TOP OF
THE BOUNDARY LAYER EVEN TAPPING INTO GALES. HOWEVER, ONLY EXPECTING
WIND GUSTS OF 25-30 KNOTS TO BE REALIZED NEAR THE WATER SURFACE.
WITH THE WEAKENING SURFACE LOW TRACKING THROUGH NORTHERN LAKE HURON
ON WEDNESDAY, THERE IS LESS OF A PRESSURE GRADIENT FOR SOUTHERN LAKE
HURON, AND WIND GUSTS MAY JUST BRIEFLY TOUCH 30 KNOTS. EVEN WITH
MOSTLY OFFSHORE FLOW, MAY HAVE JUST ENOUGH WAVE ACTION TO GET TO 4
FEET WITH THE UNSTABLE LOW LEVEL PROFILES AND HAVE EXTENDED THE
SMALL CRAFT ADVISORIES FOR SOUTHERN LAKE HURON. A SECONDARY COLD
FRONT SINKS SOUTH WEDNESDAY EVENING, AND 850 MB TEMPS DROP SOLIDLY
INTO THE NEGATIVE LOW SINGLE NUMBERS, WITH WILL ASSURE WELL MIXED
BOUNDARY LAYER AND WINDS LIKELY GUSTING 25-30 KNOTS OVER LAKE HURON
OUT OF THE NORTHWEST THURSDAY AND THURSDAY NIGHT. SMALL CRAFT
ADVISORIES WILL LIKELY NEED TO BE EXTENDED FURTHER. GRADUAL
WEAKENING OF THE WINDS THURSDAY NIGHT AND ESPECIALLY ON FRIDAY AS
HIGH PRESSURE ARRIVES.
PREV DISCUSSION
ISSUED AT 120 PM EDT MON OCT 20 2025
AVIATION...
MAINLY CLEAR SKIES - WITH A SMATTERING OF SHALLOW CUMULUS AND A
FILAMENT OR TWO OF CIRRUS - WILL PREVAIL THROUGH THE BALANCE OF THE
DAYLIGHT HOURS. WINDS WILL HAVE A MILD GUST COMPONENT THIS AFTERNOON
- UNDER GOOD MIXING CONDITIONS. THE FLOW WILL QUICKLY QUELL OUT THIS
EVENING AND BACK TO THE SOUTH. OTHERWISE, HIGH CLOUDS WILL
OVERSPREAD THE REGION TONIGHT AS THE NEXT SYSTEM APPROACHES FROM THE
WEST. THE ASSOCIATED WARM FRONT WILL SWING A BAND OF MVFR CLOUDS AND
A RIBBON OF SHOWERS THROUGH THE LOCAL AIRSPACE IN THE PREDAWN HOURS
TUESDAY. THERE WILL ALSO BE A WINDOW OF LOW-LEVEL WIND SHEAR IN THIS
FRONTAL ZONE AS THE SOUTH/SOUTHWEST FLOW ALOFT QUICKLY RAMPS UP TO
40 KNOTS IN THE LOWEST COUPLE THOUSAND FEET. THE MVFR CLOUDS WILL
LINGER INTO THE MID/LATE MORNING BEFORE MIXING OUT WITH A FRESHENING
WEST/SOUTHWEST FLOW - GUSTING TO AROUND 20 KNOTS. THE LOWER
ATMOSPHERE WILL DESTABILIZE THROUGH THE AFTERNOON - ENOUGH TO
SUPPORT SHOWERS AND A POSSIBLE THUNDERSTORM AS THE AFTERNOON HOURS
WEAR ON.
FOR DTW/D21 CONVECTION...THERE IS A SLIGHT CHANCE FOR A THUNDERSTORM
LATE TUESDAY AFTERNOON - MAINLY AFTER 21Z.
DTW THRESHOLD PROBABILITIES...
* MEDIUM FOR CEILINGS AT OR BELOW 5000 FEET TUESDAY MORNING.
* LOW FOR A THUNDERSTORM AFTER 21Z TUESDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 2 AM TUESDAY TO 4 AM EDT THURSDAY FOR
LHZ421-422-441>443.
LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 2 AM TUESDAY TO 4 AM EDT THURSDAY FOR
LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 2 AM TUESDAY TO 4 AM EDT THURSDAY FOR
LEZ444.
DISCUSSION...TF
MARINE.......SF
AVIATION.....MANN
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