830
FXUS63 KDTX 290749
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
349 AM EDT TUE SEP 29 2026
KEY MESSAGES
- AREAS OF FOG POSSIBLE THIS MORNING.
- DRY AND PLEASANT CONDITIONS AGAIN TODAY.
- RAIN CHANCES INCREASE WEDNESDAY AND CONTINUE THROUGH FRIDAY WITH
COOLER TEMPERATURES EXPECTED FRIDAY INTO THE WEEKEND.
DISCUSSION
1018 MB SURFACE HIGH PRESSURE DRIFTS OVERHEAD THIS MORNING, CAUSING
CALM WINDS TO ORGANIZE OUT OF THE SOUTHWEST BY EARLY AFTERNOON. FOR
NOW, WEAK GRADIENT FLOW AND CLEAR SKIES HAS LED TO EARLY STAGES OF
RADIATIVE FOG DEVELOPMENT. THE BEST SIGNAL FOR THIS HOLDS OVER THE
SAGINAW VALLEY/THUMB IN CLOSER PROXIMITY TO LAKE MOISTURE, BUT NOT
OUT OF THE QUESTION TO SEE SOME PATCHY FOG DEVELOP FURTHER SOUTH.
OTHERWISE, EXPECTING ANOTHER SUNNY AND DRY FALL DAY WITH HIGHS IN
THE MID-70S.
IN REGARDS TO OUR LATE WEEK SYSTEM, THERE HAVE BEEN A FEW NOTABLE
TRENDS IN THE 18Z/00Z GUIDANCE. THE FIRST IS WEDNESDAY, IN WHICH
MODELS ARE TRENDING TOWARD A STRONGER SOUTHERN STREAM LOW LIFTING
ALONG THE EASTERN CONUS RIDGE AND INTO NORTHERN LOWER MI. THE
STRONGER WAVE IS ABLE TO FLATTEN THE WESTERN FLANK OF THE RIDGE TO
BRING FORCING/MOISTURE AND THUS RAIN CHANCES INTO THE SAGINAW
VALLEY/THUMB REGIONS WEDNESDAY MORNING. THERE ARE STILL CONCERNS
ABOUT HOW WELL THE LOW LEVELS CAN TOP-DOWN SATURATE GIVEN THE LAG IN
GULF MOISTURE TRANSPORT, BUT RECENT SOUNDINGS SHOW A SHALLOWER LAYER
OF DRY AIR. NBM POPS HAVE INCREASED ACCORDINGLY WITH 40-60% RAIN
CHANCES SHOWING UP NORTH OF M-59 FOR WEDNESDAY. ELSEWHERE, INCREASING
CLOUD COVER IS EXPECTED BUT GREATER DEPTH TO THE DRY AIR SHOULD KEEP
PRECIPITATION LIMITED WEDNESDAY.
SECOND TREND HAS BEEN A MORE UNCERTAIN FORECAST FOR WEDNESDAY NIGHT
INTO THURSDAY AS HURRICANE POLO MAKES ITS EXTRATROPICAL TRANSITION
AND SENDS A WARM FRONT INTO THE GREAT LAKES. THE TREND HAS BEEN FOR
THE BULK OF MOISTURE TRANSPORT TO BE ANCHORED MORE CLOSELY TO THE
DEFORMATION AXIS, KEEPING IT WEST OF SE MICHIGAN. DISJOINTED COLUMN
MOISTURE THUS LIMITS CONFIDENCE IN RAIN CHANCES UNTIL THE NEXT WAVE
OF MOISTURE ARRIVES THURSDAY NIGHT. REGARDLESS OF MOISTURE
TRANSPORT, THE STRONG SW LLJ WILL ENSURE WARMER TEMPERATURES THURSDAY
WITH HIGHS IN THE UPPER 70S AND BREEZY CONDITIONS (20-25 MPH GUSTS).
WHILE MODEL DIVERGENCE INCREASES DAYTIME THURSDAY, IT THEN CONVERGES
AGAIN AS THE COLD FRONT SLIDES THROUGH EARLY FRIDAY MORNING AND
CONNECTS WITH THE SHEARING TROPICAL MOISTURE. THIS WILL BE OUR BEST
CHANCE AT HEAVY RAINFALL AS MODELS HINT AT FRONTOGENETIC ENHANCEMENT
TO THE PRECIPITATION AXIS, EVEN AS MUCAPE HOLDS UNDER 500 J/KG. ONE
OF THE OTHER NOTABLE TRENDS IN THE GUIDANCE WAS THE PHASING OF THE
PACIFIC CLOSED LOW WITH THE NORTHERN STREAM TROUGH, WHICH ULTIMATELY
DELAYS THE CLEARANCE OF THE SURFACE TROUGH TO FRIDAY AFTERNOON. THIS
KEEPS RAIN CHANCES GOING THROUGH AT LEAST THE FIRST HALF OF FRIDAY,
WHICH COMBINED WITH EARLIER START TO PRECIPITATION WEDNESDAY BOOSTS
QPF TOTALS TOWARD AN INCH OR GREATER BY FRIDAY NIGHT. THIS WILL
ESPECIALLY BE THE CASE NORTH OF M-59, WHERE THERE HAS BEEN AN
INCREASE IN THE NUMBER OF 1+ INCH ENSEMBLE MEMBER FORECASTS.
AGGRESSIVE DRYING TREND ARRIVES FRIDAY NIGHT INTO SATURDAY POST-
FRONT. ASSUMING SATURATED GROUND AND FULL CLEARING, RADIATIVE FOG
POTENTIAL RETURNS SATURDAY MORNING. ENCROACHING THERMAL TROUGH WILL
BRING HIGH TEMPERATURES FOR NEXT WEEKEND INTO THE MID-60S WITH LOWS
IN THE 40S.
MARINE
LIGHT AND VARIABLE WINDS MAINLY UNDER 15 KNOTS TODAY AS HIGH
PRESSURE SLOWLY SLIDES EAST OF THE CENTRAL GREAT LAKES. SOUTH TO
SOUTHWEST WINDS WILL THEN INCREASE AHEAD OF THE NEXT COLD FRONT,
WHICH SLOWLY MOVES THROUGH ON THURSDAY. WITH THE 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. A BETTER CHANCE TO BRIEFLY EXCEED 25 KNOTS EXISTS BEHIND THE
FRONT THURSDAY EVENING/NIGHT WITH COLD ADVECTION, AS 850 MB TEMPS
LOWER INTO THE MID SINGLE DIGITS BY FRIDAY MORNING.
ANOTHER LARGE AREA OF HIGH PRESSURE BUILDING IN ON FRIDAY AND
SATURDAY WILL PROMOTE LIGHT 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.
PREV DISCUSSION
ISSUED AT 1145 PM EDT MON SEP 28 2026
AVIATION...
HIGH AMPLITUDE H3 TO H5 RIDGING WILL REMAIN IN PLACE OVER THE
CENTRAL GREAT LAKES THROUGHOUT THE TAF PERIOD. FORECAST DATA
SUPPORTS THE CENTER OF THE SURFACE ANTICYCLONE WILL ARRIVE CAUSING
THE LAST OF THE NORTHERLY GRADIENT COMPONENT TO BREAK DOWN.
EXPECTING MORE IN THE WAY OF CALM AND VARIABLE WINDS TUESDAY
MORNING. GIVEN TIME OF YEAR CONSIDERATIONS WITH LATE SEASON
EVAPOTRANSPIRATION, BR AND FM REMAIN A POSSIBILITY. KEPT WITH THE
INHERITED MENTION FOR TUESDAY MORNING. MOS IS DECIDEDLY MORE BULLISH
ON LIFR AND IFR VISIBILITY RESTRICTIONS AT DAYBREAK. FORECASTED
ENVIRONMENTAL PROFILE SUPPORTS CUMULUS DEVELOPMENT AT THE TOP OF THE
BOUNDARY LAYER TUESDAY AFTERNOON.
D21/DTW CONVECTION...NO THUNDERSTORMS FORECAST THROUGH THE TAF
PERIOD.
DTW THRESHOLD PROBABILITIES...
* LOW FOR CEILING/VISIBILITY AT/BELOW 200 FT / 1/2 SM EARLY TUESDAY
MORNING.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...MV
MARINE.......SF
AVIATION.....CB
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page