929
FXUS63 KDTX 202245
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
645 PM EDT SUN JUL 20 2025
KEY MESSAGES
- DRY WITH SEASONABLE TEMPERATURES THROUGH TUESDAY.
- HOT AND HUMID WEDNESDAY AND THURSDAY. THE HEAT INDEX MAY APPROACH
100 DEGREES ON THURSDAY.
- LOW CHANCE (<15% CHANCE) OF SHOWERS AND THUNDERSTORMS ACROSS THE
TRI-CITIES AND THUMB REGIONS WEDNESDAY. WIDESPREAD CHANCES FOR
SHOWERS AND THUNDERSTORMS RETURN LATE THURSDAY THROUGH FRIDAY.
AVIATION
ONGOING DRY AIR ADVECTION AND THE LOSS OF DIURNAL HEATING WILL
SUPPORT CLEAR SKIES TONIGHT AND MONDAY MORNING. THE DRY AIR
ADVECTION IS BEING DRIVEN BY HIGH PRESSURE NOW EXPANDING FROM
NORTHERN ONTARIO INTO THE SOUTHERN AND EASTERN GREAT LAKES. THE
WEAKENING GRADIENT ASSOCIATED WITH THIS HIGH WILL ALSO SUPPORT LIGHT
NORTHEAST WINDS THROUGH THE PERIOD.
FOR DTW/D21 CONVECTION...THUNDERSTORMS ARE NOT EXPECTED.
THRESHOLD PROBABILITIES...
* NONE.
PREV DISCUSSION
ISSUED AT 326 PM EDT SUN JUL 20 2025
DISCUSSION...
HIGH PRESSURE WILL CONTINUE TO BUILD SOUTHEAST ACROSS GREAT LAKES
THROUGH MONDAY NIGHT, USHERING IN A MUCH DRIER, SEASONABLE AIR MASS.
TONIGHT INTO MONDAY, WINDS BECOME EAST-NORTHEAST AS THE SURFACE HIGH
MOVES ACROSS LAKE HURON AND SOUTHERN ONTARIO. THE EASTERLY COMPONENT
TO THE WIND WILL AID IN KEEPING DAYTIME HIGHS LOCALLY COOLER ALONG
THE LAKE HURON SHORELINE FOR MONDAY, WITH A HIGH PROBABILITY FOR
TEMPERATURES TO ONLY CLIMB INTO THE UPPER 60S/NEAR 70 CLOSE TO THE
LAKESHORE. FURTHER INLAND AND ACROSS THE REST OF SOUTHEAST MICHIGAN,
DAYTIME HIGHS CLIMB INTO THE MID 70S TO LOWER 80S. OVERNIGHT LOWS
WILL ALSO BE QUITE PLEASANT DURING THIS STRETCH, WITH MOSTLY MID 50S
TO LOWER 60S.
TUESDAY WILL FEATURE A WARMER DAY, AS WARM AIR ADVECTION RETURNS
BEHIND THE DEPARTING SURFACE HIGH AND AHEAD OF UPPER-LEVEL RIDGE
BUILDING ACROSS THE MID-MISSISSIPPI REGION. WEATHER CONDITIONS LOOK
TO REMAIN DRY, BUT WE WILL SEE A SLICK UPTICK IN HUMIDITY AND
DAYTIME HIGHS CLIMBING INTO THE LOWER 80S. THE HEAT AND HUMIDITY
WILL CONTINUE TO BUILD EACH DAY, WEDNESDAY AND THURSDAY AS WARM AIR
ADVECTION GRADUALLY INCREASES ACROSS SOUTHEAST MICHIGAN.
UNCOMFORTABLE DEWPOINTS ARE FORECAST TO RETURN AS WELL, WITH SOUTH-
SOUTHWEST FLOW USHERING IN BETTER LOW-LEVEL MOISTURE AND 70 DEGREE
DEWPOINTS. WE WILL KEEP A CLOSE EYE ON CONVECTIVE TRENDS ACROSS THE
REGION AND WHETHER OR NOT ANY MCS ACTIVITY TRACKS OUR WAY. IF WE GET
ROUNDS OF DECAYING CONVECTION OR CLOUD COVER FROM AN UPSTREAM MCS,
THE REMNANT CLOUD COVER COULD HAVE A IMPACT ON TEMPERATURES AND THUS
HEAT INDEX VALUES. RIGHT NOW, NORTHERN LOWER MICHIGAN HAS BETTER
CHANCES AT SEEING ONE OF THESE RIDGE-RIDING MCSS WEDNESDAY MORNING.
BETTER CHANCES FOR CONVECTIVE ACTIVITY ACROSS SOUTHEAST MICHIGAN
ARRIVE LATE THURSDAY AND LINGER THROUGH THE END OF THE WEEK, AS THE
UPPER-LEVEL RIDGE GRADUALLY BREAKS DOWN AND FLOW BECOMES MORE ZONAL
ACROSS THE REGION. AS A SHORTWAVE FEATURE HELPS FLATTEN THE UPPER-
LEVEL RIDGE, A SLOW MOVING COLD FRONT AT THE SURFACE WILL ALSO
SLOWING DROP SOUTHEAST ACROSS THE AREA. THIS FRONT WILL KNOCK DOWN
TEMPERATURES SLIGHTLY, BUT WE WILL STILL MAINTAIN A WARM, MUGGY
ENVIRONMENT. WITH THE SURFACE BOUNDARY AND EMBEDDED VORT MAXES
TRAVERSING THE MORE ZONAL FLOW ALOFT INTO NEXT WEEKEND, WE MAY
MAINTAIN A MORE UNSETTLED PATTERN OVER THE REGION.
&
MARINE...
HIGH PRESSURE OVER LAKE SUPERIOR AND NORTHWESTERN ONTARIO BUILDS
INTO THE CENTRAL GREAT LAKES TONIGHT TO PROMOTE DRY AND BENIGN
MARINE CONDITIONS THROUGH MONDAY. THE INBOUND HIGH CAUSES NORTH WIND
TO SHIFT TO NORTHEAST AND PERK UP TO AROUND 15 KT OVERNIGHT. WAVE
HEIGHTS WILL INCREASE ALONG THE THUMB SHORELINE BUT ARE FORECAST TO
REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA. THE HIGH PROGRESSES INTO
THE EASTERN GREAT LAKES BY TUESDAY, OFFERING LIGHT PREVAILING WIND
FROM THE SOUTHEAST. A WARM FRONT LIFTS INTO THE NORTHERN GREAT LAKES
WEDNESDAY INTO THURSDAY, BRINGING THE NEXT CHANCES FOR THUNDERSTORMS
MAINLY ACROSS NORTHERN LAKE HURON.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....SC
DISCUSSION...JA
MARINE.......TF
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