113
FXUS63 KDTX 151918
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
318 PM EDT FRI AUG 15 2025
KEY MESSAGES
- HEAT AND HUMIDITY RETURN THIS WEEKEND AS HEAT INDICES PEAK IN THE
UPPER 90S SATURDAY AFTERNOON.
- CHANCE OF THUNDERSTORMS SATURDAY THROUGH SUNDAY MORNING WITH AN
ISOLATED SEVERE STORM POSSIBLE SATURDAY AFTERNOON-EVENING.
- COOLER AND LESS HUMID EARLY NEXT WEEK.
DISCUSSION
SE MI REMAINS UNDER THE WESTERN EDGE OF BROAD SURFACE HIGH PRESSURE
CENTERED OVER WESTERN QUEBEC WITH A PASSING MID-LEVEL TROUGH
SUPPORTING TRANSIENT AREAS OF STRATOCUMULUS ATOP DIURNAL CUMULUS.
AMPLE RESULTANT INSOLATION HAS BROUGHT A RETURN OF HIGHS BACK IN THE
MID-UPPER 80S.
INFLUENCE OF SAID HIGH WANES THROUGH THE NIGHT ALLOWING
SOUTHWESTERLY LOW LEVEL RETURN FLOW TO DEVELOP. THIS DRAWS A PIECE
OF THE UPPER PLAINS AIRMASS INTO THE CENTRAL GREAT LAKES PUSHING
850MB TEMPS WELL INTO THE UPPER TEENS (C) AND HIGHS NEAR 90 AS
SURFACE DEWPOINTS EXCEED 70F. RAIN CHANCES SATURDAY ARE DEPENDENT ON
THE PROGRESSION OF UPSTREAM CONVECTION OVER THE UPPER MIDWEST WHICH
LEADS TO INHERENT LOW PREDICTABILITY/HIGH UNCERTAINTY. A SERIES OF
PV ANOMALIES ARE EXPECTED TO GENERATE NOCTURNAL MCS(S) OVER THE
UPPER MIDWEST/PLAINS THOUGH CAMS ARE STRUGGLING TO HANDLE
INITIATION, PARTICULARLY WITH THE LEAD WAVE OVER THE UPPER
MISSISSIPPI VALLEY. SOME SOLUTIONS LIKE THE HRDPS OR NAM NEST ARE
MORE AGGRESSIVE AT A TRUE MCS TO DEVELOP AND DRIFT SOUTHEASTERLY
TOWARDS SOUTHERN LAKE MICHIGAN/FAR SW LOWER MI GIVEN THE INSTABILITY
GRADIENT AND SOUTHERLY INFLOW WINDS. THESE OUTCOMES WOULD HAVE THE
LARGEST POTENTIAL IMPACT ON LATER DAY CONVECTIVE CHANCES LOCALLY AS
MORE CLOUD DEBRIS WORKS ACROSS SOUTHERN LOWER MI LEADING TO MORE
DIFFERENTIAL HEATING OR, IN THE CASE OF THE NEST, THE REMNANT MCV
SPARKS EARLIER DAY CONVECTION (BY EARLY AFTERNOON). CONVERSELY
OTHERS LIKE THE HRRR/RAP FAIL TO SUFFICIENTLY ORGANIZE LEADING TO
MORE SCATTERED CONVECTION AND LITTLE IMPACTS LOCALLY. MORE CONSENSUS
ON THE SECOND WAVE ROUNDING THE RIDGE INTO LOWER MI BY SATURDAY
AFTERNOON. WHILE EXACTLY HOW MUCH OF THE PRIOR NOCTURNAL CONVECTION
TIED TO THIS WAVE SURVIVES INTO MI IS UNCLEAR, WITH THE INITIAL WAVE
TRACK FAVORED TO OUR SOUTHWEST, MLCAPE WOULD BE ABLE TO BUILD TO
AROUND 1500 J/KG ACROSS SE MI BY TIME OF ARRIVAL. THIS WOULD BE MORE
THAN ENOUGH TO ALLOW FOR LOCAL INITIATION AND/OR RE-INVIGORATION OF
ANYTHING STILL ONGOING FROM WEST MI. A FEW STRONG CELLS CAPABLE OF
DAMAGING WIND GUSTS ARE STILL VERY MUCH IN PLAY AS MID LEVEL WINDS
INCREASE WITH THE WAVE ALLOWING FOR GREATER ORGANIZATION POTENTIAL
IN ADDITION TO WELL-MIXED BOUNDARY LAYERS YIELDING DCAPES OVER 1000
J/KG. ALL OF SE MI HAS BEEN ADDED TO A DAY 2 MARGINAL RISK BY SPC.
COLD FRONT THEN SAGS INTO SOUTHERN LOWER MI SUNDAY. LATEST
DETERMINISTIC RUNS HAVE BEGUN TO CONVERGE ON THIS BOUNDARY STALLING
OUT OVER THE REGION OFFERING LINGERING SHOWER/STORM CHANCES DURING
SUNDAY. ANOTHER SHORTWAVE DROPS OUT OF THE UPPER MIDWEST ALONG THIS
BOUNDARY MONDAY-TUESDAY KEEPING UNSETTLED WEATHER LIKELY FOR THE
FIRST HALF OF THE NEW WORK WEEK.
MARINE
LIGHT SOUTHERLY WINDS (UNDER 15 KNOTS) THIS AFTERNOON OVER THE
CENTRAL GREAT LAKES WILL CONTINUE INTO TOMORROW AHEAD OF A COLD
FRONT. CONTINUED LOW LEVEL WARMING INTO SATURDAY AHEAD OF A COLD
FRONT SHOULD CAP WIND SPEEDS IN THE 15 TO 20 KNOT RANGE. NUMEROUS
SHOWERS AND THUNDERSTORMS DEVELOPING BY SATURDAY EVENING AS THE COLD
FRONT ENTERS THE REGION. THE FRONT IS EXPECTED TO DROP SOUTH OF THE
STATE SUNDAY MORNING, SUPPORTING JUST A CHANCE OF SHOWERS AND
THUNDERSTORMS OVER SOUTHERN LOWER MICHIGAN. 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 SOLD COLD
ADVECTION (850 MB TEMPS LOWERING INTO LOWER TEENS/AROUND 10 C) 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.
PREV DISCUSSION
ISSUED AT 127 PM EDT FRI AUG 15 2025
AVIATION...
STRONG H5-H3 GEOPOTENTIAL HEIGHT RISES IS FORECASTED TODAY AND
TONIGHT AS AN EXTENSION TO UPPER LEVEL RIDGING BUILDS INTO
SOUTHEAST MICHIGAN AND THE CENTRAL GREAT LAKES. THERE IS A VERY GOOD
SIGNAL FOR WARMING ALOFT WITH ACTIVE SUBSIDENCE IN THE 5.0 TO 13.0
KFT AGL LAYER. MODELS SUGGEST CONVECTIVE REMNANTS WITH ASSOCIATED
MOISTURE WILL ARRIVE OVER THE AREA AFTER 15Z SATURDAY. THERE MAY BE
ENOUGH MIDLEVEL MOISTURE AND COOLING TO ERODE STABILITY OVER THE
REGION TO RESULT IN SOME SPORADIC SHOWERS OR THUNDERSTORM ACTIVITY.
UNCERTAINTY IS HIGH AND CONFIDENCE IS LOW, BUT DID INTRODUCE A
PROB30 GROUP FOR -TSRA AT DTW.
FOR DTW/D21 CONVECTION...LOW CHANCE FOR A THUNDERSTORM BETWEEN 19-
22Z SATURDAY.
THRESHOLD PROBABILITIES...
* LOW FOR CEILING AT OR BELOW 5 KFT DURING THE AFTERNOON.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KDK
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