635
FXUS63 KDTX 222255
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
655 PM EDT TUE JUL 22 2025
KEY MESSAGES
- HEAT AND HUMIDITY INCREASE WEDNESDAY WITH HEAT INDICES IN THE
UPPER 80S TO AROUND 90F.
- THURSDAY WILL BE THE HOTTEST DAY OF THE WEEK WITH HIGHS IN THE
LOW TO MID 90S; MAX HEAT INDICES SHOULD PEAK NEAR 100F.
- STORMS ARE POSSIBLE THURSDAY, ESPECIALLY DURING THE EVENING AND
OVERNIGHT HOURS.
- WARM AND MUGGY CONDITIONS PERSIST FRIDAY AND THROUGH THE WEEKEND
WITH ADDITIONAL SHOWER/STORM CHANCES.
AVIATION
VERY QUIET AVIATION WEATHER CONDITIONS THROUGH WEDNESDAY. LIGHT
WINDS TONIGHT WILL EMERGE OUT OF THE SOUTH EARLY WEDNESDAY. THE
AGGRESSIVE HEATING WILL CERTAINLY RESULT IN A FAIR AMOUNT OF DRY
MIXING IN THE BOUNDARY LAYER DURING THE AFTERNOON - BUT NOT ENOUGH
MOISTURE TO PRODUCE MUCH IN THE WAY OF DIURNAL CUMULUS. SOME MINOR
LAKE BREEZE ACTIVITY FROM LAKE ERIE AND ST CLAIR WILL FORCE A SLIGHT
DIRECTIONAL TURN TO THE WINDS AT THE DETROIT AREA TERMINALS LATE
WEDNESDAY AFTERNOON. OTHERWISE, JUST SCATTERED PATCHES OF CIRRUS
FLOATING OVERHEAD FROM UPSTREAM THUNDERSTORM ACTIVITY.
FOR DTW/D21 CONVECTION...NO THUNDERSTORMS WILL OCCUR THROUGH THE TAF
PERIOD.
THRESHOLD PROBABILITIES...
* NONE.
PREV DISCUSSION
ISSUED AT 304 PM EDT TUE JUL 22 2025
DISCUSSION...
SEASONABLY COOL CONDITIONS (A COUPLE DEGREES BELOW CLIMO) CONCLUDE
TODAY WITH ONE MORE COMFORTABLE NIGHT IN STORE AS LOWS DROP INTO THE
UPPER 50S TO LOWER 60S. SURFACE HIGH PRESSURE CONTINUES TO ADVANCE
EASTWARD ACROSS SOUTHERN CANADA, TRACKING INTO THE NORTHEAST
TONIGHT. LIGHT SOUTHEASTERLY WINDS DROP OFF OVERNIGHT WITH SOME
PASSING HIGH CLOUDS OVERHEAD.
HEAT AND HUMIDITY BUILD IN WEDNESDAY AS LONGWAVE RIDGING AMPLIFIES
OVER CENTRAL NORTH AMERICA. THIS MARKS THE DEPARTURE FROM THERMAL
TROUGHING OVER THE GREAT LAKES AS A WARMER AIRMASS ADVECTS
DOWNSTREAM INTO LOWER MICHIGAN. GRADIENT WINDS REMAIN WEAK
WEDNESDAY, VEERING MORE SOUTHEASTERLY, WHICH DELAYS THE ARRIVAL OF
HIGHER DEWPOINTS. LATEST CAMS/BLENDS ARE IN GOOD AGREEMENT BY
KEEPING RAINFALL FROM CONVECTION TIED TO AN UPPER MIDWEST SPEED MAX,
NORTHWEST OF THE CWA. FORECAST SOUNDINGS INDICATE A LACK OF
AVAILABLE MOISTURE AND A CAPPING INVERSION NEAR 5 KFT HOLDS
SBCAPE/MLCAPE VALUES NEAR ZERO, IN SPITE OF SURFACE DEWPOINTS
CREEPING INTO THE LOWER 60S BY MID-AFTERNOON. THE ONE POSSIBLE
EXCEPTION WILL BE FOR PORTIONS OF MIDLAND AND BAY COUNTIES WHERE THE
INBOUND THETAE RIDGE COULD CLIP THE FORECAST AREA, SENDING DEWPOINTS
CLOSER TO 70F. MODERATION OF OVERNIGHT LOWS BEGINS WITH THE
HUMIDIFYING AIRMASS, LIMITING NOCTURNAL COOLING TO AROUND 70F.
A WARM START PRECEDES A HOT AND HUMID DAY ON THURSDAY. EVEN WITH 850
MB TEMPERATURES COMPARABLE TO WEDNESDAY'S (LOW 20C RANGE). NWP
SOLUTIONS REMAIN CONSISTENT IN HIGH TEMPERATURES CLIMBING SOME 10F
ABOVE CLIMATOLOGICAL NORMALS, INTO THE LOW, PERHAPS MID, 90S. GIVEN
THAT DEWPOINTS SHOULD LIKELY HOLD IN THE LOWER 70S, MAX HEAT INDICES
SHOULD PEAK NEAR 100F, PERHAPS A COUPLE DEGREES ABOVE. BARRING ANY
MAJOR SHIFTS IN THE MODEL DATA, A HEAT ADVISORY IS LIKELY FOR MOST,
IF NOT ALL, OF SOUTHEAST MICHIGAN THURSDAY.
INFLUX OF GULF MOISTURE ALONG AN INCREASINGLY CONFLUENT LLJ ENSURES
SHRINKING DEWPOINT DEPRESSIONS DURING THE AFTERNOON THROUGH THE
LOWER PORTION OF THE COLUMN. LOTS OF MID-LEVEL DRY AIR TO OVERCOME
WHICH LIMITS CONVECTIVE POTENTIAL. MODELS ARE LIGHT ON QPF/COVERAGE
FOR DAYTIME STORMS IN SPITE OF 1000-1500 J/KG OF MLCAPE. CAP SHOULD
STILL BE IN PLACE THROUGH MID-AFTERNOON, AND WITHOUT BETTER
SATURATION ALOFT OR DYNAMICS IN-PLACE, 30-35 KFT CONVECTIVE DEPTHS
WILL LARGELY GO UNUSED. CAN'T COMPLETELY RULE OUT ISOLATED PULSE
STORMS, THEREFORE WILL KEEP THE INHERITED SLIGHT CHANCE NBM POPS
AFTER 18Z. PRECIPITATION CHANCES RAMP UP DURING THE EVENING HOURS AS
CAP-LAYER WINDS VEER WESTERLY WITH AN APPROACHING COLD FRONT,
BREAKING DOWN THE INVERSION. EXPECT WIDESPREAD COVERAGE OF SHOWERS
AND STORMS WITH TRANSITING SHORTWAVE PERTURBATION ALONG THE
BOUNDARY, BEFORE ACTIVITY WANES INTO FRIDAY MORNING. SPC DAY 3
MARGINAL RISK WILL MAINLY BE FOR A VERY ISOLATED SEVERE WIND RISK
SHOULD TIMING ALIGN FOR ORGANIZED EVENING MULTICELLULAR CONVECTION,
BEFORE INSTABILITY WANES RAPIDLY. WET-BULB ZERO HEIGHTS SHOULD
LIMITED SEVERE HAIL THREAT.
IT COULD TAKE UNTIL MIDDAY FOR THE FRONTAL BOUNDARY TO DROP SOUTH OF
LOWER MICHIGAN WHICH WOULD KEEP PRECIPITATION IN THE FORECAST FOR
MUCH OF THE DAY. WELL-SATURATED COLUMN (PWATS AROUND 2 INCHES) COULD
SUFFICE IN A PROLONGED WINDOW FOR ISOLATED TO SCATTERED STORMS, EVEN
AS CAPE DENSITY LOOKS LEAN. SLIGHTLY LESS HOT, BUT STILL HUMID
FRIDAY AND THROUGH THE WEEKEND WITH DEWPOINTS HOLDING IN THE LOWER
70S. THE WARM AND MUGGY AIRMASS PRESENTS SEVERAL ADDITIONAL
OPPORTUNITIES FOR SHOWERS/STORMS.
MARINE...
REGION REMAINS UNDER THE INFLUENCE OF HIGH PRESSURE THROUGH THE
EVENING MAINTAINING LIGHT WINDS AND QUIET WEATHER. NORTHERN PLAINS
LOW PRESSURE LIFTS A WARM FRONT THROUGH THE CENTRAL GREAT LAKES
WEDNESDAY STRENGTHENING SOUTHERLY FLOW WITH GUSTS 20-25KTS EXPECTED
OVER THE NORTHERN PORTIONS OF LAKE HURON BY AFTERNOON. LESSER FETCH
AIDS IN KEEPING GUSTS CLOSER TO 15-20KTS FOR THE REST OF THE AREA.
LOW TRACKS ACROSS LAKE SUPERIOR LATE WEDNESDAY-THURSDAY SUPPORTING
SHOWERS AND THUNDERSTORMS OVER THE NORTHERN HALF OF LAKE HURON- A
FEW STORMS COULD BE STRONG TO SEVERE WITH WIND GUSTS >34KTS BEING
THE MAIN HAZARD. THE ASSOCIATED COLD FRONT THEN SAGS SOUTH THROUGH
THE CENTRAL LAKES LATE THURSDAY-FRIDAY EXPANDING STORMS CHANCES OVER
THE REST OF THE REGION, AGAIN A FEW STRONG TO SEVERE STORMS WITH
DAMAGING WIND GUSTS WILL BE POSSIBLE WITHIN THIS ACTIVITY. ACTIVE
WEATHER HAS THE POTENTIAL TO LINGER INTO FIRST HALF OF THE WEEKEND,
PARTICULARLY OVER THE SOUTHERN GREAT LAKES, AS THERE ARE SOME MODEL
SOLUTIONS THAT SUGGEST THE FRONT WILL STALL OUT NEAR THE MI-OH
BORDER BECOMING THE FOCAL POINT STORM DEVELOPMENT/TRACK SATURDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....MANN
DISCUSSION...KGK
MARINE.......KDK
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AT WWW.WEATHER.GOV/DETROIT.
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