447
FXUS63 KDTX 210735
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 AM EDT TUE JUL 21 2026
KEY MESSAGES
- THERE IS AN ISOLATED RISK FOR STRONG TO MARGINALLY SEVERE
THUNDERSTORMS THIS MORNING AND AGAIN EARLY THIS AFTERNOON WITH THE
ARRIVAL OF A COLD FRONT.
- MOSTLY DRY CONDITIONS WITH TEMPERATURES DIPPING BELOW AVERAGE
DURING THE MID TO LATE WEEK PERIOD.
- NEXT CHANCE AT PRECIPITATION OVER THE WEEKEND.
DISCUSSION
A CLUSTER OF THUNDERSTORMS WILL CONTINUE TO SWEEP ACROSS
NORTH/CENTRAL LOWER MICHIGAN ALONG THE LEAD EDGE OF AN INSTABILITY
GRADIENT AND WARM FRONT EARLY THIS MORNING. THERE IS A RESPECTABLE
WARM LAYER ALOFT OVER SOUTHEAST MICHIGAN PER 00Z DTX RAOB LAST
EVENING WITH MESOANALYSIS SHOWING VERY LIMITED SURFACE INSTABILITY.
THIS SHOULD HELP LIMIT OVERALL CONVECTIVE POTENTIAL AS THE CLUSTER OF
THUNDERSTORMS MOVE THROUGH. MID-LEVEL LAPSE RATES WITH 20-30 KNOTS
OF EFFECTIVE BULK SHEAR WILL STILL ALLOW FOR ANY STRONGER UPDRAFTS TO
POSE AN ISOLATED DAMAGING WIND THREAT AS THIS LEAD WAVE WORKS
THROUGH THE SAGINAW VALLEY AND THUMB. THE ARRIVAL OF DEEPER MOISTURE
WILL ALSO SUPPORT BRIEF HEAVY DOWNPOURS.
EVENING SUITE OF HI-RES MODELS ARE STRUGGLING TO CAPTURE THE LACK OF
CONVECTION WITH SOUTHERN EXTENT AS SEVERAL HAVE MUCH HIGHER COVERAGE
THAT REACHES SOUTHERN AREAS OF SOUTHEAST MICHIGAN. THUS, THE
ISOLATED SEVERE THREAT LOOKS CONFINED ALONG AND NORTH OF I-69
THROUGH THE REMAINDER OF THE EARLY MORNING HOURS. THERE IS A
SECONDARY WEAK WAVE THAT MAY MOVE OUT OF NORTHERN IL THAT MAY LEAD TO
AN EXPANSION OF SHOWERS ACROSS SOUTHERN PORTIONS OF THE CWA TOWARDS
12Z, BUT CONFIDENCE IS LOW WITH HOW THIS PLAYS OUT. FOCUS THEN TURNS
TO THE TRAILING SHORTWAVE MOVING OUT OF MINNESOTA AND THROUGH
WISCONSIN THROUGHOUT THE MORNING. THIS WAVE AND ASSOCIATED COLD FRONT
SHOULD LEAD TO BETTER EROSION OF THIS MID LEVEL WARM LAYER AND
PROVIDE AN OPPORTUNITY FOR AN UPTICK IN CONVECTION BEHIND MORNING
CONVECTION AS IT ARRIVES TOWARDS THE EARLY AFTERNOON. INCREASING
INSTABILITY PROFILES WITH MORE FAVORABLE DIURNAL TIMING AND BETTER
CAPE DEPTH WITH BULK SHEAR OF 20+ KNOTS ALLOWS FOR A CHANCE AT
ISOLATED STRONG TO POSSIBLY SEVERE THUNDERSTORM DEVELOPMENT. ACTIVITY
WILL POSE MAINLY A DAMAGING WIND THREAT WITH A CHANCE FOR SMALL HAIL
AS WELL. FAVORED AREAS WILL INCLUDE AREAS EAST OF THE I-75 CORRIDOR,
MAINLY DURING THE EARLY TO MID AFTERNOON PERIOD. ASIDE FROM
THUNDERSTORM POTENTIAL, EXPECT WESTERLY WINDS TO INCREASE THROUGHOUT
THE MORNING WITH BREEZY NORTHWEST WINDS BEHIND THE FRONT LATER TODAY
AS COLD AND DRY AIR ADVECTION COMMENCES.
TEMPERATURES FALL TO WELL BELOW AVERAGE FOR JULY STANDARDS AS 850 MB
TEMPERATURES DIP INTO THE SINGLE DIGITS C BRINGING DAYTIME HIGHS FOR
WEDNESDAY IN THE LOW TO MID 70S. COMFORTABLE HUMIDITY ALSO EXPECTED
WITH DEWPOINTS TO TO AROUND 50 DEGREES. THESE DRY AND COOL
CONDITIONS WILL CARRY OVER INTO THURSDAY. HIGH PRESSURE CONTINUES TO
LIMIT CONVECTIVE POTENTIAL INTO FRIDAY, BUT SOUTHERLY FLOW WILL
BEGIN TO KICK IN TO CLOSE OUT THE WORK WEEK. THIS WILL A SLIGHT
MODERATION IN THE COOLER AIRMASS AND HELP LIFT DAYTIME HIGHS UP TO
AROUND 80 DEGREES. NEXT PROSPECTS FOR PRECIPITATION LOOK TO BE
DURING THE LATER HALF OF THE WEEKEND WHEN A WAVE MOVES OUT OF THE
NORTHERN PLAINS ALONG THE NORTHERN PERIPHERY OF THE SW CONUS RIDGE.
MARINE
A COLD FRONT SWEPT ACROSS THE GREAT LAKES OVERNIGHT, WITH LINGERING
THUNDERSTORMS EXITING EAST OF THE LOCAL WATERS THIS MORNING. BREEZY
WESTERLY FLOW HAS EMERGED POST-FRONT WITH SMALL CRAFT ADVISORIES IN
EFFECT FOR BOTH WIND AND WAVE CONCERNS THROUGH WEDNESDAY. ACTIVE
PATTERN CONTINUES AS AN UPPER LEVEL DISTURBANCE GLANCES OVERHEAD
THIS AFTERNOON, LEADING TO ADDITIONAL THUNDERSTORM CHANCES WHICH
COULD PRODUCE A STRONG TO SEVERE STORM OVER THE WATERS. A SECOND
FRONT THEN SWEEPS ACROSS THE AREA THIS EVENING-OVERNIGHT, SHIFTING
WINDS FURTHER TO THE NORTHWEST AND RAMPING UP WIND GUSTS TOWARD GALE
FORCE FOR A BRIEF PERIOD THIS EVENING (CENTERED AROUND 00Z/8PM
LOCAL). GUSTS SHOULD QUICKLY DIMINISH WITH THE FRONTAL PASSAGE, THUS
PRECLUDING GALE HEADLINES AT THIS TIME. STRONG COLD ADVECTION FILLS
IN BEHIND THE FRONT WHICH KEEPS BREEZY CONDITIONS IN PLACE THROUGH
WEDNESDAY, ALTHOUGH DRIER WITH THE ARRIVAL OF HIGH PRESSURE THAT
PERSISTS THROUGH LATE THIS WEEK.
PREV DISCUSSION
ISSUED AT
AVIATION...
MID LEVEL CAPPING HAS BEEN HOLDING CONVECTION ACROSS SRN LOWER MI AT
BAY LATE THIS EVENING AS THE STRONGER LARGE SCALE FORCING HAS BEEN
LIMITED TO NORTHERN MICHIGAN. A MID LEVEL SHORT WAVE FORECAST TO
ADVANCE ACROSS LOWER MI LATE TONIGHT IN COMBINATION WITH THE
ADVECTION OF HIGHER MID LEVEL INSTABILITY INTO SE MI WILL CONTINUE
TO WARRANT A CHANCE OF THUNDERSTORMS LATE TONIGHT INTO EARLY TUESDAY
MORNING. A FRONTAL PASSAGE TUES AFTERNOON WILL LEAD TO A VEERING OF
THE WINDS TOWARD THE WNW WITH GUSTS AT OR ABOVE 25 KNOTS EXPECTED
GIVEN FORECAST MIXING DEPTHS.
D21/DTW CONVECTION...THE INFLUX OF ELEVATED INSTABILITY DURING THE
09Z TO 12Z TIME FRAME WILL WARRANT THE RISK OF CONVECTION ACROSS THE
METRO AIRSPACE. ALTHOUGH THERE IS A CHANCE FOR ADDITIONAL CONVECTIVE
REDEVELOPMENT LATE TUES MORNING AND EARLY AFTERNOON, THE CHANCES ARE
QUITE LOW (LESS THAN 30 PERCENT) AT THIS TIME.
DTW THRESHOLD PROBABILITIES...
* LOW IN THUNDERSTORMS OVERNIGHT AND TUESDAY MORNING.
* LOW FOR WESTERLY CROSSWINDS TUESDAY AFTERNOON.
DTX WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT FROM 8 AM EDT THIS MORNING THROUGH
WEDNESDAY EVENING FOR MIZ049.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 PM EDT WEDNESDAY FOR LHZ421.
SMALL CRAFT ADVISORY UNTIL 4 PM EDT WEDNESDAY FOR LHZ422.
SMALL CRAFT ADVISORY UNTIL 10 PM EDT WEDNESDAY FOR LHZ441>443.
LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LEZ444.
DISCUSSION...AA
MARINE.......MV
AVIATION.....SC
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