673
FXUS63 KDTX 211446
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1046 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 SATURDAY NIGHT INTO SUNDAY.
UPDATE
12Z DTX RAOB SHOWED A MODEST EROSION OF THE 850-700MB WARM LAYER,
RELATIVE TO LAST EVENING'S 00Z RAOB, IN ADDITION TO RESPECTABLE
INSTABILITY (1300 J/KG SBCAPE | 1700 J/KG MLCAPE). A SECONDARY PV
FEATURE TIED TO THE SURFACE COLD FRONT OVER WI/NORTHERN LAKE MI IS
SET TO SWEEP INTO SE MI BY EARLY AFTERNOON (~17-19Z) OFFERING THE
NEXT WINDOW FOR POTENTIAL CONVECTION TODAY. WHILE THE ELEVATED WARM
LAYER IS WEAKER, IT STILL PARTIALLY REMAINS IN PLACE WITH CAM
GUIDANCE VARIED ON THE DEGREE OF FURTHER EROSION LATE THIS MORNING.
AS SUCH, COVERAGE TODAY CARRIES A FAIR DEGREE OF UNCERTAINTY EVEN
NOW. HIGHEST CONFIDENCE FOR SCATTERED SHOWERS/STORMS THIS AFTERNOON
IS OVER THE THUMB WHERE THE CORE OF THE PV ANOMALY TRACKS OVERHEAD
AS WELL AS BEING THE REGION WHERE SOUNDINGS ADVERTISE THE WEAKEST
WARM LAYER (ALSO SEEN BY THE AGITATED CU FIELD ACROSS CENTRAL MI).
FOR THE REMAINING SOUTHERN HALF OF THE AREA, CHANCE POPS (~40%)
STILL APPEAR REASONABLE GIVEN THE HIGHER UNCERTAINTY. FOR SEVERE
CHANCES, SPC HAS NOT CHANGED THEIR DAY 1 OUTLOOK, WITH THE
EASTERNMOST SLIVER OF SE MI BEING UNDER A MARGINAL RISK. THAT SAID,
WHILE CAMS ADVERTISE DECREASING SHEAR OVER THE COURSE OF THE DAY
CAN'T RULE OUT AN ISOLATED STRONGER CELL IN THE THUMB AS WELL GIVEN
MLCAPE IS ALREADY NEARING THE 2000 BALLPARK. DAMAGING WIND GUSTS
WOULD BE THE PRIMARY THREAT IN ANY STRONGER STORM WITH HAIL A MORE
LIMITED HAZARD DUE TO SUBPAR MID-LEVEL LAPSE RATES RANGING 6-
6.5C/KM.
PREV DISCUSSION
ISSUED AT 559 AM EDT TUE JUL 21 2026
AVIATION...
ACTIVE DAY ACROSS THE REGION AS A LOW PRESSURE SYSTEM TRACKING EAST
ACROSS THE NORTHERN GREAT LAKES PULLS A COLD FRONT THROUGH THE
REGION. EARLY IN THE FORECAST THERE IS A WAVE TRACKING ACROSS THE
OHIO BORDER WHICH WILL BRING THUNDER CHANCES TO THE DETROIT AREA TAF
SITES. THEN WE TURN OUR FOCUS TO THE COLD FRONT OVER WI THAT WILL
SWEEP THROUGH THE REGION LATER TODAY BRINING ANOTHER ROUND OF
POSSIBLE STORMS. EXPECTING SCATTERED SHOWERS AND THUNDERSTORMS TO
WORK SOUTHWARD FROM MBS TO DTW FROM ABOUT 15Z TO 19Z, AND ACTIVITY
WILL LINGER THROUGH THE DIURNAL CYCLE. ISOLATED STRONG TO SEVERE
STORMS WILL BE POSSIBLE. THE FRONT WILL THEN VEER WINDS FROM SW TO
NW BRINGING STRONGER GUSTS TO AROUND 25 KNOTS. WINDS LOOK TO HOLD
THROUGH THE OVERNIGHT, THOUGH NOT AS GUSTY.
D21/DTW CONVECTION...A WAVE TRACKING ALONG THE OHIO BORDER WILL
BRING THE RISK OF CONVECTION ACROSS THE METRO AIRSPACE. AFTER A
BRIEF LULL THROUGH THE LATE MORNING, THERE MAY BE ANOTHER ROUND OF
CONVECTION IN THE EARLY AFTERNOON. INCLUDED ANOTHER PROB30 GROUP FOR
THIS ACTIVITY WHICH LOOKS SCATTERED.
DTW THRESHOLD PROBABILITIES...
* LOW IN THUNDERSTORMS THIS MORNING AND AFTERNOON.
* LOW FOR WESTERLY CROSSWINDS THIS AFTERNOON.
PREV DISCUSSION...
ISSUED AT 335 AM EDT TUE JUL 21 2026
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.
DTX WATCHES/WARNINGS/ADVISORIES
MI...BEACH HAZARDS STATEMENT THROUGH WEDNESDAY EVENING FOR MIZ049.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 PM EDT WEDNESDAY FOR LHZ421-441>443.
SMALL CRAFT ADVISORY UNTIL 4 PM EDT WEDNESDAY FOR LHZ422.
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.
UPDATE.......KDK
AVIATION.....DRK
DISCUSSION...AA
MARINE.......MV
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