748
FXUS63 KDTX 210337
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1137 PM EDT MON JUL 20 2026
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS TONIGHT WILL POSE AN ISOLATED RISK FOR
SEVERE WEATHER.
- ADDITIONAL SCATTERED SHOWERS AND THUNDERSTORMS ON TUESDAY, THEN
MOSTLY DRY CONDITIONS WITH TEMPERATURES DIPPING BELOW AVERAGE DURING
THE MID TO LATE WEEK PERIOD.
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 123Z 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.
PREV DISCUSSION
ISSUED AT 857 PM EDT MON JUL 20 2026
UPDATE...
A CLUSTER OF STORMS STRETCHING FROM THE EASTERN UP INTO NE WISCONSIN
IS TIED TO A REGION OF COUPLED UPPER DIVERGENCE/LOW LEVEL
CONVERGENCE ALONG THE LEAD EDGE OF AN INSTABILITY GRADIENT. THIS
DYNAMICALLY DRIVEN REGION OF ASCENT WILL DRIFT ACROSS NORTHERN LOWER
MI TONIGHT. IT IS NOTABLE THAT CONVECTION HAS BEEN STRUGGLING BETWEEN
THESE STORMS AND THE MCS NOW OVER IOWA AND NW ILLINOIS. REGIONAL
ACARS SOUNDINGS INDICATE A MID LEVEL WARM LAYER ACROSS SOUTHERN
WISCONSIN, LIKELY PROVIDING ENOUGH INHIBITION TO LIMIT CONVECTION
IN THIS AREA. THE 00Z DTX SOUNDING ALSO HAD RESPECTABLE AMOUNT OF
WARM AIR IN THE MID LEVELS. THIS IS LIKELY TO ALSO RESULT IN SOME
LIMIT OF CONVECTIVE POTENTIAL ACROSS SE MI DURING AT LEAST THE EARLY
PORTION OF THE OVERNIGHT HOURS AS THE AFOREMENTIONED LARGER SCALE
FORCING RESIDES TO THE NORTH. REGIONAL WATER VAPOR IMAGERY INDICATES
SOME MID LEVEL SHORT WAVE ENERGY ADVANCING INTO MINNESOTA, EXPECTED
TO ROTATE INTO CENTRAL LOWER MI LATE TONIGHT AND EARLY TUES MORNING,
WHICH SHOULD OFFER A MORE NOTABLE EROSION OF THE MID LEVEL WARM
LAYER. THIS FEATURE WILL ALSO COINCIDE WITH THE LEAD EDGE OF THE
ELEVATED INSTABILITY AXIS. GIVEN THIS AND REGIONAL RADAR TRENDS,
TIMING OF THE BETTER CONVECTION CHANCES HAVE BEEN PUSHED BACK LATER
INTO THE NIGHT. GIVEN THE DEGREE OF FORECAST ELEVATED INSTABILITY AND
STEEP MID LEVEL LAPSE RATES, AN ISOLATED SEVERE RISK LATE TONIGHT CAN
NOT BE RULED OUT.
PREV DISCUSSION...
ISSUED AT 351 PM EDT MON JUL 20 2026
DISCUSSION...
BENIGN CONDITIONS CARRY THROUGH THE AFTERNOON AND EVENING AS
STABILITY HOLDS WITHIN THE WARMER RETURN FLOW OF HIGH PRESSURE NOW
EXITING OFF THE MID-ATLANTIC COAST. SMOKE MODELS AND AQI
OBSERVATIONS INDICATE THE REMNANT WILDFIRE SMOKE WILL LINGER ACROSS
THE REGION, BUT EGLE FORECASTS CALL FOR CONCENTRATIONS TO GRADUALLY
DECLINE SO THE AIR QUALITY ALERT WILL BE ALLOWED TO EXPIRE TONIGHT.
A FAVORABLE SETUP FOR SEVERE WEATHER IS IN PLACE OVER WISCONSIN AND
THE WESTERN UP THIS AFTERNOON AND EVENING AS A POTENT SHORTWAVE
PIVOTS ACROSS THE NORTHERN GREAT LAKES. POTENTIAL FOR SUPERCELLS
EXISTS WEST OF LAKE MICHIGAN WITH ANTICIPATED EVOLUTION INTO A
BROKEN LINE OR CLUSTERS OF STORMS THAT MIGRATE E TO ESE INTO THE
LOWER PENINSULA LATE THIS EVENING. THE BEST SYNOPTIC/UPPER JET
FORCING DRIVING THIS CONVECTION IS SLATED TO PASS OVERHEAD BETWEEN
02Z AND 10Z TONIGHT, OUTPACING THE NARROW PLUME OF UPSTREAM
INSTABILITY THAT WILL LAG BEHIND. REMNANT LOW-LEVEL STABILITY NOTED
IN MODEL SOUNDINGS AND THE NOCTURNAL TIMING DEVOID OF SURFACE-BASED
INSTABILITY LIKELY RESULT IN A WEAKENING TREND AS CONVECTION ARRIVES
LATE THIS EVENING, AND A TRANSITION OF SURVIVING CONVECTION TO AN
ELEVATED CHARACTER. PEAK COVERAGE IS ANTICIPATED BETWEEN MIDNIGHT
AND 6AM, WITH SCATTERED TO NUMEROUS SHOWERS AND EMBEDDED
THUNDERSTORMS. THE MAIN THREAT WOULD BE ISOLATED WIND GUSTS IN
EXCESS OF 40 MPH, BUT THIS CARRIES LOW CONFIDENCE GIVEN THE NEAR-
SURFACE STABILITY. IF UPSTREAM CONVECTION HOLDS TOGETHER AND
MARGINAL INSTABILITY WORKS INTO THE WESTERN SAGINAW VALLEY LATE THIS
EVENING, THIS WOULD BE THE MOST LIKELY AREA TO SEE SEVERE WIND
GUSTS. A MARGINAL RISK FOR SEVERE WEATHER AND EXCESSIVE RAINFALL
EXISTS ACROSS THE AREA TONIGHT.
A POCKET OF FORCED ASCENT ALONG THE LLJ PASSES OVER THE SOUTHERN
FORECAST AREA BETWEEN 12Z AND 15Z TUESDAY MORNING WHICH OFFERS
POTENTIAL FOR A FLARE-UP OF SHOWERS/STORMS, BUT LATEST CAM OUTPUT
SUGGESTS THE HIGHER POTENTIAL FOR CONVECTIVE RESPONSE MAY RIDE THE
CAPE GRADIENT AND TRACK FARTHER SOUTH INTO IN/OH. OTHERWISE,
INCREASING LOW-LEVEL MOISTURE AND STEEPENING MID-LEVEL LAPSE RATES
CAUSE A PLUME OF INSTABILITY TO SPREAD ACROSS LOWER MI TUESDAY
MORNING AHEAD OF THE COLD FRONT SET TO TRACK THROUGH IN THE LATE
AFTERNOON. THIS IS SUFFICIENT TO MAINTAIN A CHANCE OF SCATTERED
SHOWERS AND THUNDERSTORMS, ESPECIALLY ACROSS THE THUMB. WILL MONITOR
AREAS EAST OF I-75 FOR ISOLATED STRONG TO SEVERE STORMS IN THE EARLY
AFTERNOON WHILE INSTABILITY AND SHEAR BRIEFLY REACH A PEAK. BREEZY
CONDITIONS AMIDST COLD AND DRY ADVECTION ENSUE BEHIND THE FRONT WITH
850MB TEMPS FALLING TO AROUND 5C WEDNESDAY MORNING, TRANSLATING TO
LOWS IN THE MID 50S.
COOL AND DRY CONDITIONS PREVAIL WEDNESDAY AND THURSDAY AS HIGH
PRESSURE EASES ACROSS THE REGION, WITH HIGH TEMPS IN THE 70S AND
LOWS IN THE 50S. DRY CONDITIONS PERSIST INTO FRIDAY WITH AN UPTICK
IN TEMPERATURES CLOSER TO THE SEASONAL AVERAGE AS SOUTHERLY RETURN
FLOW ENSUES. THE NEXT WINDOW FOR MORE ACTIVE WEATHER LOOKS TO ARRIVE
LATE IN THE WEEKEND AS THE NEXT COLD FRONT SWEEPS ACROSS THE GREAT
LAKES.
MARINE...
LOW PRESSURE TRACKS ACROSS ONTARIO AND INTO QUEBEC THROUGH THE FIRST
HALF OF THE WEEK, ESTABLISHING AN ACTIVE PATTERN ACROSS THE GREAT
LAKES. BREEZY SOUTHWEST FLOW HAS ALREADY STARTED TO DEVELOP AHEAD OF
A COLD FRONT THAT WILL TRACK THROUGH LATE TONIGHT INTO TUESDAY
MORNING. A LINE OF THUNDERSTORMS IS EXPECTED WITH THE FRONTAL
PASSAGE, TRACKING ACROSS NORTHERN LAKE HURON THIS EVENING AND INTO
LAKE ERIE BY EARLY TUESDAY MORNING. GREATEST POTENTIAL FOR STRONG TO
SEVERE INTENSITY WILL BE OVER NORTH/CENTRAL LAKE HURON THIS EVENING,
WHERE DAMAGING WIND WILL BE THE MAIN THREAT. SCATTERED THUNDERSTORMS
THEN REMAIN POSSIBLE TUESDAY UNTIL A SECOND FRONT SWINGS THROUGH IN
THE EVENING, SHIFTING WINDS FROM WEST TO NORTHWEST AND PROVIDING A
BRIEF OPPORTUNITY FOR GALE FORCE GUSTS CENTERED AROUND 00Z (8PM
LOCAL). SHORT DURATION GUST POTENTIAL PRECLUDES HEADLINES AT THIS
TIME, ALTHOUGH A SHORT-FUSED WARNING IS PLAUSIBLE TUESDAY EVENING IF
OBSERVATIONS WARRANT. BREEZY NORTHWEST FLOW THEN PERSISTS THROUGH
MID-WEEK ALTHOUGH WITH DRIER CONDITIONS AS HIGH PRESSURE BUILDS IN.
SMALL CRAFT ADVISORIES ARE IN EFFECT THROUGH WEDNESDAY, WITH BEACH
HAZARDS CONCERNS FOR TUESDAY-WEDNESDAY AS WELL.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
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 FROM 4 AM TUESDAY TO 10 PM EDT WEDNESDAY FOR
LHZ441>443.
LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 4 AM TO 10 PM EDT TUESDAY FOR LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 4 AM TO 10 PM EDT TUESDAY FOR LEZ444.
AVIATION.....SC
UPDATE.......SC
DISCUSSION...TF
MARINE.......MV
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