299
FXUS63 KDTX 181656
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1256 PM EDT FRI JUL 18 2025
KEY MESSAGES
- SHOWERS AND THUNDERSTORMS LIKELY ON SATURDAY, SOME OF WHICH MAY
BECOME SEVERE.
- DRY SUNDAY AND MONDAY WITH MAX TEMPS AROUND 80 DEGREES.
AVIATION
RESIDENT DRY AIRMASS HAS LIMITED CLOUD DEVELOPMENT EARLY THIS
AFTERNOON. THERE IS A REGION OF ENHANCED BOUNDARY CLOUDS NEAR LAKE
ERIE - WHICH IS FLIRTING WITH DTW AND THE SOUTH WINDOW OF THE NEAR
AIRFIELD AIRSPACE. THIS CLOUD FIELD WILL CHURN THROUGH THE AFTERNOON
- WITH EXPECTATIONS FOR THE BROKEN CLOUDS STAYING TO THE SOUTH.
ELSEWHERE, LIGHT EASTERLY WINDS WILL BECOME VARIABLE THEN SOUTHERLY
TONIGHT BEFORE SHIFTING TO SOUTHWEST SATURDAY MORNING. MID/HIGH
LEVEL CLOUDS WILL FILTER IN FROM THE WEST STARTING EARLY SATURDAY AS
THE NEXT SYSTEM APPROACHES. THE NEAR SURFACE MOISTURE INCREASE WILL
COMMENCE THROUGH THE MORNING HOURS - HELPING TO ESTABLISH AN
EMERGING CUMULUS FIELD BY MIDDAY. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO BE BECOME PREVALENT ACROSS THE AIRSPACE SATURDAY
AFTERNOON INTO THE EARLY EVENING.
FOR DTW/D21 CONVECTION... THUNDERSTORMS CHANCES RETURN TOMORROW
AFTERNOON - ESPECIALLY AFTER 20Z.
THRESHOLD PROBABILITIES...
* MEDIUM FOR CEILINGS AT OR BELOW 5000-FT SATURDAY MIDDAY AND
AFTERNOON.
* MEDIUM FOR THUNDERSTORMS AFTER 20Z SATURDAY.
PREV DISCUSSION
ISSUED AT 245 AM EDT FRI JUL 18 2025
DISCUSSION...
LOW CLOUDS THROUGH THE MAJORITY OF THE DAY OVER SOUTHEAST MICHIGAN
KEPT MAX TEMPERATURES UNDER 80 DEGREES YESTERDAY, ONLY THE SECOND
TIME THIS MONTH. THERE IS A GOOD CHANCE WE COME UP JUST SHORT OF 80
DEGREES AGAIN TODAY (EVEN WITH A GOOD DEAL OF SUNSHINE) WITH THE
LIGHT EASTERLY FLOW AND COOL START TO THE DAY. GFS/NAM/EURO MOS ALL
INDICATING MAXES HOLDING IN THE UPPER 70S.
BIGGER FORECAST CONCERNS FOR SATURDAY. JET STREAM ALONG THE NORTHERN
CONUS WITH ZONAL FLOW IN PLACE WILL LEAD TO SEVERE THUNDERSTORM
CONCERNS. TIMING OF CONVECTION AND MULTIPLE SHORTWAVES/UPPER LEVEL
PV MAKING A RUN EAST THROUGH THE GREAT LAKES/OHIO VALLEY MAKES FOR
COMPLICATED FORECAST. ONE SUCH UPPER LEVEL WAVE IS COMING OUT OF THE
FOUR CORNERS REGION, WITH A SECOND WAVE AND JET MAX COMING OUT OF
THE NORTHERN ROCKIES. TIMING OF MAIN MOISTURE AXIS/850-700 MB THETA-
E SURGE/RIDGE AXIS LOOKS FAVORABLE, ARRIVING LATE IN THE DAY.
INITIAL, LEAD SURGE/GRADIENT IS IN THE MORNING 9-14Z SATURDAY, AND
WITH DECENT MID LEVEL LAPSE RATES OF 6.5 C/KM - 7 C/KM, THIS LEAD
SURGE MAY BE ABLE TO TRIGGER ELEVATED SHOWERS AND THUNDERSTORMS. IF
THIS ACTIVITY DEVELOPS AND PERSISTS THROUGH THE MORNING HOURS, COULD
HAVE SIGNIFICANT IMPACT ON THE DAYTIME INSTABILITY BUILDING UP, AND
THE FORECASTED MLCAPES IN EXCESS OF 1000 J/KG, TO PERHAPS 2000 J/KG
MAY BE OVERDONE. OTHERWISE, WITH FAVORABLE 0-6 KM BULK SHEAR OF 35 TO
50 KNOTS (NEAR SAGINAW BAY), ORGANIZED/SEVERE STORMS ARE A CONCERN.
WEAK SURFACE REFLECTION MAY BE JUST ENOUGH TO INCREASE 0-1 KM BULK
SHEAR ABOVE 15 KNOTS, SEE NAM/EURO, SUPPORTING AN ISOLATED TORNADO
THREAT AS WELL. SPC HAS INCLUDED SOUTHEAST MICHIGAN IN THE SLIGHT
CHANCE CATEGORY.
THE OTHER SCENARIO, WHICH IS ALSO A GOOD POSSIBILITY IS THE
SHORTWAVE COMING OUT OF THE FOUR CORNERS REGION BECOMES ACTIVE OVER
THE MIDWEST FRIDAY NIGHT AND TRACKS THROUGH THE OHIO VALLEY, ROBBING
US OF THE MOISTURE TRANSPORT AND LIMITING THE INSTABILITY ON
SATURDAY AS WELL. EVEN SO, WOULD THINK AT LEAST A MARGINAL/ISOLATED
THREAT IS STILL VALID IN THIS SCENARIO DUE TO THE SEASONABLY STRONG
MID LEVEL WIND FIELDS.
QUIET WEATHER TO END THE WEEKEND INTO MONDAY WITH A LARGE AREA OF
HIGH PRESSURE TRACKING ACROSS THE CENTRAL GREAT LAKES. HOWEVER,
POTENTIAL ACTIVE WARM FRONT DEVELOPING OVER THE WESTERLY GREAT LAKES
BRINGS A LOW CHANCE OF SHOWERS AND STRONG THUNDERSTORMS MONDAY NIGHT
RIGHT THROUGH THURSDAY, AS THE FAST ZONAL FLOW RETURNS, ALONG WITH
MULTIPLE SHORTWAVES TO CONTEND WITH.
MARINE...
HIGH PRESSURE SPREADS OVER THE CENTRAL GREAT LAKES TODAY PROMOTING
LIGHT AND VARIABLE WINDS. THE HIGH DEPARTS EAST OVERNIGHT WITH WIND
ORGANIZING OUT OF THE SOUTH ON SATURDAY, SENDING A WARM FRONT INTO
THE AREA. THIS WILL BRING THE NEXT ROUND OF HUMID, UNSTABLE WEATHER
WITH SCATTERED SHOWERS AND STORMS THROUGH THE DAY. WIND SPEEDS AND
WAVE HEIGHTS WILL HOLD BELOW SMALL CRAFT ADVISORY CRITERIA BUT MAY
BE LOCALLY HIGHER IN AND AROUND THUNDERSTORMS. THE COLD FRONT CLEARS
THE AREA SUNDAY WITH MODERATE NORTH WIND TO WRAP UP THE WEEKEND.
HIGH PRESSURE PASSING TO THE NORTH CAUSES LIGHT WIND TO VEER TO
EASTERLY ON MONDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....MANN
DISCUSSION...SF
MARINE.......TF
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