624
FXUS63 KDTX 181851
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
251 PM EDT FRI APR 18 2025
KEY MESSAGES
- SHOWERS AND WITH POSSIBLE EMBEDDED THUNDERSTORMS THIS MORNING
MAINLY NORTH OF M-59.
- WARM AND WINDY TODAY WITH HIGH TEMPERATURES WELL INTO THE 70S TO
NEAR 80 DEGREES. SOUTHERLY WIND GUSTS OF 30-40 MPH EXPECTED IN THE
AFTERNOON.
- THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE TODAY-
TONIGHT.
- CHANCE (30-40%) FOR STORMS TO DEVELOP OVER THE SAGINAW VALLEY AND
THUMB THIS EVENING BETWEEN 8-10PM. AN ISOLATED SEVERE STORM CAPABLE
OF DAMAGING WIND GUSTS OR 1" HAIL POSSIBLE WITH ANYTHING THAT
MANAGES TO FORM.
- WIDER SPREAD SHOWERS AND STORMS ARRIVE TONIGHT MAINLY BETWEEN
10PM-5AM AS A SLOW MOVING COLD FRONT CROSSES. CAN'T COMPLETELY RULE
OUT A STRONG STORM BUT CHANCES ARE UNLIKELY. SHOWER CHANCES END BY
SATURDAY MORNING AS THE FRONT FINALLY DEPARTS.
AVIATION
THE LINE OF SHOWER AND THUNDERSTORM ACTIVITY DRIVEN BY INERTIA
GRAVITY WAVE DYNAMICS IS CURRENTLY TRACKING EASTWARD OUT OVER LAKE
HURON. A FEW SURFACE WIND GUST OBSERVATIONS OF 35 TO 60 MPH WERE
ASSOCIATED WITH THIS ACTIVITY. SURFACE WINDS ARE NOW FORECASTED TO
UNIFORMLY RESPOND OUT OF THE SOUTHWEST 20 TO 35 KNOTS THIS AFTERNOON
AHEAD OF APPROACHING COLD FRONT. LOW CONFIDENCE EXISTS ON THE
EXPECTED TIMING AND DURATION OF ADDITIONAL SHOWER AND THUNDERSTORM
ACTIVITY THIS EVENING AND TONIGHT. CONVECTIVE INHIBITION FROM WARM
AIR ALOFT IS EXPECTED TO LIMIT ACTIVITY POSSIBLY UNTIL SOMETIME 04-
09Z. THERE IS SOME MODEL SIGNAL THAT SUGGESTS THUNDERSTORM ACTIVITY
COULD SPLIT THE AREA TO THE NORTH AND SOUTH.
FOR DTW...UNCERTAIN TIME WINDOW FOR THUNDERSTORM DEVELOPMENT WITH
THE PASSAGE OF A COLD FRONT BETWEEN 07Z AND 09Z TONIGHT.
DTW THRESHOLD PROBABILITIES
* LOW FOR CEILING 5000 FT OR LESS THROUGH THIS EVENING, THEN HIGH
TONIGHT.
* LOW FOR THUNDERSTORMS AFTER MIDNIGHT FRIDAY NIGHT.
PREV DISCUSSION
ISSUED AT 1040 AM EDT FRI APR 18 2025
UPDATE...
STRONG WARM ADVECTION ONGOING UPSTREAM IS DRIVEN BY A 55 KT LLJ,
PROVIDING THE MOISTURE AND ELEVATED INSTABILITY FOR AN EARLY MORNING
ROUND OF SEVERE CONVECTION OVER SE WISCONSIN WHERE HAIL UP TO
BASEBALL SIZE WAS REPORTED. THIS CONVECTION IS TRACKING ACROSS LAKE
MICHIGAN AND WEST MICHIGAN WITH SLIGHT WEAKENING AS IT OUTPACES
AVAILABLE MUCAPE, BUT IS GENERALLY HOLDING TOGETHER BETTER THAN MOST
HI-RES GUIDANCE SUGGESTED. LATEST MESOANALYSIS SHOWS THE 500-1000
J/KG MUCAPE GRADIENT IS HELD NEAR THE LAKE MICHIGAN SHORELINE WHICH
SUGGESTS THE STORMS SHOULD CONTINUE TO WANE IN INTENSITY AS THEY
PROGRESS EASTWARD INTO THE AREA. DID INCREASE POPS AND THUNDER
MENTION THROUGH THE MID TO LATE MORNING AS THIS WAVE ROLLS THROUGH,
BUT PROBABILITY FOR SEVERE WEATHER (MAINLY LARGE HAIL) REMAINS LOW
GIVEN CURRENT RADAR PRESENTATION AND RECENT REPORTS.
12Z RAOB OUT OF ILX SAMPLED THE INBOUND EML CHARACTERIZED BY 700-500
MB LAPSE RATES OF 9.3 C/KM AND A 776 MB TEMP OF 17.1 C. THESE VALUES
ARE EXPECTED TO DAMPEN BEFORE THEY REACH THE AREA LATER THIS
AFTERNOON, BUT ARE STILL INDICATIVE OF A STRONG CAP THAT IS EXPECTED
TO MAINTAIN MLCIN TO KEEP MOST OF THE AREA DRY TODAY AFTER THE
MORNING CONVECTION DEPARTS. ADDITIONAL CONVECTION IS EXPECTED TO
FIRE OFF UPSTREAM THIS AFTERNOON NEAR A DEVELOPING LOW PRESSURE
CENTER AND RIDE THE FRONTAL BOUNDARY AND INSTABILITY GRADIENT
NORTHEAST. THIS MAY REACH PORTIONS OF THE SAGINAW VALLEY LATE
AFTERNOON TO EARLY EVENING AND OFFERS POTENTIAL FOR ISOLATED SEVERE
STRONG TO SEVERE STORMS GIVEN A WEAKER CAP AND MARGINAL SURFACE
BASED INSTABILITY AVAILABLE THERE. LARGE HAIL AND DAMAGING WIND
APPEAR WILL BE THE MAIN THREATS BUT A TORNADO WOULD BE POSSIBLE AS
WELL, PARTICULARLY IF ANY STORM LATCHES ONTO THE HELICITY AROUND THE
WARM FRONTAL BOUNDARY STALLED IN THE VICINITY.
PREV DISCUSSION...
ISSUED AT 330 AM EDT FRI APR 18 2025
DISCUSSION...
UPPER MIDWEST SURFACE LOW PRESSURE SLOWLY TRACKS INTO THE GREAT
LAKES TODAY WITH THE ELEVATED PORTIONS OF ITS ATTENDANT WARM FRONT
CURRENTLY WORKING ACROSS LOWER MI THIS MORNING. WHILE THERE IS
HEALTHY MOISTURE TRANSPORT AT/ABOVE 850MB WITH THIS FRONT, OVERALL
ASCENT ALONG THIS PORTION OF THE FRONT IS RATHER LACKLUSTER OWING TO
THE DETACHMENT FROM THE PARENT WAVE/TROUGH WHICH HAS RESULTED IN
ONLY A NARROW ARC OF SHOWERS ON RADAR. DESPITE THESE RETURNS,
REMNANT DRY NEAR-SURFACE LAYER FROM DEPARTING HIGH PRESSURE IS
RESULTING IN ACTUAL SURFACE OBS CLOSER TO SPRINKLES OR A BRIEF LIGHT
SHOWER. THIS ACTIVITY CLEARS THE AREA BY 09Z AS THE SURFACE WARM
FRONT BEGINS LIFTING THROUGH SE MI. ADDITIONAL SHOWERS, PERHAPS WITH
A RUMBLE OF THUNDER, ARE POSSIBLE LATE MORNING ALONG THIS FRONTAL
BOUNDARY TIED TO THE PASSAGE OF A STRONG RIBBON OF VORTICITY AND ITS
REMNANT OVERNIGHT CONVECTION FROM THE NORTHERN PLAINS- BEST
POTENTIAL NORTH OF I-69. BY AFTERNOON ALL, OR NEARLY ALL, OF SE MI
WILL RESIDE WITHIN THE SYSTEM'S WARM SECTOR AS THE SURFACE FRONT
STALLS OUT SOMEWHERE BETWEEN THE TIP OF THE THUMB AND ALPENA.
FORECAST SOUNDINGS STILL SUGGEST AN EML LIFTS OVERHEAD BEHIND THE
SURFACE WARM FRONT SUPPORTING A STRONG ENOUGH CAPPING INVERSION TO
KEEP THE AREA DRY INTO THE FIRST HALF OF THE EVENING. POTENTIAL
EXCEPTION IS THE NORTHERN THUMB/TRI-CITIES, THOUGH THIS IS HIGHLY
DEPENDENT ON THE EXACT POSITIONING OF THE FRONT, AS A SERIES OF
SMALL VORTICITY ANOMALIES RIDE ALONG THE FRONT GENERATING SCATTERED
SHOWERS/THUNDERSTORMS THROUGH THE AFTERNOON-EVENING. THE BEST
CHANCES FOR THIS STILL LOOKING TO OCCUR OVER NORTHERN LOWER MI SO
HAVE KEPT RUNNING POPS (15-30%) LARGELY THE SAME FROM THE PRIOR
FORECAST FOR THESE NORTHERNMOST AREAS.
BETTER CHANCES FOR STORMS COMES LATE EVENING AS THE SLOW MOVING
ATTENDANT COLD FRONT FINALLY BEINGS TO CROSS SOUTHERN LOWER MI.
WHILE THE MAIN WINDOW FOR THIS ACTIVITY COMES AFTER 03Z, THERE IS
SIGNAL AMONGST A SUBSET OF THE HIGH RES SOLUTIONS (00Z ARW & 03Z RAP
IN PARTICULAR) FOR SCATTERED CONVECTIVE DEVELOPMENT AROUND 00Z AS
THE EML PEELS AWAY WEAKENING THE CAP COINCIDENT WITH A SURGE IN
LOWER LEVEL (<850MB) THETA-E FOLDING INTO SOUTH-CENTRAL MI. THIS
FALLS MORE FAVORABLY WITHIN THE DIURNAL CYCLE WITH MLCAPE STILL
HOLDING AROUND 1000J/KG AND MID-LEVEL LAPSE RATES AROUND 7 C/KM;
THOUGH SHEAR IS A BIT MORE MARGINAL IN THIS TIMEFRAME AT ONLY AROUND
30-35KTS. SHOULD THIS CONVECTION OCCUR (CONFIDENCE IS LOW IN ACTUAL
OCCURRENCE), AN ISOLATED ORGANIZED CELL CAPABLE OF DAMAGING WINDS
GUSTS AND/OR 1" HAIL WOULD BE POSSIBLE NORTH OF M-59, IF NOT
CONFINED ALONG/NORTH OF I-69. THIS WINDOW IS LIKELY THE ""BEST""
CHANCE FOR SE MI TO SEE A SEVERE STORM FRIDAY THOUGH LIKE MENTIONED
PRIOR, THERE IS LOW CONFIDENCE IN CONVECTION DEVELOPING DURING THIS
EVENING TIMEFRAME. THE ACTUAL FRONTAL CONVECTION THEN CROSSES SE MI
BETWEEN ~03-09Z. NOCTURNAL TIMING GREATLY LIMITS AVAILABLE
INSTABILITY WITH MUCAPE VALUES HOLDING UNDER 1000J/KG BY THIS TIME
WITH THE ONLY FAVORABLE FACTOR FOR ORGANIZED STORMS IS BULK SHEAR
INCREASING TO 40-45KTS. BECAUSE OF THIS, CAN'T COMPLETELY RULE OUT
AN ISOLATED STRONG TO SEVERE STORM TONIGHT THOUGH OVERALL
PROBABILITY IS LOW. DUE TO ALL THESE FACTORS, ALL OF SE MI HAS BEEN
DOWNGRADED TO A DAY 1 MARGINAL RISK FROM SPC.
COLD FRONTAL BOUNDARY CLEARS THE REGION BY SATURDAY MORNING ENDING
FURTHER SHOWER CHANCES BEFORE IT EVENTUALLY STALLS OUT OVER CENTRAL
OH/IN. MID-UPPER TROUGHING SLIDES EAST OF THE REGION BY LATE DAY
SATURDAY ALLOWING SURFACE HIGH PRESSURE TO BRIEFLY BECOME
ESTABLISHED OVER THE CENTRAL GREAT LAKES SATURDAY NIGHT-EARLY
SUNDAY. NORTHEASTERLY SURFACE FLOW AROUND THIS HIGH DRAWS IN COOLER
AIR SOUTH OUT OF NORTHERN ONTARIO DROPPING 850MB TEMPS TO AROUND 0C.
HIGHS SUNDAY ONLY REACH THE MID TO LOW 50S FOR AREAS OUTSIDE THE
THUMB WITH THE BULK OF THE THUMB LIKELY REMAINING IN THE 40S GIVEN
FLOW DIRECTLY OFF THE OPEN WATERS OF LAKE HURON.
A SOUTHERN STREAM TROUGH EJECTING OUT OF THE DESERT SOUTHWEST PHASES
WITH A WEAKER NORTHERN STREAM SHORTWAVE OVER MIDWEST LATE SUNDAY
LIFTING THE AFOREMENTIONED STALLED FRONTAL BOUNDARY BACK NORTH AS A
WARM FRONT. MILD BUT RAINY MONDAY AS THE MATURE SURFACE LOW LIFTS
INTO THE WESTERN GREAT LAKES AND TOWARDS THE ST MARY'S RIVER. WINDY
CONDITIONS (GUSTS >30MPH) ALSO LOOKING PROBABLE MONDAY GIVEN THE
CURRENT FAVORED TRACK OF THE LOW CENTER JUST TO OUR WEST SETTING UP
A STRONG GRADIENT ACROSS THE CENTRAL GREAT LAKES.
MARINE...
AN ACTIVE STRETCH OF WEATHER IS EXPECTED TODAY THROUGH SATURDAY
MORNING. THIS BEGINS WITH A CLUSTER OF SHOWERS AND THUNDERSTORMS
THAT ORIGINATED ALONG THE UPSTREAM FRONTAL ZONE, BUT WERE DRIVEN
EASTWARD BY A LOW LEVEL DISTURBANCE. THIS SAME DISTURBANCE IS ALSO
CONTRIBUTING TO ADVISORY LEVEL WINDS AND WAVES ACROSS THE NEARSHORE
ZONES. DEPARTURE OF MORNING CONVECTION GIVES WAY TO A QUIETER
AFTERNOON AND EARLY EVENING UNTIL THE AFOREMENTIONED FRONTAL ZONE
REACHES LOWER MICHIGAN TONIGHT. WINDS AHEAD OF THE FRONT VEER TO THE
SOUTHWEST AND SUBSIDE BELOW ADVISORY THRESHOLDS. THE MAIN IMPACT OF
THE FRONT WILL BE THE REINVIGORATION OF SHOWERS/STORMS ALONG IT, IN
WHICH SOME COULD BECOME STRONG TO SEVERE ESPECIALLY IF THEY DEVELOP
EARLIER IN THE EVENING. THE FRONT EVENTUALLY SETTLES SOUTH OF LAKE
ERIE BY SATURDAY MORNING, BRINGING AN END TO PRECIPITATION CHANCES.
THIS WILL BE FOLLOWED BY GENERALLY BENIGN MARINE CONDITIONS FOR THE
WEEKEND UNTIL THE NEXT WAVE OF LOW PRESSURE IMPACTS THE REGION EARLY
NEXT WEEK.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR LHZ421-422-
441>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.
AVIATION.....
UPDATE.......TF
DISCUSSION...KDK
MARINE.......MV
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AT WWW.WEATHER.GOV/DETROIT.
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