410  
FXUS63 KDTX 281928 CCA  
AFDDTX  
 
AREA FORECAST DISCUSSION...CORRECTED  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
303 PM EDT WED SEP 28 2016  
   
DISCUSSION
 
 
FIRST MAJOR VORTICITY SPOKE HAS PIVOTED NORTH TO NORTHWEWT INTO  
SOUTHEAST LOWER MICHIGAN AROUND PARENT UPPER LEVEL LOW PRESSURE  
SYSTEM NOW DROPPING GRADUALLY SOUTH THROUGH THE OHIO VALLEY. RAIN  
SHIELD ASSOCIATED WITH THIS WAVE HAS FEATURED LIGHT TO OCCASIONALLY  
MODERATE RAIN FOR THE MOST PART WITH ISOLATED THUNDERSTORMS ALSO  
NOTED DURING THE DAY ALONG THE NORTHEAST PERIPHERY OF THE MAIN AREA  
OF RAIN WHERE SOLAR INSOLATION FROM THE SOUTHERN TIP OF LAKE HURON  
ON INTO THUMB REGION HAS LED TO A POCKET OF BETTER INSTABILITY.  
 
WHILE THE HIGHER RESOLATION MODEL SOLUTIONS VARY CONSIDERABLY IN  
THE MESOSCALE DETAILS OF THE ANTICIPATED BANDS OF MODERATE TO  
LOCALLY HEAVY RAINFALL, THERE IS A STRONG CONSENSUS OF MAINTAINING A  
RATHER PERSISTENT ARC OF RAIN FROM WESTERN LAKE ERIE/FAR SOUTHEAST  
LOWER MICHIGAN NORTHWESTWARD THROUGH A BULK OF THE 1/2 TO 2/3 OF THE  
FORECAST AREA. WILL INCREASE PRECIPITATION CHANCES INTO THE 80-100  
PERCENT RANGE ALONG THIS AXIS OF MOST PERSISTENT RAIN AND TAPER OFF  
FROM THAT, PARTICULARLY OVER THE NORTHERN FORECAST AREA. THAT SAID,  
EVEN LOCATIONS FROM PARTS OF THE SAGINAW VALLEY BACK TO THE THUMB  
WILL HAVE A GOOD CHANCE OF SHOWERS ALONG WITH A FEW THUNDERSTORMS,  
ESPECIALLY INTO EVENING BEFORE DAYTIME HEATING AND INSTABILITY  
SUBSIDE.  
 
FORECAST THINKING HAS NOT CHANGED MUCH THROUGH THE REST OF THE WEEK  
AS THE UPPER LOW SETTLES SOUTH TO KENTUCKY AND THE FEED OF MOISTURE  
BACK WEST TO NORTHWEST INTO THE AREA REMAINS STEADY. IN FACT, AS AN  
INCREASING LEVELS OF MOISTURE FROM THE ATLANTIC IS DRAWN INTO THE  
AREA WITHIN THIS FLOW AND PRECIPITABLE WATER VALUES CLIMB TO 1.50  
INCHES OR SO, PERIODS OF RAINFALL SHOULD BECOME MORE PROLIFIC FROM  
TONIGHT INTO FRIDAY.  
 
THE MOST PERSISTENT RAIN WILL FOCUCED ROUGHLY ALONG/SOUTH OF M-59  
DURING THIS TIME FRAME, BUT A GRADUAL EXPANSION NORTH THROUGH THE  
REST OF THE AREA SHOULD ALSO OCCUR AS THE OVERALL ABUNDANCE OF  
MOISTURE EXPANDS. WHILE NOT ALL LOCATIONS WILL RECEIVE HEAVY  
RAINFALL AMOUNTS, SEVERAL INCHES OF RAIN CAN BE EXPECTED WHERE  
THE THIS MOST PERSISTENT BANDING BECOMES ESTABLISHED.  
 
WITH THE INCREASE IN MOISTURE AND A MORE OR LESS PERSISTENT SHIELD  
OF CLOUDS OVER THE AREA, TEMPERATURES WILL REMAIN RATHER STEADY WITH  
HIGHS IN THE MID/UPPER 60S FOR THE REST OF THE WEEK AND LOWS IN THE  
MIDDLE 50S.  
 
UPPER LOW PROJECTED TO DRIFT BACK NORTHWARD ACROSS LOWER MICHIGAN  
THIS WEEKEND WITH UNSETTLED WEATHER CONTINUING. UPPER RIDGING BUILDS  
IN EARLY NEXT WEEK AHEAD OF DEEP TROUGHING OVER THE WESTERN CONUS,  
LEAVING SOUTHEAST MICHIGAN DRY WITH A MODEST WARMING TREND INTO  
MIDWEEK.  
 

 
   
MARINE
 
 
STRONG NORTHEAST WINDS WILL DEVELOP OVER THE CENTRAL GREAT LAKES  
TONIGHT AS HIGH PRESSURE SETTLES IN OVER ONTARIO AND AS LOW PRESSURE  
DROPS INTO THE OHIO VALLEY AND THEN KENTUCKY. THIS PATTERN WILL  
REMAIN FAIRLY STAGNANT INTO FRIDAY, PROVIDING A PROLONGED PERIOD OF  
NORTHEAST WINDS WITH SUSTAINED SPEEDS IN THE 15 TO 25 KNOT RANGE.  
THE PERSISTENT NORTHEAST WIND AND LARGE FETCH OVER BOTH LAKE HURON  
AND WESTERN LAKE ERIE WILL ALLOW LARGE WAVES TO BUILD FROM TONIGHT  
INTO FRIDAY NIGHT. SMALL CRAFT ADVISORIES REMAIN IN EFFECT FOR ALL  
MARINE AREAS INTO LATE FRIDAY NIGHT DUE TO LARGE WAVES AND GUSTY  
WINDS. THE AREA OF LOW PRESSURE WILL LIFT BACK NORTHWARD INTO  
MICHIGAN LATE FRIDAY NIGHT INTO SATURDAY. THIS WILL DECREASE THE  
SURFACE PRESSURE GRADIENT AND TURN WINDS MORE TO THE EAST, ALLOWING  
WIND SPEEDS AND WAVE HEIGHTS TO DECREASE OVERNIGHT.  
 
MOISTURE WILL MEANWHILE CONTINUE TO WRAP AROUND THE AREA OF LOW  
PRESSURE INTO THE WEEKEND, PROVIDING NUMEROUS SHOWERS BUT ONLY A LOW  
CHANCE FOR THUNDERSTORMS. THE COOL AIRMASS WILL PROVIDE A CHANCE FOR  
WATERSPOUTS TONIGHT AND THURSDAY AS THE COLDER AIR RESIDES OVER THE  
WARM LAKE WATERS.  
 

 
   
HYDROLOGY
 
 
A LARGE AREA OF UPPER LEVEL LOW PRESSURE WILL REMAIN POSITIONED  
BETWEEN KENTUCKY AND MICHIGAN INTO THE WEEKEND, KEEPING A COOL AND  
SHOWERY PATTERN IN PLACE THROUGH SATURDAY. TOTAL RAINFALL THIS  
EVENING THROUGH FRIDAY NIGHT IS EXPECTED TO GENERALLY RANGE BETWEEN  
1 AND 2 INCHES, ALTHOUGH SOME LOCATIONS NEAR THE OHIO BORDER MAY  
RECEIVE HIGHER AMOUNTS. PERIODS OF STEADIER AND SLIGHTLY HEAVIER  
RAIN ARE EXPECTED TO OCCUR OVER THE NEXT FEW DAYS. THE FIRST IS  
EXPECTED TO IMPACT AREAS ALONG AND SOUTH OF M-59 LATE TONIGHT AND  
THURSDAY, AND ANOTHER IS EXPECTED TO IMPACT JUST ABOUT ALL OF  
SOUTHEAST MICHIGAN LATE THURSDAY NIGHT THROUGH FRIDAY. THE RAIN IS  
EXPECTED TO CAUSE RISES ON AREA CREEKS AND STREAMS, AND MAY ALLOW  
SOME PONDING TO DEVELOP ON ROADWAYS AND LOW-LYING AREAS.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO MIDNIGHT EDT FRIDAY  
NIGHT FOR LHZ421-422-441>443.  
 
LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 8 AM THURSDAY TO MIDNIGHT EDT FRIDAY  
NIGHT FOR LCZ460.  
 
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 8 AM THURSDAY TO MIDNIGHT EDT FRIDAY  
NIGHT FOR LEZ444.  
 

 
 

 
 
DISCUSSION...DG/DT  
MARINE.......HLO  
HYDROLOGY....HLO  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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