067  
FXUS63 KDTX 290359  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
1159 PM EDT FRI APR 28 2017  
   
AVIATION
 
 
LATE EVENING OBSERVATIONS CONTINUE TO SUGGEST THE MAIN AREA OF  
SHOWERS WILL REMAIN TO THE NORTH AND SOUTH OF THE SE MICHIGAN AREA  
WITH JUST MINIMAL SHOWER COVERAGE BEFORE ACTIVITY EXITS EASTWARD BY  
SUNRISE. THERE REMAINS A SHORT TIME WINDOW FOR MVFR CEILING CONFINED  
TO LOCATIONS SOUTH OF FNT AS THE REMNANTS OF THE CENTRAL GREAT LAKES  
TROUGH MERGE WITH THE OHIO VALLEY FRONT. A RISING CEILING TREND WILL  
THEN BE AIDED BY DRY AIR ARRIVING ON WIND BECOMING MODERATE  
NORTHEAST FROM HIGH PRESSURE BUILDING OVER THE NORTHERN GREAT LAKES.  
LOW PRESSURE WILL CONCURRENTLY MOVE FROM TEXAS ALONG THE OHIO VALLEY  
FRONT AND BRING THE NEXT ROUND OF RAIN TO OUR REGION SPREADING FROM  
OHIO BORDER NORTHWARD THROUGH THE DAY.  
 
FOR DTW... LIGHT SHOWERS WILL BRUSH THE TERMINAL FROM THE NORTHERN  
FRINGES OF THE OHIO VALLEY FRONT DURING THE MORNING BEFORE SUNRISE.  
MEANWHILE, THE CENTRAL GREAT LAKES FRONT WILL WASH OUT AND MERGE  
WITH THE OHIO FRONT, AND MAY PRODUCE A SHORT PERIOD OF MVFR CEILING  
IN THE PROCESS. THE MAIN CONCERN WILL BE THE WIND TURNING NORTHEAST  
BY SUNRISE AND BECOMING MODERATE IN SPEED THROUGH THE DAY WHICH WILL  
LIKELY DIRECT NE TRAFFIC FLOW OPERATIONS.  
 
//DTW THRESHOLD PROBABILITIES...  
 
* MODERATE CONFIDENCE FOR CEILINGS 5000 FT OR LESS THROUGH THE  
MORNING AND AGAIN SATURDAY NIGHT.  
 

 
   
PREV DISCUSSION
 
 
ISSUED AT 1055 PM EDT FRI APR 28 2017  
 
UPDATE...  
 
AN INTERESTING SET UP THIS EVENING AS A DOUBLE BARREL FRONTAL  
STRUCTURE IS SUPPORTED BY A BROAD 130 KNOT LEVEL JET. THE RESULTING  
COMPLEX FRONTAL CIRCULATIONS RESULTED IN SURFACE BASED CONVECTION  
ALONG THE PRIMARY FRONT OVER THE OHIO VALLEY AND A BROAD BAND OF  
ORDINARY SHOWERS TO THE NORTH OF THE TROUGH/FRONT OVER THE CENTRAL  
GREAT LAKES. WEAKER SHOWERS ON THE FRINGES OF THESE AREAS HAS  
BRUSHED SE MICHIGAN DURING THE EVENING WITH AN OCCASIONAL POCKET  
DEVELOPING OVERHEAD AND MOVING QUICKLY EASTWARD. ALL OF THIS  
CONTINUES TO BATTLE DRY AIR IN THE LOW LEVELS, MAINLY BELOW ABOUT 750  
MB WITH THE END RESULT BEING SCATTERED LIGHT RAIN SHOWERS ACROSS THE  
AREA. THE SAME GENERAL PATTERN WILL CONTINUE THROUGH THE NIGHT  
BEFORE A DIMINISHING TREND IS FORCED MAINLY BY THE SHORT WAVE RIDGE  
BUILDING INTO THE MIDWEST AND GREAT LAKES AHEAD OF THE LARGE SYSTEM  
DIGGING INTO TEXAS. THE RELATIVE BREAK IN THE ACTION WILL LAST  
THROUGH THE MORNING BEFORE A RENEWED SURGE OF MOISTURE DEVELOPS  
THROUGH THE REST OF SATURDAY.  
 
PREV DISCUSSION...  
ISSUED AT 320 PM EDT FRI APR 28 2017  
 
DISCUSSION...  
 
12Z DTX SOUNDING REVEALED AN 850 MB DEW PT DEPRESSION OF 31 C, WITH  
PW VALUE OF 0.42 INCHES. NONE-THE-LESS, LOOKS LIKE THERE WILL BE  
JUST ENOUGH ISENTROPIC ASCENT (295 K) AND MOISTURE ADVECTION  
WORKING THROUGH SOUTHEAST MICHIGAN (MAINLY SOUTH OF M-59) THIS  
EVENING/OVERNIGHT TO SUPPORT SOME LIGHT SHOWERS BASED ON LATEST  
SATELLITE/RADAR TRENDS AND HI-RES SOLUTIONS OF HRRR AND RAP13.  
NEGATIVE LI'S STAY SOUTH OF THE BORDER, AND LEFT THUNDER MENTION  
OUT. SURFACE COLD FRONT SINKING SOUTH AND EXITING JET FORCING UP  
NORTH WILL ALSO SUPPORT CHANCE/SCATTER POPS THERE.  
 
LATEST WATER VAPOR IMAGERY SHOWS HIGHLY AMPLIFIED UPPER LEVEL  
PATTERN OVER NORTH AMERICA, WITH LONGWAVE TROUGH OVER THE ROCKIES  
AND EXCELLENT UPPER LEVEL JET ENERGY TRACKING INTO FOUR CORNERS  
REGION.  
 
A CONVERGENCE OF PACIFIC MOISTURE/PINEAPPLE CONNECTION, COUPLED WITH  
THE GULF OF MEXICO/CARIBBEAN MOISTURE AS LARGE BERMUDA HIGH WILL  
REMAIN IN PLACE THROUGH THE WEEKEND, DRAWING FLOODING CONCERNS BY  
MONDAY AS LARGE AND POWERFUL 500 MB LOW DEVELOPS OVER THE CENTRAL  
CONUS OVER THE WEEKEND. THE SYSTEM WILL BE LIFTING NORTHEAST INTO  
THE MIDWEST (IOWA) BY MONDAY MORNING.  
 
MOISTURE PARAMETERS WILL BE RECORD/NEAR RECORD FOR END OF  
APRIL/START OF MAY THIS FAR NORTH, AS 700 MB DEW PTS APPROACH 5 C  
TOWARD MONDAY MORNING, NEARING TROPICAL STATUS, WITH 850 MB DEW PTS  
EQUALLY IMPRESSIVE CHECKING IN BETWEEN 13-15 C. WITH SUFFICIENT  
DESTABILIZATION/CONVECTIVE ELEMENTS, SHOWALTER INDEX GOING SLIGHTLY  
NEGATIVE AND DEEP WARM CLOUD LAYER, SEVERAL INCHES OF RAINFALL IS  
CERTAINLY POSSIBLE FOR THE SECOND HALF OF THE WEEKEND INTO MONDAY,  
WHICH WILL CREATE FLOOD CONCERNS. UNFORTUNATELY, PLACEMENT OF HEAVY  
RAIN AXIS REMAINS DIFFICULT, BUT GOOD LOW LEVEL FGEN/ISENTROPIC  
ASCENT WILL BE ESTABLISHED BY SUNDAY, AS STRONG HIGH (1032-1034 MB)  
REMAINS PARKED OVER/NEAR JAMES BAY. DO THINK THE SURFACE WARM FRONT  
WILL NOT CLEAR MUCH PAST THE SOUTHERN MICHIGAN BORDER DURING THE DAY  
ON SUNDAY (LAKE ERIE INFLUENCE), WHICH SHOULD HELP SHOWERS PERSIST  
EVEN IN SOUTHERN AREAS, BUT MAX MID LEVEL FORCING DOES APPEAR TO BE  
LINING UP ACROSS NORTHERN SECTIONS OF THE CWA INTO NORTHERN LOWER  
MICHIGAN SUNDAY NIGHT.  
 
AS OF RIGHT NOW, IT APPEARS THE ROBUST MAX 6HR HEIGHT FALL CENTER  
WILL ALREADY BE OVER CENTRAL GREAT LAKES MONDAY AFTERNOON, THUS  
STRONG COLD FRONTAL/OCCLUSION PASSAGE WITH GOOD UPPER LEVEL SUPPORT  
WILL OCCUR EARLY IN THE DAY. MOISTURE/INSTABILITY AXIS PASSING EAST  
BY AROUND NOON, HELPING TO MITIGATE ANY SEVERE THREAT. STILL NOT OUT  
OF THE WOODS SUNDAY NIGHT WITH 65 KNOT JET AT 850 MB, BUT MEAGER  
LAPSE RATES WITHIN THE MOIST AIRMASS SHOULD BE HINDRANCE. BOTTOM-  
LINE, HEAVY RAIN REMAINS THE BIGGEST CONCERN, AND FLOOD WATCH WILL  
LIKELY BE NEEDED FOR THE SECOND HALF OF THE WEEKEND.  
 
LINGERING PRECIPITATION AND GUSTY CONDITIONS WILL BE POSSIBLE MONDAY  
EVENING INTO TUESDAY AFTERNOON AS LOW PRESSURE TRAVELS NORTHEAST  
FROM WISCONSIN INTO THE UPPER PENINSULA. COOLER AIR THAT IS EXPECTED  
TO WRAP AROUND THE LOW AND PUSH INTO MICHIGAN THROUGHOUT MONDAY  
AFTERNOON WILL HELP TO INCREASE STABILITY, MINIMIZING THE CHANCE FOR  
THUNDERSTORMS, AS CONDITIONS REMAIN BREEZY. THE LOW PRESSURE SYSTEM  
WILL CONTINUE TO PUSH NORTHEAST THROUGH QUEBEC LATE TUESDAY INTO  
WEDNESDAY, AS A SURFACE HIGH EDGES EASTWARD ACROSS THE GREAT LAKES  
REGION. THIS WILL ACT TO KEEP US DRY AND WILL KEEP WINDS LIGHT  
THROUGH THE MIDDLE OF THE WEEK, AS TEMPERATURES REMAIN MODERATE WITH  
DAYTIME HIGHS CAPPED IN THE MID-50S.  
 
THE NEXT CHANCE FOR RAIN WILL RETURN THURSDAY INTO FRIDAY AS A WARM  
FRONT SLOWLY PUSHES NORTH INTO THE MI/OH BORDER. THE GEM MODEL RUN  
SUGGESTS THAT THE WARM FRONT WILL PROTRUDE INTO MICHIGAN, ALLOWING  
RAIN SHOWERS TO FALL OVER OUR SOUTHERN COUNTIES THAT BORDER OHIO,  
HOWEVER, SEVERAL OTHER LONG-RANGE MODELS HOLD THE RAIN SOUTH OF  
MICHIGAN THROUGH THE END OF THE WEEK.  
 
MARINE...  
 
GUSTY SOUTHWESTERLY WINDS OVER THE MORNING WILL SLOWLY CONTINUE TO  
DIMINISH THIS AFTERNOON. RELATIVELY LIGHT WINDS ARE THEN EXPECTED  
BY EARLY TONIGHT BEFORE STRONG HIGH PRESSURE BUILDS INTO ONTARIO AND  
LOW PRESSURE BEGINS TO ORGANIZE OVER THE PLAINS. THIS WILL BRING AN  
INCREASE IN NORTH/NORTHEAST WINDS TO THE MARINE AREAS AND  
POTENTIALLY ALLOWING WAVES TO BUILD HIGH ENOUGH TO WARRANT A SMALL  
CRAFT ADVISORY FOR NEARSHORE WATERS OF LAKE HURON AND SAGINAW BAY.  
MONDAY WILL THEN SEE WAVE HEIGHTS DECREASING AS SOUTHERLY WINDS TAKE  
OVER AHEAD OF A COLD FRONT. HOWEVER, WINDS WILL ONCE AGAIN GUST UP  
TO 30 KNOTS. AS THE LOW APPROACHES THE GREAT LAKES REGION THIS  
WEEKEND, AN INCREASINGLY UNSETTLED, WET PATTERN WILL SET UP.  
THUNDERSTORMS WILL ALSO BE POSSIBLE SUNDAY INTO MONDAY.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...NONE.  
LAKE HURON...SMALL CRAFT ADVISORY FROM 3 AM SATURDAY TO 6 AM EDT MONDAY FOR  
LHZ421-422.  
 
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
AVIATION.....BT  
UPDATE.......BT  
DISCUSSION...SF/AM  
MARINE.......SS  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT.  
 
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