070  
FXUS63 KDTX 011102  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
702 AM EDT TUE SEP 1 2015  
 
   
AVIATION
 
 
EXISTING IFR/MVFR VISIBILITY RESTRICTIONS IN FOG WILL LIFT 13-14Z AS  
DAYTIME HEATING ENSUES. SOME INCREASE IN MOISTURE WILL TODAY WILL  
PROVIDE A GREATER POTENTIAL FOR A PERIOD OF SCT-BKN VFR DIURNAL CU  
FOR THE AFTERNOON PERIOD. SIMILAR ENVIRONMENT TONIGHT WILL AGAIN  
PROMOTE FOG AND/OR LOW STRATUS DEVELOPMENT...FAVORING A PERIOD OF  
LOW MVFR/IFR AT ALL TERMINALS DURING THE EARLY MORNING PERIOD.  
 
//DTW THRESHOLD PROBABILITIES...  
 
* MEDIUM FOR CIG AOB 5KFT AFTER 18Z TODAY  
 

 
   
PREV DISCUSSION
 
ISSUED 340 AM EDT TUE SEP 1 2015  
 
SHORT TERM...TODAY AND TONIGHT  
 
HIGH AMPLITUDE UPPER RIDGING WILL MARK CONDITIONS THROUGH TONIGHT AS  
IT CENTERS SQUARELY OVER SOUTHEAST MICHIGAN. THE INCREMENTAL  
INCREASE IN MEAN THICKNESSES AND HIGH DEGREE OF INSOLATION...UNDER A  
BACKGROUND OF LIGHT SOUTHWEST FLOW WILL EFFECTIVELY NUDGE DAYTIME  
TEMPERATURES UP ANOTHER TIER TODAY. HIGHS OF MIDDLE AND UPPER 80S  
REMAIN ON POINT FOR THIS AFTERNOON GIVEN THE MIXING POTENTIAL AND  
850 MB TEMPERATURES OF 17C. DEWPOINTS INCHING UP INTO THE UPPER 60S  
WILL PROVIDE A NOTEWORTHY UPTICK IN HUMIDITY AS WELL...WITH HEAT  
INDICES CREAPING TOWARD 90 DEGREES.  
 
CONSOLIDATED SHORTWAVE ENERGY AND ACCOMPANYING CORE OF SLIGHTLY  
COOLER MID LEVEL TEMPERATURES WILL CONTINUE TO DRIFT EAST-NORTHEAST  
ACROSS THE OHIO VALLEY TODAY. WHILE THE CENTER OF THIS CIRCULATION  
AND SUBSEQUENT BETTER ASCENT/LAPSE RATES WILL RESIDE SOUTH OF THE  
OHIO BORDER...THERE REMAINS AN OUTSIDE CHANCE FOR A SHOWER/  
THUNDERSTORM TO DEVELOP ACROSS PAR SOUTHERN SECTIONS THIS AFTERNOON  
AND EVENING AS THE OUTER PERIPHERY GLANCES ACROSS THIS REGION. THIS  
CONTINUES TO WARRANT AN ISOLATED MENTION FROM THE OHIO BORDER UP  
THROUGH THE I-94/ANN ARBOR-DETROIT CORRIDOR.  
 
PATTERN PERSISTENCE SUGGESTS ANOTHER ROUND OF AT LEAST PATCHY  
/LOCALLY DENSE/ FOG AGAIN TONIGHT...ALTHOUGH A LIGHT SOUTHWEST WIND  
MAY TEND TO FAVOR A VERY LOW STRATUS DECK INSTEAD. THE ELEVATED  
NEAR SURFACE MOISTURE CONTENT WILL CAP LOWS IN THE VICINITY OF THE  
UPPER 60S MOST LOCALES BY MORNING.  
 
LONG TERM...  
 
UPPER LEVEL RIDGE BUILDING/EXPANDING NORTH THROUGH THE PLAINS  
WEDNESDAY/THURSDAY...ALLOWING FOR MODEST HEIGHT FALLS AND SURFACE  
HIGH PRESSURE TO BUILD IN FROM ONTARIO ON THURSDAY...LEVELING OFF  
OUR WARMUP...AND LIKELY SUPPORTING COOLER TEMPS ON THURSDAY COMPARED  
TO WEDNESDAY. LATEST GUIDANCE AND 850 MB TEMPS UP AROUND 20 C ON  
WEDNESDAY STILL SUGGESTING MAXES NEAR 90 DEGREE.  
 
SEVERAL SHORTWAVES EMBEDDED IN THE UPPER LEVEL NORTHWEST FLOW WILL  
MUDDLE THE FORECAST...AS WELL AS BACKDOOR COLD FRONT SLIDING THROUGH  
WEDNESDAY NIGHT. MODERATE INSTABILITY BUILDING ON WEDNESDAY...WITH  
MLCAPES IN THE 1500-2500 J/KG RANGE. 00Z NAM IS TOO MOIST...WITH  
SURFACE DEW PTS IN THE MID 70S...AND THUS FORECASTED 4000 J/KG OF  
CAPE LOOKS UNREALISTIC. ALTHOUGH 0-6 KM BULK SHEAR VALUES WILL BE  
LOW...BELOW 15 KNOTS...WITH THE DRY MID LEVELS AND CORRESPONDING  
HIGH DOWNDRAFT CAPES (1500 J/KG)...CAN'T TOTALLY RULE OUT ISOLATED  
SEVERE STORMS IF THEY DO IN FACT DEVELOP LATE IN THE DAY. PER 00Z  
GFS...MID LEVEL COLD POOL (-11 C AT 500 MB) TRACKING THROUGH THE  
CENTRAL GREAT LAKES WEDNESDAY NIGHT COULD PROVE SUFFICIENT TO  
DEVELOP/SUSTAIN SOME CONVECTIVE ACTIVITY AS WEAK FRONTAL BOUNDARY  
ALSO PROGRESSES SOUTHWARD. MID LEVEL LAPSE RATE (700-500 MB) ALSO  
LOOK TO BE RUNNING HIGH 7+ C/KM. SHARPENING WEST TO EAST 850-700  
MB THETA-E GRADIENT SETTING UP ON THURSDAY. 00Z EURO IS SLOWEST  
AND STRONGER WITH SHORTWAVE TROUGH OVER THE WESTERN GREAT LAKES  
WEDNESDAY NIGHT...TRACKING INTO LOWER MICHIGAN ON  
THURSDAY...SUPPORTING HIGHER POPS. CLOUDS...LIGHT NORTHEAST  
FLOW...AND POSSIBLE CONVECTIVE ACTIVITY WILL LIKELY KEEP MAXES  
DOWN IN THE LOW TO MID 80S ON THURSDAY.  
 
MARINE...  
 
WARM AND HUMID AIR OVER THE CENTRAL GREAT LAKES WILL PROMOTE LIGHT  
WINDS AND POSSIBLE FOG AT TIMES. A WEAK COLD FRONT PASSING THROUGH  
WEDNESDAY NIGHT WILL BRING THE RISK OF SHOWERS AND  
THUNDERSTORMS WEDNESDAY AFTERNOON THROUGH THURSDAY. LIGHT SOUTHERLY  
WINDS TODAY INTO TOMORROW WILL SHIFT TO A NORTHERLY DIRECTION BEHIND  
THE FRONT AS WE HEAD INTO WEDNESDAY NIGHT...CONTINUING INTO THURSDAY.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...DENSE FOG ADVISORY UNTIL 9 AM EDT THIS MORNING FOR MIZ047>049-  
053>055-060>063.  
 
LAKE HURON...NONE.  
LAKE ST CLAIR...NONE.  
MICHIGAN WATERS OF LAKE ERIE...NONE.  

 
 

 
 
AVIATION.....MR  
SHORT TERM...MR  
LONG TERM....SF  
MARINE.......SF  
 
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE  
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).  
 
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