357  
FXUS63 KDTX 231953  
AFDDTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI  
353 PM EDT WED JUL 23 2014  
   
SHORT TERM
 
THROUGH TONIGHT  
 
SURFACE HIGH PRESSURE HAS BEGUN BUILDING INTO THE AREA IN THE WAKE  
OF THIS MORNINGS COLD FRONT. THIS HIGH WILL MOVE EASTWARD FROM  
SOUTHERN MANITOBA TOWARD THE WESTERN GREAT LAKES BY MORNING. THIS  
WILL KEEP US UNDER WEAK NORTHERLY CAA FLOW THROUGH THE OVERNIGHT  
WHILE ADVECTING DRIER AIR INTO THE AREA. THE HEALTHY DIURNAL CU  
FIELD SHOULD ERODE QUICKLY AFTER SUNSET WITH THE DRY MID LEVEL AIR  
MOVING IN LEAVING MOSTLY CLEAR SKIES FOR THE OVERNIGHT WITH ONLY  
SOME HIGH CLOUDS AROUND. A MID LEVEL PV ANOMALY WILL SURGE SE ACROSS  
THE STATE PULLING THE THERMAL TROUGH AXIS OVER SOUTHERN MI BY EARLY  
THURSDAY MORNING. 850MB TEMPS WILL DROP FROM ABOUT 14C AT PRESS TIME  
DOWN TO AROUND 7C BY 12Z THURSDAY. MIN TEMPS TONIGHT MAY BE TRICKY  
AS THE DRY COOL AIR...BUILDING HIGH PRESSURE...AND DECREASING MID  
LEVEL HEIGHTS WILL WANT TEMPS TO FALL PRETTY GOOD BUT 15-20 KNOT  
FLOW IN THE 850-950MB LAYER WILL KEEP THE LAYER FAIRLY MIXED WHICH  
SHOULD CURB DECOUPLING IN THE BL. OVERALL EXPECT TEMPS TO FALL  
INTO THE LOW 50S...BUT MAY TAKE A WHILE TO GET THERE AND LAST ONLY A  
COUPLE HOURS BEFORE MORNING. IF WINDS SHOULD DROP OFF MORE THAN  
MODELS ARE ADVERTISING...A FEW COLDER LOCATIONS MY DIP INTO THE  
UPPER 40S TO 50. AT THAT POINT DEWPOINTS WILL STEP IN TO LIMIT THE  
AMOUNT OF COOLING.  
 

 
   
LONG TERM
 
 
MASS GRADIENT BETWEEN THE HIGH AMPLITUDE WESTERN U.S. RIDGE AND THE  
NORTHEAST CANADA VORTEX WILL DRIVE STRONGLY CONFLUENT UPPER FLOW  
ACROSS THE GREAT LAKES REGION FOR THE REMAINDER OF THE WORK WEEK.  
ASSOCIATED SURFACE HIGH PRESSURE WILL TRANSLATE ACROSS THE REGION  
DURING THIS TIME AS THE UPSTREAM RIDGE AXIS DEAMPLIFIES AND FOLDS  
EAST IN ADVANCE OF THE COMPACT PAC NW LOW, WHICH IS PROGGED TO EJECT  
ACROSS THE CANADIAN ROCKIES. THE DOMINANCE OF SURFACE HIGH PRESSURE  
MEANS THE RESIDENT AIRMASS WILL HANG TIGHT THROUGH FRIDAY WITH ONLY  
AN INCREMENTAL 2-3 DEGREES OF MODERATION EACH DAY. THE COOL NATURE  
OF THE AIRMASS WILL SUPPORT DEEP DIURNAL BOUNDARY LAYER GROWTH.  
THUS, BOTH THURS AND FRI ARE FORECAST TO FEATURE A HEALTHY COVERAGE  
OF HIGH-BASED FAIR WEATHER CU TO ALONG WITH HIGHS IN THE MID/UPPER  
70S.  
 
PACNW LOW IS PROGGED TO HAVE SIGNIFICANTLY DAMPENED THE UPSTREAM  
RIDGE BY FRIDAY NIGHT. INCREASING LOW-LEVEL FLOW IN ADVANCE OF THIS  
APPROACHING COMPACT CIRCULATION WILL ALLOW DEWPOINTS TO RISE INTO  
THE UPPER 60S IN THE LOWER PENINSULA ON SATURDAY, LEADING TO MODEST  
POTENTIAL FOR SOME DESTABILIZATION. CONVECTIVE POTENTIAL WILL BE  
TIED TO UPSTREAM CONVECTIVE TRENDS, BUT WITH PORTIONS OF LOWER MI  
INVOF THE INSTABILITY GRADIENT AND UNDER THE INCREASING INFLUENCE OF  
ENERGETIC WESTERLY FLOW ALOFT, POTENTIAL FOR SHOWERS WARRANTS AT  
LEAST A CHANCE POP WITH MENTION OF THUNDER FRI NIGHT THRU SAT.  
 
WEAK LOW PRESSURE WILL EXIT TO THE NORTHEAST AND A BRIEF DRY PERIOD  
WILL BEGIN STARING SATURDAY NIGHT. DRY CONDITIONS WILL CONTINUE INTO  
SUNDAY MORNING BEFORE THE NEXT LOW PRESSURE SYSTEM SWINGS THROUGH  
THE GREAT LAKES REGION. THIS LOW WILL BRING ANOTHER ROUND OF RAIN  
SHOWERS AND THUNDERSTORMS TO SOUTHEAST MICHIGAN SUNDAY AFTERNOON  
THROUGH SUNDAY NIGHT. HIGH PRESSURE THEN WILL BUILD INTO THE WESTERN  
GREAT LAKES ON MONDAY AND EVENTUALLY BUILD INTO THE OHIO VALLEY WITH  
DRY CONDITIONS RETURNING ONCE AGAIN THROUGH MID-WEEK. TEMPERATURE  
WISE...HIGHS ON SUNDAY WILL BE IN THE LOW 80S BEFORE MUCH COOLER  
TEMPS FILTER INTO THE REGION BRINGING HIGHS INTO THE LOW TO MID 70S  
THROUGH WEDNESDAY. WHILE LOW TEMPERATURES WILL START OFF IN THE MID  
60S ON SATURDAY NIGHT...THE COOLER AIR WILL DROP LOWS INTO THE MID  
50S THROUGH THE REST OF THE EXTENDED PERIOD.  
 

 
   
MARINE
 
 
MODERATE NORTHERLY FLOW GUSTING TO AROUND 20 KNOTS WILL DECREASE  
TONIGHT AS THE SURFACE PRESSURE GRADIENT WEAKENS AND THE INFLUX OF  
COOL AIR ACROSS THE WATERS EASES. IT WILL...HOWEVER...BE ENOUGH TO  
SUPPORT 3 TO 6 FOOT SIGNIFICANT WAVE HEIGHTS WITHIN THE EXPOSED  
NEARSHORE WATERS OF THE THUMB THROUGH LATE TONIGHT. THE SMALL CRAFT  
ADVISORY FOR THESE AREAS HAS BEEN EXTENDED AN ADDITIONAL 6 HOURS  
ACCORDINGLY. WINDS WILL THEN REMAIN ON THE LIGHT SIDE THROUGH THE  
WEEKEND BEFORE RAMPING UP AGAIN EARLY NEXT WEEK AS ANOTHER ROUND OF  
COOL AIR SPREADS ACROSS THE GREAT LAKES.  
 

 
   
AVIATION
 
ISSUED 142 PM EDT WED JUL 23 2014  
 
//DISCUSSION...  
 
THE PURE STRATUS DECK IN THE WAKE OF THE COLD FRONT IS ABOUT GONE AS  
THE DIURNALLY FORCED CU FIELD KICKS IN FOR THE AFTERNOON. CIGS  
HOLDING AROUND 3KFT THOUGH THEY SHOULD LIFT INTO THE EVENING HOURS  
BEFORE SCATTERING OUT. THE LACK OF HEATING COMBINED WITH HIGH  
PRESSURE AND DRY AIR MOVING INTO THE AREA WILL HELP SCOUR OUT THE  
CLOUDS FOR THE OVERNIGHT PROVIDING CLEAR SKIES. GUSTY WINDS WILL  
CONTINUE THROUGH THIS EVENING BEFORE RELAXING OVERNIGHT. HIGH  
PRESSURE WILL BE OVERHEAD THURSDAY KEEPING WINDS LIGHT WITH A  
DIURNAL CU FIELD DEVELOPING ONCE AGAIN...LIKELY AOA 5KFT.  
 
//DTW THRESHOLD THREATS...  
 
* HIGH CONFIDENCE CEILINGS WILL BE BELOW 5000 FT THROUGH MID  
AFTERNOON.  
 

 
   
DTX WATCHES/WARNINGS/ADVISORIES
 
 
MI...BEACH HAZARDS STATEMENT...MIZ049-MIZ055...UNTIL 4 AM THURSDAY.  
 
BEACH HAZARDS STATEMENT...MIZ063...UNTIL 10 PM WEDNESDAY.  
 
LAKE HURON...  
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS  
FROM PORT AUSTIN TO PORT SANILAC...UNTIL 4 AM THURSDAY.  
 
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT SANILAC TO PORT  
HURON...UNTIL 10 PM WEDNESDAY.  
 
LAKE ST CLAIR...NONE.  
MI WATERS OF LAKE ERIE...NONE.  
 

 
 

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