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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
140 PM EDT TUE APR 28 2015


.AVIATION...

DAYTIME HEATING HAS LED TO THE SLOW DEVELOPMENT OF THE CU FIELD 
ACROSS PARTS OF THE AREA ALTHOUGH NOT AS EXPANSIVE DUE TO THE LACK 
OF MOISTURE. THERE IS STILL A SHORT WINDOW FOR CU TO DEVELOP YET 
LATER THIS AFTERNOON.  WITH HIGH PRESSURE CONTINUING OVER THE AREA 
THROUGH THE OVERNIGHT HOURS...WINDS WILL WEAKEN AND BECOME VARIABLE 
LATER THIS EVENING.  CLOUDS DO START INCREASING IN COVERAGE ONCE 
AGAIN ON WEDNESDAY WITH VFR CONDITIONS PREVAILING THROUGH THE TAF 
CYCLE.

FOR DTW...ASIDE FROM THE POTENTIAL FOR DAYTIME CLOUD ENHANCEMENT 
THIS AFTERNOON...A WEAK SFC GRADIENT WILL SUPPORT LAKE BREEZE 
DEVELOPMENT IN THE 21 TO 23Z TIME FRAME.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM IN CLOUDS AT OR BELOW 5000 FT THIS AFTERNOON AND INTO THE 
  EVENING.

&&

.PREV DISCUSSION...ISSUED 327 AM EDT TUE APR 28 2015 

SHORT TERM...TODAY AND TONIGHT

THE DEEP CYCLONIC FLOW WHICH HAS BEEN IN PLACE ACROSS LOWER MI THE 
LAST SEVERAL DAYS WILL FINALLY LOOSEN ITS GRIP ON THE AREA TODAY AS 
THE ELONGATED MID LEVEL TROUGH AXIS PUSHES OFF THE EAST COAST. MID 
LEVEL RIDGING WILL IN TURN BUILD INTO LOWER MI FROM THE WEST. THE 
REGIONAL WATER VAPOR LOOP IS IN SUPPORT OF MODEL SOLUTIONS DEPICTION 
OF A WEAK MID LEVEL IMPULSE OVER NRN LOWER MI. THIS FEATURE WILL 
SLOW CONSIDERABLY AS IS ADVANCES INTO SRN LOWER MI THIS AFTERNOON 
DUE TO THE WEAKENING IN THE MID LEVEL FLOW. HI RES SOLUTIONS SUGGEST 
THIS FEATURE WILL SUSTAIN A WEAKNESS IN THE MID LEVEL HEIGHT FIELD 
OVER LOWER MI TODAY...WHICH WILL AID IN THE DEVELOPMENT OF A 
THERMALLY INDUCED SFC TROUGH OVER LOWER MI. 

REGIONAL SATELLITE DATA OVERNIGHT HAS SHOWN A CONSIDERABLE AMOUNT OF 
CLOUD COVER ACROSS LAKE HURON. ONGOING N-NE LOW LEVEL FLOW HAS 
BROUGHT SOME INCREASE IN LOW LEVEL MOISTURE INTO SE MI...ALTHOUGH THE 
CLOUDS HAVE THUS FAR HAD A DIFFICULT TIME SUSTAINING THEMSELVES. BOTH 
00Z DTX AND APX SOUNDINGS SHOWED A DEEP LOW LEVEL INVERSION. SLIGHT 
WARMING ABOVE THE INVERSION BASE TODAY SHOULD SUSTAIN THIS INVERSION 
DESPITE DAYTIME HEATING. THE LOW LEVEL FLOW WILL BACK TOWARD THE 
NORTHWEST THIS MORNING...THUS DECREASING THE FEED OF LOW LEVEL 
MOISTURE INTO SE MI. ENOUGH MOISTURE SHOULD STILL BE IN PLACE UNDER 
THE INVERSION TO ALLOW THE ONSET OF DAYTIME HEATING TO CAUSE THE 
RAPID DEVELOPMENT OF A BROKEN TO OVERCAST STRATO CU FIELD. THESE 
CLOUDS SHOULD HAVE DIFFICULTY DECREASING DURING THE LATTER HALF OF 
THE DAY CONSIDERING THE DEPTH OF THE INVERSION AND NO REAL PUSH OF 
DRIER AIR. YESTERDAYS TEMPS CERTAINLY STRUGGLED WITH THE CLOUD 
COVER. MODEL SOUNDINGS SUGGEST THE MOISTURE DEPTH WILL NOT BE AS 
HIGH AS YESTERDAY AND THERE APPEARS TO BE A BETTER POTENTIAL FOR 
SOME INTERVALS OF SUN TODAY...ESPECIALLY THIS MORNING. SO OPTIMISTIC 
AFTERNOON HIGHS AROUND 60 WILL BE MAINTAINED. THE LOSS OF DAYTIME 
HEATING WILL LEAD TO SOME EROSION OF THE CLOUDS THIS EVENING. THE 
BOUNDARY LAYER WILL RAPIDLY DECOUPLE UNDER ANY PERIOD OF CLEAR SKIES 
TONIGHT GIVEN THE WEAK GRADIENT FLOW. THIS WILL SUPPORT FCST MIN 
TEMPS DOWN INTO THE 30S TONIGHT /40S IN URBAN DETROIT/.

LONG TERM...WEDNESDAY THROUGH MONDAY

MID TO UPPER LEVEL RIDGING IN PLACE AT 12Z WEDNESDAY WILL BREAK DOWN 
RAPIDLY AS A ROBUST SHORTWAVE WILL DIVE SOUTHWARD THROUGH THE 
WESTERN GREAT LAKES DURING THE DAY. AN ATYPICAL SYSTEM TO DEAL WITH 
GIVEN THE LARGER WAVLENGTH OF THE SHORTWAVE ALONG WITH THE NEAR 
STRAIGHT SOUTHWARD TRAJECTORY OF THE CIRCULATION. NORTHERLY SYSTEMS 
TEND TO BE DRY ONES FOR THE AREA. MODELS PROG DRY AIR TO BEGIN THE 
DAY...WITH DEEPER SYSTEM MOISTURE NOT PIVOTING INTO THE WESTERN AND 
CENTRAL SECTIONS OF THE LOWER PENINSULA UNTIL AFTER 20Z. FORECASTED 
THERMODYNAMIC PROFILES SUGGEST DIURNAL HEATING WILL BE NEEDED TO 
GENERATE A CONVECTIVELY UNSTABLE (<100 J/KG MUCAPE) LAYER BETWEEN  
SHOWERS 5-12 KFT AGL LAYER. A GOOD CONSENSUS EXISTS THE BEST 
POTENTIAL WILL RESIDE ACROSS THE WESTERN PART OF THE STATE. DRIER 
AIR IN THE LOWER TROPOSPHERE STILL SUPPORTS TEMPERATURES REACHING 
THE LOW TO MID 60S.

THE QUESTION THEN BECOMES WHAT SORT OF POTENTIAL WILL EXIST FOR 
CONTINUED SHOWERS WEDNESDAY NIGHT WITH THE LACK OF DIURNAL HEATING. 
MODELS SEEM TO BE CONVERGING ON A SIGNAL THAT HEART OF THE CYCLONIC 
CIRCULATION AND DEEPER MOISTURE WILL TUMBLE OR WOBBLE RAPIDLY DOWN 
INTO SECTIONS OF IL/IN FOR WEDNESDAY NIGHT. MODELS ARE NOW 
STRUGGLING TO KEEP SHOWERS GOING...LIKELY DUE TO THE LACK OF A 
FORCING MECHANISM. WILL KEEP A LOW CHANCE MENTION GOING OUT OF 
RESPECT FOR THE CYCLONIC FLOW. OVERALL A LOW CHANCE/LOW QPF TYPE 
FORECAST.

FORECAST DETAILS AND REASONING HAS CHANGED SINCE 24 HOURS AGO 
CONCERNING THE THURSDAY FORECAST. A CONSENUS IS EMERGING THAT 
COLDEST OF MIDLEVEL AIR WILL REMAIN WEST OF MICHIGAN. IN 
FACT...MODEL DATA IS NOW SUGGESTING THAT WARMER 850MB TEMPERATURES 
WILL ADVECT FROM THE NORTHEASTERN UNITED STATES WESTWARD INTO THE 
CENTRAL GREAT LAKES. THE INBOUND AIRMASS WILL CONTAIN HIGHER Theta-e 
CONTENT AS WELL. NWP SUGGESTS A POTENTIAL FOR DECENT CONVECTIVE 
DEPTHS DEVELOPING DIURNALLY AND WILL CONTINUE THE LOW CHANCE POPS 
FOR THURSDAY. THE MESSAGE IS AGAIN A LACK OF A FORCING 
MECHANISM/TRIGGER. TEMPEATURES ON THURSDAY ARE NOW EXPECTED TO REACH 
THE 60 DEGREE MARK.

MARINE...

FAVORABLE MARINE CONDITIONS TODAY AS SURFACE HIGH PRESSURE WILL 
RESIDE ACROSS THE CENTRAL GREAT LAKES...PROVIDING LIGHT WINDS AND 
LOW WAVES. WEAKENING HIGH PRESSURE WILL BE REPLACED BY WEAK SURFACE 
TROUGHING TONIGHT...BUT WINDS ARE STILL EXPECTED TO REMAIN BELOW 20 
KNOTS. HOWEVER...WINDS WILL BE NORTHERLY...AND THERE COULD BE 
ONSHORE COMPONENT TO SUPPORT SLIGHTLY HIGHER WAVES ALONG THE 
NEARSHORE WATERS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....SS
SHORT TERM...SC
LONG TERM....CB
MARINE.......CB


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