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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
658 AM EDT SUN APR 26 2015


.AVIATION...

THE UPPER LEVEL LOW PRESSURE SYSTEM OVER PORTIONS OF EASTERN NORTH 
AMERICA WILL EXPAND IN SIZE TODAY AND TONIGHT. THIS LOW WILL AGAIN 
INFLUENCE THE WEATHER ACROSS SOUTHEASTERN MICHIGAN. TWO WAVES OF 
MIDLEVEL ENERGY AND MOISTURE WILL ROTATE BACK INTO SOUTHEASTERN 
MICHIGAN FROM THE NORTHEAST. THIS EVOLUTION WILL YIELD VFR CIGS THIS 
AFTERNOON EVENTUALLY TRANSITIONING TO MVFR OVERNIGHT. WILL LEAVE 
PRECIPITATION OUT OF THE TAF FORECAST AT THIS TIME AS A CONSIDERABLE 
AMOUNT OF UNCERTAINTY STILL EXISTS.

//DTW THRESHOLD PROBABILITIES...

* HIGH CONFIDENCE IN CIGS BELOW 5000 FT LATE TONIGHT. LOW CONFIDENCE 
  IN EXACT TIMING.

&&

.PREV DISCUSSION...ISSUED 358 AM EDT SUN APR 26 2015 

SHORT TERM...TODAY AND TONIGHT

SUPPRESSION OF GEOPOTENTIAL HEIGHTS OVER THE SOUTHEASTERN UNITED 
STATES WILL ALLOW THE BROADENING CLOSED LOW ANOMALY OVER PORTIONS OF 
NORTHEASTERN NORTH AMERICA TO REACH BACK AND REGAIN AN INFLUENCE 
OVER THE GREAT LAKES REGION TODAY AND TONIGHT. THE STRENGTHENING 
DEEP COLUMN CYCLONIC FLOW WILL NOT ONLY BRING ANOTHER DAY OF BELOW 
NORMAL TEMPERATURES...IT WILL BACKDOOR A COUPLE OF SPOKES OF WEAK 
SHORTWAVE ENERGY AND RIBBONS OF DEEPER MOISTURE FROM NORTHEAST TO 
SOUTHWEST ACROSS LAKE HURON AND DOWN INTO INTERIOR SECTIONS OF THE 
LOWER PENINSULA. 

FOR THE SHORT TERM FORECAST...THE ITEM OF UNCERTAINTY IS WHEN CLOUDS 
WILL PUSH ACROSS THE LAKE AND SPREAD ACROSS THE CWA. THE MODEL 
CONSENSUS IS VERY BULLISH...SUGGESTING CLOUDS WILL BE HERE ALREADY 
BY MID TO LATE MORNING. THE PROBLEM IS CURRENT...IR SATELLITE 
IMAGERY SHOWS AREAS VOID OF CLOUD CLEAR BACK ACROSS LAKE HURON TO 
ONTARIO. THE POCKET OF CLOUD THAT HAD ADVECTED DOWN INTO THE SAGINAW 
BAY AREA EARLIER HAS SINCE ERODED. FOR SKY COVER...WENT WITH A BLEND 
OF GUIDANCE AND GUT FEELING. OVERALL...FAVOR MORE SUN DURING THE 
MORNING BEFORE CLOUDS INCREASE DURING THE AFTERNOON EITHER FOR 
INCREASE IN DIURNAL CUMULUS/STRATOCUMULUS OR ADVECTION OF MIDLEVEL 
CLOUD. ADDING TO THIS POINT...FIRST SPOKE OF CVA IS EXPECTED TO 
COLLAPSE DOWN UPON THE AREA DURING THE LATE AFTERNOON. THE SECOND 
SPOKE OF MIDLEVEL ENERGY WILL ARRIVE LATE TONIGHT...LIKELY AFTER 9Z. 
MODEL SOUNDINGS SUPPORT A FAIRLY RESPECTABLE DEPTH OF DEEPER 
MOISTURE WITH THIS SECOND WAVE. KEPT THE SLIGHT TO LOW CHANCE OF A 
RAIN SHOWER FOR THE EASTERN THUMB/LAKE HURON SHORELINE. THE 
POTENTIAL MAY HINGE ON MORE OF A DRIZZLE/WEAK STRATIFORM RAIN 
POTENTIAL WITH VERY WEAK LAPSE RATE STRUCTURES FORECASTED.

LONG TERM...MONDAY THROUGH SATURDAY

DEEP LAYER N-NE FLOW WILL PERSIST ACROSS SE MI ON MONDAY AS THE 
FORECAST AREA WILL REMAIN UNDER THE INFLUENCE OF AN UPPER LOW AND 
ELONGATED TROUGH AXIS EXTENDING FROM NRN NEW ENGLAND ACROSS THE 
GREAT LAKES. A REGION OF MID LEVEL SUBSIDENCE WILL HOWEVER 
OVERSPREAD THE FORECAST AREA MON AFTERNOON IN THE WAKE OF A MID 
LEVEL SHORT WAVE IMPULSE DROPPING SOUTH ACROSS ERN LOWER MI. WHILE 
SOME DEGREE OF LOW-MID LEVEL MOISTURE WILL CONTINUE TO STREAM INTO 
SE MI FROM THE NORTHEAST...MID LEVEL WARMING WILL LIMIT CONVECTIVE 
CLOUD DEPTHS. THIS WILL SUPPORT A DRY AFTERNOON FORECAST...ALTHOUGH 
THERE IS LIKELY TO BE A HEALTHY CU/STRATO CU FIELD. THE CONTINUED 
NORTHERLY FLOW AND DAYTIME CLOUD COVER WILL KEEP MONDAY HIGHS IN THE 
50S. A HIGH AMPLITUDE MID LEVEL RIDGE WILL THEN BUILD INTO LOWER MI 
ON TUES. THE LOSS OF THE NORTHERLY WIND COMPONENT AS SFC HIGH NUDGES 
INTO THE AREA FROM THE WEST AND BETTER DIURNAL HEATING POTENTIAL 
WILL SUPPORT TUES HIGHS INTO THE LOW 60S AFTER RELATIVELY CHILLY 
EARLY MORNING TEMPS IN THE 30S. 

THE 00Z GFS HAS TRENDED STRONGER WITH MID LEVEL SHORT WAVE ENERGY 
DROPPING INTO THE GREAT LAKES FROM CENTRAL CANADA IN THE WED-THURS 
TIME FRAME AND ACTUALLY DEVELOPS A CUT OFF CIRCULATION OVER LOWER MI 
WED NIGHT. THE 00Z ECMWF /WHOSE SOLUTION FOR THE WED-THURS TIME 
FRAME HAS BEEN BY FAR MORE CONSISTENT/ IS ALONG A SIMILAR LINE 
ALTHOUGH NOT NEARLY AS DEEP AS THE GFS. A DRY FORECAST WILL BE 
MAINTAINED IN THE WED-THURS TIME FRAME WITH CONTINUED MODEL 
DISCREPANCIES AND IN CONSIDERATION OF THE OVERALL DRY AIRMASS 
RESIDING OVER THE GREAT LAKES. IN LIGHT OF THE TRENDS...HIGH TEMPS 
FOR THURS HAVE BEEN NUDGED DOWN A FEW DEGREES /UPPER 50S TO LOW 
60S/. THE DEPARTURE OF THIS SYSTEM LATE IN THE WEEK WILL THEN OFFER 
AN OPPORTUNITY FOR A SUBSTANTIAL WARMING TREND HEADING INTO NEXT 
WEEKEND AS MID LEVEL HEIGHTS REBOUND ACROSS THE REGION.

MARINE...

PERSISTENT LOW PRESSURE ALONG THE EAST COAST AND STRENGTHENING HIGH 
PRESSURE BUILDING ACROSS THE WESTERN GREAT LAKES TODAY INTO TONIGHT 
WILL ACTUALLY STRENGTHEN THE N-NW GRADIENT ACROSS LAKES HURON AND 
ERIE TODAY INTO TONIGHT. THE NET RESULT WILL BE A STRENGTHENING OF 
THE N-NW WINDS THIS AFTERNOON THROUGH TONIGHT. WINDS AND WAVES WILL 
THEN SLOWLY DECREASE MONDAY INTO TUESDAY MORNING AS HIGH PRESSURE 
BUILDS INTO THE REGION FROM THE WEST.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT MONDAY FOR 
     LHZ421-441>443.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

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


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