Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 071939
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
339 PM EDT TUE JUL 7 2015

.SHORT TERM...THROUGH TONIGHT

THE COLD FRONT IS CURRENTLY COMPLETING ITS PASSAGE ACROSS SE
MI...CURRENTLY ALIGNED ALONG THE DETROIT RIVER. SOME ENHANCED
MOISTURE BEHIND THE FRONT IS LEADING TO SOME LIGHT RAIN AND
DRIZZLE...BUT THAT WILL NOT LAST LONG AS DRY AIR QUICKLY SURGES
SOUTHEASTWARD ACROSS THE STATE. DEWPOINTS ACROSS NORTHERN MI AREA
ALREADY DOWN BELOW 50 DEGREES WITH MID 50S ACROSS MID MI. MODELS
ADVERTISE THE FRONT TO SLOWLY TAKE ON A MORE E/W ORIENTATION ACROSS
THE NORTHERN OHIO VALLEY OVERNIGHT AS AN AREA OF SFC HIGH PRESSURE
BUILDS IN ACROSS THE GREAT LAKES. THE RESULT WILL BE A DECENT
DEWPOINT GRADIENT ACROSS THE AREA RANGING FROM THE UPPER 40S ACROSS
THE SAGINAW VALLEY UP TO THE MID 50S NEAR THE OHIO BORDER. THIS WILL
IN TURN SET THE LIMIT TO THE COOLING POTENTIAL OVERNIGHT EVEN AS
SKIES CLEAR UNDER A SHORTWAVE RIDGE SLIDING OVERHEAD AND SFC HIGH
PRESSURE IN PLACE...AND 925MB TEMPS FALL TO 12C. THE BIG QUESTION IS
HOW MUCH ARE THE MODELS OVER DOING THE BL MOISTURE BEHIND THE FRONT?
WILL LEAN TO A DRIER FORECAST WITH MOSTLY CLEAR SKIES AS THE VISIBLE
SATELLITE IS ALREADY SHOWING THE CU FIELD ERODING OVER THE UP AND
NORTHERN MI.

&&

.LONG TERM...

EXPANSIVE HIGH PRESSURE CURRENTLY OVER THE NORTHERN PLAINS WILL TAKE
OVER DURING THE DAY ON WEDNESDAY AS IT MOVES EAST INTO THE GREAT
LAKES REGION.  THIS HIGH WILL BRING A DAY OF DRIER CONDITIONS BEFORE
THE NEXT LOW ENTERS BACK INTO THE PICTURE. LOW PRESSURE WILL BE IN
THE PROCESS OF MOVING IN FROM THE SOUTHWEST LATE WEDNESDAY NIGHT
BRINGING ANOTHER CHANCE FOR RAIN.  BETTER CHANCE FOR RAIN WILL OCCUR
ACROSS SOUTHERN AREAS OF THE CWA...ESPECIALLY AREAS CLOSER TO THE
OHIO BORDER AS THE LOW SKIRTS ALONG NORTHERN OHIO AND LAKE ERIE.
THIS CORRELATES TO WHERE THE BETTER INSTABILITY WILL BE AS THE SYSTEM
QUICKLY MOVES ACROSS AND OFF TO THE EAST. CURRENT TIMING OF THE
HEAVIER RAIN LOOKS TO BE THURSDAY MORNING...BUT WITH TIMING ISSUES
IN THE VARIOUS MODELS THIS WILL BE NARROWED DOWN WITH LATER FORECAST
ISSUANCES.  THIS SYSTEM IS EXPECTED TO BRING AREAS OF HEAVIER RAIN
AS THE LATEST SOUNDINGS ARE ADVERTISING PWAT VALUES CLIMBING INTO
THE 1.5 TO 2 INCH RANGE.  RAIN THEN DIMINISHES BY LATE THURSDAY
AFTERNOON AS HIGH PRESSURE BUILDS BACK IN OVER THE AREA LASTING
THROUGH THE OVERNIGHT HOURS.

FRIDAY THROUGH MONDAY...STRONG UPPER RIDGE OVER THE SOUTHEASTERN US
WILL RETROGRADE TO THE WEST. THE RIDGE NEVER QUITE BUILDS ALL THE
WAY INTO THE GREAT LAKES...LEAVING US ON THE ACTIVE OUTER FRINGES
WITH PERIODIC DISTURBANCES ARGUING FOR SHOWER AND THUNDERSTORM
CHANCES. DEEP-LAYER MOISTURE WILL INCREASE INTO THE WEEKEND AS WELL
WITH PWATS AOA 1.5 INCHES FROM SATURDAY ONWARD. FORECAST TEMPS LOOK
TO BE NEAR TO SLIGHTLY ABOVE NORMAL.

&&

.MARINE...

WINDY CONDITIONS BEHIND THE PASSING COLD FRONT WILL CONTINUE TO
DIMINISH THROUGH THE EVENING AS HIGH PRESSURE BUILDS IN OVERNIGHT
AND INTO WEDNESDAY.  SMALL CRAFT ADVISORIES REMAIN IN EFFECT THOUGH
EARLY TOMORROW MORNING FOR THE NEARSHORE WATERS OF SOUTHERN LAKE
HURON.  HIGH PRESSURE...AVERAGING 30.10 INCHES...WILL HOLD THROUGH
THE DAY AND INTO THE EVENING ON WEDNESDAY BEFORE A WEAK LOW PRESSURE
SYSTEM MOVES ACROSS THE SOUTHERN GREAT LAKES.  THIS LOW WILL
INCREASE EASTERLY/NORTHEASTERLY FLOW ACROSS LAKE ST CLAIR AND LAKE
ERIE BEFORE WINDS BECOME LIGHT FOR THE REMAINDER OF THE WEEK.

&&

.AVIATION...ISSUED 133 PM EDT TUE JUL 7 2015

COLD FRONT IS CURRENTLY MAKING ITS WAY THROUGH SOUTHEAST MI AND
ABOUT TO PASS THROUGH PTK. IT WILL PASS THROUGH THE DETROIT TAFS IN
THE NEXT HOUR OR SO. THIS WILL BRING A QUICK WIND SHIFT TO THE NW
WITH GUSTS UP TO 20 KNOTS. CIGS...ALTHOUGH VARIABLE ACROSS THE
REGION...ARE PREDOMINATELY MVFR BUT MAY DROP TO IFR ALONG AND
IMMEDIATELY BEHIND THE FRONT. THE ONGOING SHOWERS WILL COME TO AN
END LATER THIS AFTERNOON ONCE THE FRONT PASSES WHICH SHOULD BE
AROUND 19-20Z. DRY AIR RUSHING IN BEHIND THE FRONT WILL QUICKLY
SCOUR OUT CLOUDS TONIGHT LEAVING ONLY SOME SCT CLOUDS BETWEEN 3-
4KFT.

FOR DTW...SHOWERS WILL MOVE EAST OF THE AREA BETWEEN 19-20Z THIS
AFTERNOON. A SHORT PERIOD OF IFR CIGS SHOULD FILL IN BEHIND THE COLD
FRONT BRIEFLY BEFORE DRY AIR MOVING INTO THE AREA LIFTS CIGS BACK TO
MVFR. NORTHERLY WINDS WILL PREVAIL THROUGH THE OVERNIGHT.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILINGS LESS THAN 5000 FT THROUGH THIS EVENING. MEDIUM
  FOR WEDNESDAY AFTERNOON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...BEACH HAZARDS STATEMENT UNTIL 10 PM EDT THIS EVENING FOR MIZ049-055-
     063.

LAKE HURON...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR LHZ441>443.

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

$$

SHORT TERM...DRK
LONG TERM....SS/DT
MARINE.......SS
AVIATION.....DRK


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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