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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 150739
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
339 AM EDT WED MAY 15 2013

.SHORT TERM...
-- Changed Discussion --
TODAY AND TONIGHT

SOUTHERN EXTENSION OF A SLIGHTLY LOWER HEIGHT FIELD ATTENDANT TO A
STRONG MID LEVEL LOW CENTERED OVER CENTRAL ONTARIO WILL RACE ACROSS
THE NORTHERN GREAT LAKES TODAY.  THIS PROCESS WILL SUPPORT THE RAPID
EASTWARD PROPAGATION OF THE ASSOCIATED SURFACE LOW THROUGH NORTHERN
LOWER MICHIGAN THIS MORNING...EFFECTIVELY DRAWING A COLD FRONT
SOUTHEAST AND ACROSS SOUTHEAST MICHIGAN TODAY.  STEADY LOW AND MID
LEVEL PRE-FRONTAL WARM AIR ADVECTION ONGOING EARLY THIS MORNING...
LEAVING A SUBSTANTIAL AMOUNT OF MID LEVEL INSTABILITY IN PLACE
(LAPSE RATES OF 7 TO 9 C/KM) WITHIN THE TRANSIENT PRONOUNCED
ELEVATED MIXED LAYER ACCOMPANYING THIS THERMAL ADJUSTMENT.  THIN
CONVERGENCE ZONE AND ELEVATED THETA-E GRADIENT ANCHORED ALONG AN
APPROACHING LEAD SURFACE TROUGH WILL WORK THROUGH AT THE SAME TIME
/09Z-14Z/.  THIS WILL CONTINUE TO SUPPORT A LOW CHANCE OF SHOWER AND
THUNDERSTORM DEVELOPMENT THROUGH THE MID MORNING HOURS.  ANY
STRONGER CORES WOULD BE CAPABLE OF GENERATING SMALL HAIL GIVEN THE
THERMODYNAMIC PROFILE.

MOISTURE AXIS PROGRESSIVELY SHIFTS TO THE SOUTH AND EAST WITH A
DRYING WESTERLY FLOW TAKING HOLD BY LATE MORNING.  HIGH TEMPERATURES
FOR TODAY REMAIN A TOUGH CALL...AS A HIGH DEGREE OF INSOLATION AND
DEEP MIXING WORK TO OFFSET A DEVELOPING WEAK COLD AIR ADVECTIVE
COMPONENT.  SUSPECT THE ADVECTION WILL BE OVERWHELMED UNDER THIS
ENVIRONMENT...ALLOWING TEMPERATURES TO RESPOND NICELY TODAY.  HARD
TO ARGUE WITH THE GOING FORECAST...HIGHS ALLOCATED FROM UPPER 70S
ACROSS THE NORTH TO MID 80S FROM ANN ARBOR-DETROIT SOUTHWARD.  THE
WELL MIXED WESTERLY GRADIENT WILL SUPPORT GUSTS IN THE 30 MPH RANGE
FOR THE AFTERNOON.

BENIGN CONDITIONS TONIGHT AS WEAK SURFACE RIDGING BUILDS IN BENEATH
CONFLUENT NORTHWEST FLOW.  SLIGHTLY COOLER POST-FRONTAL AIRMASS
RETURNING LOWS TO MORE SEASONABLE LEVELS...READINGS MAINLY UPPER
40S/LOWER 50S.
-- End Changed Discussion --

&&

.LONG TERM...

-- Changed Discussion --
ABOVE NORMAL TEMPERATURES CAN BE EXPECTED OVER THE EXTENDED
PERIOD...AS JET STREAM REMAINS TO OUR NORTH. FRIDAY LOOKS TO BE THE
COOLEST DAY WHERE TEMPERATURES COME IN CLOSE TO NORMAL...BUT IT NOW
APPEARS THE WARMUP FOR THE WEEKEND WILL BE ACCELERATED.

TEMPERATURES LOOK TO CLIMB TOWARD 80 DEGREES AGAIN ON
THURSDAY...SUPPORTED BY 850 MB TEMPS IN THE LOWER TEENS (BLEND OF
WARM REGIONAL GEM VS NAM/GFS)...WITH HINT OF WEAK COLD FRONT FROM
THE NAM/GFS DROPPING SOUTH DURING THE AFTERNOON. DIFFERENTIAL
HEATING/LAKE BREEZE INTERACTION MAY BE SUFFICIENT TO GENERATE ENOUGH
LOW LEVEL CONVERGENCE TO TRIGGER A CELL...AS LI`S SEEN APPROACHING
TOWARD ZERO. STILL...NAM/GFS USUALLY A BIT OVERDONE WITH LOW LEVEL
MOISTURE...AND DON`T THINK A SHOWER OR TWO IS EVEN WORTH
MENTIONING...AS LOCATION IS A BIT UP IN THE AIR AS WELL IF ANYTHING
DOES MATERIALIZE.

HIGH PRESSURE BUILDING INTO ONTARIO/NORTHERN GREAT LAKES THURSDAY
NIGHT WILL ALLOW COOLER AIR TO SLIP INTO SOUTHEAST MICHIGAN...WITH
THE SURFACE HIGH MOVING OVER LAKE HURON ON FRIDAY. MEANWHILE...WARM
FRONT LOOKS TO BE LIFTING INTO THE WESTERN GREAT LAKES...WITH SOME
MID LEVEL CLOUDS SPILLING OVER INTO LOWER MICHIGAN. THE COMBINATION
OF THE LIGHT NORTHEAST FLOW OF LAKE HURON...COOLER START...AND
MID/HIGH CLOUDS MOVING IN ARE EXPECTED TO HOLD TEMPERATURES CLOSER
TO 70 DEGREES...OR NEAR NORMAL.

THE 00Z MEDIUM RANGE MODELS HAVE TRENDED FARTHER WEST WITH THE UPPER
LEVEL RIDGE AXIS (NOW OVER MINNESOTA/WISCONSIN) AND TROUGH COMING
OUT OF THE FOUR CORNERS REGION ON SATURDAY. THE UPPER LEVEL RIDGE
DOES PUSH TO THE EAST OVER THE WEEKEND...WITH HEIGHTS REBOUNDING
NICELY OVER OUR AREA. AIRMASS CERTAINLY WILL BE ABLE TO SUPPORT
TEMPS IN THE 70S ON SATURDAY AND LOWER 80S ON SUNDAY...AS 850 MB
TEMPS SEEN CLIMBING INTO THE MID TEENS ON SUNDAY.  THE LIGHT
EASTERLY STABLE LOW LEVEL FLOW WILL BE FLEETING...AND AIRMASS WILL
ATTEMPT TO DESTABILIZE ON SUNDAY AS MOISTURE ADVECTS IN FROM THE
SOUTH...BUT UNDER THE BACKDROP OFF THE UPPER LEVEL
RIDGE...INDICATIONS ARE WE WILL BE DRY OR ACTIVITY WILL BE LIMITED
AT BEST. KEEP IN MIND...WE ARE HEADING INTO SUMMER WHERE DIURNAL
ISOLATED/SCATTERED SHOWERS/THUNDERSTORMS WILL BECOME COMMONPLACE.

LARGE UPPER LEVEL LOW OVER THE CENTRAL/NORTHERN PLAINS ON
MONDAY...WITH GOOD SURGE OF MOISTURE (HUMID AIR WITH DEW PTS IN THE
60S) SPREADING INTO THE GREAT LAKES REGION WITH UPPER LEVEL RIDGE
AXIS MOVING OFF TO THE EAST. THERE REMAINS A VERY GOOD CHANCE FOR
SHOWERS AND THUNDERSTORMS MONDAY-TUESDAY...AND WITH SUCH AN
ANOMALOUSLY DEEP TROUGH/UPPER LOW...SEVERE WEATHER IS A POSSIBILITY.
-- End Changed Discussion --

&&

.MARINE...

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A WELL MIXED WESTERLY WIND WILL DEVELOP TODAY BEHIND A COLD FRONT.
THIS WILL RESULT IN GUSTS OF 20 TO 25 KNOTS THROUGH THE AFTERNOON
PERIOD...WARRANTING A SMALL CRAFT ADVISORY ACROSS ALL NEARSHORE
WATERS.  HIGHER DEGREE OF STABILITY ACROSS THE OPENWATERS WILL
CONTAIN THE GUST POTENTIAL AT 25 KNOTS OR LESS.  WINDS DIMINISH WITH
WEAK HIGH PRESSURE BUILDING INTO THE REGION TONIGHT AND THURSDAY.  A
STRONGER HIGH PRESSURE MOVING OUT OF SOUTHERN CANADA WILL MAINTAIN A
WEAKER NORTHEAST WIND THROUGH THE END OF THE WEEK.
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
ISSUED 1154 PM EDT TUE MAY 14 2013

//DISCUSSION...

A COLD FRONT WILL MOVE ACROSS SE MI BETWEEN 09Z AND 12Z THIS
MORNING. AMPLE INSTABILITY ALOFT WILL TRAVERSE SRN MI EARLY THIS
MORNING...LEADING TO SOME SCATTERED THUNDERSTORMS ALONG/IN ADVANCE
OF THE COLD FRONT. DRY AND STABLE AIR IN THE LOW LEVELS HOWEVER WILL
BE A MAJOR LIMITING FACTOR FOR WIDESPREAD THUNDERSTORM DEVELOPMENT.

FOR DTW...THE MOST PROBABLE TIME PERIOD FOR THUNDERSTORMS WILL BE
CENTERED AROUND 10 TO 12Z THIS MORNING. THE PASSAGE OF THE COLD
FRONT THIS MORNING WILL ALLOW WINDS TO TURN WESTERLY /AROUND 280
DEG/ BY 15Z...WITH GUSTS EXPECTED TO EXCEED 25 KNOTS THROUGH THE
AFTERNOON.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE ON THUNDERSTORM POTENTIAL BETWEEN 09Z AND 12Z THIS
MORNING.

* MEDIUM CONFIDENCE WESTERLY WIND GUSTS WILL EXCEED CROSS WIND
THRESHOLDS WEDNESDAY AFTERNOON.
-- End Changed Discussion --

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING SAGINAW BAY...FROM 10 AM WEDNESDAY TO 4 PM
     WEDNESDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...FROM 10 AM WEDNESDAY TO 4 PM WEDNESDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...FROM 10 AM WEDNESDAY TO 4 PM WEDNESDAY.
-- End Changed Discussion --

&&

$$

SHORT TERM...MR
LONG TERM....SF
MARINE.......MR
AVIATION.....SC


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