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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 161956
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
356 PM EDT SUN JUN 16 2013

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

THE MAIN JET STREAM AXIS WILL REMAIN IN PLACE OVER THE GREAT LAKES
REGION RESULTING IN STATIC ADVECTIONS OR LITTLE AIRMASS TURNOVER.
THIS WILL BE REFLECTED AT THE SURFACE WITH NO SURFACE PRESSURE
TENDENCY AND A WEAK SURFACE TROUGH OR COL LIKE STRUCTURE. THE
NEUTRAL ADVECTION PATTERN HAS AN IMPACT HERE YET THIS AFTERNOON AS
THE LACK OF MIDLEVEL COOLING SHOULD KEEP A SUBTLE CAP IN PLACE
CENTERED AT 775MB. THERE STILL REMAINS SOME TIME FOR AN ISOLATED
CELL TO INITIATE IN SOME WEAKNESS OF THE CAPPING...POSSIBLY AIDED BY
SOME LAKE CONVERGENCE FORCING. HOWEVER...THE LIKELIHOOD OF THIS TO
OCCUR IS CERTAINLY 20 PERCENT OR LESS.

THE LACK OF ADVECTION OR POSITIVE SURFACE PRESSURE TENDENCY SHOULD
SIGNAL THE LACK OF ANY SIGNIFICANT LOW TO MIDLEVEL INVERSION
TONIGHT. THIS INCREASES CONFIDENCE THAT SKIES SHOULD BE
PREDOMINATELY CLEAR FOR THE DURATION OF THE NIGHT. THE ONE EXCEPTION
WILL BE OVER THE NORTHERN CWA LATE IN THE FORECAST PERIOD AS SOME
LEFTOVER CONVECTIVE DEBRIS AHEAD OF A WEAK SURFACE BOUNDARY MAY
SURVIVE THE TRIP SOUTHWARD. CONFIDENCE IN THIS OCCURRING REMAINS LOW.
-- End Changed Discussion --

&&

.LONG TERM... 
-- Changed Discussion --
MONDAY THROUGH SUNDAY

AFTERNOON WATER VAPOR SATELLITE IMAGERY AND SURFACE ANALYSIS
INDICATE THE UPPER LEVEL TROUGH SHEARING SOUTHWARD FROM CENTRAL
CANADA AND CARRYING THE ASSOCIATED COLD FRONT INTO THE UPPER
MIDWEST. THIS SYSTEM WILL BE THE FOCUS OF CONDITIONS IN SE MICHIGAN
MONDAY AND MONDAY NIGHT AND PRESENTS A FAIRLY STRAIGHTFORWARD
FORECAST SCENARIO FOR SHOWERS AND THUNDERSTORMS. AT FIRST, IT LOOKED
LIKE BOUNDARY LAYER MOISTURE RETURN WOULD BE ONE OF THEM BUT PERHAPS
NOT CONSIDERING HOW CONVECTION IS DEVELOPING TODAY OVER THE NORTHERN
GREAT LAKES. LOWER 50S SURFACE DEWPOINT IS GOOD ENOUGH IN THAT
AREA WHERE TEMPERATURES ALOFT ARE ABOUT -16C AT 500 MB. THERE IS
GOOD AGREEMENT AMONG THE NEW MODEL OUTPUT SHOWING SOME OF THIS
COLD AIR ALOFT SETTLING OVER SOUTHERN LOWER MICHIGAN BY MONDAY
AFTERNOON TAKING 500 MB TEMPS DOWN TO BETWEEN -14 AND -16C. EXPECT
THIS WILL PERMIT LOWER TO MID 50S SURFACE DEWPOINT TO GENERATE
CAPE AROUND 1500 J/KG, GOOD ENOUGH FOR CONVECTION TO BECOME
ORGANIZED WITHIN A STRONG WIND FIELD FEATURING NEARLY 60 KNOTS OF
WESTERLY FLOW AT 500 MB AND 45 KNOTS OF 0-6KM BULK SHEAR. THE
STRONG UNIDIRECTIONAL NATURE OF THE SHEAR PROFILE INDICATES A
DISCRETE SUPERCELL MODE IS POSSIBLE EARLY WITH ENHANCED UPDRAFTS
CAPABLE OF LARGE HAIL DUE TO FREEZING LEVEL ON THE LOW SIDE,
ABOUT 10500 FEET, FOR THIS TIME OF YEAR. A QUICK EVOLUTION INTO A
LINEAR MODE COULD FOLLOW WITH A DAMAGING WIND COMPONENT.

WESTERLY UPPER LEVEL FLOW AND DAYTIME SURFACE HEATING SOUTH OF THE
FRONT WILL BUY SOME DRY CONDITIONS DURING MONDAY MORNING. THE MAIN
FORECAST ADJUSTMENT IS TO DELAY HIGHER POPS INTO THE AFTERNOON IN
THE TRI CITIES AND EXTEND TO THE SOUTH AND INTO MONDAY EVENING
TOWARD THE OHIO BORDER. MODEL CROSS SECTIONS ALSO INDICATE THE
SHALLOWNESS OF THE COLD FRONT WILL HAVE AN IMPACT ON SOUTHWARD
PROGRESSION AS SURFACE HEATING OVER INTERIOR LOWER ERODES THE
PRESSURE FIELD. NOT UNTIL MONDAY EVENING WILL THE FRONT RELEASE
THE REST OF THE WAY THROUGH LOWER MICHIGAN WITH A BOOST FROM LAKE
HURON AND LAKE MICHIGAN, AND ALSO WITH A BOOST FROM EXTRA HEIGHT
FALLS WITH THE SHARPENING UPPER TROUGH OVER NORTHERN ONTARIO AND
QUEBEC. EXPECT THEN A STEADY DECREASE IN POPS THROUGH THE NIGHT
AS THE LOW LEVEL BAROCLINIC ZONE MOVES FARTHER SOUTH OF THE REGION
TOWARD TUESDAY MORNING.

FRESH CANADIAN HIGH PRESSURE THEN REMAINS ON TRACK TO SETTLE OVER SE
MICHIGAN FOR THE MID WEEK PERIOD. THE NEW MODEL SOLUTIONS REMAIN
ROCK SOLID ON THE SCENARIO THROUGH THURSDAY WHEN HINTS OF A DRY
BACKDOOR COLD FRONT SHOW UP THURSDAY NIGHT INTO FRIDAY. THIS IS
SYMPTOMATIC OF NORTHWEST FLOW ALOFT PERSISTING LONGER OVER THE GREAT
LAKES AS THE UPPER LEVEL BLOCK MATURES OUT WEST. IT ALSO MEANS
CONDITIONS BECOMING MORE UNSETTLED FOR NEXT WEEKEND.
-- End Changed Discussion --

&&

.MARINE...

-- Changed Discussion --
FAVORABLE MARINE CONDITIONS WILL PERSIST ACROSS AREA WATERWAYS WITH
A BENIGN PATTERN IN PLACE. WIND AND WAVE CONDITIONS WILL OTHERWISE
REMAIN FAVORABLE UNTIL MONDAY AFTERNOON WHEN THE NEXT COLD FRONT IS
DUE THROUGH THE REGION. WINDS ARE EXPECTED TO AGGRESSIVELY TURN TO
THE NORTHEAST BEHIND THE FRONTAL PASSAGE DURING THE LATE AFTERNOON
OR EARLY EVENING HOURS. SMALL CRAFT ADVISORIES MAY BE A POSSIBILITY
FOR THE NEARSHORE WATERS OF LAKE HURON INCLUDING SAGINAW BAY.
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
ISSUED 138 PM EDT SUN JUN 16 2013

//DISCUSSION...

THE JET STREAM AXIS WILL REMAIN IN A WEST TO EAST FASHION DIRECTLY
OVER THE GREAT LAKES REGION. THIS WILL MAKE DRY AIR ADVECTION A
STUBBORN PROCESS WITHIN THE LOW LEVELS. THERE REMAINS ENOUGH NEAR
SURFACE MOISTURE TO CARRY A SLIGHT CHANCE POP FOR A SHOWER OR
THUNDERSTORM THIS AFTERNOON BETWEEN 20-23Z. HOWEVER...THE
POTENTIAL REMAINS TOO LOW TO CARRY AN EXPLICIT MENTION. ADVECTIONS
WILL REMAIN WEAK AGAIN TONIGHT WITH ANY BACKGROUND MIDLEVEL
INVERSIONS NON-EXISTENT. BELIEF IS THAT ONCE WE CAN MIX OUT CLOUDS
TOWARDS SUNDOWN...SKIES WILL REMAIN SKC FOR THE OVERNIGHT.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE THAT CEILINGS BELOW 5KFT WILL BREAK THIS
  AFTERNOON.

* HIGH CONFIDENCE FOR A VERY LOW THUNDERSTORM PROBABILITY.
-- End Changed Discussion --

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...CB
LONG TERM....BT
MARINE.......CB
AVIATION.....CB


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