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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 141735
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
135 PM EDT TUE MAY 14 2013


.AVIATION...

-- Changed Discussion --
//DISCUSSION...
MID-LEVEL CLOUDS WILL CONTINUE TO STREAM OVER THE AREA AS AN
ELEVATED WARM FRONT LIFTS NORTH THROUGH THE CENTRAL GREAT LAKES.
DRIER AIR IN THE LOWER LEVELS WILL KEEP THE AREA DRY THROUGH THE
AFTERNOON HOWEVER...WITH CLOUD BASES REMAINING AT OR ABOVE 5000
FEET.

LOW PRESSURE TRACKING ACROSS THE NORTHERN GREAT LAKES WILL PUSH A
COLD FRONT ACROSS SOUTHEAST MICHIGAN BETWEEN 08-12Z WED MORNING.
SHOWERS/TSTORMS WILL BE POSSIBLE AHEAD OF AND ALONG THE FRONT...WITH
BEST POTENTIAL OVER CENTRAL MICHIGAN AND THE THUMB LATE. HAVE
INTRODUCED SOME LATE NIGHT SHOWERS TOWARDS MBS AND FNT. LOWER
CHANCES EXIST FROM PTK SOUTH (FROM JUST BEFORE SUNRISE THROUGH MID
MORNING)...AND HAVE LEFT MENTION OUT OF THE TAFS FOR NOW. A FEW
THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS THE AREA. WINDS AT THE
SURFACE WILL BECOME LIGHTER OVERNIGHT...HOWEVER AN ELEVATED CORE OF
WINDS ALOFT NECESSITATES THE MENTION FOR WIND SHEAR. WESTERLY WINDS
WILL INCREASE TO ABOUT 40 KNOTS AROUND 07-09Z...BEFORE WINDS PICK UP
AT THE SURFACE WITH THE PASSAGE OF THE SURFACE COLD FRONT.

DEEPER MIXING BEHIND THE FRONT AND LOW PRESSURE TRACKING NORTH OF
THE AREA WILL BRING GUSTY WINDS TOMORROW...WITH WESTERLY GUSTS UP TO
30 KNOTS.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS BELOW 5KFT THIS AFTERNOON THROUGH
TONIGHT.

* LOW CONFIDENCE IN COVERAGE OF THUNDERSTORMS WEDNESDAY FROM EARLY
MORNING THROUGH MID MORNING.
-- End Changed Discussion --

&&

.PREV DISCUSSION...ISSUED 332 AM EDT TUE MAY 14 2013

SHORT TERM... TODAY AND TONIGHT

SOUTHEAST MICHIGAN NOW FIRMLY POSITIONED ALONG THE NORTHEAST
PERIPHERY OF THE EXPANDING MID LEVEL HEIGHT FIELD ATTENDANT TO THE
ELONGATING UPPER RIDGE SPRAWLED ACROSS THE SOUTH-CENTRAL CONUS.
EXTENSIVE CORRIDOR OF LOW TO MID LEVEL WARM AIR ADVECTION WITHIN
STRENGTHENING SOUTHERLY FLOW WORKING ACROSS THE EASTERN RIDGE
INTERFACE ESTABLISHING A WELL-DEFINED WARM FRONTAL ZONE ACROSS THE
UPPER MS VALLEY.  THIS PROCESS DRIVING THE EASTWARD PROPAGATION OF A
NARROW STRIP OF ENHANCED 300K ISENTROPIC ASCENT INTO LOWER MICHIGAN
EARLY THIS MORNING.  SUFFICIENT 700-500 MB MOISTENING TRANSLATING
INTO AN EXTENSIVE CORRIDOR OF MID LEVEL CLOUD COVER...WITH THE
SATURATION DEPTH PROVING SUFFICIENT IN GENERATING SOME POCKETS OF
VERY LIGHT RAIN/SPRINKLES.   DEEP AMBIENT DRY LAYER BELOW 700 MB
REMAINS A LARGE HINDRANCE AS THIS ASCENT FOLDS ACROSS SE MICHIGAN
THIS MORNING.  GIVEN THE CURRENT RADAR PRESENTATION...AND 00Z
ASSESSMENT BY THE HI RES SOLUTIONS...LIKELY LOOKING AT QUITE A BIT
OF VIRGA WITH THE OCCASIONAL BRIEF SHOWER/SPRINKLE SURVIVING THE
TRIP.

ELEVATED WARM FRONTAL SLOPE AND ATTENDANT THETA-E GRADIENT WILL EASE
INTO THE REGION THROUGH THE LATTER HALF OF THE DAY.  A FAIRLY
EXTENSIVE ELEVATED MIXED LAYER WILL ACCOMPANY THIS EXPANSION...
LEAVING AN INCREASINGLY CAPPED/STABLE THERMODYNAMIC PROFILE FOR THE
AFTERNOON/EVENING PERIOD.  NUISANCE MID LEVEL CLOUD MAY TEND TO FILL
IN BEHIND THIS LEAD 700-500 MB MOISTURE GRADIENT...BUT A LACK OF
DEEPER MOISTURE TRANSPORT AND LARGE SCALE FORCING SUGGEST
PRECIPITATION POTENTIAL WILL BE LIMITED.  THE HIGH TEMPERATURE
FORECAST REMAINS COMPLICATED BY THE PRESENCE OF THE EARLY DAY CLOUD
COVER AND A SOMEWHAT RESTRICTED MIXING PROFILE UNDER A PREVAILING
SFC-925 MB SOUTHEAST GRADIENT.  THE TRUE BOUNDARY LAYER WARM AIR
ADVECTIVE PROCESS WILL LIKELY HOLD OFF UNTIL AFTER THE PEAK HEATING
CYCLE.  THE GENERAL RISE IN THE THICKNESS FIELD AS HEIGHTS CLIMB
WILL EFFICIENTLY MODERATE THE AIRMASS...WITH ANY ADDITIVE LATE DAY
INSOLATION HELPING THE PROCESS.  THIS WILL SUPPORT A DEFINED
GRADIENT IN HIGH TEMPERATURES RANGING FROM AROUND 70 WEST TO UPPER
50S ACROSS THE THUMB.

STRONG SHORTWAVE NOTED ON WATER VAPOR EARLY THIS MORNING QUICKLY
SHEARING OVER THE UPPER RIDGE PERIPHERY ACROSS FAR SOUTHERN MANITOBA
WILL CONTINUE TRANSLATING EASTWARD...ARRIVING JUST NORTH OF LAKE
SUPERIOR BY TONIGHT.  THIS PROCESS WILL SUPPRESS THE HEIGHT FIELD
JUST ENOUGH TO INDUCE MODEST SURFACE CYCLOGENESIS AND A
STRENGTHENING OF THE DOWNSTREAM SOUTHWEST GRADIENT.  THIS WILL
EFFECTIVELY PULL THE STAGNANT SURFACE WARM FRONT NORTHEAST AND
ACROSS SOUTHEAST MICHIGAN LATE THIS EVENING.  THIS WILL CUT SHORT
THE NOCTURNAL COOLING PROCESS EARLY ON...WITH TEMPERATURES BOTTOMING
OUT IN THE 50S/LOWER 60S EARLY TONIGHT BEFORE GRADUALLY CLIMBING.

RESIDENT TIME OF THIS MODIFYING WARM SECTOR WILL BE RATHER
SHORT-LIVED GIVEN THE PROGRESSIVE ARRIVAL OF A WEAK LEAD COLD
FRONTAL BOUNDARY DURING THE EARLY MORNING HOURS.  PROSPECTS FOR
CONVECTIVE INITIATION ALONG THIS BOUNDARY WILL BE COMPROMISED BY
THE PRONOUNCED CAPPING...A LACK OF BETTER LOW LEVEL MOISTURE QUALITY
AND THE UNFAVORABLE TIMING/DIURNAL MINIMUM.  GREATEST OPPORTUNITY
MAY EXIST ACROSS THE NORTH...GIVEN A CLOSER PROXIMITY TO STRONGER
CONVERGENCE TIED TO A WEAK SHORTWAVE AND NOCTURNAL LOW LEVEL JET
FORCING WORKING ALONG THE FRINGE OF THE EASTWARD TRACKING SURFACE
LOW.

LONG TERM...

UPPER LEVEL RIDGE OVER THE NORTHERN PLAINS EXTENDING INTO SOUTH
CENTRAL CANADA EARLY THIS MORNING (NOTED HIGHS IN THE 80S/90S IN
THAT AREA YESTERDAY)...WITH COMPACT BUT POTENT SHORTWAVE TROUGH NOW
PUSHING INTO MONTANA. THE MAIN HEIGHT FALLS ON WEDNESDAY WILL BE
OCCURRING OVER THE NORTHERN GREAT LAKES AND ONTARIO. INITIAL COLD
FRONT COMING THROUGH WEDNESDAY MORNING LOOKS RATHER WEAK. 850 MB
TEMPS ARE FORECASTED TO START THE DAY OUT VERY WARM...UPPER
TEENS...WITH 700 MB TEMPS EVEN AROUND +10 C (PER CANADIAN)...WHICH
SUGGEST WE WILL PROBABLY BE DRY AND CAPPED. WITH THE FAVORABLE LOW
LEVEL WESTERLY FLOW AND STRONG MAY SUNSHINE...MUCH OF THE COLD
ADVECTION OF THE INITIAL FRONT WILL WASH OUT...AND DO LIKE THE
UKMET DEPICTION AT 18Z WEDNESDAY OF 850 MB TEMPS OF 11+ C FAR NORTH
TO 15+ C SOUTH...SUPPORTIVE OF HIGH IN THE UPPER 70S TO LOWER
80S...WITH EVEN FEW MID 80S POSSIBLE ARB-DTW SOUTH.

UPPER LEVEL CONFLUENT FLOW WEDNESDAY NIGHT WILL ALLOW HIGH PRESSURE
TO BUILD INTO THE CENTRAL GREAT LAKES REGION THURSDAY INTO FRIDAY.
HIGH TEMPERATURES LOOK TO RISE INTO THE 70S BASED ON 850 MB TEMPS
HOVERING AROUND 10 C....BUT INCREASING EASTERLY FLOW ON FRIDAY WILL
LIKELY KEEPS TEMPS DOWN IN THE LOWER 70S.

AN UPPER LEVEL RIDGE IS FORECASTED TO BUILD THROUGH THE
WEEKEND...BUT RETURN MOISTURE COMING UP FROM THE SOUTH COULD TRIGGER
CONVECTIVE ACTIVITY (SEE GFS)...ALTHOUGH THAT SOLUTION LOOKS
SUSPECT. THE OTHER SCENARIO...UPSTREAM CONVECTION LIKELY DEVELOPS
OVER NORTHERN MINNESOTA/WISCONSIN/UPPER PENINSULA...AND ATTEMPTS
TO TRACK SOUTHEAST ALONG THE ORIENTATION OF THE THICKNESS FIELDS.
LOW LEVELS WILL BE RELATIVELY DRY AND STABLE ON SATURDAY...BUT NOT
OUT OF THE QUESTION SOME HIGHER BASED ACTIVITY MAY SURVIVE. EITHER
SCENARIO WORTHY OF SLIGHT CHANCE/LOW CHANCE POPS FOR THE WEEKEND...ULTIMATELY
WILL DEPEND ON WHERE EXACTLY THAT UPPER LEVEL RIDGE AXIS SETS UP.

MUCH BETTER CHANCE FOR SHOWERS AND THUNDERSTORM ACTIVITY EARLY NEXT
WEEK AS UPPER LEVEL LOW/TROUGH OVER THE CENTRAL CONUS ADVANCES
EAST...WITH GOOD SUPPLY OF PACIFIC AND GULF OF MEXICO MOISTURE
LIFTING UP THROUGH THE GREAT LAKES REGION...LEADING TO SOLID
DESTABILIZATION (SHOWALTER INDEX -1 TO -3 C PER 00Z EURO).

MARINE...

SOUTHEAST WINDS WILL INCREASE TODAY AND TONIGHT AS A WARM FRONT
ENTERS THE REGION.  HOWEVER A RELATIVELY STABLE ENVIRONMENT WILL
CONTAIN THE WIND GUST POTENTIAL AND WAVE GROWTH DURING THIS TIME. A
COLD FRONT WILL MOVE THROUGH TONIGHT AND EARLY WEDNESDAY BRINGING A
CHANCE OF THUNDERSTORMS ACROSS ALL MARINE WATERS.  WESTERLY WINDS
WILL DEVELOP BEHIND THIS FRONT ON WEDNESDAY.  A WEAK RIDGE OF HIGH
PRESSURE WILL BRING FAVORABLE MARINE CONDITIONS FOR THE END OF THE
WEEK.

&&

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

&&

$$

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


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