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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 182257
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
657 PM EDT TUE JUN 18 2013


.AVIATION...

-- Changed Discussion --
//DISCUSSION...

VFR CONDITIONS EXPECTED THROUGH THE NEXT 24 HOURS AND BEYOND. HIGH
PRESSURE LOCKED OVER THE GREAT LAKES WILL PRODUCE FAVORABLE AVIATION
CONDITIONS THROUGH WEDNESDAY. AFTERNOON CU IS DISSIPATING AND WILL
FORM AGAIN ON WEDNESDAY...BUT NO BETTER THAN FEW TO SCT. WINDS
GUSTING TO 20 MPH FROM THE NORTHEAST WILL DISSIPATE QUICKLY BY 01Z.
WINDS WILL VEER TO THE EAST AND REMAIN LIGHT OVERNIGHT AND WEDNESDAY
AS THE HIGH DROPS FURTHER SOUTH.

//DTW THRESHOLD THREATS...

* NONE
-- End Changed Discussion --

&&

.PREV DISCUSSION...
-- Changed Discussion --
ISSUED 344 PM EDT TUE JUN 18 2013

SHORT TERM...THROUGH TONIGHT

SURFACE HIGH PRESSURE SYSTEM IS DROPPING INTO THE STATE FROM CANADA
THIS EVENING. THIS LOWER MI WILL BECOME FIRMLY ENTRENCHED UNDER THIS
HIGH BY WEDNESDAY MORNING. IN ADDITION...AN AREA OF MID LEVEL
SUBSIDENCE NORTH OF A SHORTWAVE DIVING SE THROUGH THE OHIO VALLEY
WILL HELP PRODUCE A DEEP LAYER OF DRY AIR THROUGH THE MID LEVELS OF
THE ATMOSPHERE. THE MAIN ISSUE WITH THIS FORECAST WILL BE MINIMUM
TEMPERATURES OVERNIGHT. DECREASING WINDS...HIGH PRESSURE CENTERED
OVER THE AREA...DECREASING SFC DEWPOINTS...AND CLEAR SKIES WOULD ALL
LEAD TO FAVORABLE RADIATIONAL COOLING. LAST NIGHT TEMPERATURES
ACROSS NORTHERN MI DROPPED INTO THE MID/UPPER 30S WITH SOME FROST
DEVELOPMENT. MODELS ARE CONTINUING TO SUGGEST THE NE WINDS WILL
NOT DECOUPLE AND STAY SOMEWHAT ELEVATED INTO THE NIGHT WHICH WOULD
PREVENT TEMPERATURES FROM DROPPING TO THEIR FULL POTENTIAL. AREAS TO
THE NORTH AROUND THE SAGINAW VALLEY WILL HAVE THE BEST CHANCE TO
DROP INTO THE LOW 40S AS THE HIGH WILL HAVE A LONGER RESIDENCE OVER
THAT AREA WHILE AREAS TO THE SOUTH WILL KEEP A TIGHTER PRESSURE
GRADIENT LONGER INTO THE NIGHT PREVENTING TEMPS FROM FALLING PAST
THE MID 40S. AS MENTIONED IN THE PREVIOUS DISCUSSION...THIS WILL
LIKELY LEAVE LOWS A DEGREE OR TWO SHY OF RECORD VALUES FOR
THE DATE AT BOTH MBS AND FNT /RECORD AT FNT 44...MBS 42/.

LONG TERM...WEDNESDAY THROUGH TUESDAY

A QUIET START TO THE EXTENDED FORECAST GIVES WAY TO INCREASINGLY
VOLATILE WEATHER THIS WEEKEND INTO EARLY NEXT WEEK. SURFACE HIGH
PRESSURE WILL BUILD SOUTHEAST THROUGH THE AREA WITHIN THE NORTHWEST
FLOW AROUND UPPER TROUGH AXIS OVER EASTERN CANADA. DRY WEATHER CAN
BE EXPECTED WEDNESDAY INTO THURSDAY AS THIS HIGH SHIFTS OVER AND
THEN JUST EAST OF THE AREA...MAINTAINING DRY...STABLE AIRMASS OVER
THE REGION. THIS CORE OF THIS CANADIAN AIRMASS WILL MAINTAIN COOL
READINGS THROUGH WEDNESDAY WITH HIGH TEMPERATURES OF 70-75. EXPECT
MODERATION INTO THURSDAY UNDER STRONG LATE JUNE SUNSHINE WITH THE
TEMPERATURES BACK TO AROUND 80.

THE PATTERN THEN UNDERGOES A NOTABLE TRANSITION OVER THE WEEKEND AS
AN UPPER RIDGE EXPANDS ACROSS THE EASTERN CONUS DOWNSTREAM OF AN
EVOLVING UPPER TROUGH OVER WESTERN NOAM. AS THIS TROUGH DEAMPLIFIES
AS AN UPPER LOW OPENS AND LIFTS FROM THE PACIFIC NORTHWEST INTO
WESTERN CANADA...UPPER FLOW PATTERN WILL SHIFT FROM SOUTHWESTERLY TO
ESSENTIALLY ZONAL WITH THE MAIN BELT OF STRONG WESTERLIES STREAMING
EAST THROUGH THE NORTHERN TIER OF THE CONUS.

NUMEROUS SHORTWAVES OF PACIFIC ORIGIN WILL RIDE THIS MAIN STORM
TRACK AND PROVIDE THE FORCING FOR A SERIES OF CONVECTIVE EPISODES.
IN ADDITION...THE AIRMASS FROM THE UPPER PLAINS/MISSISSIPPI WILL
WARM SIGNIFICANTLY OVER THE WEEKEND WITH A STEADY FEED OF GULF OF
MEXICO MOISTURE ALSO WORKING NORTH ON SOUTH/SOUTHWEST WINDS. THIS
BUILDING INSTABILITY WILL STEADILY SHIFT EAST INTO THE GREAT LAKES
AS UPPER FLOW BECOMES MORE ZONAL WITH TIME LATE THIS WEEKEND INTO
NEXT WEEK. THE JUXTAPOSITION OF THE BUILDING POOL INSTABILITY TO THE
BAND OF STRONGER WESTERLIES AND EMBEDDED UPPER IMPULSES WILL LEAD
TO MULTIPLE DAYS FROM SATURDAY INTO TUESDAY WHERE THE POTENTIAL FOR
CONVECTIVE COMPLEXES WILL BE ENHANCED.

WHILE THE BROAD SYNOPTIC PATTERN WOULD SUGGEST THAT THE POTENTIAL
FOR THUNDERSTORMS WILL INCREASE EVERY DAY FROM SATURDAY INTO TUESDAY
AS THE AIRMASS OVER THE CENTRAL GREAT LAKES BECOMES MORE AND MORE
UNSTABLE AND AS THE UPPER WESTERLIES SETTLE SOUTH CLOSER TO THE AREA
WITHIN ZONAL FLOW...THE EVENTUAL DAY-TO-DAY CHANCES FOR STORMS WILL
BE MODULATED AS LEAST AS MUCH BY THE MESOSCALE INFLUENCES OF THE
THUNDERSTORM COMPLEXES THEMSELVES. DURING THIS PERIOD OF ACTIVE
WEATHER...TEMPERATURES WILL BE MUCH MORE SUMMER-LIKE...WARMING WELL
INTO THE 80S TO AROUND 90 WITH MINIMUM TEMPERATURES OVERNIGHT AROUND
70.

MARINE...

CANADIAN HIGH PRESSURE SINKING INTO THE GREAT LAKES WILL ALLOW GUSTY
NE FLOW TO DECREASE TONIGHT WHILE BECOMING MORE EASTERLY. THIS WILL
RESULT IN LOWER WAVE HEIGHTS AS WELL FALLING TO LESS THAN 2 FEET BY
WEDNESDAY MORNING. CURRENTLY WAVES ALONG THE LAKE HURON SHORELINE
ARE SLIGHTLY ELEVATED TO AROUND 3-4 FEET WITH THE FAVORABLE
FETCH...BUT WILL FALL SHORT OF A SMALL CRAFT ADVISORY. THE SURFACE
HIGH...IN ADDITION TO MID LEVEL SUBSIDENCE NORTH OF A
SHORTWAVE...WILL LEAD TO FAVORABLE MARINE CONDITIONS INTO FRIDAY.
-- End Changed Discussion --

&&

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

&&

$$

AVIATION.....RBP
SHORT TERM...DRK
LONG TERM....DG
MARINE.......DRK


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