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000
FXUS63 KDTX 141658
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1258 PM EDT FRI JUN 14 2013

.AVIATION...

//DISCUSSION...

SURFACE HIGH PRESSURE WILL REMAIN IN FIRM CONTROL OF THE WEATHER
OVER SE MICHIGAN FOR THE REST OF TODAY THROUGH TONIGHT. ANY
COMPLEXITIES AFFECTING AVIATION OPERATIONS WILL BE ASSOCIATED WITH
NORTHERLY WIND AUGMENTED BY LAKE BREEZE INTERACTION DURING THE LATE
AFTERNOON THROUGH THE EVENING BEFORE THE HIGH SETTLES OVERHEAD
THROUGH SUNRISE SATURDAY. CONDITIONS WILL REMAIN VFR THROUGH
SATURDAY WITH A LIGHT WIND RETURNING FROM THE SOUTH AS HIGH PRESSURE
EXITS EASTWARD. THE FIRST SIGNS OF THE NEXT LOW PRESSURE SYSTEM WILL
BE IN THE FORM OF GRADUALLY THICKENING HIGH CLOUDS THROUGH
SATURDAY AFTERNOON.

//DTW THRESHOLD THREATS...

* NONE.

&&

.PREV DISCUSSION...ISSUED 336 AM EDT FRI JUN 14 2013

SHORT TERM...TODAY AND TONIGHT

SOUTHEAST MICHIGAN CAN EXPECT A TRANQUIL SHORT TERM PERIOD AS A
BROAD CORRIDOR OF HEIGHT RISES ASSOCIATED WITH A PROGRESSIVE
UPSTREAM RIDGE WORKS ACROSS THE AREA. THE ASSOCIATED SURFACE HIGH,
CURRENTLY OVER CENTRAL ONTARIO, WILL TRANSLATE ACROSS THE FORECAST
AREA DURING THE NEXT 24 HOURS AND WILL BE FURTHER ENHANCED BY LAKE
AGGREGATE. NORTHERLY FLOW OFF OF LAKE HURON WILL KEEP HIGH
TEMPERATURES CONFINED TO THE 70S IN MOST PLACES...60S ALONG THE
IMMEDIATE LAKE HURON SHORELINE...DESPITE THE MOSTLY CLEAR SKIES
SUGGESTED BY DRY REGIONAL FORECAST SOUNDINGS. MID AND HIGH LEVEL
CLOUD DEBRIS ADVECTING OVER THE RIDGE AXIS WILL EVENTUALLY
OVERSPREAD THE AREA AS THE BOUNDARY LAYER DECOUPLES BENEATH THE DOME
OF HIGH PRESSURE. LOWS WILL FALL INTO THE MID 40S TO LOW 50S BEFORE
WINDS MAKE THEIR EVENTUAL TURN TO LIGHT SOUTHERLY BY EARLY SATURDAY
MORNING.

LONG TERM...SATURDAY THROUGH THURSDAY

MID LEVEL RIDGING MARKING CONDITIONS TODAY ACROSS THE PLAINS WILL
PROGRESSIVELY DAMPEN WITH TIME THROUGH THE EARLY PART OF THE
WEEKEND...AS THE HEIGHT FALL EXTENSION OF A CLOSED LOW CENTERED OVER
ALBERTA ROTATES THROUGH THE NORTHERN ROCKIES/PLAINS.  THIS EVOLUTION
WILL COMMENCE COINCIDENT WITH THE NORTHEASTWARD SHEARING OF THE
CLOSED MID LEVEL CIRCULATION AND ATTENDANT GULF MOISTURE PLUME NOTED
ON WATER VAPOR NOW LIFTING INTO SOUTHWEST TEXAS.  BENIGN WEATHER
CONDITIONS WILL EXIST LOCALLY FOR A MAJORITY OF THE SATURDAY PERIOD
WITH RESIDUAL SURFACE RIDGING SLOW TO RELEASE EASTWARD...WHILE THE
EMERGING WARM/MOIST AIR ADVECTIVE COMPONENT LOOKS RATHER WEAK AT THE
ONSET.  THIS PROCESS WILL ALLOW FOR SOME DEGREE OF INCREASING MID
CLOUD THROUGH THE LATTER HALF OF THE DAY AIDED BY ANY REMNANT DEBRIS
CLOUD SPILLING EASTWARD FROM EARLIER UPSTREAM CONVECTION.  A HIGHER
DEGREE OF INSOLATION EARLY ON INTO THE GRADUALLY MODERATING LOW
LEVEL THERMAL PROFILE WILL SUPPORT HIGHS MAINLY IN THE UPPER 70S.

MAIN PIECE OF THE SOUTHERN MID LEVEL WAVE WILL FUNNEL ALONG THE EDGE
OF THE DEAMPLIFYING RIDGE AND ACROSS THE NORTHERN OHIO VALLEY/LOWER
MICHIGAN CENTERED ON THE SATURDAY NIGHT PERIOD.  A SHARP BUT
NARROW CORRIDOR OF HIGHER 850-700 MB THETA-E AIR WILL ALIGN ALONG
THE STRENGTHENING LOW LEVEL SOUTHWEST FLOW...THE EDGE OF THIS
GRADIENT ARRIVING ACROSS SE MICHIGAN AS EARLY AS SATURDAY EVENING
/AFTER 21Z/.  GENERAL MOISTENING/DESTABILIZATION THROUGH THIS
PROCESS MAY SUPPORT SOME WIDELY SCATTERED SHOWERS/THUNDER PRODUCTION
DURING THIS TIME.  HOWEVER...GREATER PRECIPITATION POTENTIAL ARRIVES
OVERNIGHT TIED TO THE SPIKE IN ASCENT LOCKED ONTO THE WAVE AND MOIST
ADVECTION CENTERED ON THE NOSE OF 30-35 KNOTS AT 850 MB.   WHILE
BOTH THE DEGREE OF FORCING AND MOISTURE TRANSPORT APPEAR MORE THAN
ADEQUATE TO YIELD A SOLID AREA OF RAINFALL/EMBEDDED THUNDER...THE
DETAILS CERTAINLY REMAIN SENSITIVE TO THE EVENTUAL TRACK OF THE
WAVE.  00Z NAM/GFS AND 12Z ECMWF DO FAVOR THE WETTER SCENARIO...WITH
HIGHER END RAINFALL AMOUNTS IN THE .5-.75" RANGE ACROSS SOUTHERN
SECTIONS OF LOWER MICHIGAN.  HOWEVER...A PLAUSIBLE SCENARIO DOES
EXIST FOR THE BETTER FORCING TO SWEEP BY TO THE SOUTH...SO AT THIS
STAGE WILL REMAIN CAUTIOUS ON POPS WITH A SIMPLE CHANCE MENTION.

SE MICHIGAN SETTLES WITHIN LOW AMPLITUDE MID LEVEL WESTERLY FLOW ON
SUNDAY.  A PERIOD OF SUBSIDENCE IN THE WAKE OF THE EXITING SHORTWAVE
AND DEEPER MOISTURE GRADIENT WILL LEAVE A BACKGROUND ENVIRONMENT
LESS SUPPORTIVE OF CONVECTIVE DEVELOPMENT DURING THE DAY.
ADDITIONAL WEAKER SHORTWAVE ENERGY WORKING THROUGH THE MEAN FLOW
WOULD PROVIDE THE ONLY WRINKLE...HARD TO IDENTIFY ANY SUCH FEATURE
AT THIS POINT AND WILL CONFINE POPS TO A MINIMAL CHANCE.  NEUTRAL
THERMAL ADVECTION IN THIS WESTERLY FLOW...GENERAL AIRMASS
MODIFICATION WITH PLENTY OF INSOLATION AND GOOD MIXING BRINGING
HIGHS TOWARD THE LOWER 80S.

FOCUS INTO THE MONDAY PERIOD TURNS TO THE EVENTUAL SOUTHEASTWARD
EJECTION OF THE LOW PRESSURE SYSTEM OVER SOUTHWEST CANADA.  A
CORRIDOR OF SOLID MID LEVEL FORCING IN THE PRESENCE OF FAVORABLE
ENTRANCE JET DYNAMICS WILL ACCOMPANY THE PASSAGE OF THIS
WAVE...ACTUAL TIMING WITHIN THE MONDAY AND MONDAY NIGHT PERIOD STILL
UP FOR DEBATE.  THE DEGREE OF DESTABILIZATION WILL BE DICTATED BY
THIS QUESTION OF TIMING...AN ARRIVAL DURING OR JUST AFTER PEAK
HEATING CERTAINLY YIELDING A MORE SUPPORTIVE ENVIRONMENT FOR
CONVECTIVE DEVELOPMENT/STRENGTH.  COOLER/DRIER CONDITIONS TAKE HOLD
IN THE WAKE OF THIS SYSTEM FOR THE MIDWEEK PERIOD.

MARINE...

PERSISTENT MODERATE NORTHERLY WINDS WILL ALLOW SIGNIFICANT WAVE
HEIGHTS TO BUILD TO 3 TO 4 FEET ACROSS THE SOUTHERN THIRD OF LAKE
HURON TODAY. WEAK SURFACE PRESSURE GRADIENT CONDITIONS WILL THEN
FAVOR LIGHT AND VARIABLE CONDITIONS FOR THE REMAINDER OF THE
FORECAST PERIOD WITH SIGNIFICANT WAVES GENERALLY REMAINING BELOW 2
FEET. A CHANCE OF THUNDERSTORMS WILL RETURN TO AREA WATERS FOR THE
LATTER HALF OF THE WEEKEND INTO EARLY NEXT WEEK.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
SHORT TERM...JVC
LONG TERM....MR
MARINE.......JVC


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