Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270346
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1146 PM EDT WED AUG 26 2015

.AVIATION...

DEFINITIVE CLEARING TREND OVER CENTRAL AND WESTERN LOWER MICHIGAN
THIS EVENING WHILE STRATUS IS SLOWER TO ERODE FOR KMBS AND POINTS
NORTH WHERE CONDITIONS REMAIN MORE FAVORABLE FOR STRATUS MAINTENANCE
IN THE SHORT TERM. AS SUCH, THE PERIOD BEGINS WITH EXPECTATION FOR
SCATTERED COVERAGE AT KFNT/KPTK WITH EXTRAPOLATION SUGGESTING THE
DETROIT SITES TO SCATTER AROUND AN HOUR LATER...APPROX 07Z. SEVERAL
HOURS OF SKC-SCT COVERAGE WILL BE POSSIBLE BEFORE DEVELOPMENT OF
MVFR CIG WITH ONSET OF DIURNAL HEATING THIS MORNINGS. CEILINGS WILL
LIFT TO LOW VFR DURING THE DAY. LIGHT NW TO NNW WINDS THIS MORNING
WILL BECOME VARIABLE UNDER HIGH PRESSURE THIS AFTN.

FOR DTW...EXPECT CLEARING AT KDTW BY AROUND 07Z. ONCE CIGS SCATTER
EXPECT CLEAR OR NEARLY CLEAR SKIES TO DOMINATE UNTIL DIURNAL
STRATOCU DEVELOPMENT GETS UNDERWAY. BEST ESTIMATE FOR CIG
REDEVELOPMENT IS 14-15Z.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AOB 5KFT THROUGH 7Z. LOW 07Z-14Z. MEDIUM AFTER 14Z.

&&

.PREV DISCUSSION...ISSUED 320 PM EDT WED AUG 26 2015

SHORT TERM...THIS EVENING AND TONIGHT

MUCH LIKE YESTERDAY...IT WILL BE ANOTHER AUTUMN-LIKE EVENING WITH
COOL TEMPERATURES AND AMPLE CLOUD COVER. DIURNALLY ENHANCED CLOUDS
WITHIN THE LOW LEVEL THERMAL TROUGH ASSOCIATED WITH THE DEEP UPPER
LOW OVER NRN QUEBEC ONCE AGAIN LED TO PRIMARILY OVERCAST SKIES
ACROSS SE MI. THERE HAS BEEN LESS IN THE WAY OF SHOWERS ACROSS THE
FORECAST AREA TODAY...WHICH HAS SUPPORTED SLIGHTLY WARMER TEMPS
COMPARED TO THIS TIME YESTERDAY /THESE TEMPS ARE STILL NEARLY 15 DEG
BELOW LATE AUGUST AVERAGES/. RECENT WATER VAPOR IMAGERY HAS BEEN
SHOWING DRIER MID LEVEL AIR ADVANCING INTO LOWER MI THIS AFTERNOON
IN THE WAKE OF A MID LEVEL SHORT WAVE IMPULSE NOW MOVING FROM SE MI
INTO NRN OHIO. THIS ALONG WITH THE DEPARTURE OF THE UPPER LOW TO THE
NORTHEAST ACROSS QUEBEC TONIGHT WILL SUSTAIN MID LEVEL SUBSIDENCE
AND DRYING. WHILE THERE HAVE BEEN SOME RECENT BREAKS IN THE CLOUDS
/ESPECIALLY IN THE LEE OF LAKE MICHIGAN/...THE EXTENT OF LOW LEVEL
MOISTURE SHOULD MAINTAIN OVERALL MOSTLY CLOUDY SKIES THIS EVENING
OVER MUCH OF SE MI.

SFC HIGH PRESSURE WILL BUILD INTO LOWER MI FROM THE WEST DURING THE
NIGHT UNDER RISING MID LEVEL HEIGHTS. THIS WILL CAUSE THE LAKE
AGGREGATE TROUGH NOW EXTENDING ACROSS THE GREAT LAKES TO WEAKEN...
LEADING TO INCREASINGLY DIVERGENT SFC FLOW. THIS ALONG WITH THE LOSS
IN DIURNAL HEATING AND AN EXPECTED SHALLOW LOW LEVEL INVERSION WILL
SUPPORT SOME DEGREE OF CLEARING OVERNIGHT. HEAT FLUX OVER THE WATER
MAY HOWEVER SUSTAIN SOME TROUGHING OVER LAKE HURON TONIGHT...AS
SHOWN BY THE NAM AND RAP. THIS MAY SUPPORT SOME LINGERING CLOUDS
/POSSIBLY LIGHT SHOWERS OR DRIZZLE/ ACROSS THE THUMB REGION. IN
ANTICIPATION OF SOME DEGREE OF CLEARING TONIGHT...FORECAST MINS DOWN
IN THE 50S LOOK REASONABLE. IF CLEARING IS MORE PROLONGED...SOME
LOWS IN THE 40S ALONG WITH SOME RADIATIONAL FOG WILL BE POSSIBLE.

LONG TERM...THURSDAY THROUGH FRIDAY NIGHT

PERSISTENT LARGE LOW PRESSURE SYSTEM THAT BROUGHT FALL LIKE WEATHER
PAST SEVERAL DAYS WILL FINALLY MOVE FAR ENOUGH EAST TO ALLOW SURFACE
HIGH PRESSURE TO BUILD IN THURSDAY.  UNFORTUNATELY A DECENT ENOUGH
AMOUNT OF LOW LEVEL MOISTURE WILL STILL LINGER OVER THE FORECAST
AREA. EXPECT DIURNAL CU TO QUICKLY FORM AFTER SUNRISE THOUGH
SCATTERED IN NATURE. THE PROBLEM IS THERE WILL BE A STRONG 850-700MB
INVERSION WHICH WILL SPREAD THE CU OUT AS IT HITS IT PRODUCING A
MOSTLY CLOUDY SKY FOR THE FIRST PART OF THE DAY.  AS DRIER AIR IN
THE LOWER LEVELS FILTER IN THE CLOUDS SHOULD DISSIPATE TO MOSTLY
SUNNY LATE IN THE DAY. WITH A BIT MORE CLOUD COVER HAVE LOWERED
HIGHS A FEW DEGREES FROM THE PREVIOUS FORECAST.

THURSDAY NIGHT INTO THE FIRST PART OF FRIDAY SHOULD SEE CLEAR SKIES
AS SURFACE HIGH PASSES OVERHEAD AND THEN TO THE EAST. RETURN FLOW
FRIDAY AFTERNOON AND ADVANCING SHORTWAVE FROM THE MIDWEST WILL BRING
AN INCREASE IN MID AND UPPER LEVEL MOISTURE AND CLOUDS FRIDAY
AFTERNOON. A DEVELOPING WARM FRONT WILL BEGIN ADVANCING TOWARDS
MICHIGAN FRI NIGHT WITH MODELS HINTING AT ENOUGH MOISTURE AND
FORCING IN THE MID LAYERS TO PRODUCE SOME POSSIBLE SHOWER ACTIVITY
LATE FRIDAY NIGHT.

EXTENDED...A SHORTWAVE EMBEDDED IN LONGWAVE TROUGHING WILL CONTINUE
TO INFLUENCE SOUTHEAST MICHIGAN BRINGING CHANCES FOR PRECIPITATION
THIS UPCOMING WEEKEND.  THE WAVE WILL BE IN THE PROCESS OF WEAKENING
AS IT SLOWLY MIGRATES EAST BEFORE DEPARTING THE AREA ON MONDAY.
BROAD UPPER LEVEL RIDGE THEN BUILDS IN OVER THE GREAT LAKES THROUGH
MUCH OF NEXT WEEK.  SOUTHERLY FLOW WILL COMMENCE ALLOWING TEMPS TO
WARM BACK INTO THE MIDDLE TO UPPER 80S.

MARINE...

EFFECTS FROM A LARGE UNSEASONABLE COLD LOW PRESSURE SYSTEM OVER
HUDSON BAY WILL STILL BRING THE THREAT FOR A FEW SHOWERS AND
POSSIBLE WATERSPOUTS THROUGH TONIGHT.

NORTHWESTERLY FLOW WILL DECREASE IN SPEED OVERNIGHT AND BECOME MORE
VARIABLE LIKE THURSDAY AS LARGE HIG PRESSURE SPREADS ACROSS THE
GREAT LAKES. WINDS WILL BECOME MORE SOUTHERLY FRIDAY AND IN CONTINUE
INTO THE WEEKEND ON THE BACKSIDE OF THE HIGH.  A STORM SYSTEM WILL
TRACK INTO THE GREAT LAKES SATURDAY WHILE WEAKENING. THIS WILL BRING
A CHANCE FOR SHOWERS AND THUNDERSTORMS MAINLY SATURDAY AND SATURDAY
NIGHT.

&&

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

$$

AVIATION.....JVC
SHORT TERM...SC
LONG TERM....DRC/SS
MARINE.......DRC


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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