Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 101424
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1024 AM EDT THU JUL 10 2014

.UPDATE...
FORECAST WAS UPDATED TO INCLUDE A SLIGHT CHANCE MENTION FOR
SHOWERS OVER FAR SOUTHEAST MICHIGAN. LOW-LEVEL THERMAL TROUGHING
IS EXPECTED TO LINGER OVER THIS AREA THIS AFTERNOON BEFORE THE
UPPER TROUGH SEEN PUSHING ACROSS THE CENTRAL GREAT LAKES ON WATER
VAPOR CLEARS THE AREA. THIS MAY PROVIDE A FOCUS FOR A FEW LIGHT
SHOWERS THIS AFTERNOON. CONVECTION SHOULD BE FAIRLY SHALLOW
HOWEVER WITH MODEL FORECAST SOUNDINGS SHOWING SUBSIDENCE FROM
INCOMING HIGH PRESSURE KEEPING A CAP UP NEAR 8000 FEET. STEEP
LAPSE RATES SHOULD DEVELOP BETWEEN THE SURFACE AND THIS LAYER AS
DAYTIME HEATING INTENSIFIES AND THE UPPER COLD POOL WORKS ACROSS.
OTHERWISE...FORECAST LOOKS ON TRACK WITH POTENTIAL FOR SHOWERS
ENDING DURING THE EARLY EVENING AS WE LOSE DIURNAL HEATING AND
HIGH PRESSURE SLIDES OVERHEAD.

&&

.AVIATION...ISSUED 641 AM EDT THU JUL 10 2014

//DISCUSSION...

HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH TONIGHT.
DAYTIME HEATING WILL RESULT IN A SCT TO BKN COVERAGE OF VFR CU THIS
AFTERNOON.  EXPECTATIONS REMAIN FOR CEILINGS TO EMERGE WITHIN THE
4500 TO 6000 FT LEVEL.  LOSS OF HEATING WILL BRING RAPID CLEARING
INTO THE EVENING.  LIGHT EASTERLY FLOW THROUGH THE PERIOD.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS AT OR BELOW 5000 FT THIS AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 352 AM EDT THU JUL 10 2014

SHORT TERM... TODAY AND TONIGHT

STEADY INCREASE IN UPPER HEIGHTS OVER THE NEXT 24 HOURS AS THE
TRAILING SECTION OF THE RECENT MID LEVEL TROUGHING FINALLY EXITS TO
THE EAST.  OVERALL AIR MASS MODIFICATION WILL OCCUR LARGELY THROUGH
SOME UPWARD ADJUSTMENT IN THE THICKNESS FIELDS...SIMPLY A MINOR
TREND ENSURING A SEASONABLY COOLER AND LESS HUMID ENVIRONMENT FOR
EARLY JULY STANDARDS REMAINS FIRMLY IN PLACE TODAY.  HIGHS MAINLY
LOWER TO MIDDLE 70S...WITH DEWPOINTS COMFORTABLY IN THE LOWER 50S.
MODEST ONSHORE FLOW WILL LEAVE THOSE LOCALES CLOSER TO THE LAKESHORE
STRUGGLING TO REACH 70F.   RESIDUAL LOW LEVEL THERMAL TROUGHING
AND DIURNAL HEATING WILL CONTRIBUTE TO A FAIR AMOUNT OF CUMULUS
DURING THE DAY.   LOW LEVEL ANTICYCLONIC FLOW IN PLACE INTO
TONIGHT.  A MOSTLY CLEAR SKY AND LIMITED GRADIENT FLOW AGAIN
YIELDING A LOW TEMPERATURE DISTRIBUTION IN THE 50S...THE COLDEST
LOCATIONS MAKING A RUN TOWARD THE UPPER 40S.

LONG TERM...

LATEST WATER VAPOR IMAGERY SHOWS THE PENDING MERGING OF 500 MB UPPER
LEVEL LOWS...ONE CURRENTLY CENTERED ALONG THE BRITISH
COLUMBIA/ALBERTA BORDER...AND THE ONE DESCENDING FROM THE ARCTIC
CIRCLE. THE 00Z MEDIUM RANGE MODELS CONTINUE TO ADVERTISE THE MERGED
POLAR VORTEX IMPACTING THE GREAT LAKES REGION BY EARLY NEXT WEEK.
BEFORE WE GET THERE...NO CONCERNS FRIDAY AS SHORTWAVE UPPER LEVEL
RIDGE RESIDES OVER THE CENTRAL GREAT LAKES...WITH RELATIVELY DRY
AIRMASS IN PLACE...PW VALUES AROUND 0.75 INCHES. 850 MB TEMPS RISING
TO 13 C SUPPORT MAXES IN THE LOWER 80S...BUT SOME CONCERN CANOPY OF
HIGH CLOUDS MAY ARRIVE DURING AFTERNOON AHEAD OF THE PENDING
MOISTURE SURGE...AS UPPER LEVEL FLOW FLATTENS OUT...AND WILL HOLD
MAXES NEAR 80 DEGREES. STILL LOTS OF UNCERTAINTY WHETHER ENOUGH
MOISTURE ADVECTION/DESTABILIZATION WILL OCCUR OVER SOUTHEAST
MICHIGAN FRIDAY NIGHT TO SUPPORT SHOWERS...MUCH LESS THUNDERSTORMS.

UPPER LEVEL RIDGING WILL REESTABLISH ITSELF OVER THE REGION ON
SATURDAY AS JET ENERGY EJECTS OUT OF THE NORTHERN ROCKIES. THAT
UPPER LATER ENERGY AND MOISTURE SURGE LOOKS TO BE OCCURRING NEAR OR
SHORTLY AFTER 00Z SUNDAY...SUPPORTING HIGH CHANCE POPS SATURDAY
NIGHT.

THE FORECAST IS BIT MORE MUDDLED SUNDAY-MONDAY AS WE RESIDE IN
RELATIVELY MOIST ENVIRONMENT (ALTHOUGH DEEPER MOISTURE IS OVER THE
OHIO VALLEY) WITH ACCELERATING HEIGHT FALLS...WITH FROPA PASSAGE
SOMETIME MONDAY. COLD POOL ALOFT/TROUGH AXIS THEN TO SWING THROUGH
THE CENTRAL GREAT LAKES ON TUESDAY...WITH 1000-500 MB THICKNESSES
ADVERTISED TO BE AROUND 552 DAM. MAXES WILL LIKELY COME UP SHORT OF
70 DEGREES IF THAT COLD AIRMASS COMES TO FRUITION.

MARINE...

HIGH PRESSURE IN CONTROL TODAY INTO TOMORROW WILL PROVIDE LIGHT
WINDS AND LOW WAVES. LIGHT SOUTHERLY WINDS FRIDAY NIGHT WILL BRING
WARMER AND MORE HUMID AIR INTO THE REGION WITH A CHANCE OF SHOWERS
AND THUNDERSTORMS FRIDAY NIGHT THROUGH THE WEEKEND...OTHERWISE WINDS
LOOK TO BE STAYING LIGHT.

&&

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

&&

$$

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


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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