Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 101718
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
118 PM EDT THU JUL 10 2014


.AVIATION...

//DISCUSSION...

LINGERING MOISTURE BEHIND AN EXITING UPPER LEVEL DISTURBANCE WILL
COMBINE WITH DAYTIME INSTABILITY TO PRODUCE A FAIRLY HEALTHY CUMULUS
FIELD (4500-7000 FEET) THIS AFTERNOON FROM FNT EASTWARD...IN
ADDITION TO A SMALL CHANCE FOR A SHOWER. PROBABILITIES FOR SHOWERS
ARE TOO LOW TO INCLUDE A MENTION IN THE TAFS...AND WOULD EXPECT
LITTLE IMPACT ANYHOW WITH ONLY LIGHT RAIN OR JUST SPRINKLES.
OTHERWISE...HIGH PRESSURE BUILDING INTO THE AREA WILL KEEP WINDS
FAIRLY LIGHT TODAY AND OVERNIGHT. BKN CU DECK IS EXPECTED TO SCATTER
OUT IN THE EARLY TO MID EVENING AS WE START TO LOSE HEATING AND AS
DRIER AIR INFILTRATES THE AREA.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE WITH BROKEN CEILINGS STAYING AT OR BELOW 5000 FT
THROUGH THE LATE AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 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.

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.

&&

$$

AVIATION.....HLO
UPDATE.......HLO
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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