Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 161934
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
334 PM EDT SAT AUG 16 2014

.SHORT TERM...THROUGH TONIGHT

DOMINATE MID/UPPER LEVEL LOW CURRENTLY LIFTING FURTHER NE THROUGH
QUEBEC. MEANWHILE AN UPPER LEVEL JET STREAK IS DIVING INTO THE WEST
SIDE OF THE TROUGH OVER LAKE HURON WHICH IS PRODUCING ONE LAST ROUND
OF CONVECTION OVER THE AREA BEFORE RIDGING BUILDS IN. THE SFC
REFLECTION OF THE LOW IS ALREADY OVER SOUTHERN ONTARIO AS IT FEELS
THE INFLUENCE OF THE LARGE SCALE ANTICYCLONE...BUT IT IS PULLING A
TRAILING COLD FRONT SOUTH THROUGH THE STATE WHICH WILL REACH MBS
AROUND 00Z AND DTW AROUND 06Z. LEADING BAND OF CONVECTION WAS WELL
ORGANIZED OVER NORTHERN LOWER BUT LOST MOST OF ITS CHARACTER AS IT
OUT RAN THE WEAK FORCING OF THE FRONT ITSELF AND STARTED GETTING
INTO MORE DRY AND STABLE AIR OVER SOUTHERN LOWER. AS
EXPECTED...INSTABILITY IS ALMOST NON EXISTENT OVER SE MI. DIURNAL
HEATING IS HELPING SOMEWHAT WITH SPC MESOANALYSIS SHOWING A COUPLE
HUNDRED J/KG JUST TO OUR WEST. SKIES STAYED PRETTY CLEAR OVER THAT
AREA TODAY WITH MOISTURE ADVECTION FROM THE SW BUMPING UP DEWPOINTS
INTO THE LOW 60S VS OUR MID 50S. FOR THE OVERNIGHT...THE FRONT WILL
INTERACT WITH DEEPER MOISTURE FROM THE SW AND ANY INSTABILITY THAT
CAN BUILD THIS AFTERNOON...IN ADDITION TO THE RIGHT ENTRANCE REGION
OF THE 80 KNOT JET STREAK...TO PRODUCE SCATTERED TO LIKELY
SHOWERS/THUNDERSTORMS ACROSS THE REGION. CONFIDENCE IS DECREASING IN
CONVECTION POTENTIAL AS THE FRONTAL FORCING IS QUITE WEAK...LAPSE
RATES ARE LESS THAT DESIRABLE OUTSIDE OF A BRIEF WINDOW OF LL LAPSE
RATES BEFORE SUNSET...AND INSTABILITY IS STRUGGLING TO ACCUMULATE AS
TEMPERATURES WERE SLOW TO RISE TODAY WITH THE EARLY CLOUDS. LOOKING
AT HIRES MODELS...THEY ARE BEGINNING TO HINT AT THE WARM FRONT
EXTENDING OUT OF THE SFC LOW OVER IL...PRODUCED FROM THE CUTOFF
UPPER LOW OVER THE MID MISSISSIPPI VALLEY...WILL ACTUALLY BECOME THE
MORE DOMINATE RAIN PRODUCER WITH ISENTROPIC ACCENT HELPING FUEL
SHOWERS ALONG AND SOUTH OF THE MI BORDER. AT THIS POINT ITS HARD TO
JUMP OFF THE COLD FRONTAL SHOWER SOLUTIONS AS IT HAS BEEN
REGENERATING PRECIP OVER WI OVER THE LAST COUPLE HOURS. WILL HOLD ON
TO MOSTLY CHANCE SHOWERS/THUNDERSTORMS WITH LIKELY POPS OVER THE I69
CORRIDOR FOR THIS EVENING. HIGH PRESSURE BUILDING INTO THE REGION
BEHIND THE COLD FRONT WILL PUT AN END TO SHOWERS THROUGH THE NIGHT
FROM NORTH TO SOUTH. THE HIGH WILL CLEAR SKIES AND BRING LIGHT WINDS
UNDER A NOCTURNAL INVERSION STRENGTHENED WITH SUBSIDENCE WHICH WILL
LIKELY BRING AT LEAST PATCHY FOG IN BEHIND THE EXITING
FRONT/SHOWERS.

&&

.LONG TERM...MONDAY THROUGH SATURDAY

ONCE COLD FRONT CLEARS AREA AND SETTLES INTO THE OHIO VALLEY...THE
WEATHER PATTERN WILL BE GENERALLY QUIET FROM SUNDAY INTO MONDAY AS
THE SOUTH EDGE OF A LARGE SURFACE HIGH SHIFTS EASTWARD THROUGH THE
GREAT LAKES AS THE CENTER OF THE HIGH PROGRESSES FROM ONTARIO INTO
QUEBEC. RESIDUAL MOISTURE ALONG THE NORTHERN FRINGE OF THE FRONTAL
BOUNDARY TO THE SOUTH WITH PROVIDE A CHANCE OF ISOLATED SHOWERS OR
THUNDERSTORMS FROM I 94 SOUTH WITH DRY WEATHER FURTHER NORTH. IF
CURRENT TRENDS CONTINUE AND THE HIGH PRESSURE SETTLES FURTHER SOUTH
ITO THE AREA...ALL MENTION OF RAIN CHANCES MAY BE ABLE TO BE REMOVED
IN COMING FORECASTS THROUGH MONDAY.

DAYS 4 THROUGH 7: A LOW PRESSURE SYSTEM DROPS OUT OF MANITOBA INTO
WISCONSIN TUESDAY AFTERNOON AND MOVES EAST ACROSS THE GREAT LAKES
REGION WEDNESDAY. SHOWERS AND THUNDERSTORMS CAN BE EXPECTED
WEDNESDAY AND THURSDAY. A RESIDUAL UPPER LEVEL TROUGH WILL LINGER
OVER THE EASTERN GREAT LAKES INTO SATURDAY AND WILL KEEP
AT LEAST SOME WEAK CHANCES FOR SHOWERS AND THUNDERSTORMS IN THE
FORECAST THROUGH THE EXTENDED PERIOD.

&&

.MARINE...

WILL ALLOW THE SMALL CRAFT ADVISORY TO EXPIRE WITH THIS ISSUANCE AS
SOUTHWEST FLOW OVER SAGINAW BAY HAS ALREADY EASED TO 15 KNOTS WITH
GUSTS ONLY TO 20 KNOTS. THIS TREND WILL CONTINUE...ESPECIALLY AS
WINDS VEER TO THE WEST WITH THE APPROACH OF A COLD FRONT.

THIS PASSING COLD FRONT WILL BRING SCATTERED SHOWERS AND A FEW
STORMS TO THE AREA THROUGH TONIGHT...SHIFTING FROM SOUTHERN LAKE
HURON THIS AFTERNOON/EVENING TO LAKE ERIE BY THE OVERNIGHT HOURS.

NORTHERLY FLOW WILL THEN BECOME ESTABLISHED BEHIND THIS FRONT AS
HIGH PRESSURE BEGINS TO BUILD INTO THE AREA. THIS PERSISTENT NORTH
FLOW WILL LEAD TO A SLIGHT INCREASE IN WAVES INTO MONDAY...BUT WIND
SPEEDS WILL GENERALLY REMAIN LOW ENOUGH TO PRECLUDE ANY ADDITIONAL
HEADLINES.

&&

.AVIATION...ISSUED 127 PM EDT SAT AUG 16 2014

//DISCUSSION...

A COLD FRONT WILL PASS THROUGH THE AREA TONIGHT WITH A LINE OF
SHOWERS AND ISOLATED THUNDERSTORMS LEADING THE WAY THIS
AFTERNOON/EVENING. THE LINE IS FEELING THE EFFECTS OF THE MORE
STABLE AIR OVER SOUTHERN MI THUS HAS BECOME QUITE UNORGANIZED THE
LAST FEW HOURS. LOOK FOR SOME REGENERATION IN THE COMING HOURS AS
AFTERNOON HEATING PRODUCES WEAK INSTABILITY OVER SE MI. WITH TRENDS
IN RADAR AND MODEL OUTPUT...FEEL LESS CONFIDENT WITH AREAL COVERAGE
OF THUNDER THUS WENT WITH A TEMPO SHRA VS TSRA. WILL MONITOR FOR ANY
AMENDMENTS IF ANY SHOWER BECOMES MORE ROBUST. AS PREVIOUSLY
MENTIONED...FOG REMAINS A CONCERN FOR ALL TAF SITES AS PRECIP MOVES
OFF AND HIGH PRESSURE SETTLES INTO THE AREA.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN THUNDERSTORM POTENTIAL LATE THIS AFTERNOON AND
  EVENING.

* LOW CONFIDENCE IN VISIBILITIES REDUCING TO LESS THAN 1 MILE SUNDAY
  MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...SAGINAW BAY...UNTIL 4 PM SATURDAY.

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

&&

$$

SHORT TERM...DRK
LONG TERM....DG/DE
MARINE.......DG
AVIATION.....DRK


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






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