Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 221427
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1027 AM EDT FRI AUG 22 2014

.UPDATE...

GRADUAL EROSION OF THE EARLY DAY STRATUS/FOG...WITH A TRANSITION TO
A BROADER DIURNAL CU FIELD NOW UNDERWAY LOCALLY.  TEMPERATURES
ALREADY IN THE LOW-MID 70S...SUGGESTING TEMPERATURES CLOSING IN ON
THE 80 DEGREE MARK REMAIN ATTAINABLE EVEN UNDER LESS OPTIMAL
INSOLATION POTENTIAL IN SOME LOCALES. WITH THAT...THIS WILL YIELD
A WEAKLY UNSTABLE ENVIRONMENT GIVEN THE ELEVATED NEAR SURFACE
MOISTURE CONTENT. DEFINED LOW-MID LEVEL THETA-E GRADIENT ANCHORED
ALONG THE NORTHEAST PERIPHERY OF STRENGTHENING UPPER RIDGING
RESIDES JUST TO THE SOUTH AND WEST LATE THIS MORNING. RECENT HI-
RES MODEL SOLUTIONS POINT TO THIS BOUNDARY AS A POTENTIAL ANCHOR
POINT FOR LOW END CONVECTIVE DEVELOPMENT FROM MID AFTERNOON INTO
THE EVENING PERIOD. HOWEVER...THIS CORRIDOR REMAINS UNDER A
THICKER CANOPY OF LOW CLOUDS AT PRESENT...SUGGESTING THE DEGREE
THE DESTABILIZATION WILL BE QUITE LIMITED. THE CURRENT SETUP
CONTINUES TO SUPPORT SIMPLY A SMALL CHANCE POP ROUGHLY ALONG AND
SOUTH OF THE I-96 CORRIDOR FOR LATE TODAY. MINOR UPDATE
FORTHCOMING MAINLY TO FRESHEN THE WORDING.

&&

.AVIATION...ISSUED 554 AM EDT FRI AUG 22 2014

//DISCUSSION...

VARIABLE CONDITIONS ACROSS THE AREA THIS MORNING AS WE TRY TO SCOUR
AWAY THE IFR FOG FROM THE OVERNIGHT. THE MOIST AIRMASS WILL REMAIN
IN PLACE THROUGH THE TAF CYCLE AS WE STILL RESIDE ON THE NORTH SIDE
OF A SLOWLY RETREATING WARM FRONT. THIS WILL RESULT IN A CHANCE OF
SHOWERS AND THUNDERSTORMS THROUGH THE DAY AND MORE FOG DURING THE
OVERNIGHT. LOW CONFIDENCE IN COVERAGE OF PRECIPITATION AS THERE IS
NO REAL FORCING MECHANISM TO KEY IN ON SO WILL LEAVE OUT OF THE TAFS
FOR NOW THOUGH BETTER CHANCES WILL BE OVER THE DETROIT TAFS AS
OPPOSED TO FNT AND MBS. SKIES WILL ATTEMPT TO CLEAR TONIGHT WHICH
WILL AIDE IN IFR/MVFR FOG FORMATION.

//DTW THRESHOLD THREATS...

* MODERATE CONFIDENCE ON CEILING BELOW 5000 FT THROUGH THIS
AFTERNOON.

* LOW CONFIDENCE IN COVERAGE AND TIMING OF ANY THUNDERSTORMS TODAY.

* LOW CONFIDENCE ON VISIBILITY DROPPING BELOW A 1/2SM TONIGHT.

&&

.PREV DISCUSSION...ISSUED 332 AM EDT FRI AUG 22 2014

SHORT TERM...TODAY AND TONIGHT

EASTERLY FLOW WILL PERSIST THROUGH THE FORECAST PERIOD AS WE WILL
REMAIN UNDER THE ELEVATED WARM FRONT WHICH IS ROOTED AT THE SFC
ALONG MI/OH BORDER. THE SFC WARM FRONT WILL NOT RETURN TO THE AREA
BEFORE IT BEGINS TO RETREAT SOUTHWARD LATER TODAY THUS WE WILL BE
DEALING WITH ELEVATED CONVECTION PERIODICALLY THROUGH THE DAY.

CURRENT RADAR MOSAIC SHOWS THE NEXT CONVECTIVE COMPLEX DEVELOPING
OVER THE CHICAGO AREA. IT...AS THE PREVIOUS MCS THURSDAY EVENING
DID...WILL TRACK TO THE SOUTH OF THE AREA AS THE SHORTWAVE OVER OHIO
CONTINUES TO REORIENTATE THE 850MB JET MORE WEST TO EAST ACROSS THE
OHIO VALLEY. EVEN WITHOUT THE FORCING OF THE JET...THE ATMOSPHERE
REMAINS VERY RIPE FOR SCATTERED SHOWERS AS RIBBON OF VERY RICH THETA
E RESIDES ACROSS SOUTHERN MI. SHOWERS HAVE PERSISTED THROUGH THE
NIGHT ON THE NORTHERN EDGE OF THIS RICH AIRMASS...PWATS AROUND 1.75
INCHES. WEAK FLOW INTO THE MID LEVELS...30 KNOTS AT 500 MB PER THE
DTX 22.00Z SOUNDING HAS LED TO A SLOW FORWARD SPEED OF THE
SHOWERS/STORMS MAKING FLOODING A CONCERN FOR ANY AREA THAT GETS A
HEALTHY STORM OR TWO.

THE OVERALL PATTERN DOES NOT CHANGE MUCH FROM WHAT WE SEE CURRENTLY
INTO THE AFTERNOON TODAY. WITH A LACK OF NOTABLE FORCING MECHANISM
OR SHORTWAVE AND MODEL FORECAST CAPE VALUES ONLY AROUND 200
J/KG...FIND IT HARD TO CONTINUE THE LIKELY POPS THUS LOWERED INTO
MID/HIGH CHANCE FOR THE SOUTHERN BORDER AND LOWERING AS ONE HEADS
NORTH. A GENERAL CHANCE POP WILL HANDLE THE SCENARIO WELL UNTIL A
MORE ORGANIZED COMPLEX SHOWS ITSELF. HIRES MODELS ALL AGREE WITH
THIS CHANGE BY HAVING MORE ORGANIZED COMPLEXES TRACKING TO THE SOUTH
WITH SPORADIC SHOWERS/THUNDERSTORMS OVER THE AREA ON THE ELEVATED
FRONTAL SFC.

THE TONIGHT PERIOD IS A LITTLE TRICKY. THE STEEPENING OF THE MID
LEVEL RIDGE OVER THE UPPER MISSISSIPPI VALLEY WILL PULL THE DEEP
MOISTURE AXIS BACK WESTWARD BUT LEAVES SOME RESIDUAL POCKETS OVER
THE AREA BEFORE HIGH PRESSURE FROM THE EAST CAN TAKE OVER. OVERALL
THE SHOWERS/THUNDERSTORMS LOOK TO SHUT OFF AROUND SUNSET ALTHOUGH
WOULD NOT BE SURPRISED TO SEE A LINGER SHOWER BETWEEN 00-03Z. WITH
THE RESIDENT BL AIRMASS CHANGING LITTLE OVER THE NEXT DAY...ELEVATED
DEWPOINTS IN THE MID 60S WILL KEEP MIN TEMPS UP BUT ALSO PRODUCE
AREAS OF FOG ONCE AGAIN AS SKIES TRY TO CLEAR TOWARD MORNING.

LONG TERM... SATURDAY THROUGH THURSDAY

ONGOING DEEPENING OF THE LONG WAVE TROUGH OVER THE PACIFIC NORTHWEST
WILL LEAD TO DOWNSTREAM AMPLIFICATION OF THE SUBTROPICAL RIDGE OVER
THE ERN US THIS WEEKEND. THE LATEST MODEL SUITE CONTINUE TO SUPPORT
FAIRLY GOOD MID LEVEL HEIGHT RISES ACROSS SE MI THIS WEEKEND AS THE
RIDGE AXIS EXTENDS ACROSS LOWER MI. THE UPPER LEVEL ANTICYCLONE NOW
PARKED OVER NRN QUEBEC WILL BUILD SOUTH BEFORE BEING ABSORBED INTO
THE EXPANDING SUBTROPICAL RIDGE. THIS WILL FORCE THE LARGE SURFACE
HIGH OVER ERN CANADA TO EXPAND INTO THE EASTERN GREAT LAKES THIS
WEEKEND...LEADING TO SLIGHTLY STRONGER E-SE FLOW ACROSS THE FORECAST
AREA. ADVECTION OF SLIGHTLY COOLER AND LESS HUMID AIR WILL RESULT.
MODEL SOUNDINGS SUGGEST DAYTIME INSOLATION WILL STILL BOOST SAT AND
SUN HIGHS INTO THE LOW 80S AND DEWPOINTS SHOULD STILL REMAIN IN THE
60S. THE MORE STABLE AIRMASS BUILDING IN FROM THE EAST AND WARMING
TEMPS IN THE MID LEVELS WILL SUPPORT A DRY FORECAST FOR THE ENTIRE
WEEKEND. ALL OF THE 00Z MODEL SOLUTIONS DO HOWEVER SUGGEST SOME
HIGHER LOW LEVEL MOISTURE ADVANCING FROM THE MID ATLANTIC INTO THE
ERN GREAT LAKES SAT NIGHT WITHIN SLIGHTLY ENHANCED SE FLOW. THIS
COMBINED WITH THE WARM LAKE ERIE WATERS MAY LEAD TO CONSIDERABLE LOW
CLOUDS AND/OR FOG SAT NIGHT INTO SUN MORNING.

ENERGY EJECTING OUT OF THE WRN US LONG WAVE TROUGH WILL TRACK INTO
CNTL AND ERN CANADA EARLY NEXT WEEK. THIS WILL DAMPEN THE MID LEVEL
RIDGE AXIS OVER THE GREAT LAKES REGION. THE LOW LEVEL FLOW WILL
HOWEVER TURN TOWARD THE S-SW AND WILL OPEN THE DOOR FOR HEAT AND
HUMIDITY TO FILTER INTO SE MI. HIGH TEMPS MON AND POSSIBLY INTO TUES
MAY TOP 90 DEGREES. MODEL SOUNDINGS ARE SUGGESTING THE ATMOSPHERE
WILL BE CAPPED ON MONDAY. THE MOST RECENT ECMWF IS ACTUALLY
SUGGESTING A STRONG CAP PERSISTING INTO TUESDAY...SO CONVECTIVE
CHANCES MAY ACTUALLY BE QUITE LOW. A TREND TOWARD A MORE PROGRESSIVE
FLOW NEXT WEEK HAS BEEN SHOWN BY THE MEDIUM RANGE MODEL SUITE...
FEATURING MID LEVEL TROUGHING ADVANCING INTO THE GREAT LAKES BY THE
MIDDLE OF NEXT WEEK /TUES NIGHT - WED NIGHT/. DESPITE POOR RUN TO
RUN CONTINUITY WITH RESPECT TO TIMING AND AMPLITUDE OF THIS
ENERGY...THE MID LEVEL HEIGHT FALLS ACROSS THE MODERATE INSTABILITY
OVER SE MI WILL SUPPORT A GOOD CHANCE OF CONVECTION DURING THIS TIME
PERIOD. COOLER AND DRIER AIR THEN LOOKS TO FUNNEL IN BY THE END OF
THE FORECAST PERIOD.

MARINE...

A FAIRLY LARGE REGION OF HIGH PRESSURE WILL EXPAND ACROSS THE
EASTERN GREAT LAKES OVER THE NEXT COUPLE OF DAYS. THIS WILL LEAD TO
LIGHT EAST-SOUTHEAST WINDS ACROSS THE LAKES. SOME SLIGHTLY GUSTIER
NE WINDS MAY OCCUR WITHIN THE WARMER WATERS OF SAGINAW BAY FROM TIME
TO TIME AS THE WIND GETS FUNNELED INTO THE BAY. OTHERWISE...WINDS
AND WAVES WILL PROVIDE FAVORABLE BOATING CONDITIONS.

&&

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

&&

$$

UPDATE.......MR
AVIATION.....DRK
SHORT TERM...DRK
LONG TERM....SC
MARINE.......SC


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





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