Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 021729
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
129 PM EDT THU OCT 2 2014


.AVIATION...

//DISCUSSION...

A STEADY INCREASE IN MID LEVEL MOISTURE WILL MAINTAIN AN EXTENSIVE
CANOPY OF HIGHER BASED CLOUD COVER THROUGH THE EVENING HOURS.  A FEW
SCATTERED SHOWERS REPRESENTING THIS MOISTURE TRANSPORT MAY IMPACT
MBS/FNT YET THIS AFTERNOON.  CEILINGS WILL GRADUALLY LOWER TONIGHT
AS A WARM FRONT LIFTS ACROSS THE REGION.  HOWEVER A DRY LOWER LEVEL
ENVIRONMENT WILL FAVOR AN EXTENDED VFR CONDITION THROUGH MUCH OF THE
NIGHT.  THE COVERAGE OF SHOWERS IN MVFR WILL INCREASE BY MID-LATE
MORNING ON FRIDAY IN ADVANCE OF A COLD FRONT.  THERE WILL BE THE
POTENTIAL FOR EMBEDDED THUNDER DURING THIS TIME...BUT THE
PROBABILITY REMAINS TOO LOW TO MENTION.  THE PRE-FRONTAL SOUTHERLY
GRADIENT WILL INCREASE LATE TONIGHT AND EARLY FRIDAY.  GUSTS IN
EXCESS OF 20 KNOTS AT TIMES POST-DAYBREAK.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN CEILINGS BELOW 5000 FT TONIGHT...HIGH CONFIDENCE
ON FRIDAY.

* LOW CONFIDENCE ON THUNDERSTORMS IMPACTING THE TERMINAL LATE
TONIGHT AND EARLY FRIDAY.

&&

.PREV DISCUSSION...ISSUED 335 AM EDT THU OCT 2 2014

SHORT TERM...TODAY AND TONIGHT

THE INTERVAL OF CLEAR SKIES LAST EVENING PROVIDED ENOUGH BOUNDARY
LAYER COOLING TO SUPPORT THE DEVELOPMENT OF A NOCTURNAL INVERSION.
SE WINDS WINDS ATOP THIS INVERSION HAVE SUSTAINED ENOUGH MOISTURE
ADVECTION FROM THE EAST TO LEAD TO BOTH LOW CLOUDS AND FOG AGAIN
THIS MORNING. SOME THICK CIRRUS WHICH HAS MOVED IN FROM THE WEST HAS
THUS FAR PROVEN TO HAVE LITTLE EFFECT IN PREVENTING FOG DEVELOPMENT.
BASED ON OBSERVATIONAL TRENDS...SOME OF THE FOG WILL BE DENSE. A
STRENGTHENING SOUTHERLY FLOW ATOP THE INVERSION AND THE ONSET OF
DAYTIME HEATING WILL ERODE THE FOG DURING THE MID-LATE MORNING.

A LOW LEVEL ANTICYCLONE EXTENDING ACROSS THE EASTERN GREAT LAKES
WILL CONTINUE ITS DEPARTURE TO THE EAST TODAY AS A PROGRESSIVE LONG
WAVE TROUGH MOVES OVER THE PLAINS. THE 00Z UPPER AIR ANALYSIS SHOWED
A LARGE REGION OF DEEP LAYER MOISTURE EXTENDING ACROSS THE MS VALLEY
INTO THE WRN GREAT LAKES AHEAD OF THIS SYSTEM. THE SHOWERS NOW
ADVANCING ACROSS LAKE MI ARE OCCURRING WITHIN AN 850-700MB THETA E
RIDGE...WHICH WILL SLOWLY MAKE ITS WAY ACROSS THE FORECAST AREA LATE
THIS MORNING THROUGH THE AFTERNOON. THIS WILL SUPPORT A CHANCE OF
SHOWERS AND A FAIR AMOUNT OF CLOUD COVER ACROSS THE FORECAST AREA
TODAY. INCREASING SOUTHERLY FLOW WILL BOOST 925MB TEMPS INTO THE
UPPER TEENS. THE NAM AND REGIONAL CANADIAN SUGGEST THE WARM FRONT
NOW EXTENDING ACROSS THE MS/OH VALLEYS WILL LIFT TOWARD THE MI/OH
BORDER BY LATE AFTERNOON. TEMPS WILL BE WELL IN THE 70S SOUTH OF
THIS BOUNDARY. TO THE NORTH /OVER SE MI/...FORECAST HIGHS WILL
REMAIN OPTIMISTIC /UPPER 60S-LOW 70S/ GIVEN THE DEGREE OF LOW LEVEL
WARMING EXPECTED.

A STRENGTHENING UPPER JET CORE AHEAD OF A RAPID AMPLIFICATION IN THE
LONG WAVE TROUGH OVER THE NRN PLAINS TONIGHT WILL LEAD TO A
DEEPENING SFC LOW. BY 12Z FRI...THE LOW IS FORECAST TO BE CENTERED
OVER LAKE SUPERIOR WITH THE TRAILING COLD FRONT ACROSS LAKE MI.
STRENGTHENING LOW LEVEL SOUTHERLY FLOW /45-50 KNOTS AT 925-850MB/
WILL SEND ANOTHER SURGE OF LOW LEVEL MOISTURE INTO SE MI. WHILE
SURFACE BASED INSTABILITY IS EXPECTED TO REMAIN SW OF THE AREA
TODAY...THIS SOUTHERLY FLOW WILL TRANSPORT SOME WEAK ELEVATED
INSTABILITY INTO THE FORECAST AREA TONIGHT. LIFT WILL ALSO BE
ENHANCED BY A REMNANT MID LEVEL SHORT WAVE IMPULSE APPROACHING FROM
THE SOUTHWEST LATE. THE RESULT WILL BE INCREASING CHANCES OF SHOWERS
AND A FEW THUNDERSTORM DURING THE NIGHT. THE ADVECTION OF LOW 60 SFC
DEWPOINTS INTO THE FORECAST AREA TONIGHT AND STRONG LOW LEVEL WIND
FIELDS WILL KEEP MIN TEMPS FAIRLY MILD /LOW-MID 60S/.

LONG TERM...

POWERFUL UPPER LEVEL LOW/TROUGH OVER WESTERN CANADA DIVING SOUTHEAST
THIS MORNING...AND WILL BE MERGING/PHASING WITH UPPER WAVE/ENERGY
EXITING THE FOUR CORNERS REGION...LEADING TO MASSIVE UPPER LEVEL
LOW/TROUGH ENCOMPASSING EASTERN NORTH AMERICA THIS WEEKEND...AND
INTO EARLY NEXT WEEK. TEMPERATURES WILL AVERAGE WELL BELOW NORMAL
(10 TO 15 DEGREES). BEFORE WE GET THERE...WILL HAVE TO CONTEND WITH
THE STRONG COLD FRONT BARRELING THROUGH SOUTHEAST MICHIGAN DURING
FRIDAY WITH DEEPENING SURFACE LOW RIDING ALONG THE FRONT. EXCELLENT
LARGE SCALE ASCENT AND PLENTY OF MOISTURE (850 MB DEW PTS OF 10-12
C) WILL ASSURE SHOWERS (NEAR 100 PERCENT)...WITH MODEST INSTABILITY
AND STRONG DYNAMICS/VERTICAL FORCING LIKELY ENOUGH TO GENERATED
ISOLATED-SCATTERED THUNDERSTORMS AS WELL. WITH STRONG LOW LEVEL JET
OF 50 KNOTS...THERE IS SOME CONCERN SOME OF THESE STRONG WINDS WILL
TRANSLATE TO THE GROUND WITH ANY VIGOROUS CONVECTION. HOWEVER...12Z
NAM/GFS BOTH SUGGESTING CAPES PREDOMINATELY UNDER 500 J/KG.

THE UPPER LEVEL TROUGH AXIS GOES NEGATIVE FRIDAY EVENING...AND
ALTHOUGH THE SURFACE FRONT WILL HAVE CLEARED THE AREA...ENOUGH WRAP
AROUND MOISTURE/DEFORMATION...COUPLED WITH THE LAKE MICHIGAN
ENHANCEMENT TO SUPPORT WIDESPREAD SHOWERS...AS CORE OF THE COLD
AIRMASS (-12 C AT 700 MB) ROTATES THROUGH THE OHIO VALLEY...WITH
SOUTHWEST FLOW LEADING TO THE GOOD COLD ADVECTION INTO LOWER
MICHIGAN. GOOD CYCLONIC FLOW ON SATURDAY WITH RESIDUAL COLD AIR (850
MB TEMPS -2 TO -3 C) WILL CONTINUE TO SUPPORT SCATTERED-NUMEROUS
SHOWERS...WITH HIGHS TOPPING AROUND 50 DEGREES...ULTIMATELY
DEPENDENT ON THE AREAL COVERAGE OF SHOWERS TO KNOCK DOWN THE
TEMPERATURE.

NORTHWEST WINDS SATURDAY NIGHT INTO SUNDAY WILL CONTINUE TO
SUPPLY/MAINTAIN SUFFICIENTLY COLD AIRMASS (-2 TO -4 C AT 850 MB) TO
PRODUCE LAKE MICHIGAN SHOWERS...WHICH SHOULD SURVIVE THE EASTWARD TO
SUPPORT SCATTERED ACTIVITY. MODEST LATE DAY WARNING (925 MB TEMPS OF
5 C PER 00Z EURO) EXPECTED TO BOLSTER MAXES INTO THE LOWER 50S MOST
LOCATIONS...WITH MID 50S TOWARD OHIO BORDER.

MARINE...

SOUTHEAST WINDS WILL STEADILY INCREASE TODAY AND TONIGHT AS
STRENGTHENING LOW PRESSURE TRACKS THROUGH THE WESTERN GREAT LAKES.
LATEST MODEL GUIDANCE POINTS TO STRONGER SOUTHERLY FLOW OVER OPEN
WATERS OF LAKE HURON...SOLIDLY AROUND 30 KNOTS...WITH THE POTENTIAL
FOR GALE FORCE WINDS EVEN WITH THE ARRIVAL OF WARMER AIR WHICH WILL
MAINTAIN A HIGHER DEGREE OF STABILITY NEAR THE SURFACE. HAVE THUS
ISSUED A GALE WATCH FOR THE CENTRAL PORTION OF LAKE HURON...WHERE
WIND SPEEDS LOOK TO BE MAXIMIZED. ISOLATED TO SCATTERED
THUNDERSTORMS ARE ALSO EXPECTED AS WIDESPREAD SHOWERS MOVE THROUGH
DURING THIS TIME. ANY THUNDERSTORM COULD PRODUCE STRONGER WINDS.
A SEASONABLY STRONG COLD AIRMASS WILL OVERSPREAD THE GREAT LAKES
REGION OVER THE WEEKEND...WITH WESTERLY WINDS OF 25 TO 30 KNOTS
EXPECTED ON SATURDAY...WITH THE POTENTIAL FOR GALE FORCE WINDS
TOWARD THE CANADIAN SIDE OF LAKE HURON DUE TO THE DEEPER BOUNDARY
LAYER MIXING.

&&

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

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     SANILAC...FROM 1 AM FRIDAY TO 8 PM FRIDAY.

     SMALL CRAFT ADVISORY...LHZ421-LHZ443...FROM 8 AM FRIDAY TO 8 PM
     FRIDAY.

     GALE WATCH...LHZ362-LHZ363-LHZ462...FROM 6 AM FRIDAY TO 5 PM FRIDAY.

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

&&

$$

AVIATION.....MR
SHORT TERM...SC
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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