Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271013
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
513 AM EST SAT DEC 27 2014


.AVIATION...

THE LEAD EDGE OF THE DEEPER MOISTURE BEGAN WORKING INTO SOUTHWEST
LOWER MI AS OF 10Z. THIS WILL PRODUCE RAIN ACROSS THE TAF SITES
MAINLY FROM 12-15Z TO START OFF THE FORECAST. AFTER AN AFTERNOON
LULL RAIN SHOULD SPREAD BACK INTO THE AREA BETWEEN ABOUT 22-04Z WITH
THE COLD FRONTAL PASSAGE. SOUTHERLY WINDS IN ADVANCE OF THE COLD
FRONT THIS AFTERNOON WILL GUST TO AROUND 20-25 KNOTS. WINDS WILL
BECOME WESTERLY POST FRONTAL WHILE RELAXING OVERNIGHT. UPSTREAM
OBSERVATIONS AND MODEL SOUNDINGS SUGGEST MVFR CIGS TODAY AND INTO
TONIGHT WITH VARIABLE VSBYS DEPENDENT ON PASSING SHOWERS. IFR
CONDITIONS CANNOT BE RULED OUT BUT WILL HOLD OFF UNTIL BETTER TIMING
OF SHOWERS CAN BE RESOLVED.

FOR DTW...CONDITIONS MAY FLUCTUATE MORE SO EARLY IN THE FORECAST
UNTIL BETTER FORCING CLOSER TO THE COLD FRONT DRAWS NEARER. THE COLD
FRONT LOOKS TO PASS OVER THE TERMINAL AROUND 03Z BRINGING ABOUT A
WIND SHIFT FROM SOUTH/SOUTHWEST TO WEST. WIND GUSTS THIS AFTERNOON
MAY REACH 20 KNOTS. TEMPERATURES NEARING 50 DEGREES THIS AFTERNOON
WILL KEEP ALL PRECIPITATION FALLING AS RAIN THROUGH THE FORECAST.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CEILING BELOW 5000 FEET THROUGH THE TAF PERIOD.

&&

.PREV DISCUSSION...ISSUED 342 AM EST SAT DEC 27 2014

SHORT TERM...TODAY AND TONIGHT

A SURFACE LOW IS COMING TOGETHER OVER EASTERN IOWA EARLY THIS
MORNING ALONG A STATIONARY FRONT EXTENDING FROM LAKE SUPERIOR DOWN
TO CENTRAL TEXAS. THE LOW IS FORECAST TO STRENGTHEN AS IT TRACKS
TOWARD THE SOO 18Z THIS AFTERNOON...THEN INTO QUEBEC TONIGHT. THE
FRONT IS ALIGNED ALONG THE UPPER LEVEL JET WHICH IS LEADING TO A
GOOD DEAL OF SHEARING FOR THE SYSTEM TO ENDURE...YET MODELS STILL
SHOW THE STRENGTHENING OF A CLOSED LOW DOWN TO 1004MB DUE TO A
POTENT 150+ KNOT JET OVERHEAD. A SURGE OF MOISTURE...WHICH LINES UP
WITH THE 850-700MB THETA E FIELD...IN THE WARM SECTOR IS HEADING
TOWARD LOWER MI AND HAS A GOOD CHANCE TO CLIP THE METRO DETROIT AREA
AROUND SUNRISE. MODEL DATA SHOWS A RELATIVE MOISTURE MINIMUM HEADING
NW TOWARD THE LOW PRESSURE CENTER WHICH CURRENTLY IS SUPPORTED BY
SCATTERED SHOWERS ON REGIONAL RADAR MOSAIC. SO INCREASED CHANCE POPS
A BIT ACROSS THE SOUTH FOR THE MORNING HOURS TO ACCOUNT FOR RADAR
TRENDS. WITH THE INFLUX OF LL MOISTURE THROUGH THE DAY WE WILL CARRY
A CHANCE OF LIGHT SHOWERS INTO THE AFTERNOON HOURS...EVEN THOUGH
MODELS AREA ADVERTISING A LULL IN THE ACTION BETWEEN THIS PREFRONTAL
RIBBON OF MOISTURE AND THE APPROACHING FRONT TO THE WEST.

A COLD FRONT WILL GET PULLED THROUGH SE MI THIS EVENING AROUND 00-
03Z. THERE IS A SECONDARY UPTICK IN MOISTURE RIGHT ALONG THE FRONT
AND THIS MOISTURE POOLING WILL ACCOUNT FOR HIGHER CHANCE POPS AGAIN
BETWEEN ABOUT 21Z-03Z THIS EVENING. DO NOT SEE ENOUGH EVIDENCE FOR A
WIDE SPREAD SWATH OF SHOWERS WORKING THROUGH THE AREA TO WARRANT
INCREASING TO LIKELY POPS AT THIS TIME. COOL AND DRY AIR WILL FILL
IN QUICKLY BEHIND THE FRONT RESULTING IN A SHARP CUTOFF TO THE
SHOWERS TONIGHT. ALL THE PRECIP AHEAD OF THE FRONT WILL FALL AS
LIQUID AS TEMPERATURES MAKE A RUN AT 50 DEGREES. A WEAK LAKE EFFECT
SIGNATURE SHOWS UP POST FRONTAL BUT WILL HOLD OFF ON ADDING ANY SNOW
OR DRIZZLE TO THE FORECAST AT THIS POINT AS CONFIDENCE IS LOW IT
WOULD SURVIVE THE TRACK ACROSS THE STATE. SOUNDINGS SHOW MOISTURE
DEPTHS UNDER 3000FT WITH A WEALTH OF DRY AIR ALOFT FROM MID LEVEL
CONFLUENT FLOW.

LAST THING OF NOTE WILL BE THE WINDS. DEPP LAYER OF SW FLOW WITH A
STRONG PREFRONTAL LL JET AROUND 60 KNOTS WILL RESULT IN GUSTY WINDS
THIS AFTERNOON. STRONGEST WINDS WILL OCCUR THROUGH CENTRAL MI WITH
GUSTS TO 25 KNOTS POSSIBLE...TAPER OFF TOWARD THE OHIO BORDER. WINDS
WILL TURN WESTERLY BEHIND THE FRONT WITH A BRIEF BURST RIGHT BEHIND
THE FRONT BUT EXPECT WINDS TO RELAX THROUGH THE OVERNIGHT.

LONG TERM... SUNDAY THROUGH FRIDAY

MID LEVEL PATTERN WILL EASE INTO A WEAKLY CONFLUENT ZONAL
CONFIGURATION FOR THE LATTER HALF OF THE WEEKEND.  THIS WILL PRESENT
A PERIOD OF BENIGN CONDITIONS AS WEAK SURFACE RIDGING EDGES IN
BEHIND THE DEPARTING TRAILING SHEAR AXIS.  RECENT MODEL SOUNDING
DATA AND RH FIELDS SUGGEST SOME LINGERING CLOUDINESS DURING THE
FIRST HALF OF THE DAY /PARTIAL COVERAGE/ WITH SOME DIURNAL
ENHANCEMENT.  LOW LEVEL FLOW THEN VEERS TO NORTHWESTERLY LATE SUNDAY
IN RESPONSE TO CHANGES IN THE PRESSURE FIELD FROM THE SOUTHWEST.
THIS WILL PROVIDE SOME RENEWED DRY AIR ADVECTION AND FAVOR A
CLEARING SKY INTO THE EVENING PERIOD.  COOLER AIRMASS IN PLACE
RELATIVE TO TODAY...BUT STILL A TOUCH ABOVE NORMAL FOR LATE
DECEMBER.  HIGHS SUNDAY RANGING FROM MID 30S NORTH TO UPPER 30S
SOUTH.

A STEADY INTRUSION OF ARCTIC AIR REMAINS ON TARGET FOR EARLY NEXT
WEEK...PROMPTED BY THE SOUTHWARD EXPANSION OF THE MAIN HEIGHTS FALLS
WORKING THROUGH THE MEAN CENTRAL CANADIAN HIGH AMPLITUDE UPPER
TROUGH.  THIS PROCESS WILL INITIATE WITH A SHALLOW LOOKING SURFACE
FRONTAL PASSAGE LATE SUNDAY NIGHT INTO MONDAY.  00Z NAM PRESENTS
SOME HINTS FOR THE TRAILING ELEVATED FRONTAL ZONE TO PERHAPS BECOME
ACTIVE ENOUGH TO GENERATE A FEW SNOWFLAKES BY MONDAY NIGHT.
DISORGANIZED APPEARANCE OF THE FRONTAL STRUCTURE AND ATTENDANT
FORCING...AS WELL AS A LACK OF GREATER MOISTURE QUALITY WILL LIMIT
THE POTENTIAL.  TEMPERATURES TRENDING DOWNWARD THROUGH AT LEAST
MIDWEEK AS THE ARCTIC AIR TAKES A FIRM HOLD.  850 MB TEMPERATURES OF
-16 TO -18C TUESDAY AND WEDNESDAY...GOOD FOR DAYTIME HIGHS IN THE
20S EACH DAY.

MARINE...

MODERATE SOUTHERLY WINDS TODAY WILL STRENGTHEN INTO THE EARLY
EVENING AS A LOW PRESSURE SYSTEM LIFTS THROUGH THE STRAITS.  THIS
WILL RESULT IN A BRIEF PERIOD OF GUSTS TO 30 KNOTS ACROSS CENTRAL
LAKE HURON.  WINDS SHIFT TO NORTHWESTERLY IN THE WAKE OF THIS SYSTEM
TONIGHT.  A PERIOD OF STRONGER WINDS WILL FAVOR NORTHERN PORTIONS OF
LAKE HURON.  THIS WILL BRING THE POTENTIAL FOR A BRIEF PERIOD OF
MARGINAL GUSTS TO GALES.  CONFIDENCE IN BOTH OCCURRANCE AND DURATION
STILL REMAIN ON THE LOWER SIDE...SUPPORTING A CONTINUATION OF THE
GALE WATCH ACROSS THIS CORRIDOR.  WINDS AND WAVES WILL THEN
GRADUALLY SUBSIDE SUNDAY INTO SUNDAY NIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM THIS EVENING THROUGH LATE TONIGHT FOR LHZ361-362.

     SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 4 AM EST SUNDAY
     FOR LHZ421-441.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

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


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


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