Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 170344
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1144 PM EDT THU OCT 16 2014


.AVIATION...

//DISCUSSION...

CONDITIONS SHOULD DETERIORATE RAPIDLY TO MVFR...THEN IFR AS AN
UPSTREAM STRATUS DECK ADVECTS TO THE EAST EARLY THIS MORNING.
ISOLATED SHOWERS ARE ALSO POSSIBLE...BUT WILL BE TOO HIT OR MISS TO
INCLUDE IN THE TAFS THEMSELVES. CONTINUED LOW LEVEL MOISTURE WILL
KEEP MVFR CIGS IN PLACE DURING THE DAY ON FRIDAY. A POWERFUL COLD
FRONT AND TIGHT PRESSURE GRADIENT WILL BRING GUSTY WINDS FRIDAY
AFTERNOON...ESPECIALLY ACROSS THE METRO AIRPORTS. STEADY RAIN
SHOWERS WILL FOLLOW BEHIND THE FRONT FRIDAY EVENING.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET MUCH OF THE TAF PERIOD.

&&

.PREV DISCUSSION...ISSUED 331 PM EDT THU OCT 16 2014

SHORT TERM...THROUGH TONIGHT

SLOW MOVING UPPER LOW IS NOW CENTERED OVER THE EASTERN GREAT LAKES
WHILE THE SFC LOW IS NOW ENTERING EXTREME SW QUEBEC. A NORTH SOUTH
ORIENTATED SFC RIDGE AXIS/WARM FRONT IS MAKING ITS WAY ACROSS WI/IL
WHICH IS POOLING MOISTURE ON THE LEAD EDGE. THIS ENHANCED MOISTURE
FIELD HAS LEAD TO A PERSISTENT STRATO-CU FIELD OVER MUCH OF THE
REGION KEEPING TEMPS SUPPRESSED SOMEWHAT OVER OUR WESTERN AND
NORTHERN PARTS TODAY. THE EASTERN COUNTIES WERE ABLE CLEAR OUT MORE
THIS AFTERNOON LEADING TO TEMPERATURES RISING INTO THE MID 60S. WITH
THE COOL AIR ALOFT THIS WAS ABLE GENERATE ENOUGH INSTABILITY AND
FAVORABLE LL LAPSE RATES TO ALLOW CONVECTIVE DEVELOPMENT AND A FEW
LIGHTNING STRIKES AS CLOUDS TOPS REACHED NEAR 20KFT. SOME PEA SIZE
HAIL HAS ALSO BEEN REPORTED WHICH IS NO SURPRISE SEEING THAT THE
FREEZING LEVEL IS ONLY AT 8KFT. THAT SHOULD BE THE MAX HAIL SIZE
THAT PEOPLE WILL SEE INTO THE EVENING. THIS WILL CONTINUE OVER THE
NEXT FEW HOURS UNTIL THE SYSTEM PUSHES EAST.

FOR TONIGHT...THE INVERSION WILL STRENGTHEN AND LOWER FURTHER
TRAPPING THE LL MOISTURE LEADING TO ANOTHER THICK STRATUS DECK.
WINDS WILL STAY A LITTLE ELEVATED TONIGHT WITH WESTERLY FLOW KEEPING
THE THERMAL ADVECTION BASICALLY NEUTRAL AND KEEPING DEWPOINTS UP
AROUND 50 WHICH WILL LIMIT COOLING OVERNIGHT. A LEAD FILAMENT OF
WEAK FGEN AND ISENTROPIC ASCENT WILL PASS OVER THE AREA TONIGHT IN
ADVANCE OF THE WARM FRONT WHICH WILL PRODUCE ANOTHER ROUND OF LIGHT
SHOWERS. WITH ABUNDANT MOISTURE IN PLACE...THERE WILL BE SOME PATCHY
FOG TOWARD MORNING BUT THE CLOUDS AND WINDS SHOULD MINIMIZE THE
IMPACTS COMPARED TO WHAT WE HAVE SEEN THE LAST TWO MORNING.

LONG TERM...

COLDER TEMPERATURES WILL SETTLE OVER SOUTHEAST MICHIGAN DURING THE
WEEKEND...AS STRONGER UPPER WAVE CURRENTLY OVER NORTH DAKOTA
ADVANCES EAST...REINFORCING THE TROUGHING/RENEWING HEIGHT FALLS OVER
THE GREAT LAKES REGION...WITH ANOTHER NORTHERN STREAM UPPER WAVE
DIVING SOUTHEAST FROM CENTRAL CANADA...AND INTO THE OHIO VALLEY ON
SATURDAY. POST WAVE SUBSIDENCE AND EXPECTED CLEARING SATURDAY NIGHT
SHOULD SET US UP FOR COLD NIGHT...AS TEMPS LOOK TO BE DROPPING BELOW
FREEZING MOST AREAS.

SOUTHWEST FLOW/LOW LEVEL WARM ADVECTION AHEAD THE COLD FRONT DURING
FRIDAY SHOULD ALLOW FOR A MILD DAY (60S)...BUT NAM IS ADAMANT LOW
LEVEL MOISTURE (925 MB RH) WILL KEEP LOW CLOUDS LOCKED IN FOR THE
MAJORITY OF THE DAY...BUT THERE REMAINS AN OUTSIDE SHOT OF 70
DEGREES ACROSS DETROIT AND POINTS SOUTH AS 925 MB TEMPS SURGE TO 14
C (PER NAM) LATE IN THE DAY. MID LEVEL (700 MB) DRY SLOT WORKING
THROUGH SOUTHEAST MICHIGAN DURING THE DAY WILL PROVIDE LITTLE
SUPPORT FOR PRECIPITATION...WITH JUST SOME VERY LIGHT
SHOWERS/SPRINKLES POSSIBLE FROM THE LOW LEVEL ISENTROPIC ASSENT
DURING THE FIRST PART OF THE DAY. LATE IN THE DAY UPPER LEVEL
SUPPORT AND ACTUAL COLD FRONT ARRIVING WILL BRING A MORE APPRECIABLE
CHANCE OF SHOWERS...CONTINUING FRIDAY NIGHT INTO SATURDAY...AS COLD
AIR (850 TEMPS OF -2 TO -4 C) FUNNELS OVER THE GREAT LAKES
REGION...PRODUCING STEEP LOW LEVEL LAPSE RATES IN THE 925-850 MB
LAYER...PUSHING CAPES UP TOWARD 50 J/KG. OBVIOUSLY...NOT VERY
IMPRESSIVE...BUT THERE WILL PROBABLY BE LOCALIZED ENHANCED
POCKETS...AND THUS WILL NOT STRAY TO FAR FROM SCATTERED 30-40
POP...EXCEPT TOWARD THE NORTHERN THUMB REGION...WHERE CONFIDENCE IS
HIGHER WITH LOCAL INFLUENCE/MOISTURE FLUX OFF SAGINAW BAY.

THE END OF THE WEEKEND WILL REMAIN DRY AS UPPER LEVEL RIDGING MOVES
OVER THE AREA WHILE AT THE SAME TIME SURFACE HIGH PRESSURE WILL BE
PUSHING EAST ACROSS THE OHIO VALLEY.  CHANGES THEN COME INTO PLAY ON
MONDAY AS A SHORTWAVE TRAVERSES THE AREA FROM THE NORTHWEST AND
MOVES ACROSS THE LOWER MICHIGAN BEFORE EXITING OFF TO THE EAST LATER
TUESDAY.  THIS WILL BRING UNSETTLED CONDITIONS TO THE AREA DURING THE
BEGINNING OF NEXT WEEK.  TEMPERATURES IN THE EXTENDED REMAIN PRETTY
STEADY BUT STILL ON THE COOL SIDE.

MARINE...

MODEST SOUTHWEST FLOW (15 KNOTS) AHEAD OF A STRONG COLD FRONT
TONIGHT INTO TOMORROW. FRONTAL PASSAGE IS EXPECTED TO OCCUR FRIDAY
EVENING ACROSS THE CENTRAL GREAT LAKES...WITH WINDS VEERING TO THE
NORTHWEST AND INCREASING TO 20 TO 30 KNOTS AS GOOD DEAL OF COLD AIR
COMES ACROSS THE RELATIVELY WARM WATERS. FREQUENT GUSTS UP AROUND
GALES ARE EXPECTED...ESPECIALLY ACROSS THE OPEN WATERS OF LAKE
HURON...WHERE A GALE WATCH HAS BEEN ISSUED WITH DEEP BOUNDARY LAYER
MIXING AND ENHANCED THERMAL TROUGHING.  WINDS WILL DECREASE SATURDAY
NIGHT INTO SUNDAY AS A RIDGE OF HIGH PRESSURE BUILDS INTO THE REGION.

&&

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

LAKE HURON...
     GALE WATCH...LHZ361-LHZ362-LHZ363-LHZ462-LHZ463-LHZ464...FROM 1 AM
     SATURDAY TO 8 PM SATURDAY.

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

&&

$$

AVIATION.....KURIMSKI
SHORT TERM...DRK
LONG TERM....SF/SS
MARINE.......SF


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





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