Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 192035
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 PM EST FRI DEC 19 2014

.SHORT TERM...TONIGHT

THE COMBINATION OF A WEAK MIDLEVEL COL AND SURFACE HIGH PRESSURE HAS
LED TO VERY WEAK FLOW OVER THE CENTRAL GREAT LAKES REGION. AS A
RESULT...THERE IS LITTLE TO NO ADVECTION ONGOING AND A LOW MEAN FLOW
SIGNAL. ALL OF THIS MAKES THE CLOUD TREND FORECAST VERY DIFFICULT.
THERE IS MODEL AND OBSERVATIONAL DATA AGREEMENT AT LEAST OUT OF THE
19.12Z INITIALIZATION AND INTO THE FIRST 6 HOURS OF THE OUTPUT. FROM
A SYNOPTIC VIEW...WILL BE LOOKING AT THE LOW TO MIDLEVEL
ANTICYCLONIC CIRCULATION PUSHING SOUTHEASTWARD ACROSS LAKE MICHIGAN
AND INTO LOWER MICHIGAN. WITH TIME...NORTHERLY FLOW WILL TRANSITION
TO A SOUTHERLY COMPONENT AND SHOULD CAUSE MOISTURE TO BEGIN ANOTHER
NORTHWARD MIGRATION. EXPECTING MANY AREAS TO CLOUD UP ONCE AGAIN
WITH AN EDGE AS FAR NORTHWARD AS FLINT TO SAGINAW BY 12Z SATURDAY
MORNING. RAISED LOW TEMPERATURES A DEGREE OR TWO TO ACCOUNT FOR THIS.

&&

.LONG TERM...SATURDAY THROUGH NEXT FRIDAY

FAIRLY QUIET WEATHER IS IN STORE FOR SOUTHEAST MICHIGAN THIS
WEEKEND. SURFACE HIGH PRESSURE WILL REMAIN OVER THE REGION THOUGH
MUCH OF THE WEEKEND. THIS HIGH WILL KEEP DRY CONDITIONS AND CALM
WINDS OVER SOUTHEAST MICHIGAN THROUGH SUNDAY AFTERNOON. A MID LEVEL
SHORTWAVE TROUGH IS THEN FORECASTED TO SLIDE ACROSS NORTHERN
MICHIGAN ON SUNDAY NIGHT. AT THIS TIME...PRECIPITATION SHOULD STAY
NORTH OF OUR CWA...BUT WILL HAVE TO KEEP AN EYE ON THIS FEATURE OVER
THE NEXT COUPLE FORECAST CYCLES.

EVEN WITH HIGH PRESSURE OVER THE AREA...CLOUDS WILL STILL BE A
CONCERN THROUGH THE WEEKEND. CURRENT MODEL SOUNDINGS SHOW ENOUGH
BOUNDARY LAYER MOISTURE TO BE PRESENT ACROSS THE CWA TO WARRANT A
FAIRLY PROMINENT CLOUD DECK TO DEVELOP BY SATURDAY MORNING. LIGHT
WINDS WILL RESULT IN  LITTLE IF ANY SCATTERING OF THESE CLOUDS
DURING THE DAY SATURDAY. A SIMILAR SET UP WILL OCCUR ON SATURDAY
NIGHT AND SUNDAY...WITH PLENTY OF MOISTURE IN THE LOW LEVELS TO
ACCOUNT FOR A MOSTLY CLOUDY FORECAST THROUGH SUNDAY.
THEREFORE...HAVE INCREASED CLOUD COVERAGE FROM THE PREVIOUS FORECAST
FOR THE ENTIRE WEEKEND. CLOUDY SKIES WILL KEEP TEMPERATURES ON THE
WARMER SIDE OF GUIDANCE THROUGH THE WEEKEND. HIGHS ON SATURDAY WILL
BE IN THE LOW TO MID 30S AND SLIGHTLY WARMER ON SUNDAY WITH HIGHS IN
THE MID TO UPPER 30S. LOW TEMPERATURES WILL FOLLOW A SIMILAR TREND
STARTING OFF IN THE MID 20S ON SATURDAY NIGHT AND JUMPING UP TO THE
UPPER 20S TO LOW 30S BY SUNDAY NIGHT.

AS HIGH PRESSURE EXITS THE REGION EARLY MONDAY...THE DOOR IS LEFT
OPEN FOR AN ACTIVE WEATHER PATTERN TO TAKE OVER FOR THE REMAINDER OF
THE WEEK. A WEAKER LOW PRESSURE SYSTEM WILL EVOLVE OVER THE NORTHERN
PLAINS MONDAY/TUESDAY...EVENTUALLY GETTING ABSORBED BY A POTENTIALLY
STRONGER STORM LIFTING NORTHWARD FROM THE DEEP SOUTH. AS WAS TRUE
YESTERDAY...THERE ARE STILL SEVERAL POSSIBLE SOLUTIONS AS TO
HOW/WHERE THIS INTERACTION TAKES PLACE...SO THE DETAILS REMAIN
SOMEWHAT MURKY. FOR NOW...IMPACTS IN TERMS OF PRECIPITATION WILL
MOST LIKELY OCCUR DURING THE MONDAY NIGHT THROUGH WEDNESDAY TIME
FRAME. MODELS SUGGEST WE HAVE A BETTER CHANCE OF BEING ON THE WARMER
SIDE OF THIS SYSTEM THROUGH WEDNESDAY AFTERNOON...WITH A MIX OF RAIN
AND SNOW EXPECTED FOR THIS PERIOD. IF ALL STAYS ON TRACK...SNOW
SHOWERS WILL DEVELOP IN THE COLDER AIR ON THE BACK SIDE OF THE FRONT
LATE CHRISTMAS EVE THROUGH CHRISTMAS DAY. STAY TUNED.

&&

.MARINE...

SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE AREA TONIGHT
AND REMAIN OVER THE GREAT LAKES REGION THROUGH THE WEEKEND RESULTING
IN CALM CONDITIONS ACROSS THE LAKES. THE HIGH WILL THEN DRIFT EAST
INTO THE EASTERN GREAT LAKES OVER BY SUNDAY NIGHT. SOUTHERLY WINDS
INCREASE ON SUNDAY NIGHT AND INTO MONDAY AS A WEAK MID-LEVEL TROUGH
SWINGS THROUGH THE NORTHERN GREAT LAKES. IN ADDITION TO INCREASED
WINDS...THE TROUGH AS THE POTENTIAL TO BRING SOME LIGHT SNOW SHOWERS
TO NORTHERN LAKE HURON ON SUNDAY NIGHT. ACTIVE WEATHER RETURNS TO
THE GREAT LAKES FOR MOST OF NEXT WEEK...HOWEVER...UNCERTAINTY IN
THE TRACK AND INTENSITY OF THIS SYSTEM IS LOW AT THIS TIME.

&&

.AVIATION...ISSUED 1252 PM EST FRI DEC 19 2014

//DISCUSSION...

LIGHT MIDLEVEL FLOW OVER THE GREAT LAKES REGION MAKES CLOUD TRENDS
VERY DIFFICULT WITH LACK OF ANY ADVECTION SIGNAL. CURRENT
OBSERVATIONAL DATA SUPPORTS THE MODEL OUTPUT WITH REGARDS TO AN
EVENTUAL LOSS OF STRATUS OVER LOWER MICHIGAN. EDGE OF THE CLOUD LINE
HAS PUSHED SOUTH OF THE I 69 CORRIDOR. THIS CLOUD EDGE SHOULD NOW
HAVE A MORE DIFFICULT TIME CONTINUING SOUTHWARD WITH THE MIDLEVEL
ANTICYLONIC CIRCULATION PASSING OVERHEAD. RETURN SOUTHERLY WILL TRY
TO ORGANIZE THIS EVENING WHICH SHOULD ALLOW THE CLOUD DECK TO FILL
BACK IN AND EXPAND NORTHWARD.

AT DTW...VERY LITTLE TO ADD IN THIS SECTION GIVEN UNCERTAINTY. STILL
SUPPORTING THE EARLIER FORECAST OF TEMPORARY LOSS OF MVFR CIGS LATE
THIS AFTERNOON OR EARLIER EVENING...BEFORE CLOUDS BUILD BACK IN THIS
EVENING AND CONTINUING THROUGH THE END OF THE PERIOD.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE IN WHEN CEILINGS OF LESS THAN 5000 FT WILL BREAK.

&&

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

$$

SHORT TERM...CB
LONG TERM....RK/DE
MARINE.......RK
AVIATION.....CB


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



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