FXUS63 KDTX 280901
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
401 AM EST SAT NOV 28 2009

.SHORT TERM...TODAY

SURFACE RIDGE AXIS CURRENTLY DRAPED OVERHEAD WILL SHIFT EAST TODAY 
WHILE THE UPPER LEVEL FLOW BECOMES INCREASINGLY ANTICYCLONIC.  THIS 
WILL ESTABLISH MORE PRONOUNCED WARM AIR ADVECTION IN THE LOWER 
LEVELS AND ALLOW ANY RESIDUAL MORNING STRATUS TO SCATTER WITHIN THE 
DEVELOPING SOUTHWESTERLY FLOW.  BACK EDGE OF THE CLEARING LINE 
CONTINUING TO GRADUALLY SHIFTING EAST-NORTHEAST PER LATEST SATELLITE 
TRENDS AND EXTRAPOLATING THIS MOVEMENT SHOWS THE LINE ROUGHLY IN THE 
VICINITY OF THE I-75 CORRIDOR BY SUNRISE. THIS POINTS TOWARD MOST 
AREAS SEEING MOSTLY SUNNY SKIES FOR THE AFTERNOON...OUTSIDE OF SOME 
THICKER CIRRUS ACROSS NORTHERN AREAS.

THE THERMAL PROFILE WILL RESPOND WELL TO THE WARM AIR ADVECTION... 
WITH A 925/850 MB TEMPERATURES CLIMBING 6-8 DEGREES FROM 24 HOURS 
AGO.  GIVEN ADDED INSOLATION TODAY...ALBEIT OF SMALLER IMPACT GIVEN 
THE LOWER SUN ANGLE...THIS WILL TRANSLATE INTO HIGHS GENERALLY IN 
THE MID-UPPER 40S OR SEVERAL DEGREES ABOVE NORMAL FOR LATE 
NOVEMBER.

&&

.LONG TERM...

PREDOMINATELY WESTERLY FLOW OVER THE NORTHERN CONUS DURING THE 
NEXT SEVERAL DAYS...ALLOWING FOR PROGRESSIVE STORM SYSTEMS...WITH 
THE TREND ON SUNDAY'S SYSTEM A BIT FASTER AS MAIN UPPER WAVE RESIDES 
OVER CENTRAL CALIFORNIA...DROPPING SOUTH-SOUTHEAST. THIS WAVE WILL 
HAVE TO BE WATCHED CLOSELY LATER IN THE WEEK FOR POSSIBLE PHASING
WITH THE NORTHERN STREAM.

FASTER FROPA ON SUNDAY WOULD TEND TO LIMIT OUR PRECIPITATION 
CHANCES...AS FLOW FAILS TO BACK TO THE SOUTHWEST-SOUTH...PREVENTING 
DEEPER PACIFIC MOISTURE FROM ADVECTING NORTH INTO LOWER MICHIGAN. 
MID LEVEL DRY SLOT THEN ARRIVES FOR SUNDAY EVENING/NIGHT. WILL BE 
KEEPING POPS JUST IN THE CHANCE CATEGORY...AS 00Z NAM/CANADIAN ARE 
BASICALLY DRY...BUT 00Z GFS/UKMET BOTH INDICATING SUFFICIENT 
CYCLOGENESIS/FGEN TO SUPPORT SOME RAIN DURING SUNDAY AS CPD'S ON THE 
290 K SURFACE QUICKLY COME CRASHING DOWN. 

THE POSITIVELY TILTED 500 MB TROUGH AXIS WILL SLIDE THROUGH THE 
CENTRAL GREAT LAKES DURING MONDAY...WITH THE AVERAGE OF 
UKMET/NAM/GFS INDICATING 850 MB TEMPS HOVERING AROUND -9 C...WHICH 
SUPPORTS MAXES IN THE UPPER 30S AT BEST. WESTERLY FLOW OFF LAKE 
MICHIGAN COUPLED WITH STEEP LOW LEVEL LAPSE RATES SHOULD BE 
SUFFICIENT FOR FLURRIES OR SCATTERED LIGHT SNOW SHOWERS. THERE COULD 
EVEN BE A QUICK RAMP UP TO THE LAKE EFFECT ACTIVITY EARLY MONDAY 
EVENING AS SHORTWAVE/LEFT EXIT REGION OF JET IMPINGE ON THE AREA. 
WITH INVERSION HEIGHTS RISING TO 10000 FEET (PER GFS 
SOUNDINGS)...POSSIBLE WE COULD HAVE A LAKE BAND LEAD TO LOCALIZED 
LIGHT ACCUMULATIONS BEFORE THE GOOD LOW LEVEL WARM ADVECTION 
TRANSLATES TO THE EAST AND SHUTS OFF THE LAKE EFFECT.

TIMING OF THE NEXT NORTHERN STREAM UPPER WAVE/TROUGH AND THE 
POSSIBLE PHASING OF THE 500 MB LOW WHICH IS EXPECTED TO BE OVER/NEAR 
THE WESTERN GULF COAST STATES DURING THE MID WEEK PERIOD ARE 
THE MAIN QUESTION MARKS. THE OVERWHELMING EVIDENCE BASED ON THE 00Z 
MEDIUM RANGE MODELS (EUROPEAN/CANADIAN/WRF-HEMI/GFS) IS FOR A
FASTER TIMING AND PHASING...THUS THE COLD AIR (-10 C OR COLDER AT
850 MB) ARRIVES BY THURSDAY. WHETHER SIGNIFICANT PRECIPITATION
(RAIN>SNOW) PRECEDES THIS COLD BLAST REMAINS TO BE SEEN...BUT WILL
MAKE DOWNWARD ADJUSTMENTS IN TEMPERATURES FOR LATE IN THE WORK
WEEK.

&&

.MARINE...

A RIDGE OF HIGH PRESSURE SLIDING ACROSS THE AREA WILL LEAD TO WEAKER 
WINDS AND LOWER WAVES TODAY AND TONIGHT.  THE PASSAGE OF ANOTHER 
COLD FRONT SUNDAY NIGHT AND MONDAY WILL ALLOW NORTHWEST WINDS TO 
INCREASE ONCE AGAIN. SMALL CRAFT CONDITIONS MAY DEVELOP DURING THIS 
TIME ACROSS THE NEARSHORE WATERS AIDED BY COLDER AIR MOVING ACROSS 
THE RELATIVELY WARMER LAKE WATERS.

&&

.PREV DISCUSSION...ISSUED 1149 PM EST FRI NOV 27 2009 

AVIATION...

A RIDGE OF HIGH PRESSURE WILL CONTINUE BUILDING INTO THE CENTRAL 
GREAT LAKES TODAY. MVFR CLOUDS WILL HANG ON DURING THE MORNING AS 
DRIER AIR ASSOCIATED WITH THE RIDGE WORKS ITS WAY INTO THE REGION. 
ONCE THE HIGH AND DRIER AIR ENTER THE AREA SCT VFR CLOUDS ARE 
EXPECTED THIS AFTERNOON AND INTO THE EVENING HOURS. THE HIGH WILL 
ALSO BRING A RELAXED PRESSURE GRADIENT INTO THE AREA...AS LIGHT WEST 
WINDS BECOME SOUTHWESTERLY LATER THIS MORNING AND CONTINUE INTO THE 
AFTERNOON HOURS.

&&

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

&&

$$

SHORT TERM...MR
LONG TERM....SF
MARINE.......MR
AVIATION.....KURIMSKI

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