FXUS63 KDTX 011148
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
648 AM EST TUE DEC 1 2009

.AVIATION...

SUSTAINED WARM AIR ADVECTION FOCUSED ALONG A WEAK FRONTAL BOUNDARY 
WILL REINFORCE AN INVERSION WHILE ENSURING MOISTURE REMAINS TRAPPED 
BENEATH THIS LEVEL.  THIS WILL RESULT IN CONTINUED STRATUS 
DEVELOPMENT THIS MORNING...ESPECIALLY AT PTK AND THE DETROIT AREA.  
CEILINGS WILL HOVER IN HIGH END MVFR/LOW VFR DURING THIS TIME.  
BETTER MIXING WILL SCATTER THIS STRATUS FROM SOUTH TO NORTH THROUGH 
THE DAY...ALTHOUGH THE MAIN AXIS OF LOW LEVEL MOISTURE WILL TEND TO 
SHIFT NORTH WITH THE FRONTAL BOUNDARY BRINGING A PERIOD OF MARGINAL 
MVFR CIGS AT MBS/FNT INTO THE AFTERNOON.  VFR CONDITIONS IN MAINLY 
CLR SKIES TONIGHT AS A SURFACE RIDGE SLIDES THROUGH.

&&

.PREV DISCUSSION...ISSUED 329 AM EST TUE DEC 1 2009 

SHORT TERM...TODAY

LATEST UPPER AIR AND WATER VAPOR ANALYSIS SHOWING THE CLIPPER 
SYSTEM RAPIDLY LIFTING ACROSS NORTHERN LAKE HURON EARLY THIS 
MORNING.  NARROW RIBBON OF MODEST ISENTROPIC ASCENT ACCOMPANYING 
THIS SYSTEM NOW EXITING THE REGION.  MOISTURE AND FORCING PROVED 
TOO LIMITED THIS FAR SOUTH TO GENERATE MUCH MORE THAN A FEW BRIEF 
SNOW SHOWERS/FLURRIES/SPRINKLES.  MOISTURE DEPTH LACKING NOW TO 
EVEN SUSTAIN A STRATUS DECK ACROSS SOUTHERN AREAS WITHIN A 
PREDOMINANT SOUTHWEST LOW LEVEL FLOW.      

WEAK SURFACE RIDGING WILL TAKE CONTROL TODAY AS THE UPPER LEVEL 
FLOW BRIEFLY BECOMES ZONAL.  RESIDUAL LOW LEVEL THERMAL GRADIENT 
WILL REMAIN IN THE WAKE OF A SFC TROUGH PASSAGE THIS MORNING.  THIS 
'WARM' FRONTAL FEATURE WILL SHIFT NORTHEAST AS THE SOUTHWEST FLOW 
REDEVELOPS INTO THE AFTERNOON. MODEST RESPONSE NOTED IN THE LATEST 
MODEL THERMAL FIELDS...WITH MIXING SUFFICIENT ENOUGH TO TAP INTO THE 
+2-3C WARMING AT 925MB.  THIS WILL TRANSLATE INTO HIGHS RANGING FROM 
LOWER 40S FAR NORTH TO UPPER 40S NEAR THE OHIO BORDER.  WEAK ASCENT 
OVER THE FRONTAL ZONE MAY PROMOTE POCKETS OF STRATUS...AIDED BY 
BETTER MORNING INSOLATION.

LONG TERM...

LATEST WATER VAPOR IMAGERY SHOWS A GOOD SOUTHWARD PUSH OVER
WESTERN CANADA...WITH THE GOOD HEIGHT FALLS OCCURRING OF THE
NORTHERN ROCKIES...THIS SHOULD ALL BUT SEAL THE DEAL FOR WEDNESDAY
NIGHTS SYSTEM...AS CUTOFF LOW/STORM SYSTEM PUSHING INTO TEXAS
TRACKS WEST OF THE APPALACHIANS. ALTHOUGH...THE 00Z GFS IS STILL
INDICATING A COLDER TRACK THROUGH PITTSBURGH PA. WITH CONVECTION
OVER THE WESTERN GULF COAST STATES BEING A KEY COMPONENT...AM
LEARY OF THE GFS SOLUTION (AS LOCAL WRF-HEMI GIVES CREDENCE TO
THIS)...AND HAVE A PREFERENCE TO THE STRONGER AND FARTHER WEST
TRACK THROUGH NORTH CENTRAL/NORTHEAST OHIO...A BLEND OF THE 00Z
UKMET/NAM. EVEN THOUGH THIS TRACK IS STILL EAST OF THE AREA...IT
LOOKS LIKE WE WILL BE DEALING WITH A MOSTLY RAIN EVENT OR WET SNOW
WHICH STRUGGLES TO ACCUMULATE. WITH THE WARM ORIGINS OF THE
SOUTHERN SYSTEM...LACK OF INITIAL COLD AIR TO START OUT WITH
(MAXES IN THE MID TO UPPER 40S WEDNESDAY)...AND WARM GROUND 
(FOLLOWING TOP 10 WARMEST NOVEMBERS ON RECORD)...CHANGEOVER TO
SNOW LOOKS TO BE OCCURRING A BIT TOO LATE TO EXPECT ANY
SIGNIFICANT SNOWFALL (ESPECIALLY ON THE ROADS). IN FACT...THE 00Z
NAM HOLDS SFC-925 MB TEMPS ABOVE FREEZING THROUGH THE ENTIRE
NIGHT. EVEN WITH THE COLDER AND FARTHER EAST SOLUTION OF THE
GFS...SURFACE WET BULB TEMPERATURES FAIL TO DROP TO 32 DEGREES
EVERYWHERE. THINKING THE EAST HALF OF THE CWA WILL BE HARD PRESSED
TO SEE MUCH ACCUMULATION...WITH THE WEST HALF (TRI-CITIES) OF THE
CWA SEEING ABOUT 2 INCHES OF WET SNOW.

STRONG SUBSIDENCE/MID LEVEL DRY SLOT PUNCHING INTO SOUTHEAST 
MICHIGAN RIGHT AROUND OR JUST AFTER 12Z THURSDAY WILL QUICKLY END 
PRECIPITATION (AT LEAST FOR A PERIOD) BEFORE LAKE MICHIGAN ACTIVITY 
GETS GOING WITH 850 MB TEMPS FALLING TO -14 C THURSDAY NIGHT. 

THERE WILL BE OPPORTUNITIES FOR LAKE ENHANCED SNOW SHOWERS FRIDAY 
AND SATURDAY AS CYCLONIC FLOW/UPPER LEVEL TROUGH AXIS PERSISTS OVER 
THE GREAT LAKES REGION...WITH SEVERAL EMBEDDED SHORTWAVES. THE FLOW 
IS THEN FORECASTED TO BECOME A BIT MORE ZONAL AS WE HEAD INTO 
SUNDAY...ALLOWING A MODEST WARMUP...AS ENSEMBLE MEAN INDICATING 850 
MB TEMPS RISING TO AROUND -10 C. IN ANY EVENT...PROBABLY LOOKING AT 
MAXES IN THE 30S WITH MINS IN THE LOW/MID 20S THURSDAY AND 
BEYOND...WITH POTENTIAL FOR MINS IN THE TEENS IF WE CLEAR OUT ANY 
PARTICULAR NIGHT.

MARINE...

GUSTY SOUTHWEST WILL CONTINUE FOR SEVERAL MORE HOURS THIS MORNING 
AS BETTER MIXING ACCOMPANIES THE PASSAGE OF A SURFACE TROUGH.   
CURRENT ADVISORY/WARNING HEADLINES WILL REMAIN UNCHANGED...WITH 
WINDS ACROSS THE LAKE HURON OPEN WATERS EXPECTED TO DROP BELOW 
GALES AFTER 12Z.    

A BRIEF PERIOD OF QUIET WEATHER WILL EVOLVE LATER TODAY INTO 
WEDNESDAY WITH SURFACE RIDGING IN PLACE. THAT WILL BE SHORT 
LIVED...HOWEVER...AS A STRONG LOW PRESSURE LIFTS FROM THE GULF COAST 
THROUGH THE OHIO RIVER VALLEY WEDNESDAY NIGHT AND THURSDAY. EXACT 
POSITIONING OF THIS STORM SYSTEM REMAINS IN QUESTION...BUT THE 
POTENTIAL FOR GALE FORCE WINDS EXISTS LATE WEDNESDAY NIGHT AND ON 
THURSDAY.

&&

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

LAKE HURON...
     GALE WARNING...LHZ362-LHZ363-LHZ462...UNTIL 7 AM TUESDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT 
     HURON INCLUDING SAGINAW BAY...UNTIL 10 AM TUESDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 10 AM TUESDAY.

MI WATERS OF LAKE ERIE...
     LOW WATER ADVISORY...UNTIL 10 AM TUESDAY.

     SMALL CRAFT ADVISORY...UNTIL 10 AM TUESDAY.

&&

$$

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

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