FXUS63 KDTX 231415
AFDDTX

SOUTHEAST MICHIGAN AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1015 AM EDT TUE SEP 23 2003

ZONES IN GOOD SHAPE.
SEND OUT QUICK UPDATE TO REMOVE THE MORNING SHOWERS. THE LAST OF THE 
SHOWERS HAVE JUST MOVED THROUGH LANSING. THIS SHOWER WILL DISSIPATE 
SHORTLY. RISING HEIGHTS/SUBSIDENCE/WARMING IS THE STORY FOR THE 
AFTERNOON...AS THE SHORTWAVE TROUGH CONTINUES TO PULL EAST OF THE 
AREA. EXPECTING PLENTY OF CU...HOWEVER...ENOUGH SUNSHINE AROUND TO 
JUSTIFY PARTLY SUNNY SKIES. BUMPED TEMPS UP A DEGREE ACROSS THE 
SOUTH...OTHERWISE NO CHANGES TO THE GOING MAXES.

SF

*********************PREVIOUS MORNING DISCUSSION*******************

...NEXT SHOT OF COLD AIR IS ON THE WAY...

CURRENT H2O-VAPOR ANALYSIS DEPICTS A POTENT SHORT WAVE ROTATING EAST 
TOWARD LOWER MICHIGAN THIS MORNING.  THIS IS THE LAST IN A SERIES OF 
WAVES THAT HAS RESULTED IN A NEGATIVE TILTED TROF OVER THE GREAT 
LAKES WHICH HAS BROUGHT THE FIRST SHOT OF FALL WEATHER.  SINCE TODAY 
IS THE FIRST DAY OF AUTUMN...IT DOES SEEM FITTING THAT UPSTREAM IS 
YET ANOTHER WAVE OVER ALBERTA THAT WILL BRING SOME OF THE COLDEST 
AIR WE HAVE SEEN IN MONTHS.  MEANWHILE...DEEP LOW WAS NEAR JAMES BAY 
AS THE CENTER OF SURFACE HIGH WAS OVER OKLAHOMA WITH ITS ASSOCIATED 
RIDGE AXIS EXTENDING WELL NORTHWEST INTO THE DAKOTAS.

TODAY...
WITH AN EXITING SHORT WAVE...WE WILL BE ON THE DOWNSIDE/SUBSIDENCE 
THIS MORNING.  THIS IS WELL HIGHLIGHTED IN THE OMEGA PATTERN ALONG 
WITH INCREASING ANTI-CYCLONIC SURFACE RIDGING TO PRECLUDE ANY 
MENTION OF PRECIP AFTER 12Z.  THE QUESTION WILL BE CLOUD COVER AS 
STEEP LOW LEVEL LAPSE RATES AND WITH SATURATED GROUND SHOULD PROVIDE 
ENOUGH CU BY THIS AFTERNOON.  IN ADDITION...UPSTREAM VISIBLE AND IR 
SHOTS OVER THE DAKOTAS/MINNESOTA YESTERDAY DID YIELD A FAIR AMOUNT 
OF CU.  TRAJECTORY FORECASTS ORIGINATE FROM SOUTHERN MINNESOTA 
WHERE TEMPERATURES CLIMBED INTO THE MID 60S.  WITH THICKNESSES 
RUNNING BELOW 550DM AND THE EXPECTED CLOUD COVER...THINKING IS THE 
MET-MOS IS TOO HIGH AND A BLEND OF THE FWC/MAV IS PREFERRED.

TONIGHT...
IN THIS FAST FLOW REGIME...WE WILL SEE THE WEATHER QUICKLY CHANGE 
OVERNIGHT.  AS COLD FRONT FROM UPSTREAM AND DEVELOPING TROF EVOLVES 
OVERNIGHT...WE WILL SEE A CLEAR START AND WINDS WILL LIKELY 
DECOUPLE.  WITH SFC DEWPOINTS PROG/D TO DROP OFF INTO THE MID 
40S...THINK MOST OF THE CWA WILL SEE TEMPS DIP INTO THE UPPER HALF 
OF THE 40S (WITH THE NOTABLE EXCEPTION IN METRO DTW).  IMPRESSIVE 
THETA-E ADVECTION (ABOVE 850MB) DEVELOPS OVER THE MISSISSIPPI RIVER 
VALLEY AND RACES NORTHEAST ON 50KT LLJ OVERNIGHT.  ETA/GFS ARE VERY 
SIMILAR DEVELOPING ELEVATED CONVECTION OVER NORTHERN INDIANA ON THE 
NOSE OF THIS AXIS TOWARD SUNRISE.  MEANWHILE...COLD FRONT WILL BE 
RACING SOUTHEAST TOWARD LAKE MICHIGAN BY 12Z TO BRING CLOUDS BACK 
INTO THE PICTURE AFTER MIDNIGHT.

WEDNESDAY...
INDEED A DAY OF TRANSITION AS COLD FRONT WILL BE APPROACHING DURING 
THE AFTERNOON.  WITH IMPRESSIVE 850-500 DPVA AND FGEN FORCING...WE 
WILL NEED TO SPEED UP THE TIMING WITH RAINFALL AND GO WITH LIKELY 
POPS DURING THE AFTERNOON (A CHANCE IN THE MORNING DUE TO 
AFOREMENTIONED WAA).  WITH 50+ KTS IN THE MID LEVELS AND THETA-E 
RIDGE AXIS IN THE VICINITY...SHOWERS AND THE CHC OF THUNDERSTORMS 
WILL BE RESULT BUT IT MIGHT BE DIFFICULT TO HAVE SURFACE BASED 
CONVECTION DEVELOP.  ETA SOUNDINGS SUGGEST DEWPOINT DEPRESSION BELOW 
850MB AOA 10C...BUT WITH THE DEGREE OF DYNAMICS ALOFT AND A HINT OF 
AN INVERTED-V SOUNDING...WE WILL HAVE TO BE ON THE LOOKOUT FOR GUSTY 
WINDS.  WITH CLOUD COVER AND SPEED OF THIS FRONT...WE WILL CUT BACK 
TEMPS A COUPLE OF DEGREES FROM OUR CURRENT GRIDS.

WEDNESDAY NIGHT...
FROPA DURING THE EVENING WITH QUICK SFC PRESSURE RISES WILL OPEN THE 
GATES FOR SOME OF THE COLDEST AIR THIS FALL...850MB TEMPS TO DROP 
AOA 0C BY SUNRISE!  RAINFALL WILL END FROM WEST TO EAST SHORTLY 
AFTER MIDNIGHT AS LAKE EFFECT CLOUDS OFF OF LAKE MICHIGAN WILL 
PREVAIL.  WITH CYCLONIC FLOW OVER THE LAKES AND COLD AIR 
ALOFT...WATERSPOUTS ARE A POSSIBILITY OVER LAKE HURON OVERNIGHT.  
TEMPERATURES WILL SLIDE BACK INTO THE 40S CWA-WIDE BUT WILL NOT GET 
OUT OF HAND DUE TO SFC GRADIENT AND PARCEL MODIFICATION FROM LAKE 
MICHIGAN.

THURSDAY...
SFC FLOW QUICKLY BECOMES ANTICYCLONIC THROUGH THE DAY WITH 850MB 
TEMPS HOVERING RIGHT AROUND 0C.  GOOD SUBSIDENCE BEHIND THE 
DEPARTING WAVE WILL PRECLUDE OUR CHANCES OF PRECIP OVER THE CWA BUT 
OVER THE LAKES IT WILL BE A BIT DIFFERENT.  WITH STEEP LAPSE RATES 
AND RELAXING FLOW...WE MAY PRODUCE MORE WATERSPOUTS OVER THE OPEN 
WATERS OF LAKE HURON.  WE WILL HOLD HIGH TEMPS BACK INTO THE LOWER 
HALF OF THE 60S OVER THE CWA.

LOOKING A BIT AHEAD...SFC HIGH SLIDES INTO THE OHIO VALLEY WITH ITS 
RIDGE SETTLING OVER THE STATE.  FOR NOW WE WILL HOLD TEMPS AROUND 40 
WITH WARMER READINGS CLOSER TO METRO DTW.  IN THE VALLEYS WE MAY SEE 
READINGS DROP BACK INTO THE MID 30S WHICH WOULD SUGGEST THE 
POTENTIAL OF FROST...STILL PLENTY OF TIME TO ASSESS.   
HOWEVER...THIS WILL LIKELY DEVELOP LAND BREEZES AND THE POTENTIAL 
YET AGAIN FOR WATERSPOUTS FOR ALL OF THE LAKE WATERS.  
HOWEVER...UPSTREAM WILL BE YET ANOTHER WAVE AS WAA EVOLVES OVER THE 
PLAINS.  THE LATEST GFS/CANADIAN GLOBAL AND THE ECMWF ARE FASTER 
WITH NEXT SHORT WAVE WHICH DIVES INTO THE NORTHERN LAKES BY FRIDAY 
MORNING.  THE CANADIAN IS THE DEEPEST INITIALLY BUT ALL POINT TOWARD 
AT LEAST A MENTION OF A CHANCE FOR SHOWERS FRIDAY AFTERNOON.  
THEREAFTER... A DEEP TROF EVOLVES OVER THE EASTERN CONUS FOR THE 
WEEKEND.

THANK YOU FOR THE COLLABORATION THIS MORNING SURROUNDING WFO/S!

.DTX...NONE.

$$

BGM

EXPERIMENTAL GRAPHICAL FORECASTS ARE AVAILABLE ONLINE AT 
HTTP://WWW.CRH.NOAA.GOV/DTX  (ALL LOWER CASE)