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)