000 FXUS63 KDTX 222349 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 649 PM EST SUN NOV 22 2009 .AVIATION... THE AMBIENT CONDITIONS REMAIN VIRTUALLY UNCHANGED FROM LAST NIGHT. AMPLE BOUNDARY LAYER MOISTURE WILL EXIST TO PROMOTE FOG/STRATUS DEVELOPMENT THROUGH THE NIGHT AS GOOD RADIATIONAL COOLING STRENGTHENS THE INVERSION. A SLIGHTLY STRONGER EAST-SOUTHEAST LOW LEVEL GRADIENT DOES EXIST TONIGHT. THIS MAY PRECLUDE A MORE WIDESPREAD DENSE FOG PROBLEM BUT AID IN THE MOISTURE FLUX /ESPECIALLY OFF LAKE ERIE/. THIS WOULD SUGGEST A COMBINATION OF FOG/STRATUS EVENTUALLY LEADING TO IFR/LIFR CONDITIONS...PRIMARILY BETWEEN 09-14Z. ONCE AGAIN ANY RESIDUAL STRATUS WILL STRUGGLE TO LIFT/SCATTER INTO MONDAY AFTERNOON GIVEN THE STRENGTH OF THE INVERSION. && .PREV DISCUSSION...ISSUED 331 PM EST SUN NOV 22 2009 SHORT TERM...TONIGHT ONCE AGAIN WITH SURFACE DEW POINTS HOVERING IN THE LOW TO MID 40S...SOUTHEAST MICHIGAN APPEARS PRIMED FOR FOG ONCE AGAIN...AS LOW STRATUS IS EXPECTED TO DISSIPATE AROUND SUNSET...SETTING US UP FOR GOOD RADIATIONAL COOLING WITH THE UPPER LEVEL RIDGE AXIS REMAINING OVERHEAD. THE DIFFERENCE TONIGHT IS A BETTER GRADIENT/SOUTHEAST WIND IN THE LOW LEVELS...WHICH AGAIN BEGS THE QUESTION OF LOW STRATUS VS FOG. THE FLIP SIDE IS THIS EAST-SOUTHEAST FLOW IS FAVORABLE...AS LAKE ERIE/LAKE ST CLAIR/SOUTHERN LAKE HURON PROVIDES SOME ADDITIONAL MOISTURE FLUX. WILL BE CARRYING AREAS OF DENSE FOG DEVELOPING IN THE ZONES...AND WILL DEFER TO THE EVENING SHIFT TO PULL THE TRIGGER ON AN ADVISORY (IF NEED BE) BASED ON TRENDS. WITH SURFACE WINDS MORE THAN LIKELY STAYING UP JUST A BIT AND BETTER CHANCE FOR QUICKER LOW STRATUS DEVELOPMENT...WOULD BE SURPRISED IF MINS ARE AS COLD AS THIS MORNING...AND WILL CARRY MINS PREDOMINATELY IN THE MID 30S. LONG TERM...MONDAY THROUGH NEXT SUNDAY AN ELONGATED SURFACE RIDGE IS FORECAST TO REMAIN OVER THE EASTERN GREAT LAKES THROUGH TUESDAY. THE LACK OF LOW LEVEL DRY AIR ADVECTION AND LIMITED MIXING DEPTHS WILL CONTINUE TO MAKE FOG AND LOW CLOUDS PROBLEMATIC OVER THE NEXT COUPLE OF DAYS...ESPECIALLY WHEN CONSIDERING THE CONTINUED EASTERLY MOISTURE FLUX OFF LAKE ERIE. WEAK SHALLOW COLD AIR ADVECTION ON MONDAY MAY PROVE SUFFICIENT ENOUGH TO STRENGTHEN THE LOW LEVEL INVERSION. THIS RAISES CONCERNS THAT RESIDUAL MOISTURE FROM MORNING FOG/LOW STRATUS WILL REMAINED TRAPPED UNDER THE INVERSION WELL INTO THE AFTERNOON /LIKE WHAT HAS HAPPENED TODAY/. HAVE THEREFORE RAISED AFTERNOON CLOUD COVER AND LOWERED TEMPS A FEW DEGREES BELOW GUIDANCE /NEAR 50/. SLIGHTLY BETTER MOISTURE ADVECTION BELOW 925MB ON MON NIGHT WITH THE HELP OF A WEAK SHORT WAVE TRACKING THROUGH THE OHIO VALLEY SHOULD RESULT IN A MUCH THICKER AND MORE PERSISTENT STRATUS DECK. HAVE ACCOUNTED FOR THIS IN BOTH MON NIGHT/TUESDAYS SKY COVER AND TEMPS /KEEPING MAX TEMPS IN THE UPPER 40S TO NEAR 50 ON TUES/. THE UPPER WAVE SHOWN ON THE CURRENT WATER VAPOR LOOP OVER THE PACIFIC NORTHWEST WILL BE THE NEXT CHALLENGE IN THE LONG TERM. THIS WAVE IS FORECAST TO AMPLIFY ACROSS THE HIGH PLAINS ON MONDAY AND THEN DEVELOP INTO A CLOSED CIRCULATION OVER KANSAS BY TUESDAY MORNING. THE 12Z MODEL SUITE APPEARED WELL INITIALIZED WITH THIS WAVE. THERE STILL HOWEVER REMAINS SOME MODEL SPREAD WITH RESPECT TO TIMING. THE 12Z ECMWF AND NAM ARE SLOWER IN COMPARISON TO THE GFS. IN LIGHT OF MODEL TRENDS OVER THE LAST TWO DAYS...PREFERENCE CONTINUES TO LIE WITH THE SLOWER ECMWF. THIS SOLUTION INDICATES THE BEST CHANCE FOR RAIN WILL BE LATE TUES NIGHT INTO WED AS THE COMPACT UPPER LOW AND ASSOCIATED MID LEVEL HEIGHT FALLS ADVANCE ACROSS THE STATE. THE UPPER LOW WILL THEN GET QUICKLY EJECTED TO THE NORTHEAST OF THE STATE BY THURSDAY AS A FAIRLY STRONG NORTHERN STREAM WAVE DIVES INTO THE DAKOTAS/UPPER MIDWEST...LEADING TO THE DEVELOPMENT OF A LARGE CUT OFF CIRCULATION OVER THE EASTERN US BY THE END OF THE WEEK. THERE IS STILL A DECENT AMOUNT OF MODEL SPREAD AMONG THE 12Z SUITE WITH RESPECT TO THE AMPLITUDE AND TIMING OF THIS WAVE...WHICH LEAD TO UNCERTAINTY IN STRENGTH AND LOCATION OF THE LARGE CUT OFF LOW. HAVE ACTUALLY LOWERED POPS A BIT ON THURSDAY AS THE BULK OF MODEL SOLUTIONS INDICATE MID LEVEL DRYING IN THE WAKE OF THE FIRST WAVE. PRECIP CHANCES THEN WILL INCREASE THURS NIGHT INTO FRI WITH THE POTENTIAL OF THE SECONDARY UPPER LOW IMPACTING THE REGION. IN LIGHT OF GFS THICKNESS FIELDS...WILL MAINTAIN A CHANCE OF BOTH RAIN AND SNOW THURS NIGHT INTO FRI /ALTHOUGH THE ECMWF CONTINUES TO SUGGEST THAT BOUNDARY LAYER TEMPS WILL SUPPORT MAINLY RAIN/. MARINE... THERE WILL BE A GRADUAL INCREASE IN SOUTHEAST WINDS MONDAY INTO TUESDAY AS THE HIGH RETREATS EAST...AWAY FROM THE AREA. THE PATTERN BECOMES ACTIVE AGAIN MID/LATE NEXT WEEK AS A STRONG SHORTWAVE AND ASSOCIATED JET STREAK DIG INTO THE UPPER MIDWEST AND LEAD TO THE DEVELOPMENT OF A LARGE UPPER LEVEL LOW OVER/NEAR THE REGION. THIS TIME FRAME WILL BRING UNSETTLED WEATHER AND HIGHER WIND AND WAVES. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....MR SHORT TERM...SF LONG TERM....SC MARINE.......SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).