000 FXUS63 KGRR 251656 AFDGRR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND RAPIDS MI 1155 AM EST WED NOV 25 2009 LATEST UPDATE...SHORT TERM... .SYNOPSIS...(431 AM EST WED NOV 25 2009) LOW PRESSURE WILL DRIFT OVER THE GREAT LAKES TODAY AND CONTINUE TO BRING ON AND OFF SHOWERS. THESE SHOWERS WILL BE MOST COMMONPLACE EARLY TODAY...THEN BECOME SCATTERED INTO THE AFTERNOON. MORE NUMEROUS SHOWERS ARE EXPECTED TONIGHT AS AN UPPER LOW MOVES IN. THIS SYSTEM WILL LINGER OVER THE REGION ON THANKSGIVING DAY. AS COOLER AIR IS PULLED OVER THE AREA THE RAIN WILL BECOME MIXED WITH OR CHANGE TO SNOW THURSDAY AFTERNOON AND CONTINUE THURSDAY NIGHT. A LIGHT SLUSHY ACCUMULATION OF SNOW WILL BE POSSIBLE BY EARLY FRIDAY MORNING...BUT TRAVEL SHOULD NOT BE HAMPERED AS ROADWAYS SHOULD REMAIN MAINLY WET. && .SHORT TERM...(1155 AM EST WED NOV 25 2009) (THIS AFTERNOON) UPPER LOW IS SWINGING NORTHEAST OF THE AREA AT THIS TIME AND THE MORE CONCENTRATED AREA OF RAIN HAS COME TO AN END. EXPECTING ONLY SCATTERED SHOWERS THROUGH THE AFTERNOON. DOMINANT MODE OF PRECIPITATION THIS AFTERNOON MAY END UP BEING DRIZZLE AS THE MID LEVEL MOISTURE IS STRIPPED AWAY. FORECAST AREA IS IN BETWEEN THE LEAD UPPER LOW WHICH IS SHIFTING OFF TO THE NORTHEAST...AND THE SECOND LOW WHICH IS DIVING INTO IOWA. TEMPERATURES WILL ONLY CLIMB INTO THE UPPER 40S FOR HIGHS. && .LONG TERM...(431 AM EST WED NOV 25 2009) (FRIDAY NIGHT THROUGH TUESDAY) UPPER LEVEL RIDGING INBETWEEN THE DEPARTING LONGWAVE TROUGH AND THE NEXT ONE DIGGING OVER THE WRN U.S. WILL RESULT IN DRY AND MILD CONDITIONS ON SATURDAY WITH HIGHS IN THE MID 40S. THINGS TURN RATHER COMPLICATED/CHALLENGING FOR SUNDAY THROUGH TUESDAY. A SFC FRONTAL BOUNDARY IS EXPECTED TO MOVE INTO THE REGION FROM THE WEST ON SUNDAY AND SHOULD BRING THE CHANCE FOR A FEW RAIN SHOWERS. UNFORTUNATELY MEDIUM RANGE MODELS DISAGREE ON WHAT HAPPENS AFTER THAT...BUT AN ENSEMBLE APPROACH WOULD SUGGEST THAT THE SFC BOUNDARY WILL EVENTUALLY STALL FROM THE EASTERN GREAT LAKES REGION SOUTH TO THE GULF OF MEXICO AS THE DEEP H5 LONGWAVE TROUGH EDGES SLOWLY EASTWARD. ANY POTENTIAL SHORTWAVES COMING OUT OF THE BASE OF THE LONGWAVE TROUGH OVER TEXAS AND RIDING NORTH NORTHEAST ALONG THE BAROCLINIC ZONE MAY PRODUCE SOME PCPN IN MI. THERE IS EVEN A SUGGESTION THAT A RATHER POTENT AND WET SYSTEM WILL LIFT STRAIGHT NORTH OUT OF THE GULF OF MEXICO TOWARD MI AND INTERACT WITH APPROACHING NRN STREAM ENERGY... BUT CONFIDENCE (AND TIMING) OF THAT HAPPENING IS VERY LOW ATTM. PCPN TYPE SHOULD BE RAIN OR A MIX OF RAIN AND SNOW MONDAY AND TUESDAY...DEPENDING HOW MUCH COLD AIR GETS INTO THE REGION BEHIND THE SFC FRONTAL BOUNDARY. && .AVIATION...(700 AM EST WED NOV 25 2009) IFR CONDITIONS HAD FOR THE MOST PART VACATED THE AREA AS OF 12Z. MOSTLY MVFR CATEGORY CIGS (1500-2500 FT) AND SCATTERED SHOWERS ARE EXPECTED THIS MORNING... WITH VSBYS OCCASIONALLY DIPPING TO 3-5 MILES IN THE SHOWERS. IFR CIGS SHOULD RETURN TO THE AREA FROM THE WEST/SOUTHWEST TOWARD 18Z WITH THE PASSAGE OF THE SFC COLD FRONT/TROUGH... ALTHOUGH CLOUD BASES COULD BE AT OR JUST ABV 1K FEET MAKING IT TECHNICALLY NON IFR. THE NEXT UPPER LOW DROPPING DOWN FROM THE NORTHWEST WILL SPREAD ANOTHER ROUND OF RAIN SHOWERS ACROSS THE AREA TONIGHT AND WE SHOULD REMAIN PREDOMINATELY IN THE IFR CATEGORY. && .MARINE...(431 AM EST WED NOV 25 2009) WINDS AND WAVES WILL BE INCREASING THROUGH THE MORNING HOURS. A SMALL CRAFT ADVISORY IS ALREADY IN EFFECT. HOWEVER EVEN HIGHER WINDS AND WAVES SHOULD DEVELOP LATE TONIGHT INTO THURSDAY AS THE COLD ADVECTION ARRIVES. SCA HEADLINES WILL LIKELY NEED TO BE EXTENDED WITH FUTURE FORECAST PACKAGES. && .HYDROLOGY...(431 AM EST WED NOV 25 2009) MOST AREAS WILL SEE AN ADDITIONAL QUARTER TO HALF INCH OF RAIN FROM TODAY THROUGH MIDNIGHT THURSDAY NIGHT. THE PERSISTENT LIGHT PCPN WILL DO LITTLE TO INFLUENCE AREA RIVERS. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...NONE. LM...SMALL CRAFT ADVISORY ST. JOE TO WHITEHALL TODAY AND TONIGHT. && $$ SYNOPSIS: JK SHORT TERM: DUKE LONG TERM: MEADE AVIATION: MEADE MARINE: JK HYDROLOGY: JK