000 FXUS63 KPAH 240334 AAA AFDPAH AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PADUCAH KY 934 PM CST FRI JAN 23 2009 .UPDATE... FOR INTERIM SENSIBLE WEATHER TRENDS FOR THE REMAINDER OF THE THE FIRST PERIOD /REST OF TONIGHT/. && .DISCUSSION... EARLY IN THE FIRST PERIOD...GENERALLY UTILIZED SHORT TERM TEXT FORECAST PRODUCT TO ACCOUNT FOR VERY LIGHT PRECIPITATION FALLING FROM DESCENDING/SATURATING POST FRONTAL CLOUD DECK. HOWEVER...WITH ISOLATED SLEET REPORTS FROM MID DECK CLOUDS /AT OR ABOVE 9KFT AGL/ AS FAR SOUTH AS PADUCAH...A MORE PRONOUNCED APPROACH WAS NECESSARY IN THE GRIDS/TEXT/TABULAR FORECAST FOR THE REMAINDER OF TONIGHT. THE SHORT TERM GUIDANCE OF VARYING RESOLUTIONS /4KM TO 40KM/ HAS HAD A DIFFICULT TIME FOCUSING ENOUGH MSTR AND LIFT TO BRING AIR PARCELS TO SATURATION TO MEET THE MODEL PRECIPITATION ALGORITHMS. HOWEVER...THE SHORT RANGE ENSEMBLE FORECAST /SREF/ GUIDANCE SEEMS AND THE OPERATIONAL 12KM RUC DO SEEM TO PICK UP ON SOME PRECIPITATION POTENTIAL THIS EVENING AND OVERNIGHT. TO ACCOUNT FOR VARYING DEPTHS OF SUBFREEZING AIR/MOISTURE AND SURFACE TEMPERATURES...I ADJUSTED GRIDS WITH A MENTION OF LIQUID VS. FROZEN MEASURABLE PRECIPITATION DURING THE EVENING...THEN TRACE SNOW OVERNIGHT...MAINLY ACROSS THE NORTHERN 2/3RDS OF THE WFO PAH FORECAST AREA. I WILL HAVE TO MONITOR THE NWD PROGRESS OF THE CURRENT PRECIPITATION OVER NRN AR TO DETERMINE WHETHER ADJUSTMENTS WILL BE REQUIRED FOR THE MO/KY BORDER COUNTIES AROUND MIDNIGHT. && .PREV DISCUSSION... /ISSUED 515 PM CST FRI JAN 23 2009/ UPDATE... UPDATED AVIATION SECTION FOR 00Z TAFS. DISCUSSION... BIGGEST PROBLEM OF THE DAY REVOLVES AROUND THE POTENTIAL FOR WINTER WEATHER NEXT WEEK. IN THE MEANTIME...TODAY...WE HAVE BEEN DEALING WITH A COLD FRONT THAT IS MAKING ITS WAY ACROSS THE AREA. HIGH PRESSURE WILL BE BUILDING INTO THE AREA WITH A VENGEANCE...SO GUSTY NORTHWEST WINDS WILL PERSIST THROUGH THE NIGHT. LOOKS LIKE QUITE A BIT OF CLOUDINESS THIS EVENING AND THROUGH THE OVERNIGHT HOURS AS TIME HEIGHTS INDICATE PLENTY OF MID TO UPPER LEVEL MOISTURE...AND EVEN SOME LOW LEVEL MOISTURE WORKING ITS WAY INTO THE AREA LATER ON. THE GFS TRIES TO GENERATE SOME MINOR QPF WITH THE ARRIVAL OF THAT LOW LEVEL MOISTURE...BUT LIKE THE LAST SHIFT WROTE...NOT SURE WHAT TO MAKE OF THIS...BUT AM INCLINED TO LEAVE IT OUT FOR THE TIME BEING. IF ANYTHING IT MIGHT JUST BE A FEW FLURRIES ACROSS SOUTHERN MISSOURI AND SOUTHERN KENTUCKY. IT APPEARS AS THOUGH THE CLOUDS WILL BE ON THEIR WAY OUT BY MID MORNING TOMORROW...AND SATURDAY ACTUALLY SHOULD BE A SUNNY DAY...BUT MUCH COLDER. PLENTY OF COLD DRY AIR GETS FILTERED DOWN ACROSS THE AREA BEHIND THE FRONT OVER THE NEXT 24 HOURS...SO WE SHOULD SEE TEMPERATURES ABOUT 30 DEGREES COLDER THAN WE HAVE GOING TODAY. SO UPPER 20S TO LOWER 30S EXPECTED FROM NORTH TO SOUTH. CLOUDS BEGIN TO INFILTRATE THE AREA LATE SATURDAY NIGHT...WHICH MIGHT HELP KEEP TEMPS FROM BOTTOMING OUT. BUT IT STILL LOOKS MIGHTY COLD THOUGH...WITH LOWS IN THE TEENS TO LOWER 20S MOST PLACES. THESE CLOUDS LOOK TO STICK AROUND FOR SUNDAY AND SUNDAY NIGHT AS WELL. EVEN THOUGH THERE IS NO CHANGE IN 850 MB TEMPS DUE TO THE ZONAL FLOW PATTERN...DUE TO THE FACT WE WILL HAVE SOME CLOUD COVER...TEMPS WILL LIKELY BE LOWER ON SUNDAY. IN ADDITION...MODELS SHOW SOME MID LEVEL ENERGY MOVING THROUGH THE ZONAL FLOW...WHICH GENERATE SOME PRECIP TO OUR NORTH. BUT WE SHOULD BE DRY FOR THE MOST PART. ON MONDAY...THE 12Z GFS INDICATES THAT DEEPER MOISTURE WILL BE ADVECTING INTO THE AREA...AS SOUTHWEST FLOW INCREASES AND DECENT WARM AIR ADVECTION TAKES PLACE. THE GFS EVEN PAINTS A LITTLE QPF OVER THE WESTERN SECTIONS OF THE AREA. THE 12Z NAM AND 00Z/12Z ECMWF ARE NOT SO EXCITED ABOUT THIS IDEA AND INDICATE FAIRLY NEUTRAL CONDITIONS. TO AVOID ANY FLIP FLOP IN THE FORECAST...WILL NOT MAKE ANY SUBSTANTIAL CHANGES TO MONDAYS FORECAST...AS IT JUST HAS A SMALL CHANCE RIGHT NOW AND THE PRECIP TYPES LOOK REASONABLE AT THIS TIME. LOW CONFIDENCE CONTINUES IN THE EXTENDED (MONDAY NIGHT THROUGH FRIDAY). WILL NOT ELABORATE ON SPECIFIC RUN-TO-RUN AND MODEL-TO- MODEL DIFFERENCES BECAUSE THERE ARE TOO MANY TO DETAIL. HOWEVER...IN THE OVERALL SCHEME OF THINGS...THE POTENTIAL FOR SIGNIFICANT MIXED WINTRY PRECIPITATION APPEARS TO BE INCREASING FOR NEXT WEEK. EVEN THOUGH TIMING AND AMOUNTS ARE NEARLY IMPOSSIBLE TO DETERMINE AT THIS POINT...MODEL CONSENSUS SEEMS TO BE HINTING AT TWO ROUNDS OF PRECIPITATION. THE FIRST IS EXPECTED TO BEGIN LATE MONDAY AND PERSIST INTO LATE TUESDAY. THE OTHER LOOKS TO OCCUR LATE WEDNESDAY INTO THURSDAY. DURING THE FIRST EVENT...WARM AIR OVERRUNNING SUB-FREEZING AIR AT THE SURFACE SHOULD LEAD TO A MIX OF SLEET AND FREEZING RAIN...WITH SNOW POSSIBLY MIXED IN THE NORTH AND RAIN IN THE SOUTH. THE SECOND EVENT WILL ALSO RESULT IN A MIX...BUT WILL STAY WITH ONLY RAIN OR SNOW AT THIS TIME FOR SIMPLICITY. EFFORT TO DELINEATE PRECIPITATION TYPES IN GREATER DETAIL WILL BE MADE AS CONFIDENCE IN MODEL DATA GROWS. OVERALL...PREFER HPC/S ENSEMBLE APPROACH TO SMOOTH OUT VARIATIONS AMONG INDIVIDUAL MODEL SOLUTIONS. FOR TEMPERATURES... STAYED FAIRLY CLOSE TO LATEST HPC GUIDANCE. AVIATION... FROPA HAVING OCCURRED AT ALL TAF SITES...TIGHTENING POST FRONTAL GRADIENT TO BEGIN EARLY THIS EVENING WITH STIFFENING NWLYS-NLYS OVERNIGHT. TIME/HEIGHT CROSS SECTIONS REVEAL SUB 850 MB MOISTURE WHERE MOS DOES NOT...SO WE KEPT THE MVFR CIGS FORECAST AFT MIDNIGHT. THIS MAY NOT COME TO FRUITION...BUT WE DO SEE A CORRIDOR OF SAME ACROSS ECNTL IL/WCNTL IN AND ITS HARD TO IGNORE THE TIME/HEIGHT SUGGESTIONS. DURING THE DAY DRIER AIR WILL WORK INTO THE COLUN WITH SKIES CLEARING AND WINDS DIMINISHING DURING THE PM/PLANNING PERIOD HOURS. && .PAH WATCHES/WARNINGS/ADVISORIES... KY...NONE. MO...NONE. IL...NONE. IN...NONE. && $$ SMITH