Issued by NWS Indianapolis, IN
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000 FXUS63 KIND 222259 AFDIND AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE INDIANAPOLIS IN 600 PM EST SUN NOV 22 2009 .AVIATION DISCUSSION...FOR THE 00Z TAFS HIGH PRESSURE WILL CONTINUE TO BE THE MAIN WEATHER SYSTEM CONTROLLING INDIANAS WEATHER. TAFS WILL START OUT VFR. SOME HIGH LEVEL HIGH LEVEL MOISTURE WAS BEING PULLED UP THE BACKSIDE OF THIS SYSTEM. THESE CLOUDS ALONG WITH CONTINUED DRYING OF SURFACE LAYERS WILL LIMIT FOG DEVELOPMENT. VISIBILITIES WILL ONLY DECREASE TO MVFR LEVELS AROUND SUNRISE. THEY WILL QUICKLY INCREASE TO VFR BY 15Z. THE HIGH WILL CONTINUE TO MOVE SLOWLY TO THE EAST. MID AND HIGH CLOUDS WILL CONTINUE TO MOVE INTO INDIANA ON THE BACKSIDE OF THE HIGH ON MONDAY BUT CONDITIONS WILL REMAIN VFR. && .DISCUSSION... FORECAST FOCUS IS ON CHANCES FOR PRECIPITATION THIS WEEK. AT 18Z HIGH PRESSURE CONTINUED TO PROVIDE WINDS FROM THE EAST ACROSS THE FORECAST AREA THIS AFTERNOON. TEMPERATURES HAVE RESPONDED WELL TO THE SUNSHINE ONCE AGAIN. MEANWHILE...A WEAKENING UPPER LOW WAS NEAR SOUTHEASTERN TENNESSEE. RADAR MOSAIC SHOWED RAIN MOVING TOWARD KENTUCKY FROM TENNESSEE. SOME DISAGREEMENT IN THE MODELS BOTH IN MONDAY/S SYSTEM AS WELL AS THE STRONGER ONE MID WEEK. FOR MONDAY...NAM IS DRIER THAN THE GFS AND KEEPS RAIN WELL EAST OF THE AREA. GFS STILL SHOWS RAIN GETTING INTO THE EASTERN PART OF THE AREA. GFS IS DOING BETTER CURRENTLY WITH THE RAIN...SO WILL GO CLOSER TO ITS SOLUTION FOR MONDAY. BY MID WEEK THE MODELS ARE SPLIT BETWEEN A FAST AND A SLOW SOLUTION. WITH NO CLEAR FAVORITE...DECIDED TO SPLIT THE DIFFERENCE...ALSO TAKING INTO ACCOUNT FORECAST CONTINUITY. TONIGHT...CLOUDS WILL INCREASE MAINLY ACROSS THE SOUTHEASTERN HALF OF THE AREA AS THE WEAKENING UPPPER SYSTEM MOVES NORTHEAST. THE WEAK LIFT FROM THE SYSTEM LOOKS TO REMAIN SOUTH OF THE AREA DURING THE NIGHT...PERHAPS GETTING INTO FAR SOUTHERN AREAS TOWARD 12Z. WITH LITTLE LIFT AND LIMITED MOISTURE...CONTINUED THE DRY FORECAST TONIGHT. GUIDANCE NUMBERS ARE SIMILAR FOR LOWS TONIGHT AND LOOK GOOD GIVEN THE INCREASING CLOUDS. THE UPPER SYSTEM PROVIDES A GLANCING BLOW TO THE AREA ON MONDAY. WEAK ISENTROPIC LIFT ACROSS SOUTHEASTERN AREAS COULD BRING SOME LIGHT RAIN...SO HAVE KEPT LOW POPS ACROSS THOSE AREAS. THICKER CLOUDS ACROSS THE SOUTHEAST WILL KEEP TEMPERATURES COOLER THAN THE NORTHWEST...AND MET GUIDANCE GENERALLY FOLLOWS THIS BETTER THAN THE MAV...SO TRENDED TOWARD MET NUMBERS FOR HIGHS. FIRST IN A SERIES OF UPPER LOWS WILL BEGIN TO BRING CHANCES FOR RAIN TO THE AREA BEGINNING TUESDAY...MAINLY IN THE AFTERNOON. AS MENTIONED EARLIER...THIS IS BETWEEN THE MODEL SOLUTIONS AND IS CLOSE TO PREVIOUS FORECAST. THE UPPER LOW WILL THEN MOVE TO THE VICINITY OF NORTHERN ILLINOIS BY 12Z WEDNESDAY. THUS WITH THE BETTER FORCING ACROSS FAR NORTHERN AREAS...UPPED POPS TO LIKELY TUE NIGHT WITH CHANCE POPS ELSEWHERE. WHILE THERE WILL BE DRY PERIODS WEDNESDAY INTO WEDNESDAY NIGHT...TIMING ISSUES PRECLUDE TIMING THE POPS...SO KEPT LOW POPS THROUGH THAT PERIOD. MUCH COLDER AIR AND ANOTHER UPPER LOW ARRIVE FOR THANKSGIVING AND THEIR ARRIVAL WILL KEEP CHANCE POPS IN THE FORECAST. STILL LOOKS LIKE THERE WILL BE THE POTENTIAL FOR MIXED PRECIPITATION...WITH THE THICKNESS OF THE WARM LAYER NEAR THE SURFACE THE MAIN QUESTION. WITH SURFACE TEMPERATURES AROUND 40 AND WET BULB TEMPERATURES NEAR FREEZING...ITS TOO TOUGH A CALL AT THIS POINT IN TIME. WILL CONTINUE CHANCES FOR RAIN AND SNOW THANKSGIVING AND THANKSGIVING NIGHT. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...CS AVIATION...SH