Issued by NWS Indianapolis, IN
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000 FXUS63 KIND 231707 AFDIND AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE INDIANAPOLIS IN 107 PM EDT THU OCT 23 2008 .AVIATION... DISCUSSION FOR 231800Z TAF ISSUANCE. A STRONG UPPER LEVEL LOW PRESSURE IN THE CENTRAL PLAINS WILL DRIFT TOWARDS CENTRAL INDIANA DURING THIS TAF FORECAST PERIOD. CONDITIONS WILL BEGIN VFR THIS AFTERNOON...WITH JUST MID TO HIGH LEVEL CLOUDINESS BUILDING IN. UNTIL THE 05-07Z TIME WHEN AN AREA OF LOWER CIGS AND VSBY AND RAIN WILL MOVE IN. THIS WILL HAVE THE EARLIEST IMPACTS AT HUF WHERE LIGHT RAIN WILL ARRIVE AS EARLY AS 05Z. BUT WITH A DRY AIRMASS IN PLACE...INITIALLY IT SHOULD REMAIN VFR. HOWEVER...BY 10Z AT HUF AND BETWEEN 11-13Z ELSEWHERE...LOWER CIGS AND VSBY WILL MOVE IN. HUF SHOULD EXPERIENCE THE WORST OF IT...AS THE HEAVIEST RAIN IS EXPECTED TO BE IN THAT AREA. IFR CONDITIONS WILL OCCUR THERE BETWEEN 10-15Z. ELSEWHERE IT SHOULD REMAIN JUST MVFR AS THE BAND OF RAIN WILL WEAKEN RATHER QUICKLY TOMORROW MORNING. IN FACT...SOME IMPROVEMENT WILL BE NOTED BY 15Z AT HUF. OTHER SITES WILL REMAIN MVFR THROUGH THE CLOSE OF THE PERIOD. && .PREV DISCUSSION... /ISSUED 703 AM EDT THU OCT 23 2008/ AN UPPER RIDGE OF HIGH PRES WAS STILL FOUND ACRS INDIANA AND OHIO EARLY THIS MORNING...PROVIDING DRY WX ACRS INDIANA. A STRONG AREA OF LOW PRES WAS FOUND ACRS KS AND NB. VERY DRY AIR REMAINED IN PLACE ACRS INDIANA AS SFC DEW POINT TEMPS WERE IN THE MIDDLE 20S. MAIN FORECAST CHALLENGE WL BE ONSET OF PCPN. MODELS HAVE COME TO A BETTER AGREEMENT WITH PCPN TIMING...AND WL USE A BLEND. THE UPPER RIDGE OVR THE AREA WL CONTINUE TO PROVIDE ANOTHER DAY OF DRY WX ACRS INDIANA TDY AS TIME HEIGHT SECTIONS SHOW A DRY COLUMN ALONG WITH SUBSIDENCE. AS FOR TEMPS...GOOD WAA IS FOUND AT H8 AS TEMPS REACH NEAR 9C. HENCE WL AIM FOR MOSUNNY SKIES ALONG WITH HIGHS IN THE LOWER 60S. MAVMOS HANDLES THIS QUITE WELL. CLOUDS WL INCREASE TONIGHT AS THE LOW APPROACHES. GOOD WAA AHEAD OF THE SYS SHUD ALSO HELP TO KEEP TEMPS UP. WL LEAN TOWARD THE WARMER SIDE OF THE MAVMOS. BEST ISENTROPIC LIFT APPEAR TO MOVE INTO WESTERN INDIANA NEAR 12Z...THUS WL NEED SOME POPS ACRS THE WESTERN AREAS. WITH SUCH DRY AIR THE LOWER LVLS OF THE ATMOS...IT MAY TAKE SOME TIME FOR SHRA TO MATERIALIZE. FORECAST SOUNDINGS ACRS THE AREA BECOME SATURATED ON FRI...AS THE 305K ISENTROPIC SFC SHOWS STRONG LIFT AND SURGE OF MOISTURE PUSHING ACRS INDIANA. HENCE GIVEN THE EXPECTED PCPN WL LEAN COOLER ON TEMPS AND CONFIDENCE FOR MEASURABLE RAIN IS HIGH. THUS WL USE NEAR CATEGORICAL POPS. ATTM IT APPEARS A DRY SLOT MOVES ACRS INDIANA FRI NIGHT AS THE BULK OF THE MOISTURE PUSHES TOWARD THE NE. STILL A STRONG UPPER LOW WL STILL BE OVER THE AREA IT APPEARS POSSIBLE THAT A STRAY SHRA STILL MAY OCCUR. WL STICK CLOSE TO MAVMOS POPS HERE. LITTLE CHANGE IN THE LATTER PARTS OF THE FORECAST AS THE UPPER LOW DEPARTS ON SAT. VERY COLD AIR WL BE FOUND ALOFT RESULTING IN CLOUDS AND INSTABILITY. ANOTHER EVEN COLDER SURGE OF AIR WILL MOVE IN STARTING SUNDAY FOR THE BEGINNING OF NEXT WEEK...LEADING TO NW FLOW AND BELOW NORMAL TEMPS. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ AVIATION...JOHNSON
