Issued by NWS Indianapolis, IN
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000 FXUS63 KIND 081805 AFDIND AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE INDIANAPOLIS IN 205 PM EDT FRI MAY 8 2009 .DISCUSSION...MCS FOUND ACRS SRN IL AND WRN KY EARLY THIS AFTERNOON WITH CLOUD AND PCPN SHIELD BEGINNING TO ADVECT TO CENTRAL INDIANA. TEMPS WERE STEADY IN THE MID 60S WITH LGT SOUTHERLY SFC FLOW. DEW POINT TEMPS WERE IN THE LOWER 60S. MAIN FORECAST CHALLENGE TDY WL BE POPS. WL USE A BLEND OF THE GFS/MAV. EVOLUTION OF ONGOING TSRA COMPLEX WL BE THE MAIN FEATURE WITHIN THE FIRST 3-6 HRS OF THE FORECAST. MODEL H8-H3 THICKNESSES PROPAGATE THE COMPLEX MAINLY EASTERLY ACRS KY...BUT DO SUGGEST GOOD FORCING ACRS SRN INDIANA AND THE SRN PARTS OF THE FA DURG THE EVENING HRS. AFTER THIS SYSTEM DEPARTS...A FRONTOGENESIS IS EXPECTED TO DEVELOP OVERNIGHT ACRS SRN INDIANA AS LOW PRES OVR THE GRT LKS DRAGS THE LINGERING BOUNDARY ACRS THE AREA AS A CD FRONT. THUS FEEL THE GFS POPS ARE TOO LOW AND WILL BUMP THEM UPWARDS...PARTICULARLY ACRS THE SRN PARTS OF THE FA...WHERE THE FORCING IS BEST. AS FOR TEMPS WL LEAN TOWARD THE COOLER SIDE OF THE MAVMOS GIVEN THE EXPECTED CLOUDS...PCPN AND CAA EXPECTED TO BEGIN LATE IN THE PERIOD. MUCH COOLER AIR ARRIVES ON SAT AS CYCLONIC FLOW WL BE IN PLACE ACRS INDIANA DUE TO THE LOW ACRS THE EASTERN GRT LKS. SOME AM PCPN WL BE POSSIBLE...MAINLY ACRS THE SERN PARTS OF THE FA WHERE THE CD FRONT MAY NOT HAVE YET EXITED. CU RULE INDICATES SCT-BKN CU DEVELOPMENT AS WELL ALONG WITH H8 TEMPS FALLING TOWARD 4C BY 00Z. FORECAST SOUNDINGS SUGGEST HIGH TEMPS ON SAT ONLY IN THE LOWER 60S. GIVEN THE CAA...WL LEAN COLDER THAN THE MAVMOS. CAA AND MOCLR SKIES EXPECTED ON SAT NIGHT AS HIGH PRES SETTLES ACRS THE CENTRAL PLAINS STS. TIME HEIGHT SECTIONS AND FORECAST SOUNDINGS SHOW A DRY COLUMN WITH GOOD SUBSIDENCE. WITH LIGHT NRNLY FLOW WL AGAIN LEAN 1-2F COOLER THAN THE MAVMOS LOWS. MORE DRY WX IN STORE FOR SUNDAY AND SUNDAY NIGHT AS THE HIGH SLOWLY SLIDES EASTWARD. PERHAPS A BIT MORE SUN ON SUNDAY AS CU RULE IS CLOSER TO LESS NEGATIVE. WL STICK CLOSE TO MAVMOS FOR HIGHS AND AGAIN FOR SUNDAY NIGHT/S LOWS. AS FOR THE EXTENDED...UPPER RIDGE WL REMAIN ACRS THE RGN ON MONDAY AND TUES PROVIDING A CONTINUATION OF THE DRY AND COOL WX. RETURN FLOW BEGINS TUES AFTERNOON AND WARM FRONT APPROACHES LATE ON TUES NIGHT AS THE UPPER RIDGE MOVES TO THE EAST. EXPECT INCREASING CLOUDS ON TUESDAY NIGHT ALONG WITH SHRA CHCS BY WED MORNING. ECMWF AND GFS THEN PUSH AN UPPER LVL SYSTEM THROUGH THE GRT LKS ON WED AND THURS...AND WITH CYCLONIC FLOW ALOFT WL NEED TO MENTION PCPN CHCS. GFS IS MORE AGGRESSIVE WITH PUSH A SFC CD FRONT SOUTH OF INDIANA ON FRI...BUT BOTH ECMWF AND GFS STILL KEEP A TROUGHY PATTERN IN PLACE ALOFT. GIVEN THIS CONFIDENCE ON FRI IS LOW BUT CHC POPS SEEM WARRANTED ATTM GIVEN THE UPPER PATTERN. && .AVIATION...DISCUSSION FOR 1800Z TAFS TSTM COMPLEX CURRENTLY MOVG EWD ACRS SRN IL WITH A LRG AREA OF RAIN/EMBEDDED TSTMS TO ITS NORTH. THIS AREA OF RAIN XPCTD TO PASS ACRS THE TERMINALS LTR THIS AFT/EVEN. LIGHTNING ACTVTY UPSTREAM SPORADIC WITH MODEL INSTABILITY INDICES SUGGESTING A CONTINUED THREAT FOR TSTMS EMBEDDED WITHIN THE RAIN AREA. MOST LIKELY AREAS AT THIS TIME APPEAR TO BE IN THE KHUF/KBMG AREAS THRU ABOUT 082100Z. MVFR/AREAS IFR CONDS XPCTD TO CONTINUE THRU AT LEAST 090600Z WITH XPCTD PCPN. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ AVIATION...JAS PUBLIC...PUMA
