EXCESSIVE RAINFALL DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 954 PM EDT SAT APR 30 2011 ...VALID 03Z SUN MAY 01 2011 - 00Z MON MAY 02 2011... ...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL... SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 25 NE HOP 10 WSW MKL 15 ESE LLQ 10 SW GGG TYR 10 NNW LNC RBD DFW DTO GLE 15 ESE AQR 35 SSE MLC 35 SW RKR 20 SE RKR 35 ESE FSM 20 ENE BPK 15 WSW MDH EVV 25 NE HOP. MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 NNE DEQ 25 W MWT 35 N BVX 35 W POF 20 N POF 10 SSW MWA 10 E HSB 20 W EHR 15 SW EHR 20 S EHR 40 SSW EHR 30 ENE DYR 25 SSE SGT 10 N ELD 30 WNW SHV 4F4 3T1 15 N TRL 15 E TKI 30 N GVT PRX 20 NNW LBR 20 NNE DEQ. HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 SSW DEQ 10 SE DEQ 30 E RUE 20 NNW ARG 15 WSW CGI 15 NNW M30 20 ENE M30 10 ESE PAH 10 SSE HKA 10 S SGT 30 ESE TXK 30 NNW DTN 25 ENE 4F4 15 NNE 4F4 10 WSW OSA 20 SSW LBR 20 SSW DEQ. TOTAL RAINFALL AMOUNTS OF FIVE INCHES WILL BE POSSIBLE TO THE RIGHT OF A LINE FROM 15 SSE POF 20 S CGI CIR 10 SSE CIR 25 S CIR BYH 30 SSE M19 20 NNW PBF 25 E M89 M89 20 W M89 25 S MWT 15 SE MWT 25 NNW LRF ARG 15 SSE POF. UPDATE... CHANGES TO THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WERE TO EXPAND THE MDT AND HIGH THREAT REGIONS NEWD INTO THE LOWER OH RIVER VALLEY. THIS IS TO ACCOUNT FOR THE CURRENT ENHANCING CONVECTION FROM CNTRL TO NERN AR INTO SERN MO WHICH SHOULD CONT TO BE MAINTAINED INTO THE EARLY MORNING HOURS IN A REGION OF VERY FAVORABLE UPR DIFFLUENCE LOW LEVEL JET/MOISTURE FLUX MAXIMUM. TRAINING OF CONVECTION IN THIS AREA MAY PRODUCE ISOLATED RAINFALL TOTALS OF 2-3"+ IN A FEW HOURS. THIS LEAD AREA OF CONVECTION MOVG TOWARD THE LOWER OH/MID MS RIVER VALLEY MAY WEAKEN POST 12Z SUN. HOWEVER...ADDITIONAL ACTIVITY LIKELY TO FROM NERN TX/FAR SERN OK SUN MORNING AND BUILD BACK TO THE NORTHEAST ACRS AR TOWARD THE CONFLUENCE OF THE OH/MS RIVERS...ALONG THE VERY SLOW MOVG FRONT ACRS THESE REGIONS. ADDITIONAL SHRT TERM PCPN AMTS OF 1-2"+ POSSIBLE DURG SUN..LEADING TO A BROAD REGION WHERE TOTAL AMTS IN EXCESS OF 5" ARE POSSIBLE. FOR THAT REASON...THE 5"+ THREAT REGION WAS EXPANDED FROM THE PREV OUTLOOK. ORAVEC PREVIOUS DISCUSSION... ...LWR OH VLY INTO ARKLATX... LATEST GUID CONTS TO ADVERTISE SPLIT FLOW DVLPG OVER THE CNTRL U.S. AS A DEEP 5H VORTEX LIFTS NEWD FM THE NRN PLNS...WHILE A TRAILING TROF BREAKS AWAY AND MOVES INTO THE 4-CORNERS REGION WITH A SEPARATE SEMI-CLOSED LOW DVLPG AT 5H. THIS WL ALLOW FOR INCRSG UPR DIFL/DVRG FLOW FM THE ARKLATX NEWD INTO THE LWR OH VLY TNGT WITH INCRSG DEEP LYRD ASCENT NR A SFC/8H FNTL BNDRY THAT WL PUSH INTO THE REGION THEN STALL. LATEST SUITE OF GUID IS SHOWG MORE SUPPORT FOR ORGANIZED HVY RNFL DVLPG THIS EVE ACRS THE ARKLATX THAT WL DVLP NEWD ALNG THE BNDRY INTO THE LWR OH VLY. MDLS ARE SUGGESTING TNGTS CNVCTN WL LIFT NEWD WITH SOMEWHAT OF A BREAK IN THE HVY RNFL VRY LATE TNGT OVR THE ARKLATX...THEN REDEVELOP ON SUN OVR NRN TX AND PUSH BACK INTO THE ARKLATX SUN AFTN/EVE. MSTR FEEDG INTO THE REGION CONTS TO BUILD WITH SATL/GPS PWS SHOWG VALUES 1.25-1.50 INCHES OVR MUCH OF ERN TX INTO WRN LA. MDLS SHOW THIS MSTR CONTG TO LIFT NEWD WITH VALUES INCRSG TO 1.50-1.75 INCHES AS MSTR POOLG TAKES PLC AND A MOD/STG LLJ CONTS TO SUPPORT MSTR FLUX/TRANSPORT. PW ANOMALIES BUILD TO NEAR TWO STDS ABV NRML...WHILE THE DVLPMENT OF A MOD/STG LLJ TNGT WL HELP INCRS MSTR TRANSPORT INTO THE REGION WITH ANOMALIES BUILDING TO 4-5 STDS ABV NRML AND AIMED INTO SWRN/SRN ARK...BEFORE WEAKENG AND LIFTG NEWD VRY LATE TNGT. MSTR FLUX WL THEN INCRS ON SUN INTO NRN TX. SFC/8H BNDRYS ARE FCST TO STALL THRU THE REGION OR MOVE VRY SLOLY...WITH A STG 8H THETA-E RDG BUILDG ALNG THE BNDRY. MDLS CONT TO SUPPORT TRAING THRU THE REGION...ESPCLY TNGT AS THE LLJ VEERS TO A MORE SWRLY DIR. MDL FCST SOUNDINGS ARE ALL SHOWG VRY FAVORABLE PROFILES FOR HVY RNFL WITH TALL SKINNY CAPES AND MIDLVL LAPSE RATES ARND 6 C/KM. EXPERIMENTAL HI-RES DENSITY PLOTS OF RNFL EXCEEDING FFG ARE SHOWING SOME THREAT OVR THE CONFLUENCE REGION OF THE OH/MS RIVERS WHERE FFG IS LOWEST...BUT INCRSG RISK HAS DVLPD FARTHER SW INTO ARK WHERE TRAINING COULD DVLP TNGT. THE MAIN THREAT FOR ORGANIZED HVY RNFL SHLD BE TNGT WITH LCL 1-2 INCH HRLY RATES AND PSBL 4-5 INCH TOTALS BY SUN EVE...ESPCLY FM THE ARKLATX NEWD INTO NERN ARK/WRN TN. ECKERT $$