EXCESSIVE RAINFALL DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 1013 AM EDT THU JUN 10 2010 ...VALID 15Z THU JUN 10 2010 - 12Z FRI JUN 11 2010... ...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL... SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 40 ENE LHB 30 ESE ACT 20 ENE ACT 10 SSW INJ INJ 15 NE INJ LNC 15 S SLR 20 NW OSA 10 ENE DEQ 25 NNE MWT 10 SE RUE 10 NW SRC 10 WSW SGT 25 W LLQ 25 ESE BAD 35 S SHV 35 ENE OCH 20 WNW LFK 35 S PSN 40 ENE LHB. SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 15 SE KACQ 15 NNW AXA 20 NW FOD 25 ESE CIN 20 ENE CSQ 15 SSW LWD 25 NNE STJ 25 SW AFK 10 SW LNK 20 NW GRI 15 SSW ODX 15 ESE BBW 10 ESE LBF 30 WSW LBF 20 S OGA 30 W OGA 10 ENE ANW 45 NNW ONL 25 E HON 10 SSE 8D3 15 NE FFM 10 ENE PWC 10 WNW HYR 10 W RRL 20 WSW MFI 15 SE KACQ. MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 S GGG 10 SE JSO 15 SE PSN 20 SSW PSN 20 WSW PSN 20 SE CRS 15 NE CRS 25 SW 3T1 3T1 15 WSW OSA OSA 10 E OSA 20 E OSA 35 ESE OSA 35 ENE 4F4 25 NE GGG 10 ESE GGG 20 S GGG. HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 E CRS 30 ESE LNC 20 W TYR 15 SSW 3T1 3T1 15 ENE 3T1 4F4 10 WSW GGG 15 NE JSO 10 E PSN 10 S PSN 10 SW PSN 10 W PSN 20 WNW PSN 20 E CRS. TOTAL RAINFALL AMOUNTS OF FIVE INCHES WILL BE POSSIBLE TO THE RIGHT OF A LINE FROM 15 N OCH 25 S PSN 40 SW PSN 40 S CRS 30 SSW CRS 25 SE INJ 15 SSE INJ 10 SSE INJ 10 ESE INJ 15 WNW CRS 20 ESE TRL 10 WNW OSA 25 SE LBR 20 S DEQ 15 NW HOT 25 SSE RUE 15 NW LZK LRF 20 NNW PBF 10 NNE ELD 15 SW SHV 15 N OCH. UPDATE... NERN TX...FAR NWRN LA...SCNTRL AR... CONVECTION REMAINS WELL DEFINED AND VERY SLOW MOVG INVOF THE SLOW MOVG MID LEVEL VORT OVR NERN TX THIS MORNING. THE PREVIOUS EXCESSIVE RAINFALL POTENTIAL OUTLOOK WAS UPGRADED GIVEN CURRENT RADAR AND SATL APPEARANCE INVOF THIS SLOW MOVG VORT. VERY SLOW MOVEMENT TO THE NORTHEAST IS EXPECTED WITH THIS FEATURE THRU THE REMAINDER OF THE DAY THURSDAY...WITH POTENTIAL FOR INCREASED FORWARD SPEED ACRS SRN AR AFTER 0000 UTC FRI. ABOVE AVG PW VALUES...2 STD ABOVE THE MEAN...INVOF THIS MID LEVEL VORT AND THE EXPECTED CONTINUED SLOW MOVEMENT WL SUPPORT ADDITIONAL VERY HEAVY AND EXCESSIVE RAINFALL AMTS ACRS NERN TX..EVENTUALLY SPREADING NEWD INTO FAR NWRN LA AND SCNTRL AR. STNRY OR VERY SLOWLY MOVG CONVECTION WL LIKELY REMAIN NEAR THIS UPR CNTR...WITH ACTIVITY POSSIBLY EXPANDING NEWD DURG THE DAY AS IT HAS OVER THE PAST FEW DAYS...AND AGAIN CONTRACTING NEAR THE CNTR IN THE OVERNIGHT HOURS EARLY FRI. PCPN AMTS OF 2"+ IN AN HR AND ISOLATED TOTALS OF 5-10" POSSIBLE NEAR THIS UPR CNTR WHERE STNRY TO VERY SLOW MOVG CONVECTION OCCURS. NERN NE...ERN SD...WRN IA...FAR NWRN MO..SRN TO CNTRL MN AND NWRN WI... THE PREVIOUS OUTLOOK AREA WAS EXPANDED SEWD INTO ERN NE AND WRN IA FOR THE CURRENT ORGANIZED SQUALL LINE PRESSING QUICKLY EWD. RAINFALL AMTS OF 1"+ POSSIBLE WITH THIS LINE IN A BRIEF PERIOD...WITH THE FORWARD SPEED OF THIS CONVECTION A LIMITING FACTOR FOR RAINFALL AMTS TO EXCEED FFG VALUES. SOME CONCERN THAT THIS CONVECTION MAY BEGIN TO PUSH MORE TO THE SOUTHEAST AND AFFECT PORTIONS OF NWRN TO NRN MO THAT HAVE LOWER FFG VALUES. IN THE WAKE OF THIS SYSTEM PUSHING EWD TODAY...ADDITIONAL ORGANIZED CONVECTION POSSIBLE LATE THU INTO THE EARLY HOURS OF FRI AS THE MOIST LOW LEVEL SLY FLOW IS EXPECTED TO STRENGTHEN ACRS PORTIONS OF THE CNTRL TO NRN PLAINS AND INTO THE UPR MS VALLEY. THIS NEXT AREA OF ORGANIZED CONVECTION LATE THU INTO EARLY FRI WL LIKELY BE FARTHER TO THE NORTH FROM THE CURRENT ACTIVITY...SUPPORTING ISOLATED PCPN AMTS OF 1.5-2" IN AN HR OR TWO FROM CNTRL NE...NEWD THRU ERN SD AND INTO SRN TO CNTRL MN...NWRN WI. ORAVEC PREVIOUS DISCUSSION... WEAK UPPER LO OVR NERN TX WHICH HAS ACTED LIKE A WEAK TROPICAL SYSTEM IS FCST TO GRADUALLY ACCELERATE AS IT LIFTS NEWD THRU THE FCST PD. THIS SHOULD REDUCE THE CHANCES FOR EXCESSIVE RAINS BUT NOT ELIMINATE THE POSSIBILITY AS HI MSTR AVBLTY..FVBL DIV FLOW ALOFT AND THE INITIALLY SLOW MOVEMENT OF THE SYSTEM ALLOWS FOR INTENSE RNFL RATES AS THE INTERACTION OF CNVCTV CELLS OCCURS. COULD SEE QUICK 2.00 INCH RNFL AMTS WITH TOTALS THRU THE PD APCHG 5 INCHES OVER LOCALIZED ALONG THE TRACK OF THIS SYSTEM. MODELS IN GNRL ARE ARGUING FOR A HVY RNFL EVENT OVR THE N CNTRL U.S. THRU THE FCST PD AS A SERIES OF SHRTWVS TAP MSTR POOLING ALONG A BROAD BAROCLINIC ZONE EXPECTED TO BE LYING ACROSS THE OUTLOOK AREA. UNFORTUNATELY..MODEL QPFS DIFFER SGFNTLY HERE SUGGESTING MESOSCALE FORCING WILL LIKELY PLAY A SGFNT ROLE IN CONCENTRATING ACTVTY. FACTORS FOR SUPPORTING SGFNT CNVTV RAINS INCLUDE A STG NWD MSTR FLUX INTO THE REGION THAT WILL INCRS PW AVBLTY AND BROADLY DIFFLUENT FLOW ALOFT TO ENHANCE THE LIFTING PROCESS. THERE IS SOME SUGGESTION RNFL MAY MAXIMIZE INVOF CNTRL MN AS A WEAK SFC WV DVLPS ALONG THE E/W ORIENTED FRONTAL BAND AS WELL AS INVOF N CNTRL/NERN NE AS A LEE LOW ENHANCES MSTR ADVCTN INTO THAT REGION. LOCALIZED AMTS OF 1.50 TO 2.00 INCHES IN AN HOUR OR TWO ARE POSSIBLE WITHIN THE OUTLOOK AREA AND WOULD NOT BE SURPRISED TO SEE SPOTTY 5.00 INCH AMTS ACROSS CNTRL MN WHERE THE BEST LLVL CNVGNC SHOULD BE CONCENTRATED. KORTY $$