EXCESSIVE RAINFALL DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 919 PM EDT SAT APR 23 2011 ...VALID 03Z SUN APR 24 2011 - 00Z MON APR 25 2011... ...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL... SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 25 ENE ADH 15 NE OKM 10 W GCM 20 NNW GCM 25 SSE CFV 25 WSW JLN 10 N JLN 30 NNW SGF 20 E AIZ CPS 10 NW BMG 20 ESE GEZ 20 WSW TZR VTA ZZV 30 SW HLG 25 S HLG 20 S AFJ MGW 10 SE MGW CKB 10 W W22 15 W 48I 30 SW CRW 40 SE FTK 20 NW BWG 25 N LRF 15 WNW SLR 10 ESE TKI 15 NNE DTO 10 E 1F0 25 ENE ADH. MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 15 WSW 3I2 20 SE SDF 10 SSW PAH 25 NE RUE 25 E FSM 20 SW JSV 25 S MKO 15 SW MKO 15 NNW MKO 15 S GCM 15 W GMJ 10 NNW SGF 35 ESE VIH MVN 20 SSE BAK 15 E ILN 10 N UNI 15 WSW 3I2. HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM 20 ENE POF 25 SSE UNO FLP 35 SSW HRO 20 S FYV 20 ESE TQH 10 NNE TQH 15 E GMJ 40 WSW FAM 25 ESE FAM 10 NW MDH 15 NW HSB 15 ENE HSB 20 SE HSB 20 NE M30 M30 20 S CGI 20 ENE POF. 03Z UPDATE... MADE ONLY VERY SLIGHT ADJUSTMENTS TO EXCESSIVE THREAT AREAS..OTHERWISE EARLIER FORECAST REASONING REMAINS VALID. LATEST RADAR IMAGERY SHOWS EARLIER CONVECTIVE COMPLEXES ACRS THE ERN OH VALLEY HAVE WEAKENED WHILE ACTIVITY HAS CONTINUED TO EXPAND ALONG AND SOUTH OF STATIONARY FROM ACRS NRN AR/SRN MO EWD INTO SRN IL AS VERY MOIST LOW LEVEL SWLY FLOW IMPINGES INTO THE WRN END OF THE FRONT. WEAK IMPULSES EJECTING OUT ACRS THE SRN PLAINS FROM THE SW U.S. WILL LIKELY KEEP ACTIVITY FAIRLY ACTIVE THRU THE OVERNIGHT PD AND INTO SUN WITH WIDESPREAD 1 TO 3 INCH RAINS A GOOD POSSIBILITY ESPECIALLY ACRS THE HIGH RISK AREA...WITH ISOLD AMOUNTS CLOSE TO 5 INCHES. SULLIVAN PREVIOUS DISCUSSION FOLLOWS... THE AXIS OF THE EXCESSIVE RAINFALL POTENTIAL OUTLOOK HAS NOT CHANGED APPRECIABLY FROM THE PREVIOUS ISSUANCE. HVY TO EXCESSIVE RAINFALL THREAT WL CONT THIS PERIOD FROM ERN PORTIONS OF THE SRN PLAINS...ENEWD INTO THE MID MS VALLEY AND OH VALLEY. OVERALL..THERE IS VERY GOOD AGRMNT THIS PERIOD WITH THE HVY TO EXCESSIVE RAIN THREAT ALONG THE STNRY FRONTAL BNDRY LYING FROM THE SRN PLAINS...ENEWD INTO MID MS VALLEY AND OH VALLEY. THE COMBINATION OF ABUNDANT PW VALUES...1-2+ STD ABOVE THE MEAN...WELL DEFINED BNDRY LAYER CONVERGENCE/MOISTURE FLUX INTO THE BNDRY AND FAVORABLE UPR DIFFLUENCE ALOFT ALONG THE BNDRY WL PROVIDE FOR A VERY FAVORABLE PATTERN FOR HVY TO EXCESSIVE RAINFALL AMTS. CONFIDENCE IS HIGH WITH THE OVERALL HVY PCPN FORECASTS THIS PERIOD..ALTHOUGH LOWER WITH THE TIMING DETAILS AT THE 6 HR TIME STEPS. GIVEN THE OVERALL VERY FAVORABLE PATTERN FOR HVY RAINS...HPC IS LEANING TOWARD THE HEAVIER IN HOUSE PSEUDO BIAS CORRECTED ENSEMBLE MEAN. WIDESPREAD 1-3" AREAL AVG PCPN AMTS DEPICTED ACRS THESE AREAS..WITH ISOLATED TOTALS OF 5"+ POSSIBLE. THIS MAY ESPECIALLY BE SO INVOF FAR NWRN AR INTO SRN MO WHERE THE MOISTURE FLUX ANOMALIES INTO THE BNDRY ARE MOST PERSISTENT. ACRS THIS AREA...A HIGH PROBABILITY IS DEPICTED. ORAVEC $$