EXCESSIVE RAINFALL DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
1039 AM EDT WED APR 27 2011
 
...VALID 15Z WED APR 27 2011 - 12Z THU APR 28 2011...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...
 

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
GTR MLU LIT HRO JLN SZL TAZ AID MNN DSV MSV SHD CRW LOZ DNN GTR.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE
FROM
ILN FFT 30 NNW BNA 35 W CHA GLH SGT CIR BMG ILN.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNE MDQ MSL UTA NQA 35 ESE PAH 40 WSW BNA 30 NNE MDQ.

 
...LWR MS VLY/NRN GULF STS NEWD THRU TN/OH VLYS INTO NRN
APLCHNS...
MRNG UPR AIR DATA/06Z MDLS SHOWS A VRY STG MID/UPR JET MAX/SHRTWV
DIVING SEWD INTO THE SRN PLNS THIS MRNG...THAT WL TURN THE CORNER
AND LIFT RAPIDLY NEWD LATER TDA/TNGT TO THE LWR GRT LKS BY THU
MRNG. SFC LOW OVR ERN OK/WRN ARK WL DEEPEN AND LIFT NEWD WHILE THE
TRAILING CDFNT ACCELERATES EWD THRU THE OH/TN VLYS AND GULF STS AS
STG MID LVL HGT FALLS PUSH EWD. THE ACCELERATING CDFNT AND MORE
PROGRESSIVE NATURE OF THE PCPN THRU THE REST OF THIS PD WAS THE
REASON FOR DROPG THE LRG FIVE INCH THREAT REGION.

MSTR FEEDG INTO THE REGION WL REMAIN ABV SEASONAL NRMLS AS STG
SRLY FLOW OFF THE GULF OF MEX CONTS. PWS IN THE 1.50-1.75 INCH RNG
OVR THE LWR MS VLY/GULF STS ARE FCST TO LIFT NWD WITH VALUES
1.25-1.50 INCHES MOVG INTO THE NERN U.S. BY THE END OF THE PD.
THESE VALUES ARE 1-2 STDS ABV NRML OVR THE OH VLY SWD...BUT 2-3
STDS ABV NRML OVR THE NRN APLCHNS. MDLS CONT TO SHOW VRY STG LOLVL
FLOW WITH 8H WNDS 40-60 KTS THAT WL PROMOTE UNSEASONABLY STG MSTR
FLUX AND 8H THETA-E RDGG. MDL FCST K-INDICES WL REMAIN IN THE
MID/UPR 30S WHICH IS WELL ABV SEASONAL NRMLS. MDLS ARE FCSTG THE
STG 8H MSTR FLUX TO BE OVR THE CNTRL GULF STS THIS AFTN...BUT
QUICKLY LIFT NWD INTO THE NRN APLCHNS BY LATER TNGT. WEAK OUTFLOW
DRAPED ACRS THE NRN/CNTRL GULF STS REMAINS A CONCERN FOR TRAING
CELLS THIS AFTN...BUT THESE SHLD BE MORE SVR RATHER THAN WDSPRD
HVY RNFL PRODUCERS AND FFG IS MUCH HIER THRU THIS REGION. LATEST
EXPERIMENTAL HI-RES DENSITY PLOTS OF RNFL EXCEEDING FFG IS SHOWG
STG SUPPORT FOR MOD/HI RISK FM THE LWR MS INTO LWR OH/TN VLY
REGIONS DUE TO THE EXTREMELY LOW FFG. XPCT ADDTNL 1-2 INCH PER HR
RATES AND SOME 2-4 INCH TOTALS BY LATER TNGT FM THE LWR MS VLY
INTO THE LWR OH/TN VLY REGION.


SLGT RISK OVR THE CNTRL INTO NRN APLCHNS IS MAINLY FOR LATER THIS
AFTN AND INTO TNGT. THE REGION REMAINS QUITE MOIST WITH GNRLY LOW
FFG. LATEST SATL/GPS DATA CONTS TO SHOW A PLUME OF TRPCL MSTR
LIFTG NWD FM THE CNTRL CARIBBEAN THAT IS WORKING UP THE ECST. PWS
ALNG THE ECST ARE NEAR 1.50 INCHES...WITH VALUES 1.25-1.50 INCHES
FARTHER INLAND. THIS MSTR WL COMBINE WITH GULF MSTR WORKING UP THE
OH VLY LATER TDA/TNGT WITH PW ANOMALIES INCRSG TO 2-3 STDS ABV
NRML. EXPECT SCT CNVCTN THIS AFTN THAT WL PRODUCE SOME ISOLD 1-2
INCH RNFL AMTS...THEN ANOTHER ROUND OF MORE ORGANIZED/WIDESPREAD
CNVCTN OVERNIGHT WITH THE APRCHG CDFNT AND MSTR SURGE LIFTG NEWD
FM THE OH VLY REGION. THIS COULD PRODUCE ANOTHER ROUND OF MORE
WIDESPREAD 1-2 INCH RNFL.

...MID MO VLY...
ELEV CNVCTN ASSOCD WITH THE STG LEFT EXIT PORTION OF THE DIGG UPR
JET AND ASSOCD MIDLVL COLD POOL WL RIDE OVR THE REGION AND PROVIDE
STG LIFT INTO THIS EVE. ALTHOU DEEP MSTR HAS BEEN SHOVED WELL TO
THE S OF THE REGION...CNVCTN SHLD CONT TO EVOLVE AND PSBLY INTO AN
ORGANIZED CLUSTER THAT WL LIFT NEWD AND ACRS REGIONS WHERE VRY HVY
RNFL OCCURRED OVR THE PAST SVRL DAYS. SOME 1-2 INCH AMTS ARE PSBL
IN SVRL HRS.

ECKERT
$$