EXCESSIVE RAINFALL DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
200 PM EDT WED APR 27 2011
 
...VALID 18Z WED APR 27 2011 - 00Z FRI APR 29 2011...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...
 

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
JBR LWV OSU LOZ TYS 1A5 4A9 GWO JBR.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE
FROM
HSV TUP MEM PAH 30 N HNB 25 E BAK LUK GLW CHA HSV.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNE MDQ MSL 20 ESE OLV MKL 15 S CKV 30 NNE MDQ.

...NCNTRL GULF STS INTO THE TN AND LWR OH VLYS...
MDLS/WV SATL IMAGERY SHOWS A POTENT UPR JET/SHRTWV MOVG INTO THE
REGION WITH AN IMPRVS UPR JET COUPLET FORMG THAT IS PROVIDG VRY
STG DEEP LYRD LIFT THIS AFTN. ASSOCD SFC LOW OVR ARK WL CONT TO
DEEPEN AND LIFT NEWD ALNG A STALLED FNTL BNDRY...WITH INCRSG DEEP
LYRD SRLY FLOW THRU THE REGION THAT CONT TO ADVECT GULF MSTR NWD.
THE ATMOS OVR THE REGION IS SOMEWHAT STABLE OVR THE NRN
REGIONS...BUT VRY UNSTBL OVR THE GULF STS WHERE RADARS SHOW NEW
CNVCTV DVLPMENT. THE BACKG MID/UPR FLOW WL HELP DIRECT THIS CNVCTN
NWD WITH SOME TRAING PSBL. MSTR REMAINS ANOMALOUSLY DEEP WITH A
POOL OF 1.25-1.50 INCH PWS AND SFC DWPTS INTO THE 60S WITH SOME
LWR 70S LIFTG NWD THRU THE CNTRL GULF STS. SRLY 8H FLOW OF 40-60
KTS IS SUPPORTING ANOMALOUS MSTR FLUX WITH THE LATEST GUID CONTG
TO SHOW MSTR FLUX ANOMALIES OVR FIVE STDS ABV NRML. MAIN THREAT
SHLD BE THRU 28/06Z...THEN THE ACCELERATING CDFNT WL BRING A PUSH
OF DRIER AIR INTO THE REGION...THEREBY ENDING THE THREAT. UNTIL
THEN SOME 1-2 INCH PER HR RATES ARE LKLY WITH LCL 3-5 INCH TOTALS
PSBL THRU 28/06Z.



SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
DSV RME 40 NNE MSV THV LYH BLF AFJ DSV.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE
FROM
ELZ 20 SSE SYR 25 NW MSV CBE LBE ELZ.

...CNTRL/NRN APLCHNS...
LATEST SATL DERIVED PW DATA SHOWS CONTD INCRS IN TRPCL MSTR WITH A
STG LINK TO THE CNTRL CARIBBEAN...WHILE LATER TNGT MSTR FM THE OH
VLY WL INVADE THE REGION. PWS ARE FCST TO REMAIN WELL ABV SEASONAL
NRMLS WITH VALUES CLOSE TO 1.50 INCHES...WHICH ARE 2-3 STDS ABV
NRML.XPCT TWO ROUNDS OF CNVCTN ACRS THIS REGION. THE FIRST WITH
THE TAIL END OF A SHRTWV TROF THAT IS LIFTG NEWD INTO THE UPR OH
VLY THIS AFTN/EVE AND THE SCND WITH THE CDFNT THAT WL PUSH THRU
THE REGION LATER TNGT. XPCT THIS AFTN/EVE CNVCTN TO BE MORE
SCT...BUT CLUSTERS OF ORGANIZED CNVCTN COULD MATERIALIZE ALNG/OFF
THE HIER TERRAIN. LCLZD 1-2 INCH PER HR RATES ARE PSBL THRU THIS
EVE. THERE SHLD BE SOMEWHAT OF A BREAK AFTER SUNSET...THEN AN
ORGANIZED LN OF CNVCTN SHLD CROSS THE REGION TNGT ASSOCD WITH THE
CDFNT THAT WL BE ACCELERATING ACRS THE REGION. MDLS SHOW THE
DVLPMENT OF A STG SRLY LLJ THAT WL PROMOTE ANOMALOUS MSTR FLUX
INTO THE REGION. ANOMALIES ARE FCST TO BUILD TO OVER FIVE STDS ABV
NRML. CELLS ARE XPCTD TO TRAIN NWD...WHILE THE LN MOVES EWD TNGT.
ANOTHER 1-2 INCHES WL BE PSBL IN SOME AREAS. BIGGEST THREAT WL BE
OVR NRN PA/SRN NY WHERE THE FFG ARE VRY LOW.



...SRN MO INTO IL...
ELEV CNVCTN ASSOCD WITH THE STG LEFT EXIT PORTION OF THE DIGG UPR
JET AND ASSOCD MIDLVL COLD POOL CONTS TO SUPPORT AN AREA OF SCT
CNVCTN...OF WHICH MUCH HAS BEEN SVR. LATEST RDR RNFL ESTIMATES ARE
SHOWG SOME HRLY AMTS CLOSE TO ONE INCH. XPCT THESE TYPES OF PCPN
AMTS TO CONT INTO THE EVE HRS AS THE COMPLEX SHIFTS NEWD. THIS WL
CAUSE SOME ISOLD RUNOFF PRBLMS...ESPCLY OVR THE MORE SLOPED
TERRAIN AND IN URBAN AREAS INTO ERLY TNGT.

ECKERT
$$