EXCESSIVE RAINFALL DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
654 AM EDT WED APR 27 2011
 
...VALID 12Z 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
NMM IER TXK LIT POF HUF MGY DSV MSV 25 N SHD CRW CSV ANB NMM.

MODERATE RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE
FROM
PKB 15 NW LOZ 45 NW CHA BHM TVR BAD 20 W PBF HKA PAH CVG PKB.

HIGH RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
10 SSE MDQ CBM ELD NQA FTK LEX 30 SSW GLW 10 SSE MDQ.

TOTAL RAINFALL AMOUNTS OF FIVE INCHES WILL BE POSSIBLE TO THE
RIGHT OF A LINE FROM 45 S MKL BNA 1M4 LLQ 45 S MKL.

 
...LWR MS VLY NEWD THRU TN VLY INTO OH VLY AND APLCHNS...
CHNGS TO EARLIER OUTLOOK WERE MOSTLY TO TAKE INTO ACCOUNT THE
RAPID ELEV CNVCTV DVLPMENT OVR THE ARKLATX THIS MRNG IN RESPONSE
TO A POTENT DIGG MIDLVL SHRTWV AND ASSOCD UPR JET STREAK. LATEST
GUID SHOWS AN IMPRVS UPR JET COUPLET...ASSOCD WITH A MIDLVL COLD
POOL THAT IS PROGRESSING EWD AND OVR A VRY MOIST/UNSTBL REGION. AT
THE SFC A WEAK CNVCTV OUTFLOW IS DRAPED ACRS THE REGION AND
PROVIDING A LOLVL FOCUS...ALTHOU CNVCTN IS CLEARLY ELEVD. SATL
DERIVED AND GPS PW DATA SHOWS A POOL OF NEAR TWO INCH VALUES OVR
LA THIS MRNG THAT WL CONT TO ADVECT NWD INTO THE REGION AND FUEL
EXPANDING CNVCTN. THESE VALUES ARE ARND 1.50 STDS ABV SEASONAL
NRMLS FM THE ARKLATX INTO THE LWR OH VLY...BUT WL INCRS TO TWO
STDS ABV NRML LATER TDA INTO THE UPR OH VLY/APLCHNS. THIS ACTVTY
SHLD INITIALLY DVLP EWD...THEN TURN NEWD THRU TDA AS MID/UPR HGT
FALLS PUSH ACRS THE REGION...WITH DEEP LYRD SRLY FLOW DVLPG THRU
THE GULF STS INTO THE OH VLY. LINEAR MCS PUSHG EWD THIS MRNG FM
THE OH VLY INTO THE GULF STS...SHLD WEAKEN AND ALLOW FOR HEATG AND
RE-DESTABILIZATION THIS AFTN/EVE OVR THE REGION WITH CNVCTN LKLY
TO INCRS OVR THE REGION AND LIFT/DVLP RAPIDLY NEWD ALNG/AHD OF THE
SYNOPTIC FNTL BNDRY THAT WL BE FM THE LWR GRT LKS INTO TX BY LATER
TDA. VRY ANOMALOUS 8H MSTR FLUX THIS MRNG AIMED INTO THE REGION IS
FCST TO REMAIN STG THRU TNGT DUE TO A STG/DYNAMICALLY FORCED LLJ
THAT WL REMAIN IN THE 40-60 KT RANGE. THIS WL ALSO SUPPORT A STG
REGION OF 8H-7H THETA-E RIDGING THAT WL EXPAND NEWD THRU THE FCST
PD. K-INDICES ARE EXPECTED TO REMAIN IN THE MID/UPR 30S...WHICH IS
QUITE UNUSUAL FOR THIS TIME OF YEAR. ONE CONCERN IS THAT THE
CNVCTN COULD BCM MORE SFC BASED INTO THIS AFTN ACRS THE LWR MS VLY
INTO GULF STS...WHICH COULD RESULT IN A MORE E-W ORIENTED CNVCTN
BAND THRU CNTRL MS INTO AL AND PSBLY NRN GA...WITH CELLS PSBLY
TRAING EWD ACRS THE REGION...UNTIL THE SYNOPTIC BNDRY ARRIVES
LATER IN THE FCST PD. HVIER RNFL SHLD BE OVR THE ARK/LA BORDER
NEWD INTO NRN GULF STS/CNTRL TN WHERE WIDESPREAD 1-2 INCH PER HR
RATES AND SOME 3-4 INCH TOTALS WL BE PSBL OVR SVRL HRS. ISOLD
TOTALS IN EXCESSIVE OF FIVE INCHES ARE STILL QUITE LKLY ACRS NRN
MS INTO NRN AL AND CNTRL TN.

EXPANSION OF THE SLGT RISK INTO PA/NY REGION WAS BASED ON CONTD
VRY LOW FFG THRU THE REGION AND EXPECTED CNVCTV DVLPMENT LATER
THIS AFTN INTO TNGT. MDLS ARE SUPPORTG VRY SLOW CELL
MOTIONS...ESPCLY LATER TNGT THRU THE REGION AS THE SYNOPTIC BNDRY
APRCHS WITH TRAING FM THE S TO N QUITE PSBL. LCL 1-2 INCH PER HR
RNFL RATES WL BE PSBL INTO THIS AREA. MGT NEED TO BOOST THE THREAT
TO MOD AFTR LOOKG AT 27/12Z DATA AND LATER ARRIVING FFG.

ECKERT
$$