EXCESSIVE RAINFALL DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
925 PM EDT THU APR 21 2011
 
...VALID 03Z FRI APR 22 2011 - 00Z SAT APR 23 2011...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NNW MSL 20 ENE OLV 20 SE M19 20 SSW FLP 30 NNW HRO
15 WSW AIZ 25 NW SET 30 NNE ALN 25 SSW TAZ 20 NW SLO ENL
15 NW HSB 30 ENE M30 15 ESE CKV BNA 20 S MQY 20 NNW MDQ
30 NNW MSL.

SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
25 NW DRT 20 ESE 6R6 40 NNE 6R6 50 S BPG 40 ESE BPG 35 SSE SWW
35 ENE SJT 25 WSW JCT 25 NE DLF DRT 25 NW DRT.

MID MS VALLEY...LOWER OH VALLEY..LOWER TN VALLEY...

THE EMPHASIS FOR ADDITIONAL ORGANIZED CONVECTION WL CONTINUE TO
SHIFT NWD DURING THE EVENING AND OVERNIGHT HOURS ACROSS PARTS OF
AR/MO INTO THE LOWER OH VALLEY...UPR TN VALLEY. KEPT A SLIGHT RISK
OVER THE MO/AR AREA DESPITE WARMING CLOUD TOPS UPSTREAM BASED ON
RECENT RAINFALL AND FFG WHICH HAD BEEN 2 INCHES OR LESS BEFORE
RAIN BEGAN FALLING EARLIER THIS AFTN.   OVERALL CONFIDENCE IN
SPECIFIC DETAILS AND EVOLUTION REMAINS QUITE LOW GIVEN THE MODEL
SPREAD WHILE THE CONFIDENCE OF THIS BEING THE BEGINNING OF AN
INCREASINGLY WET PATTERN IS PRETTY HIGH. 

WHILE MODELS HAVE GENERAL EVOLUTION TO THE LARGE SCALE FLOW WITH
AN AMPLIFYING TROF MOVG OUT OF THE NWRN U.S/GREAT BASIN AND INTO
THE NRN TO CNTRL PLAINS...THEY DIFFER WITH THEIR RESPECTIVE QPF
AXES ALONG THE NEWD LIFTING WARM FRONT FROM THE LOWER MS VALLEY
INTO THE OH VALLEY.  THE HI RES ARW AND NMM WERE FOLLOWED MORE
CLOSELY THIS PERIOD FOR THE QPF AXES AS IT WAS FARTHER TO THE
SOUTH WITH THIS AXIS THAN THE OTHER OPERATIONAL
GUIDANCE...ESPECIALLY WITH THIS FIRST ROUND OF CONVECTION. 
ANOTHER ROUND OF ORGANIZED CONVECTION THAT MAY FORM FARTHER TO THE
NORTH FRI OVR MO AND SPREAD EWD INTO THE LOWER TO MID OH RIVER
VALLEY.  

WITH BOTH OF THESE ROUNDS OF CONVECTION...MDT TO HVY TOTALS ARE
POSSIBLE..WITH AREAL AVG .50-1"+ AMTS DEPICTED FROM THE MID MS
VALLEY EWD INTO THE LOWER TO MID OH RIVER VALLEY...LOWER TN VALLEY
AND CUMBERLAND VALLEY AREA...WITH ISOLATED SHRT TERM TOTALS OF
1-2"+ POSSIBLE.  THIS MAY PRODUCE ISOLATED RUNOFF ISSUES ACRS
THESE AREAS.

W TEXAS...

ANOTHER ROUND OF CONVECTION FORMED NEAR THE PEAK OF DIURNAL
HEATING EAST OF THE DRY LINE INVOF KFST.  SOME OF THESE STORMS
COULD PRODUCE LOCALLY HEAVY RAINS UNTIL THEY WEAKEN LATER TONIGHT.
 RAFL AMOUNTS ON THE ORDER OF AN INCH ARE POSSIBLE UNDERNEATH THE
HEAVIEST CONVECTION...AND THIS COULD LEAD TO LOCALIZED RUN OFF
PROBLEMS. 

BANN


$$