MESOSCALE PRECIPITATION DISCUSSION 0006
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
408 AM EDT THU APR 11 2013
 
AREAS AFFECTED...SOUTHEAST TEXAS...WESTERN AND NORTHWESTERN
LOUISIANA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 110808Z - 111213Z
 
SUMMARY...THERE IS AN INCREASING THREAT OF EXCESSIVE
RAINFALL/FLASH FLOODING FROM HOUSTON, TEXAS NORTHEAST ACROSS
WESTERN AND NORTHERN LOUISIANA.

DISCUSSION...THUNDERSTORMS WITH HEAVY RAINFALL HAVE INCREASED IN
AREAL COVERAGE AND INTENSITY SINCE 01Z/8 PM CDT WEDNESDAY ACROSS
WESTERN LOUISIANA AND THE PINEY WOODS AND BIG THICKET OF EASTERN
TEXAS.  RAINFALL RATES ARE ON THE RISE AND FLASH FLOOD GUIDANCE
VALUES HAVE FALLEN TO THREE INCHES IN THREE HOURS' TIME.  HOUSTON
WAS INCLUDED WITHIN THIS AREA AS RAINFALL RATES AS LOW AT 1-2
INCHES PER HOUR CAN CAUSE SIGNIFICANT ISSUES ON U.S. HIGHWAY 59, A
MAJOR ARTERY AROUND THE SOUTH AND EAST SIDE OF THE CITY.  

RECENT RAP AND ARW MESOSCALE GUIDANCE RUNS DO NOT SEEM TO BE
HANDLING THIS SITUATION VERY WELL, INSISTING THAT THE RAINFALL
SHOULD MOVE OUT OF THE REGION WITHIN THE NEXT HOUR WITH BOTH
PIECES OF GUIDANCE PLACING A RAINFALL MINIMUM IN THIS AREA. 
RECENT CONVECTIVE TRENDS IN THE HILL COUNTRY OF TEXAS AHEAD OF A
SHORTWAVE MOVING INTO TEXAS FROM MEXICO REINFORCE THE IDEA THAT
THIS THUNDERSTORM ACTIVITY COULD STICK AROUND UNTIL DAWN. 
PRECIPITABLE WATER VALUES OF 1.75 INCHES OR GREATER COMBINED WITH
A SLOW-MOVING LOW LEVEL JET ON THE ORDER OF 30-40 KNOTS AT THE 850
HPA LEVEL HAVE SET THE STAGE FOR CELL TRAINING...AND LOCAL TOTALS
OF 3-6 INCHES IN TOTAL ARE EXPECTED.

ROTH


ATTN...WFO...HGX...LCH...SHV...

LAT...LON   37358900 37478957 38039019 38989050 39938983 40358901
            40588810 40518724 39448722 38338793 37358900