MESOSCALE PRECIPITATION DISCUSSION 0210
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1105 PM EDT THU JUL 17 2014
 
AREAS AFFECTED...SOUTHEASTERN TX...SOUTHWEST LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 180300Z - 180700Z
 
SUMMARY...ADDITIONAL HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED
OVERNIGHT. VERY INTENSE RAINFALL RATES WILL PROMOTE ADDITIONAL
FLASH FLOOD CONCERNS.


DISCUSSION...THE LATEST WV SAT IMAGERY CONTINUES TO SHOW A
SHORTWAVE TROUGH DIGGING TWD THE LWR MS VLY ATTM WHICH IS
INTERACTING WITH A FRONTAL ZONE AND FOSTERING A LARGE AREA OF
MODERATE TO HEAVY SHOWER AND THUNDERSTORM ACTIVITY THROUGHOUT THE
LWR MS VLY REGION.

IR SAT AND RADAR IMAGERY CONFIRMS THAT THE STRONGEST CONVECTIVE
ACTIVITY IS OVER PORTIONS OF SERN TX AND INTO CNTRL LA WHERE THERE
ARE LOCALLY VERY SLOW MOVING AND INTENSE CONVECTIVE CELLS. WHILE
THE STRONGEST SFC-BASED INSTABILITY IS SITUATED ALONG AND SOUTH OF
THE WRN GULF COAST...THERE APPEARS TO BE SUFFICIENT LARGE SCALE
ASCENT COURTESY OF THE DIGGING UPR LVL TROUGH THROUGHOUT ERN TX/LA
FOR SUSTAINABLE AND STRONGER UPDRAFTS FOR DEEPER AND LOCALLY
ORGANIZED CONVECTION.

PWATS ARE VERY HIGH AND BASED ON GPS DATA ARE OM THE ORDER OF 2.1
TO 2.3 INCHES LOCALLY AND THIS MOISTURE ENVIRONMENT COUPLED WITH
SUSTAINABLE UPDRAFTS SHOULD YIELD LOCALLY VERY INTENSE RAINFALL
RATES THAT MAY EXCEED 3 INCHES/HR. THIS COUPLED WITH SLOW MOVEMENT
WILL PROMOTE VERY HEAVY SHORT TERM RAINFALL AMTS.

THE LATEST HI-RES MODEL GUIDANCE INCLUDING THE 00Z NAM-CONEST AND
EVEN THE 12Z NMMB ARE TERRIBLE IN DIAGNOSIS THE CURRENT CONVECTIVE
ENVIRONMENT. THE BEST MODELS APPEAR TO AN EXTENT BE THE 12Z ARW
AND 12Z GEM REGIONAL WHICH AT LEAST SHOW THE FOCUSING THROUGH 06Z
OF LOCALLY VERY INTENSE RAINFALL WHICH HAS ALREADY BEEN OCCURRING
THE LAST COUPLE OF HOURS.

EXPECT THERE TO BE AT LEAST LOCALIZED AND POTENTIALLY SEVERE FLASH
FLOODING BASED ON THE VERY INTENSE RAINFALL RATES.

ORRISON

ATTN...WFO...JAN...LIX...LCH...SHV...HGX...FWD...EWX...

ATTN...RFC...LMRFC...WGRFC...

LAT...LON   30619868 31259721 31749501 31869300 31549212 30999146
            30129125 29639183 29809362 29639578 29339827 29909896
            30619868