MESOSCALE PRECIPITATION DISCUSSION 0212
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 AM EDT FRI JUL 18 2014
 
AREAS AFFECTED...SOUTHEAST TX...CENTRAL/SOUTHERN LA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 180650Z - 181030Z
 
SUMMARY...ADDITIONAL VERY HEAVY RAINFALL IS ANTICIPATED THROUGH
THE REMAINDER OF THE NIGHT ACROSS SOUTHEAST TX...WITH THE FOCUS IN
TIME TRANSITIONING MORE INTO CENTRAL/SOUTHERN LA. FLASH FLOODING
IS LIKELY GIVEN THE PERSISTENT NATURE OF THE ACTIVITY AND
EXTREMELY INTENSE RAIN RATES.

DISCUSSION...GOES-RGB SAT IMAGERY IS SUGGESTING SOME AMPLIFICATION
TO THE SHORTWAVE TROUGH SEEN DIGGING ACROSS THE LWR MS VLY ATTM.
THE INTERACTION BETWEEN THE SHORTWAVE ENERGY AND A STALLED OUT
FRONTAL ZONE CONTINUES TO FOCUS A LARGE AREA OF HEAVY SHOWER AND
THUNDERSTORM ACTIVITY THROUGHOUT PORTIONS OF SERN TX AND WRN LA.

IR SAT IMAGERY SHOWS THE COLDEST CONVECTIVE TOPS PRIMARILY OVER
SOUTHEAST TX WHERE VWP DATA SHOWS S/SWLY H85 FLOW OF 30 TO 40 KTS
NEARLY PARALLEL TO THE FRONTAL ZONE AND WITHIN A VERY HIGH PWAT
ENVIRONMENT. THE LATEST GPS DERIVED DATA SHOWS PWATS OF 2.1 TO 2.3
INCHES OVER MUCH OF SOUTHEAST TX. THE LATEST RAP ANALYSIS SHOWS A
POOL OF VERY UNSTABLE AIR POOLED ALONG THE WRN GULF COAST...WITH
MUCAPE VALUES OF 3000 J/KG TO 4000 J/KG. THIS HIGHLY FAVORABLE
THERMODYNAMIC ENERGY WILL BE TAPPED THROUGH THE REMAINDER OF THE
NIGHT WITH THE DIGGING SHORTWAVE TROUGH TO THE NORTH AND
INTERACTION WITH THE FRONT. THE RESULT SHOULD BE A CONTINUATION OF
SLOW-MOVING CONVECTIVE CLUSTERS INCLUDING CELL-MERGERS AND
BACK-BUILDING OF CELLS.

THE CONSENSUS OF THE LATEST HI-RES AND GLOBAL MODEL GUIDANCE
INDICATES SOME ADDITIONAL INCREASE AND VEERING OF THE LOW LVL FLOW
NEAR THE FRONT WHICH SHOULD FACILITATE A SUSTAINABLE THREAT FOR
REPEATING CONVECTION. RAINFALL RATES HAVE ALREADY BEEN REPORTED TO
BE OVER 4 INCHES/HR LOCALLY...AND WITH THE AFOREMENTIONED
CONVECTIVE MODES...THIS WILL PROMOTE SEVERE FLASH FLOOD POTENTIAL.

IT SHOULD BE NOTED THAT THE MAIN FOCUS FOR THE NEXT FEW HOURS
SHOULD TEND REMAIN IN SERN TX...BUT WILL BE GRADUALLY
TRANSITIONING MORE INTO CNTRL/SRN LA TWD DAWN AND THEREAFTER AS A
WELL-DEFINED MOISTURE/INSTABILITY FEED IN OFF THE WRN GULF OF
MEXICO BECOMES ESTABLISHED. THIS IS ALREADY STARTING TO OCCUR NOW.
THE 00Z NAM-CONEST AND 00Z ARW IN PARTICULAR STRONGLY SUGGEST A
THREAT FOR EXTREMELY HEAVY RAINS/FLASH FLOODING BEYOND THIS PERIOD
BETWEEN 12Z AND 18Z ACROSS SRN LA...AND THIS WILL NEED TO BE
MONITORED VERY CLOSELY. 

ORRISON

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

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

LAT...LON   30019940 30849814 31509657 31819527 32059360 31819219
            31349150 30599098 29759113 29349177 29489317 29629485
            29409608 28959743 28439881 28649957 29469970 30019940