MESOSCALE PRECIPITATION DISCUSSION 0781
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
258 AM EST SAT DEC 03 2016
 
AREAS AFFECTED......UPPER TEXAS COAST INTO COASTAL SOUTHWEST LA... 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 030800Z - 031400Z
 
SUMMARY...A CLUSTER OF HEAVY SHOWERS AND THUNDERSTORMS HAS FORMED
IN THE VICINITY OF A WARM FRONT THAT IS FORECAST TO MOVE NORTH TO
THE COAST THIS MORNING ...PRODUCING PERIODS OF HEAVY RAIN. FLASH
FLOODING WILL BE POSSIBLE IN THE UPPER TEXAS COAST TO SOUTHWEST LA
COAST. 

DISCUSSION...SHOWERS AND THUNDERSTORMS ARE GRADUALLY EXPANDING IN
COVERAGE AND INTENSITY IN THE VICINITY OF WARM FRONT DRIFTING
NORTH ACROSS THE GULF OF MEXICO TOWARDS THE UPPER TEXAS COAST AND
ADJACENT LA COAST.  RADAR ESTIMATES SEVERAL INCHES OF RAIN HAS
FALLEN OVER THE GULF WITH IS ACTIVITY. 

THE SHOWERS/STORMS ARE FOCUSED ON A WARM FRONT AND ASSOCIATED
SURFACE MOISTURE CONVERGENCE AND INSTABILITY AXIS OFF THE UPPER
TEXAS COAST. THE MODEL GUIDANCE FORECAST THE WARM FRONT TO MOVE
NORTH THIS MORNING...WITH THE SHOWERS AND STORMS MOVING NORTH IN
TANDEM WITH THE FRONT.

A POOL OF HIGH AVAILABLE PRECIPITABLE WATER VALUES OF 2-2.25
INCHES IS IN PLACE. THIS IS 2-2.5 STANDARD DEVIATIONS ABOVE
NORMAL. UPPER DIVERGENCE MAXIMA CENTERED OVER SOUTHEAST TEXAS TO
SOUTHWEST LA WILL AID THE FRONTAL CONVERGENCE IN PRODUCING ASCENT.
STRONG MOISTURE TRANSPORT/THETA-E ADVECTION ON THE NOSE OF AN 850
MB JET NEAR 40 KT IS ALSO EXPECTED TO CONTINUE TO REINFORCE
AVAILABLE MOISTURE AND CELL REDEVELOPMENT.

THE 05-06Z HIGH RES RAPID REFRESH RUNS ARE INDICATING 6 HOUR
RAINFALLS OF 6-8 INCHES ALONG THE UPPER TEXAS COAST JUST WEST OF
THE LA BORDER.  THE HIGH RES WRF ARW/NMMB/NSSL WRF ARE LOWER
AROUND 3-4 INCHES BUT TARGET THE SAME REGION. 
INITIAL FLASH FLOOD GUIDANCE VALUES ARE 3-4 INCHES IN 6 HOURS SO A
POSSIBLE THREAT LEVEL IS INDICATED...WHICH MAY BE UPGRADED TO
LIKELY LATER.

PETERSEN

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

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

LAT...LON   30089385 30049260 29559275 29299393 29099471 
            28579573 29029586 29349546 29549518 29849470