MESOSCALE PRECIPITATION DISCUSSION 0005
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
713 PM EST FRI JAN 08 2016
 
AREAS AFFECTED...SOUTHEAST TX...LA...FAR SOUTHWEST MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 090000Z - 090600Z
 
SUMMARY...MERGING SUPERCELL THUNDERSTORMS ARE POSSIBLE THIS
EVENING WHICH MAY ENHANCE THE THREAT FOR LOCALIZED FLASH FLOODING.

DISCUSSION...RADAR IMAGERY SHOWS A RATHER RAPID EXPANSION OF HEAVY
SHOWERS AND THUNDERSTORMS OVER PORTIONS OF SOUTHEAST TX AND INTO
SOUTHWEST LA. THE CONVECTION WHICH INCLUDES SOME DISCRETE
SUPERCELLS IS BEING FOSTERED BY THE APPROACH OF A STRONG SHORTWAVE
TROUGH EJECTING OUT ACROSS THE SOUTHERN HIGH PLAINS. THIS ENERGY
IS INTERACTING WITH A NORTHWARD SURGE OF AT LEAST MODEST
INSTABILITY...WITH MUCAPE VALUES AS HIGH AS 1500 TO 2000
J/KG...ALTHOUGH PWATS AT THIS POINT STILL REMAIN RELATIVELY LOW
AND GENERALLY UNDER 1 INCH AS PER LATEST GPS DATA. ADDITIONALLY
THE CONVECTION IS BEING AIDED BY THE INCREASE IN WARM ADVECTION
AND INTERACTION WITH A COASTAL TROUGH LIFTING NORTH AND JUST
INLAND FROM THE GULF OF MEXICO.

THE HIRES MODELS THOUGH LED BY MULTIPLE RUNS OF THE HRRR...AND
COUPLED WITH THE LATEST ARW/NMMB AND NSSL-WRF SUGGEST CONVECTION
WILL EXPAND IN COVERAGE OVER THE NEXT FEW HOURS AS STRONGER JET
DYNAMICS ALOFT...INCLUDING A 250 MB JET COUPLET INTERACTS WITH A
MOISTENING 30 TO 40 KT SOUTHERLY LOW LEVEL JET IN OFF THE GULF OF
MEXICO. THIS WILL FAVOR AN UPTICK IN CONVECTIVE ORGANIZATION THAT
WILL PROMOTE AT LEAST SOME POTENTIAL FOR LOCALLY VERY HEAVY
RAINFALL AND SOME RESULTING FLASH FLOODING/RUNOFF PROBLEMS.

THE PRIMARY CONCERN WILL BE CELL-MERGERS AND ESPECIALLY WITH SOME
OF THE MORE DISCREET SUPERCELLS WHERE LOCALLY VERY INTENSE
RAINFALL RATES MAY RESULT. THE HIRES GUIDANCE ALSO HINTS AT SOME
POTENTIAL FOR CELL-TRAINING...WITH SOME SW/NE ORIENTED BANDS OF
CONVECTION PROGGED. RAINFALL AMOUNTS OF AS MUCH AS 2 TO 3 INCHES
IN A VERY SHORT AMOUNT OF TIME...WITH ISOLATED HEAVIER AMOUNTS
WILL BE POSSIBLE.

GRADUALLY THE CONVECTION THIS EVENING WILL PUSH EAST THROUGH THE
REMAINDER OF THE LOWER MS VALLEY AS DEVELOPING LOW PRESSURE OVER
NORTHEAST TX LIFTS INTO SOUTHERN AR BY 06Z...BUT EXPECT AT LEAST
LOCALIZED FLASH FLOODING/RUNOFF CONCERNS THROUGH THIS TIME PERIOD.

ORRISON

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

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

LAT...LON   32979223 32769125 32079085 31089090 30259125 
            29799220 29609384 29239466 28989534 29219596 
            29809629 30849607 31689538 32339428 32799312