MESOSCALE PRECIPITATION DISCUSSION 0695
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST FRI DEC 25 2015
 
AREAS AFFECTED...EXTREME NORTHWEST LA...SOUTHEAST AR...NORTHWEST
MS...WESTERN TN 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 250630Z - 251230Z
 
SUMMARY...SHOWERS AND THUNDERSTORMS WILL EXPAND IN COVERAGE OVER
THE NEXT SEVERAL HOURS. SOME POTENTIAL WILL EXIST FOR SOME
TRAINING CONVECTION AND THIS MAY RESULT IN SOME LOCALIZED FLASH
FLOODING.

DISCUSSION...THE LATEST IR SATELLITE IMAGERY IS SHOWING AN
EXPANSION OF COLD-TOPPED CONVECTION OVER FAR NORTHWEST
LA...SOUTHEAST AR AND INTO FAR NORTHWEST MS. THE CONVECTION IS
FOCUSED ALONG A COLD FRONT WHICH IS IN THE PROCESS OF STALLING
OUT. IT IS CURRENTLY DRAPED FROM THE ARKLATEX NORTHEAST INTO THE
MID MS VALLEY.

THE THUNDERSTORMS WILL CONTINUE TO EXPAND IN COVERAGE OVER THE
NEXT FEW HOURS AS THE LOW-LEVEL FLOW INCREASES FROM THE SOUTH AND
AROUND THE WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE NOSING
GRADUALLY WEST ACROSS THE GULF OF MEXICO. THE LAST COUPLE RUNS OF
THE HRRR AND ALSO THE 00Z ARW AND 00Z NMMB SOLUTIONS FAVOR A
RATHER SIGNIFICANT EXPANSION OF CONVECTION ACROSS SOUTHEAST AR AND
INTO NORTHWEST MS AND WESTERN TN BY 09Z AND CONTINUING THROUGH 12Z.

THE LATEST BLENDED-TPW PRODUCT SHOWS PWATS INCREASING ACROSS THE
REGION IN VICINITY OF THE FRONT...WITH VALUES APPROACHING 1.5
INCHES. THIS WILL INCREASE FURTHER OVER THE NEXT FEW HOURS AS A
SOUTH-SOUTHWEST LOW LEVEL JET INCREASES TO 30 TO 40 KTS BY 12Z
ACROSS THIS REGION...AND WITH A NOTABLE AREA OF SPEED CONVERGENCE
SUGGESTED BY THE HIRES GUIDANCE IN VICINITY OF THE FRONT.
INCREASING PWATS AND FORCING WILL RESULT IN INCREASING RAINFALL
RATES WHICH MAY APPROACH 2 INCHES/HR. THE DEEP LAYER SOUTHWESTERLY
FLOW RUNNING NEARLY PARALLEL TO THE FRONT WILL FOSTER A THREAT OF
TRAINING CONVECTION AS A RESULT...AND THUS SOME LOCALLY VERY HEAVY
RAINFALL AMOUNTS WILL BE POSSIBLE.

EXPECT AS MUCH AS 2 TO 4 INCHES OF RAIN LOCALLY WITH ISOLATED
AMOUNTS TO OVER 5 INCHES THROUGH 12Z. AT LEAST SOME LOCALIZED
FLASH FLOODING WILL BE POSSIBLE AS A RESULT. WILL CONTINUE TO
MONITOR.

ORRISON

ATTN...WFO...JAN...LZK...MEG...OHX...SHV...

ATTN...RFC...ABRFC...LMRFC...

LAT...LON   36458858 35618770 34159002 33149204 32579369 
            33319388 34879167