MESOSCALE PRECIPITATION DISCUSSION 0702
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST SAT DEC 26 2015
 
AREAS AFFECTED...NORTHEAST LA...EXTREME SOUTHEAST AR...FAR WESTERN
MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 260635Z - 260930Z
 
SUMMARY...CLUSTERS OF SLOW-MOVING THUNDERSTORMS CONTINUE TO FOCUS
LOCALLY VERY HEAVY RAINFALL AND WILL PROMOTE SOME ADDITIONAL RISK
OF FLASH FLOODING OVER THE NEXT FEW HOURS.

DISCUSSION...IR SATELLITE IMAGERY SHOWS COOLING CONVECTIVE TOPS
OVER NORTHEAST LA AND FAR SOUTHEAST AR AND IN ASSOCIATION WITH A
SLOW-MOVING CLUSTER OF STRONG THUNDERSTORMS.

THE ACTIVITY IS BEING SUPPORTED BY A PERSISTENT SOUTHERLY LOW
LEVEL JET OF 30 TO 40 KTS AS PER AREA VWP DATA INTERACTING WITH A
STATIONARY FRONTAL ZONE...AND IS HELPING TO MAINTAIN A VERY MOIST
AIRMASS WITH PWATS NEAR 1.75 INCHES AS PER GPS-DERIVED DATA. THIS
IS ALSO TRANSPORTING AT LEAST A MODEST DEGREE OF INSTABILITY NORTH
FROM THE GULF OF MEXICO. MEANWHILE...THE CONVECTION IS EMBEDDED
WITHIN A FAIRLY DIVERGENT WIND FLOW PATTERN ALOFT WHICH IS
YIELDING SOME LARGER SCALE ASCENT OVER THE REGION.

THE LAST COUPLE RUNS OF THE HRRR SEEMS TO HAVE A REASONABLE HANDLE
OF THE ONGOING CONVECTION AND SUGGESTS LOCALLY AN ADDITIONAL 1 TO
3 INCHES OF RAIN OVER THE NEXT FEW HOURS. THE 00Z ARW AND 00Z NMMB
ARE LIKELY A BIT TOO QUICK TO WEAKEN THE CONVECTION GIVEN SOME OF
THE LARGER SCALE ASCENT OVER THE REGION...AND SO WILL LEAN TOWARD
THE HRRR GUIDANCE AT THIS TIME BASED ON THE LATEST CONVECTIVE
TRENDS.

SOME ADDITIONAL FLASH FLOODING WILL BE POSSIBLE GIVEN THE LOCALLY
WET ANTECEDENT CONDITIONS AND WITH THE SLOW CELL MOTION...SOME
ADDITIONAL FLASH FLOODING WILL BE POSSIBLE.

ORRISON

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

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

LAT...LON   34249094 34079013 33509012 32909095 32489215 
            32679271 33049279 33729226