MESOSCALE PRECIPITATION DISCUSSION 0655
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
942 PM EST TUE NOV 17 2015
 
AREAS AFFECTED...LOWER MS VALLEY/MID-SOUTH 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 180241Z - 180841Z
 
SUMMARY...A BAND OF HEAVY RAINFALL WITH EMBEDDED THUNDERSTORMS
COULD PRODUCE HOURLY RAIN RATES UP TO 2". FLASH FLOODING IS
POSSIBLE, PARTICULARLY WITHIN URBAN AREAS.

DISCUSSION...AN OCCLUDED CYCLONE WITH A DEFINED WARM CONVEYOR BELT
IS MOVING ACROSS THE LOWER TO MID MISSISSIPPI VALLEY.  VAD WIND
PROFILES SHOW 50-70 KTS OF INFLOW INTO THE SYSTEM OUT OF THE
SOUTH.  HOURLY RAIN RATES WITHIN THE BROAD HEAVY RAIN BAND HAVE
BEEN PEAKING IN THE 1-1.5" PER HOUR RANGE, DESPITE PRECIPITABLE
WATER VALUES OF 1.7-2.2".  THIS IS SOMEWHAT INDICATIVE OF THE
MINIMAL AVAILABLE INSTABILITY, AS MUCAPES OF 500-1500 J/KG LIE
AHEAD OF THE SYSTEM FROM EASTERN LA INTO WEST-CENTRAL MS.  THE
MOVEMENT OF THE THUNDERSTORM BAND HAS BEEN EAST AT 15 KTS, WHILE
INDIVIDUAL THUNDERSTORMS HAVE BEEN MOVING NORTHEAST AT ROUGHLY 55
KTS, IN LINE WITH THE MEAN 850-400 HPA WIND AND FORWARD
PROPAGATING CONVECTIVE VECTORS.

THE CAM GUIDANCE ADVERTISES LOCAL AMOUNTS IN THE 3-4" RANGE OVER
THE NEXT SEVERAL HOURS, WHICH COULD FALL QUICKLY.  RAP GUIDANCE
INDICATES THAT THE LINE'S MOTION COULD SLOW TO 10 KTS AS THE
PARENT OCCLUDED CYCLONE MOVES NORTH-NORTHEAST INTO THE UPPER MS
VALLEY.  THIS COULD ALLOW THE RAIN RATES WITHIN THE BAND TO
INCREASE TOWARDS 2", PARTICULARLY WITHIN ITS SOUTHERN PERIPHERY. 
THE BAND IS MOVING INTO AN AREA WITH HIGHER FLASH FLOOD GUIDANCE,
SO CHOSE THE POSSIBLE CATEGORY.  FLASH FLOODING MORE PROBABLE
WITHIN URBAN AREAS.  

ROTH

ATTN...WFO...BMX...HUN...JAN...LCH...LIX...LZK...MEG...MOB...
PAH...SHV...

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

LAT...LON   36609062 36548859 35748807 34338816 32138865 
            29208996 28979048 29149132 29349145 29479147 
            29479170 29449182 29529211 29679272 31379208 
            34329163 36279115