MESOSCALE PRECIPITATION DISCUSSION 0620
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
322 AM EDT FRI AUG 04 2017

AREAS AFFECTED...CENTRAL GULF COAST

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 040720Z - 041320Z

SUMMARY...SHOWERS AND THUNDERSTORMS ARE EXPANDING IN COVERAGE
ACROSS SOUTHEAST LA, SOUTHERN MS, AND SOUTHERN AL.  HOURLY RAIN
RATES UP TO 2.5" WITH LOCAL AMOUNTS TO 4" ARE POSSIBLE.

DISCUSSION...A STATIONARY THERMAL BOUNDARY HAS BEEN NOTED IN
OVERNIGHT SURFACE OBSERVATIONS LOCATED JUST NORTH OF THE 30TH
PARALLEL JUST INLAND OF THE CENTRAL GULF COAST.  THE GRADIENT IN
THE MU CAPE FIELD ACROSS THE REGION HAS BEEN CREEPING INLAND,
HELPING TO FUEL THE THUNDERSTORM ACTIVITY.  PRECIPITABLE WATER
VALUES OF 2-2.4" ARE SEEN HERE ON RECENT GPS DATA.  INFLOW AT 850
HPA IS WEST-SOUTHWEST AT 20-25 KTS, NEAR THE MAGNITUDE OF THE
850-400 HPA MEAN WIND.  NEAR AND JUST NORTH OF THE SUBTROPICAL
JET, THERE APPEARS TO BE AN ELONGATED SET OF SHORTWAVES RIGHT OVER
THE BOUNDARY WHILE IN THE SOUTHERN STREAM OF THE WESTERLIES ACROSS
SOUTHWEST MO AN ADDITIONAL SHORTWAVE IS NOTED.

THE MESOSCALE GUIDANCE HAS A SIGNAL FOR HEAVY RAINFALL ACROSS THE
AREA, THOUGH AGREEMENT IS NOT IDEAL.  SLIGHTLY VEERING LOW-LEVEL
INFLOW HINTS AT AN EASTWARD PROGRESSION TO THE FORMING
THUNDERSTORM AREA INTO THE FL PANHANDLE SHOULD BE ANTICIPATED. 
HOURLY RAIN RATES UP TO 2.5" ARE POSSIBLE WHERE CELLS TRAIN, WITH
LOCAL AMOUNTS UP TO 4" EXPECTED.  FLASH FLOOD GUIDANCE ACROSS
SOUTHEAST LA HAS LOWERED DUE TO THE HEAVY RAIN THERE THIS TIME
YESTERDAY.  URBAN AREAS ALONG THE MS COAST, NEAR MOBILE, AND IN FL
NEAR PENSACOLA AND FORT WALTON BEACH COULD BE IMPACTED.

ROTH

ATTN...WFO...JAN...LCH...LIX...MOB...TAE...

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

LAT...LON   31128729 30938556 30378529 29858535 30248623
            30178760 30058856 29398895 29098895 28898942
            29128984 28929045 28929062 29019095 29239141
            29299155 29559219 30099140 30579078 31018939