MESOSCALE PRECIPITATION DISCUSSION 0311
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 PM EDT WED JUN 07 2017

AREAS AFFECTED...SOUTHEAST GA & NORTHEAST FL

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

VALID 071745Z - 072345Z

SUMMARY...THUNDERSTORMS SHOWING SLOW MOTION ARE BUILDING ACROSS
THE REGION.  HOURLY RAIN RATES TO 2.5" WITH LOCAL AMOUNTS TO 5"
ARE POSSIBLE.

DISCUSSION...THUNDERSTORMS ARE STARTING TO BUILD IN COVERAGE AHEAD
OF A WEAK SURFACE WAVE NEAR TALLAHASSEE FL IN THE VICINITY OF A
COLD FRONT WHICH IS SLOWLY SAGGING SOUTH THROUGH SOUTHERN GA.  THE
REGION IS JUST AHEAD OF A WEAKENING UPPER LOW/DEEP LAYERED
CYCLONE.  PRECIPITABLE WATER VALUES ARE ~2" PER THE MORNING
SOUNDINGS.  INFLOW AT 850 HPA IS WEAK, CYCLONIC AT 10-20 KTS PER
VAD WIND PROFILES.  HOWEVER, EFFECTIVE BULK SHEAR HAS BEEN
TRENDING UPWARD LATELY, WITH VALUES ~30 KTS. 

MLCAPES ARE IN THE 1000-1500 J/KG RANGE, AND SHOULD INCREASE
SLIGHTLY FURTHER BEFORE CONVECTIVE COVERAGE PEAKS 19-22Z PER THE
06Z SSEO NEIGHBORHOOD PROBABILITIES OF EXCEEDING FLASH FLOOD
GUIDANCE.  INSTABILITY FIELDS INDICATE THAT INCREASING CONVECTIVE
COVERAGE IS EXPECTED OVER TIME AS ANOTHER SURFACE WAVE IN THE GULF
OF MEXICO APPROACHES CEDAR KEY.  CELL MOTIONS ARE EXPECTED TO BE
SLOW, EASTWARD AT 10-15 KTS FOR MORE ORGANIZED STORMS.  CELL
MERGERS AND THOSE THAT STALL OUT ARE CONSIDERED TO BE THE MAIN
HEAVY RAIN THREAT.  AS THE LOW OFFSHORE THE GA COAST STRENGTHENS
-- APPARENT IN 16-17Z OBSERVATIONS -- THE COLD FRONT SHOULD SWING
SOUTHWARD PAST I-10 AND THE BULK OF THE HEAVY RAIN THREAT SHOULD
END.  THIS IS EXPECTED TO BE AROUND 00Z.  THE GUIDANCE INITIALLY
DOES NOT APPEAR TO BE FAR ENOUGH TO THE NORTH WITH THE ACTIVITY SO
FAR.  HOURLY RAIN RATES UP TO 2.5" WITH LOCAL AMOUNTS UP TO 5"
COULD CAUSE ISSUES OVER SOILS SATURATED BY THE LAST FEW DAYS OF
RAINFALL.

ROTH

ATTN...WFO...CHS...JAX...TAE...TBW...

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

LAT...LON   31658206 31578110 30808135 30258130 29708115
            29568111 29168290 29588396 30078472 30678416
            31428376