MESOSCALE PRECIPITATION DISCUSSION 0178
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
353 AM EDT MON MAY 21 2018

AREAS AFFECTED...PORTIONS OF THE FL PANHANDLE...EXTREME SOUTHWEST
GA

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

VALID 210750Z - 211350Z

SUMMARY...EXTREMELY HEAVY RAINFALL RATES ARE EXPECTED WITH THE
STRONG CONVECTION MOVING IN OFF THE NORTHEAST GULF OF MEXICO.
LOCALLY ENHANCED RUNOFF PROBLEMS AND FLASH FLOODING WILL BE
POSSIBLE.

DISCUSSION...THE LATEST GOES-16 CLEAN IR SATELLITE IMAGERY SHOWS A
CONCENTRATED BALL OF CONVECTION MOVING INLAND ACROSS THE FL
PANHANDLE WITH A FOCUS IN PARTICULAR ON WAKULLA...FRANKLIN AND
LIBERTY COUNTIES. THE CONVECTION IS ASSOCIATED WITH A LOW TO MID
LEVEL LOW CIRCULATION WITH ENHANCED LOW LEVEL CONVERGENCE SEEN
AROUND ITS EASTERN FLANK. IN FACT...THERE HAS BEEN SOME WEAK
CONVECTIVE BANDING FEATURES NOTED ALSO AROUND THE EASTERN
SEMICIRCLE OF THE CIRCULATION.

THE ACTIVITY OVER WAKULLA...FRANKLIN AND LIBERTY COUNTIES IS
CHARACTERIZED BY PERSISTENTLY COLD CONVECTIVE TOPS AND EMBEDDED IN
A VERY MOIST PWAT ENVIRONMENT WITH PWATS OF NEAR 2 INCHES. THE
RAINFALL RATES HERE ARE EXPECTED TO BE VERY HIGH...AND LIKELY
APPROACHING 3 INCHES/HR GIVEN THE PERSISTENTLY STRONG CONVECTIVE
FORCING AND AND RELATIVELY SLOW CELL MOTION. THE RAINFALL RATES IN
THE BANDS OF CONVECTION FARTHER EAST ARE LIKELY NOT AS HIGH...BUT
COULD STILL LOCALLY BE CAPABLE OF REACHING 2 INCHES/HR.

OVER THE NEXT SEVERAL HOURS...CONVECTION WILL CONTINUE TO MOVE
GRADUALLY FARTHER INLAND...ALONG THERE WILL BE POTENTIAL FOR
CONVECTIVE CELL TRAINING AS SUGGESTED BY THE LATEST SATELLITE AND
RADAR TRENDS.

THE 00Z HIRES CAM GUIDANCE AND RECENT RUNS OF THE HRRR/HRRRX
GUIDANCE HAVE BEEN UNIFIED IN SUGGESTING ENHANCED RAINFALL
POTENTIAL DURING THE OVERNIGHT HOURS AND WITH AS MUCH AS 4 TO 7
INCHES OF RAIN FORECAST.

EXPECT SOME LOCALLY ENHANCED RUNOFF PROBLEMS AND CONCERNS FOR
FLASH FLOODING GIVEN SUCH HEAVY RAINFALL RATES AND STORM TOTAL
POTENTIAL GOING THROUGH MID-MORNING. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...TAE...

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

LAT...LON   31108478 31008419 30728368 30248328 29858324
            29708343 29888384 29878422 29748459 29628496
            29638523 29778534 29908548 30238574 30568580
            30968541