MESOSCALE PRECIPITATION DISCUSSION 0064
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
131 PM EDT MON MAR 19 2018

AREAS AFFECTED...FL PANHANDLE

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

VALID 191730Z - 192200Z

SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS ARE EXPECTED OVER THE
NEXT SEVERAL HOURS WITH POTENTIAL FOR TRAINING CELLS. SOME FLASH
FLOODING WILL BE POSSIBLE AND ESPECIALLY WITH LOCALLY WET
ANTECEDENT CONDITIONS.

DISCUSSION...THE GOES-16 10.3 MICRON/IR IMAGERY SHOWS IMPRESSIVELY
COLD CONVECTIVE TOPS DEVELOPING OVER THE FL PANHANDLE IN
ASSOCIATION WITH AN UPSTREAM SHORTWAVE IMPULSE NEAR THE CENTRAL
GULF COAST INTERACTING WITH A SUBTLE SURFACE TROUGH/OUTFLOW
BOUNDARY FROM EARLIER CONVECTION THAT HAS BEEN LEFT IN PLACE. THIS
BOUNDARY IS HELPING TO FOCUS DEEPER MOISTURE AND INSTABILITY IN
OFF THE GULF OF MEXICO AHEAD OF THE UPSTREAM SHORTWAVE ENERGY.

THE LATEST RAP ANALYSIS SHOWS AS MUCH AS 1500 J/KG OF MLCAPE
ACROSS THE THREAT AREA...WITH THE LATEST GPS-DERIVED PWATS SEEN
APPROACHING 1.5 INCHES. THIS FAVORABLE THERMODYNAMIC ENVIRONMENT
ALONG WITH NEARLY 50 KTS OF EFFECTIVE BULK SHEAR AND THE
APPROACHING UPPER SUPPORT WILL FOSTER A SUSTAINABLE AXIS OF
CONVECTION OVER THE NEXT SEVERAL HOURS ACROSS THE FL PANHANDLE.
SOME OF THE CONVECTION HAS ALREADY ORIENTED ITSELF NEARLY PARALLEL
TO THE 850/300MB FLOW AND THIS WILL CERTAINLY PROMOTE A CONCERN
FOR TRAINING CONVECTIVE CELLS.

GOES-16 DAY CONVECTION RGB IMAGERY IS SUGGESTING SOME VERY STRONG
UPDRAFTS ALREADY ALONG WITH IR IMAGERY SHOWING SOME OVERSHOOTING
TOP ACTIVITY...AND THEREFORE SOME LOCALLY VERY HEAVY RAINFALL
RATES ARE LIKELY. EXPECT RATES TO LOCALLY APPROACH 2 INCHES/HR.
THESE RATES COUPLED WITH THE TRAINING POTENTIAL WILL FAVOR SOME
STORM TOTAL AMOUNTS OVER THE NEXT FEW HOURS OF AS MUCH AS 3 TO 4
INCHES WHICH IS ALSO CONSISTENT WITH RECENT HRRR OUTPUT AND THE
12Z ARW.

GIVEN THESE ADDITIONAL RAINS FALLING ON AREAS THAT HAVE SEEN
LOCALLY HEAVY RAINFALL OF AS MUCH AS 3 TO 5 INCHES OVER THE LAST
24 HOURS...THERE WILL BE CONCERNS THIS AFTERNOON FOR ENHANCED
RUNOFF AND POSSIBLE FLASH FLOODING.

ORRISON

ATTN...WFO...JAX...MOB...TAE...TBW...

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

LAT...LON   30918548 30808490 30688396 30368287 29848222
            29308230 29058261 29398334 29728363 29948392
            29968427 29688470 29658496 29758527 29968548
            30188597 30398632 30638647 30848616