Mesoscale Precipitation Discussion 1201
NWS Weather Prediction Center College Park MD
204 AM EST Sun Dec 17 2023

Areas affected...much of Florida and southern through southeastern
Georgia

Concerning...Heavy rainfall...Flash flooding possible

Valid 170703Z - 171300Z

Summary...Widespread areas of moderate to heavy rain are expected
to potentially cause localized flash flooding through 13Z.  This
potential will be higher where heavier rainfall can occur atop
urbanized areas and/or areas that have experienced 2+ inch storm
total rainfall - especially across central and northern Florida.

Discussion...A sub-1000mb low continues to quickly deepen over
northeastern Gulf of Mexico waters approximately 90 miles
west-northwest of PIE/Pinellas County, FL.  To the east of that
low, ascent along and north of a warm front has allowed for
multiple hours of ~0.25-0.75 inch/hr rain rates across central and
northern Florida generally from I-4 northward to I-10.  These
rates have resulted in 2-4 inch storm totals, wetting soils while
prompting potential for mainly minor, isolated flash flooding in
the short term.

Meanwhile south of this area, a warm front was advancing northward
in tandem with the deepening low and extended from west to east
very near I-4 (PIE to MLB).  Along and south of this boundary,
more isolated, but deeper convection has materialized in response
to stronger instability (around 500-1000 J/kg over land - higher
over water).  The stronger convection has resulted in more
isolated, but heavier rain rates exceeding 1 inch/hr at times. 
Some concern exists that heavier convection near/northwest of
Tampa could migrate northward toward the regions that have
experienced heavier rainfall and wet soils so far tonight (closer
to Ocala/Gainesville) and result in a brief increase in flash
flood potential over the next 2-4 hours.

An additional area of concern is for isolated heavier rainfall to
materialize with scattered convection over populated areas in
southeastern Florida.  One cluster of storms recently produced an
estimated 1-1.5 inch/hr rain rates just west of Miami/Dade Metro,
and the urbanized nature of ground conditions in that area could
lead to spots of flash flooding through 13Z.

Overall, the entire regime is expected to continue to translate
northward in conjunction with the deepening low over the Gulf and
warm front over central Florida.  Flash flood potential will
increase toward northeastern Florida and southeastern Georgia over
time - especially in the 09-13Z timeframe.

Cook

ATTN...WFO...CHS...FFC...JAX...MFL...MLB...TAE...TBW...

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

LAT...LON   32118226 32118096 30988123 29108087 26607978
            25618020 26168059 27378182 27838288 28908327
            29998400 31028363