941
AWUS01 KWNH 071738
FFGMPD
FLZ000-072300-

Mesoscale Precipitation Discussion 1093
NWS Weather Prediction Center College Park MD
137 PM EDT Mon Oct 07 2024

Areas affected...southern FL

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

Valid 071735Z - 072300Z

Summary...Slow moving and training thunderstorms will pose a flash
flood risk for southern FL through 22Z. Due to the environment,
rainfall rates will easily have the potential for 2-3 in/hr, and
may even exceed 3 in/hr on a localized basis.

Discussion...While the exact placement is a little uncertain, 17Z
surface observations showed a quasi-stationary front extending
southwestward into Palm Beach County, through the northern
Everglades before curving westward into the eastern Gulf near
Naples. Local 88D radar and visible satellite imagery showed
multiple mesoscale lows near and south of the front, while
infrared imagery showed two areas of colder cloud tops, one west
of the Lee Island Coast and the other west of the Lower Keys, that
have been progressing eastward over the past few hours. Out ahead
of these two relatively larger scale areas of lift were a couple
of slow moving cells that have recently developed over northern
Broward and southern Palm Beach counties. The environment near and
south of the front consisted of 500-2000 J/kg MLCAPE (highest to
southwest) and precipitable water values of approximately 2.3 to
2.5 inches via 12Z sounding and 17Z SPC mesoanalysis data.

Using the 850-300 mb layer as a proxy for storm motions, mean cell
movement will be from the SW to WSW at 10-20 kt. Similarly
oriented 850 mb winds of about the same magnitude will promote
slow moving and training of cells over the southwestern and
southeastern coasts into the Keys. Near the coast of St. Lucie and
Martin counties, low level winds were from the east just north of
a low located just above the surface (925-850 mb) where 850-300 mb
mean winds were weakest across the region at 5-10 kt. Therefore,
the northern Treasure Coast will have the potential for slow
moving to stationary cell movement near the coast given sufficient
instability in place.

Much of southern FL will see an increase in thunderstorm coverage
over the next couple of hours with potential for 2 to 3+ in/hr as
forcing increases from the west, beneath a diffluent flow pattern
in the upper levels. Flash flooding will be possible through 23Z,
but is expected to remain localized and focused across urban
corridors.

Otto

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...KEY...MFL...MLB...TBW...

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

LAT...LON   27298033 27227985 26377972 25308004 24628070
            24468159 24568189 24818201 25328171 26018214
            26448225 26728193 26458152 26378109 26398077
            26608041 27028044