Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Aug 17 2023 18:12:42

AWUS01 KWNH 171812
FFGMPD
FLZ000-180011-

Mesoscale Precipitation Discussion 0938
NWS Weather Prediction Center College Park MD
211 PM EDT Thu Aug 17 2023

Areas affected...Central FL...South FL

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

Valid 171811Z - 180011Z

Summary...Thunderstorm coverage continues to expand across
portions of Central and South Florida. Widespread, slow moving
thunderstorms with 2-3"/hr rates (locally higher) could result in
some flash flooding this afternoon, particularly in urban areas.

Discussion...GOES Visible imagery and regional radar mosaic show
increasing coverage of thunderstorms this afternoon across much of
Central and South Florida, focused in part by frictional
convergence along the Sun Coast within westerly low level flow.

Owing to persistent westerly flow south of a stalled cold front,
abundant moisture to support efficient heavy rainfall continues to
pool across the Florida Peninsula. In fact, the 12Z sounding out
of MFL sampled a PWAT of 2.03" (in the 75th percentile for MFL),
before recent mesoanalysis estimates showed 2.2-2.3" PWATs across
South Florida (above the 90th percentile for MFL). The
increasingly moist profile combined with strong insolation
supports 2500-3000 J/kg of MLCAPE with little to no CIN in the
vicinity of the convection, which will allow for rapid expansion
of thunderstorms containing 2-3"/hr rates (locally higher) over
the next several hours.

Little to no vertical shear (5-10 kts) in the vicinity of the
convection will limit individual cell longevity and organization,
but could also serve to prolong rainfall duration given slow storm
motions and redevelopment focused along outflows from  collapsing
cells. The westerly inflow advecting moisture and instability
inland could also allow for periods of loosely training storms as
it orients parallel to the east-west storm motions. By 0z tonight,
the 12Z HREF neighborhood probabilities suggests localized
rainfall totals exceeding 5" are possible across portions of
Central and South Florida where convection can focus. Accordingly,
instances of flash flooding are possible this afternoon, focused
atop vulnerable urban areas along the coastline. NASA SPoRT 0-40
cm soil moisture percentiles highlight an area of relatively
saturated soils southeast of Okeechobee, which also could be
particularly sensitive to additional rainfall.

Asherman

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!5-AUJIW4uRo_5nLAw98adcjnPpzdRhPs40ddgzC4CQdizhcdW9MnkHASeZlj__UaRUrR=
jkQDH40xKuAGOLQX3Jt_kxQ$  for graphic product...

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

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

LAT...LON   28368044 26687991 25878002 25348030 25398091=20
            25628117 26148143 26798247 27638259 27928205=20
            27928131=20

=3D =3D =3D
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