AWUS01 KWNH 220952
FFGMPD
FLZ000-GAZ000-221500-

Mesoscale Precipitation Discussion 0918
NWS Weather Prediction Center College Park MD
551 AM EDT Thu Aug 22 2024

Areas affected...southeastern GA into northeastern FL

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

Valid 220950Z - 221500Z

SUMMARY...Slow moving showers/thunderstorms, capable of localized
rainfall rates over 3 in/hr will likely continue for another few
hours in the vicinity of the GA/FL border near the coast.
Localized flash flooding will be possible, especially with any
overlap of urban areas.

DISCUSSION...0930Z radar imagery from KJAX showed a small region
of slow moving showers and thunderstorms located between I-95 and
the coast in Camden and Nassau counties (southern GA/northern FL).
Local Wunderground.com reporting stations showed agreement with
KJAX rainfall estimates showing hourly rainfall of 2 to 3 inches
associated with cells observed on radar. This region was located
just north of a stationary front with 0-1 km AGL flow from the
east between 10-20 kt, advecting warm moist air in from the
Atlantic. SPC mesoanalysis data from 09Z showed SBCAPE over 2000
J/kg just offshore and a narrow axis of weaker but sufficient and
uninhibited instability inland, straddling the GA/FL border. Area
surface observations showed a convergence axis located near or
just east of I-95, coincident with the ongoing slow moving showers/thunderstorms.

There is little change to the overall setup expected over the next
3 to 6 hours, although the onset of daytime heating after sunrise
may disrupt the existing gradient/convergence axis in place.
Nonetheless, some degree of frictional convergence with continued
low level onshore flow within the instability axis is expected to
continue a threat for slow moving showers and thunderstorms in the
vicinity of the GA/FL border. There is some concern for the
ongoing activity to build south toward the Jacksonville metro
region which would have greater sensitivity to flash flood impacts
due to the urban nature compared to surrounding, more rural area.
Within the slow moving areas of heavy rain, hourly rainfall of 2-3
inches is expected but values could surpass 3 inches in an hour in
the more persistent activity with 6-hr rainfall totals possibly
exceeding 6 inches in some locations. Flash flooding will be
possible as a result.

Otto


ATTN...WFO...CHS...JAX...

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

LAT...LON 31458177 31308115 30838124 29898118 29728169
29918219 30348235 30918221
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AWUS01 KWNH 090921
FFGMPD
FLZ000-GAZ000-ALZ000-091520-

Mesoscale Precipitation Discussion 0053
NWS Weather Prediction Center College Park MD
520 AM EDT Sun Mar 09 2025

Areas affected...Far Southern GA...FL Panhandle into Northern FL

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

Valid 090920Z - 091520Z

SUMMARY...Locally training clusters of heavy showers and
thunderstorms this morning may result in isolated areas of flash flooding.

DISCUSSION...The latest GOES-E IR satellite imagery along with
dual-pol radar shows clusters of heavy showers and thunderstorms
gradually expanding in coverage across portions of the central and
eastern Gulf Coast region as southerly warm air advection and
moisture transport interacts with a quasi-stationary front
extending east from a wave of low pressure just east of New
Orleans, LA. A modest low-level jet of 20 to 30+ kts is focused
out ahead of this low pressure wave, with the primary nose of this
situated up into the FL Panhandle region where PWs are gradually
increasing along with instability.

MIMIC-PW data shows the pooling of 1.5 to 1.75 inch PWs currently
near the central Gulf Coast with the latest RAP analysis showing
MUCAPE values of 500 to 1000+ J/kg. However, the 3-hour MUCAPE
differentials are on the order of +400 to +600 J/kg across far
southern AL through the western part of the FL Panhandle and this
is where some of the more organized clusters of convection have
been developing over the last couple of hours.

As a positively-tilted mid-level trough and associated closed low
continues to eject east out of the southern Plains and toward the
Lower MS Valley this morning, there will be a gradual increase in
downstream upper-level divergence along with a corresponding
subtle increase in the low-level jet. This coupled with proximity
of the front across especially the FL Panhandle vicinity should
help facilitate a further expansion and organization of convection
in a general west to east fashion which will bring a concerns for
locally training showers and thunderstorms.

The HRRR has been generally trending wetter over its last few
model runs, and the HRRR coupled with the 00Z NSSL-MPAS guidance
support rainfall rates of 1 to 2 inches/hour, with sufficient
levels of cell-training to generate totals of as much as 3 to 5
inches by late this morning. These rains will be falling over
areas that are relatively dry based off the latest NASA SPoRT soil
moisture data, but given some of the wetter model trends overnight
along with the latest radar and satellite data, it will be
possible that enough rain falls this morning for some isolated
areas of flash flooding.

Orrison

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

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

LAT...LON 31198337 31148199 30858134 30458130 30138148
30008205 29898300 29848401 29668506 29908550
30268609 30308699 30608721 30878690 31038587
31088475
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