Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 272344
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
744 PM EDT Wed Mar 27 2024

.SYNOPSIS...
An area of low pressure and an associated cold front will
progress through the area tonight and then offshore Thursday
morning. High pressure will build in Friday and prevail through
early next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Radar presentation early this evening showed scattered
showers with a few thunderstorms moving across far interior
SC/GA, with little activity elsewhere. Model guidance continues
to indicate increasing coverage across the entire area as we
move further into the evening, though perhaps a bit later than
initially anticipated. Given this, adjustments were made to the
ongoing PoP scheme. Otherwise no notable changes were needed.

A wet and stormy night is ahead. Late afternoon surface observations
suggest the approaching cold front continues to slow down as it
becomes increasing parallel to the upper flow aloft. The front
should slowly meander east tonight. Southern stream shortwave
energy moving out of the upper Texas coast will initiate the
development of a frontal wave along the quasi- stationary front
later this afternoon, which will traverse over the area later
tonight. Weak pressure falls and a distinct kinking of the
isobars over the northeast Gulf of Mexico suggest the wave is
already in its preliminary stages of development. As the large
corridor of forcing for ascent ahead of the approaching
shortwave spreads into the area later this evening, expect a
rapid increase in showers/tstms, possibly as early late
afternoon south of I-16. The various CAMs show a fairly
widespread area of showers/tstms in place later this evening
along/ahead of the front. The intensity of this activity is
expected to increase by mid-late evening as the frontal wave
approaches and additional forcing from the right entrance region
of a 140 kt jet streak passes through. The bulk of these
shower/tstms should translate slowly east after midnight with
the back edge of the main rain band likely clearing the I-95
corridor by daybreak Thursday as the frontal wave exits the area
and the cold front pushes off the coast. Categorical pops of
90-100% look good for all areas tonight.

There will be a risk for locally heavy rainfall tonight as high
PWATs >1.50" combine with some solid nocturnal instability.
Localized rainfall rates in excess of 1 in/hr in/near tstms
could occur which could be enough to produce some minor
flooding of low-lying and poor drainage areas. The risk for
minor flooding looks greatest across the interior, near and
just to the north of where the frontal cyclone is expected to
track. Flash flooding should not be too much of an issue given
the anticipated rainfall rates should remain low enough not to
significantly overwhelm the already wet, sandy soils. There will
also be a risk for some minor urban flooding in Downtown
Charleston, especially near high tide late this evening. A Flood
Watch is not needed given flash flooding should not be much of
an issue tonight, but a few Area Flood Advisories could be
issued. Storm total rainfall amounts of 1-2" look on track,
highest inland. An isolated strong tstm or two could also occur
with hail (generally <1") and gusty winds possible.

Breezy conditions will develop just before daybreak for areas
behind the front. Lows will range from the mid 50s well inland
to the upper 50s at the coast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday and Thursday night: Aloft, a deep trough will swing
through the eastern portion of the CONUS during the day and
then shift offshore overnight. At the surface, the day will
begin with the cold front situated right along the coast with
the surface low just to the east. The front will shift offshore
in the morning and the post- frontal airmass will steadily
filter in through the rest of the day. The most active portion
of the entire period will be the morning when the front is still
lingering in the vicinity. The eastern half of the forecast
area will see scattered to numerous showers for a few hours
Thursday morning, and possibly an isolated thunderstorm. These
rain chances will quickly diminish from west to east and we
should be rain-free by around or just after noon. With the front
shifting offshore, winds will be gusty out of the north-
northwest with frequent gusts into the 20-25 mph range. Cloud
cover will decrease through the day and clear skies should
arrive by the evening and prevail through the overnight.
Thursday highs are forecast to peak in the mid to upper 60s with
overnight lows in the low to mid 40s.

Lake Winds: Strong north-northwesterly winds are expected across
Lake Moultrie on Thursday as a cold front moves offshore. Gusts
could be near 25 knots and a Lake Wind Advisory could be needed.

Friday through Saturday: Dry high pressure will build in Friday
and prevail into the first half of the weekend. Friday highs
are forecast to top out right around 70 with overnight lows
mostly in the mid to upper 40s. Saturday will bring a notable
warm up with above normal temperatures. Highs are forecast to
reach the upper 70s in most areas away from the immediate
coastline.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Broad ridging will gradually build across the eastern CONUS
late this weekend and through early next week, with the
possibility of the next trough approaching the area by the
middle of next week. Dry conditions and warm temperatures are
expected through most of the period. Highs are expected to reach
the low to mid 80s Sunday through at least Tuesday, with a
return to the 70s for Wednesday as a front moves in for
Wednesday and also brings our next chance of rain.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
Conditions are expected to deteriorate to MVFR and eventually
IFR levels later this evening and overnight as rain and low
clouds spread into the terminals. Maintained tempo group for
best timing of thunder and lower visibilities. Rain should exit
Thursday morning shortly after daybreak, but low clouds will
linger through much of the day. VFR should return late in the
day. In addition, gusty north winds in the 20-25 kt range will
develop as a cold front moves offshore in the morning.

Extended Aviation Outlook: VFR conditions will prevail.

&&

.MARINE...
Tonight: Showers/tstms will impact the coastal waters overnight
as low pressure moves through the area along a quasi-stationary
front. Southerly winds will become more southwest overnight.
Sustained winds will largely remain below 15 kt outside of
tstms. Wind gusts to 35kt could occur with any of the stronger
tstms, so Special Marine Warnings may be needed at various
times through the night. The cold front is expected to clear the
coast just before daybreak Thursday. Winds will pick up quickly
after FROPA with gusts near 25 kt. The bulk of these will hold
off until after sunrise. Seas will hold 2-4 ft nearshore waters
within 20 NM and 4-6 ft over the Georgia offshore waters from
20-60 NM offshore. A Small Craft Advisory continues for the
Georgia offshore waters tonight.

Thursday through Monday: The cold front will be positioned along
or just off the coast Thursday morning. The front and an area of
low pressure will move away from the coast through the rest of
the day and a period of strong north-northwesterly flow is
expected into at least early Friday morning. A period of solid
Small Craft Advisory conditions is expected for all waters. The
outer Georgia waters advisory is already in effect and runs
through Friday morning. We have issued advisories for all
nearshore waters, going into effect Thursday morning and then
ending at various times Thursday afternoon through late Thursday
evening. Frequent gusts into the 25-30 knot range are expected,
strongest in the Charleston County waters and the outer Georgia
waters. An advisory might also be needed for Charleston Harbor
for the daytime hours on Thursday, with gusts near 25 knots.
Conditions will improve significantly late Thursday night
through Friday morning as the gradient relaxes. Then this
weekend into early next week, southwest flow will settle in and
prevail with periods of time where wind speeds will surge into
the 15-20 knot range at times.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from 8 AM to 10 PM EDT Thursday for
     AMZ350.
     Small Craft Advisory from 8 AM to 6 PM EDT Thursday for AMZ352.
     Small Craft Advisory from 8 AM to 4 PM EDT Thursday for AMZ354.
     Small Craft Advisory until 8 AM EDT Friday for AMZ374.

&&

$$

NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...


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