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367
FXUS62 KCHS 161635
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1235 PM EDT Thu May 16 2024

.SYNOPSIS...
High pressure will prevail today and persist into Friday. A
storm system will affect the area this weekend, followed by
high pressure from the north next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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At 1230 PM, visible satellite indicated that a field of shallow
cumulus clouds has developed along and north of the Savannah
River. The 12Z observed KCHS sounding showed a significant
inversion at H65 with CIN in excess of 300 J/kg. Surprisingly,
the latest run of the HRRR showed a few showers developing over
the CHS Tri-county late this afternoon. However, based on the
observed profile, the forecast will remain dry this afternoon.
Temperatures are on track to peak in the mid to upper 80s this
afternoon.

Tonight: Quiet weather conditions are expected overnight with sfc
high pressure in place and a mid-lvl ridge axis placed across the
Southeast United States aloft. Conditions should be favorable for
radiational cooling, with winds decoupling early under clear skies
and remaining light/calm for several hours away from the immediate
coast for much of the night. Late night, some guidance suggests an
increase in high clouds from the west, suggesting low temps to occur
a few hours prior to daybreak before slightly warming as cloud cover
increases aloft. In general, lows should range between the low-mid
60s well inland to upper 60s/lower 70s near the coast.
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&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday: Zonal flow aloft will develop through the daylight hours
while a positively tilted mid level trough is positioned over
ArkLaTex. At the surface high pressure will retreat out into the
Atlantic waters. To the west of the region a low pressure system is
forecast to be located in the vicinity of Oklahoma. This feature
will slowly progress towards the local forecast area through the
day. Generally a quiet weather day is expected across the region,
with high temperatures reaching into the mid to upper 80s. Cloud
cover will increase throughout the day ahead of the approaching
disturbance. By sunset isolated to scattered showers and
thunderstorms will be possible across the far inland counties. A
warm front is forecast to lift north through the region overnight
Friday into Saturday, with PWATs increasing to around 2" by Saturday
morning. Precipitation coverage will continue to increase through
the overnight hours. Between the rainfall and cloud cover overnight
low temperatures will be rather mild, only reaching into the upper
60s far inland with low to mid 70s elsewhere.

Saturday and Sunday: Saturday will start with a warm front to the
north of the forecast area, putting the region solidly within the
warm sector. A cold front will slowly approach from the west, with
increasing precipitation chances as the day progresses. Saturday
afternoon numerous to widespread showers and thunderstorms will be
possible. Both the GFS and ECMWF depict about 1000 J/kg of ML CAPE,
which in the presence of 40+ knots of shear could produce a strong
to maybe severe thunderstorm on Saturday afternoon. The mid level
trough is expected to be rather slow moving and still positioned
over the forecast area on Sunday. Models have come into agreement
that the an additional surface low pressure system is expected to
develop off the NC coastline. A lull in showers and thunderstorms is
expected Saturday night, with another round of showers and
thunderstorms on Sunday, associated with the low pressure. High
temperatures both Saturday and Sunday are forecast to reach into the
mid to upper 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
By Monday morning the aforementioned mid level trough and associated
surface low pressure system will likely be positioned off the NC/SC
coastline. Isolated to scattered showers and thunderstorms will be
possible, especially along the SC coastal counties. Additionally,
with the positioning of the low there is the possibility of a wedge
type set up. Some guidance has hinted that high temperatures on
Monday may only reach into the upper 70s across southeastern SC. The
current forecast does not reflect temperatures this low and instead
is a blend showing low to mid 80s. Model trends will need to be
watched. After Monday ridging will build in aloft along with high
pressure at the surface. Through the middle of the week the forecast
features minimal rain chances and warming temperatures, with some
locations reaching into the low 90s on Wednesday.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR conditions are expected to prevail at CHS/JZI/SAV terminals
through 12Z Friday.

Extended Aviation Outlook: Showers and thunderstorms could bring
flight restrictions to all terminals on Saturday and Sunday as a low
pressure system impacts the region.

&&

.MARINE...
Today and Tonight: Weak cold air advection in wake of a departing
cold front will allow west-northwest winds to gust up to 15 kts
early morning, but a gradual decrease in wind speeds is expected
by mid morning as high pressure settles across local waters and
results in the pressure gradient weakening. Winds will gradually
turn more southerly this afternoon, remaining around 10 kt or
less for the rest of the day. Seas will subside throughout the
day as well, generally from 2-4 ft to 1-3 ft, remaining largest
across offshore Georgia waters and beyond 15 NM from the
Charleston County coast. Overnight, conditions remain very quiet
across local waters while high pressure prevails. In general,
south winds will be no higher than 5-10 kt while seas range
between 1-2 ft.

Friday through Tuesday: Conditions through the period are expected
to remain below Small Craft Advisory criteria. A cold front will
push through the region on Saturday, shifting winds more to the W
and surging slightly to around 15 knots with gusts to 20 knots. Seas
are expected to build on Saturday as well, increasing to 3 to 4 ft.
By Monday winds will shift to the NW, generally around 10 knots with
seas diminishing to around 1 to 2 ft. High pressure will build in
thereafter.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$

NEAR TERM...NED
SHORT TERM...CPM
LONG TERM...CPM
AVIATION...NED
MARINE...CPM/DPB