168
FXUS62 KCHS 172009
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
409 PM EDT Fri May 17 2024

.SYNOPSIS...
A storm system will bring impacts to our area this weekend.
High pressure returns to our region next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
So far this afternoon the forecast area has been covered under a
layer of mid and high clouds. As a result, temperatures have been
limited generally to the upper 70s inland to the low 80s along the
coast, over dewpoints around 70 degrees. The BL temperatures
combined with an inversion centered at H75 should yield rather
shallow lapse rates through this evening. In fact, SPC mesoanalysis
indicates that normalized CAPE values remain near zero across the
forecast area, with values only approaching 0.1 near the FL/GA line.
The challenge this evening will be the intensity, placement, timing
of developing thunderstorms across south central AL. Steering flow
should result in this convection to track east through mid-evening.
The convection should gradually weaken as it pushes across southern
GA. It is possible that as the cluster of thunderstorms approaches
the GA coast this evening, some cells may produce gusty winds along
with cloud-to-ground lightning. Residual showers and thunderstorms
may continue through the rest of tonight. Min temperatures are
forecast to range from the upper 60s inland to the low 70s along the
coast.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
Much of this period is expected to be the most active for the entire
forecast period through the next work week. Models show an upper
level trough over the lower MS River Valley early Saturday, moving
eastward toward the forecast area through Sunday. Conditions look
the most favorable for showers/thunderstorms later Saturday
afternoon through Sunday. Peak values of CAPE and bulk shear will be
later Saturday afternoon and Saturday evening, which is the main
time frame that the SPC has our entire region in a SLT Risk for
severe storms. Have kept high likely/low end categorical PoPs for
much of the area on Saturday and Saturday evening, chance Saturday
night, and then likely again Sunday. The threat for any severe
storms looks too low to mention for Sunday due to a significant
decrease in CAPE, despite the passage of a surface cold front and
the presence of the upper level trough. By later Sunday night and
Monday, the upper trough axis will move offshore, allowing a cold
front to push south of the area. High pressure builds in from
the northwest Sunday night and Monday, which will bring slightly
cooler and drier conditions.

Temperatures above normal Saturday, near normal Sunday and possibly
a tad below normal behind the cold front on Monday.

Heavy Rainfall Potential: Blended models solutions continue to point
toward later Saturday afternoon and evening for the most likely
window for locally heavy rainfall. The area with the highest chance
for heavy rainfall appears to be our coastal counties, especially
from the Charleston Tri-county region, southward to the Savannah
River. However, there continues to be uncertainty in the exact
placement of the heavy rainfall, since localized boundaries produced
by convection/thunderstorms will likely dictate where the heaviest
rainfall occurs. Thunderstorm induced boundaries could collide with
a weak seabreeze close to the coast Saturday afternoon, which is why
we are leaning toward higher chances for the heaviest rainfall to be
over our coastal counties.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
This period looks to be much quieter, with little/no chances for any
significant rainfall and temperatures above normal. Another cold
front may impact the area later Thursday and Friday with at least
slight chances for showers/thunderstorms. However, the timing of
this front and whether or not there will be sufficient deep layer
moisture to support precipitation remains uncertain. Temperatures
expected to be above normal during this period, especially by
Thursday and Friday as a deep layer ridge builds to the south-
southwest of the area, keeping our region under low level west-
southwest flow.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Prior to the 18Z TAFs, KCLX detected scattered showers streaming
across SE GA, with showers passing over and near KSAV. Showers
and thunderstorms should gradually increase across SE GA through
mid-evening. The KSAV TAF will feature a TEMPO between 0-3Z for
VFB10G15kt during TSRA. KCHS and KJZI may see passing showers
this evening into the late night hours. MOS and forecast
soundings indicate that MVFR ceilings are expected to develop
over the terminals late tonight remaining into mid Saturday
morning. Conditions are expected to become VFR by 14Z Saturday.

Saturday through Sunday: Periods of showers and thunderstorms are
expected with brief flight restrictions possible, especially later
Saturday afternoon and evening. Isolated to scattered strong to
severe storms will be possible Saturday afternoon and evening.

Sunday night through Wednesday: VFR expected to prevail.

&&

.MARINE...
The sfc pattern should support south winds between 10 to 15 kts,
with gusts around 20 kts 15 nm and beyond. Wave heights are forecast
to gradually build to 2-3 ft by late tonight. A cluster of strong
thunderstorms may push off the GA coast late this evening. It is
possible that a Special Marine Warning or Statement could be issued
later tonight.

No highlights are expected through the period. The waters will
remain under the influence of a ridge of high pressure well to the
southeast and lower pressure well inland, to the northwest. This
will keep southwest winds of 15 knots or less and seas generally 2
to 4 feet through Sunday. A cold front is expected to push through
the waters during the day on Sunday. Behind this front, winds will
veer to north-northwest and increase to 15 to 20 knots. Seas
building to 3 to 5 feet.  The increased winds/seas are not expected
to persist long. They should begin to subside a bit by later Monday
as winds become more northeast at 15 knots or less, with seas 2 to 4
feet Monday night through Wednesday.

&&

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

&&

$$

NEAR TERM...NED
SHORT TERM...RFM
LONG TERM...RFM
AVIATION...NED/RFM
MARINE...NED/RFM