-- Discussion containing changed information from previous version are highlighted. --
953
FXUS62 KCHS 180231
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1031 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/...
-- Changed Discussion --
The MCS over Georgia and northern Florida is trending slightly
south of due east per latest trends, and also per the Corfidi
Vectors. Poor lapse rates, limited MLCAPE, weak Normalized
Cape, along with increasing CINH, all point toward any severe
weather having come to an end. In fact, with a 3C inversion
around 8-9K feet, we are now showing no more than isolated to
scattered PoPs within a very moist south-southwest synoptic
flow. Although we do need to focus our attention upstream, as
convection in the lower Mississippi Valley will be moving into
western Georgia by 6 am, as it has plenty of CAPE and shear to
work with through the night. What happens with that activity
could have implications on how the local weather unfolds
Saturday.

There will be the formation of areas of stratus developing,
which then builds down, as depicted by the LAMP and to some
extent the HREF. Even so, geostrophic winds look a little too
high for any serious fog concerns.

Low temperatures will be well above normal given the elevated
dew points and extensive cloud cover.
-- End Changed Discussion --

&&

.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 /02Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
KCHS/KJZI/SAV: In all likelihood there won`t be anything more
than scattered showers around through the night, so we have just
VCSH and generally VFR. Late tonight and Saturday morning there
could be several hours of flight restrictions as stratus
develops. Some guidance indicates potential for IFR ceilings.
But went no worse than MVFR between 09Z and 15Z. There is a
greater chance for SHRA/TSRA Saturday afternoon, and VCTS is
included for now. Some guidance though actually shows the
greater probabilities Saturday morning. Figure on refinements in
future TAFs.

Extended Aviation Outlook: Saturday night 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.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
The surface pattern will support S o SSW winds between 10 to 15
kts, with wave heights forecast to gradually build to 2-3 ft by
late 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.
-- End Changed Discussion --

&&

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

&&

$$

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