514
FXUS62 KCHS 091956
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
356 PM EDT Thu May 9 2024

.SYNOPSIS...
A cold front will approach the area tonight, then move offshore
Friday. High pressure will prevail for the weekend into early
next week. A storm system could affect the area by the middle
of next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Radar indicates the line of strong thunderstorms is moving off
the coast of SC, and is near the coast of our GA counties.
Instability ahead of the line has peaked, but both the
instability and shear should sustain the thunderstorms for
another hour. The enhanced wind threat persists down there and
a tornado also cannot be ruled out.

We continue to adjust the POPs/weather grids based on the radar
trends. The CAMs have a better grasp of the overall line now,
with the southern end moving slower across our GA counties. Once
the line of thunderstorms moves offshore, expect 1-2 hours of
stratiform precipitation, followed by clearing by mid-evening.
The rest of the night should remain generally dry. However, a
second MCS will arrive from the west after the pre-dawn hours
Friday morning. Rain-cooled temperatures are expected to remain
nearly steady around 70 degrees tonight.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
The forecast for Friday is quite tricky. A quasi-zonal flow will
persist aloft, though we will see several potent shortwaves
ripple through the area during the day. Given the high theta-e
airmass across the Southeast, ample instability should be in
place to support convective development with these upper vort
maxima. Furthermore, the presence of 50-60 kt of 0-6 km bulk
shear will favor organization of the convection once it become
established. Most of the guidance continues to indicate the most
impressive shortwave will move through southeast SC/GA between
15Z and 18Z.

There is surprising agreement between the synoptic models and
the CAMs that a large area of showers and thunderstorms will
move across the forecast area between 9am and 3pm Friday. It
appears that an MCS could be ongoing across south central GA at
daybreak that then pushes east through our area. Thus, the
greatest coverage of convection would occur over our southeast
GA zones. This is also where the strongest convective indices
are expected, so our primary focus for severe weather potential
is in southeast GA and extreme southern SC. Damaging winds
appear to be the primary threat assuming the convection becomes
organized into a line. Isolated large hail or tornadoes can
never be completely ruled out. Farther to the north in SC, at
least scattered showers and thunderstorms will move through, but
extensive cloud cover in the morning and less available
instability should reduce the overall severe weather potential.
Rainfall totals on Friday will range from 1-1.5" in southeast GA
and 0.5-1.0" in southeast SC.

The brunt of the convection is expected to be off the coast by
3pm. A secondary shortwave will drop into SC early Friday
evening, pushing the cold front into the area. A big question
mark is what convection, if any, develops out ahead of the
front. It will heavily depend on what happens in southern SC
with the first batch of convection and whether or not the
airmass gets worked-over as a result. If convective coverage is
limited during the early afternoon activity, a greater degree of
destabilization could occur in southern SC, allowing for a more
conducive airmass for convective development late Friday
afternoon or early evening. For now we penciled in scattered
PoPs across eastern Berkeley/Charleston Counties late afternoon
and early evening.

Saturday will be dry and noticeably cooler with highs in the
upper 70s. Sunday will warm up a bit due to upper ridging, with
highs in the mid 80s.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Early next week will briefly start off quiet before a warm front
extending across the Deep South lifts north. Conditions look quite
unsettled beginning late Monday night into Wednesday due to
plentiful upper forcing and deep moisture building in. Several
rounds of showers and thunderstorms are expected.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
20z TAFs: Radar indicates the line of strong thunderstorms has
moved east of the TAF sites. We amended CHS and JZI, to improve
conditions, since the storms have moved offshore. But we`re
holding off on amending SAV as the storms are still nearby.
Behind the storms, stratiform precipitation will persist for
about another 1-2 hours. The precipitation should end by this
evening, with VFR persisting into part of the night. MOS and
some of the ensembles then indicate IFR ceilings developing over
the terminals late tonight, which we kept in the TAFs. Finally,
another round of showers and thunderstorms is expected to bring
impacts to the TAF sites late in the TAF time period.

Extended Aviation Outlook: Scattered to numerous showers and
thunderstorms could continue into Friday afternoon with flight
restrictions and gusty winds possible within convection. VFR
conditions will return for the weekend into early next week.
Scattered convection expected Monday night and Tuesday.

&&

.MARINE...
Through Sunset: A line of thunderstorms is moving though the
coastal waters. Some of these storms could produce gusts in
excess of 40 kts and possibly a waterspout. The main line of
storms should move east our waters and dissipate by about
sunset.

Tonight: Expect winds to be mainly SW 10-20 kt. A few gusts
up to 25 kt are possible across the Charleston County waters
this evening, especially across the far northeastern portion of
the zone. But the time and areal extend don`t appear to be
enough to warrant a Small Craft Advisory. Seas should be in the
2-4 ft range.

Friday: A decent SW gradient expected in advance of a cold
front, though winds will be quite variable once convection moves
offshore midday. Late in the afternoon and early evening, wind
gusts could approach 25 kt, so it`s not out of the realm of
possibility that a short-duration Small Craft Advisory is
needed. Due to the low confidence we will hold off on any
issuance with this package.

Marine conditions will improve Saturday morning as high pressure
builds in from the west. Winds/seas expected to increase Monday
night into Tuesday ahead of the next storm system.

&&

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

&&

$$

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