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205
FXUS62 KCHS 151332
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
932 AM EDT Wed May 15 2024

.SYNOPSIS...
A cold front will move through late today, followed by high
pressure 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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This morning: The day is off to a quiet start with no ongoing
convection and areas of low stratocumulus across the forecast
area. This cloud cover will gradually mix out over the next
couple of hours and we might have a clear period before diurnal
cumulus begins developing this afternoon. Water vapor imagery
shows a well defined shortwave upstream of the area across the
Tennessee Valley and plenty of mid-level dry air streaming
across the Southeast. Surface analysis shows a front situated
upstream of the forecast area that will steadily track to the
east and into the area this afternoon. Surface winds will be
west to west-southwest into the afternoon, which will keep the
diurnal sea breeze pinned along the coast, despite mid to upper
80s for highs inland. We should be convection-free through the
morning and into the mid afternoon thanks to the westerly flow,
some mixing out of dew points, and the dry air aloft. However,
beginning around mid afternoon the pinned sea breeze could serve
as the initiation of convection. This seems most likely along
the Charleston County coast, approximately in the 3-5 pm time
period. Additional thunderstorms will be possible, primarily
across the South Carolina counties. For any storms that do
develop, the ambient environment will be supportive of a low end
severe threat. Model soundings show MLCAPE values of 2,000 J/kg
with DCAPE values approaching 1,000 J/kg. There is also still
about 50 kts of mid-level flow and lapse rates could approach
6.5 C/km. All this to say, we will have the potential for severe
weather, with the primary threat being damaging wind gusts and
large hail will also be possible. Convective coverage is
expected to be limited to isolated to scattered which will help
keep the overall severe threat more limited. The main time
period will be roughly 3-8 pm.

Tonight: Showers and/or thunderstorms will likely weaken
considerably and/or shift offshore with a weak sfc front shortly
after sunset, ending precip across the entire area for the rest
of the night. Dry high pressure will then settle in for the
night with temps dipping into the low-mid 60s inland to upper
60s/around 70 near the coast.
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&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
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The local forecast area will be positioned along the southern
periphery of a mid level trough situated off the Mid-Atlantic
coast. A nice day is expected on Thursday, owing to the NW flow
aloft and high pressure briefly building in at the surface. High
temperatures will reach into the mid to upper 80s, with mostly
clear skies and dry conditions forecast. Overnight lows Thursday
will be in the mid 60s inland with 70 along the beaches.

The flow aloft will briefly transition to a zonal flow on
Friday, with surface high pressure retreating out into the
Atlantic waters. To the west a mid level trough and associated
surface cold front will begin trekking towards the Deep South.
Ahead of the approaching cold front isolated showers and
thunderstorms are possible across the far inland zones late
Friday. Otherwise, another rain-free forecast with high
temperatures again reaching into the mid to upper 80s. Overnight
lows will be rather mild, given the increasing cloud cover
ahead of the approaching cold front. Low temperatures are
forecast to only dip into the mid 60s inland with low 70s along
the coastline.

Saturday is expected to be another active weather day as a low
pressure system impacts the forecast area. A warm front is
forecast to lift northward early, with a cold front pushing
through later. PWATs are forecast to reach 1.5+ inches Saturday
afternoon. Additionally, both the GFS/ECMWF show a decent amount
of instability across the region (around 1000 J/kg of CAPE).
Given the favorable environment, numerous showers and
thunderstorms will be possible. Showers and thunderstorms as
well as thick cloud cover will likely hinder high temperatures
on Saturday, only reaching into the low to mid 80s.
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&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
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The aforementioned mid level trough will slip offshore Saturday
night/Sunday morning, with broad ridging building in behind it.
High pressure will also build in at the surface and dominate
through the remainder of the weekend and into early next week.
Apart from Sunday afternoon which could see a greater coverage
of showers and thunderstorms due to lingering dynamics from the
departing trough, rain chances through early next week remain
minimal as subsidence builds into the region. Under plentiful
sun, ridging aloft, and surface high pressure temperatures each
day will reach into the upper 80s with some locations across
southeastern GA possibly touching 90.
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&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
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MVFR cigs will likely persist at the SAV terminal for the next
1-2 hours (12-14Z) until sfc winds increase and dry air filters
into the region from the west. Low clouds could also briefly
impact CHS/JZI terminals early this morning, where tempo MVFR
cigs are in place between 12-13Z. Expect VFR conditions to
prevail at all terminals thereafter, but gusty west-southwest
winds around 20 kt are anticipated much of the afternoon. There
is a small risk for showers and/or thunderstorms near the
CHS/JZI terminal late this afternoon, but confidence remains too
low to include in the latest TAF issuance.

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

.MARINE...
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Today and Tonight: A somewhat enhanced pressure gradient will
persist across local waters today ahead of a weak cold front
advancing toward the coast late day and early night. The pattern
supports southwest winds generally up to 15-20 kt by late
morning and through afternoon hours, before stronger wind fields
shift to the north-northeast and the pressure gradient weakens
post fropa. Cold air advection behind the front will be somewhat
marginal, keeping marine conditions below advisory levels
through the night. However, winds will shift to west and
continue to gust in the 15-20 kt range. Seas should generally
range between 3-5 ft today, highest across offshore Georgia
waters and Charleston County waters. Overnight seas will subside
to 2-4 ft.

Thursday through Monday: Conditions through the period are
expected to remain below Small Craft Advisory criteria. High
pressure will briefly build in at the surface on Thursday, with
winds generally around 10 knots and seas averaging 2 to 3 ft. 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.
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&&

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

&&

$$

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