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000
FXUS62 KCHS 180833
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
433 AM EDT Thu Apr 18 2024

.SYNOPSIS...
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High pressure will persist through tonight. A slow moving front
will bring unsettled weather to our area Friday through early
next week. High pressure returns by the middle of next week.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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Today: Aloft, zonal flow between broad ridging across the Gulf of
Mexico and weak troughing exiting off the Mid-Atlantic and Northeast
coast will favor a west-northwest flow early, before ridging becomes
stronger across the local area this afternoon. At the sfc, high
pressure across the western Atlantic will maintain a hold across the
Southeast, while slowly nudging south as a weak trough exits further
offshore to the north. The pattern will favor another day of dry
weather conditions with ample sun across most areas once a band of
cirrus shifts offshore late morning. Strong sfc heating along with
light southwest winds tipping more west by mid-late morning suggests
high temps to become a few degrees warmer than the previous day,
especially if a seabreeze remains somewhat pinned near the coast
into early afternoon hours. Latest 1000-850mb thicknesses favor
highs in the upper 80s to potentially around 90 degrees inland.
Closer to the coast, highs should peak in the upper 70s to lower
80s.

Tonight: High pressure will prevail across the local area well ahead
of a front advancing eastward across the Great Lakes region and Deep
South late. Conditions will remain dry through the night with less
cirrus in place than the previous night. Winds will also remain
light from the southwest and/or go calm late while a fair amount of
radiational cooling takes place. Overnight lows should range in the
low-mid 60s, coolest across inland areas of southeast South
Carolina.
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&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
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Friday: Mid-level ridging over the East Coast in the morning will
shift offshore into the afternoon. Zonal flow then develops in the
evening and persists overnight. Surface High pressure located to our
southeast in the morning will move away into the afternoon.
Meanwhile, a trough will form along the coast. At the same time, a
cold front will approach from the northwest. The front should reach
our inland counties around daybreak Saturday. Moisture creeps higher
ahead of the front, with PWATs rising to ~1.5" in the afternoon.
Synoptic models and the long range CAMS indicate scattered
convection developing in the afternoon. One area will be well ahead
of the front, inland and moving towards the coast. The other area
will be associated with the afternoon sea breeze, moving inland.
Skies will start out mostly sunny, which will allow temperatures to
rapidly rise. The combination of warm 850 mb temperatures and low-
level thickness values support well above normal highs in the upper
80s to lower 90s, except cooler at the beaches. These temperatures
will generate some instability in the afternoon, with MLCAPEs
exceeding 800 J/kg in some spots. Shear is weak in the 0-1 km, but
increases in the 0-6 km layer. DCAPEs exceed 800 J/kg across
portions of our area. Therefore, a few marginally severe storms with
damaging winds and/or large hail are possible. Locally heavy
rainfall is also possible. The SPC has the Charleston Tri- County
under a Marginal Risk for severe thunderstorms, and this seems
reasonable, and the spot we`re most likely to have the most
convection. Any convection will dissipate in the evening, with it
becoming dry after midnight. Lows will be very mild, generally in
the 60s.

Saturday: The mid-levels will consist of zonal flow over our region.
Though, heights will gradually lower with time. At the surface, a
cold front located across our inland zones at daybreak will slowly
move southeast across our area during the day and into the evening,
becoming located just to our south and southeast overnight. Plenty
of moisture will remain in place in the vicinity of the front, with
PWATs ranging from 1.25-1.5". The combination of lift from the front
and the afternoon sea breeze trying to move inland will generate
scattered convection in the afternoon. Before the convection
develops, highs will peak well above normal, generally in the upper
80s to around 90 degrees, except cooler at the beaches. This heat
will provide enough instability, with MLCAPEs exceeding 1,000 J/kg
in some spots. Shear remains weak in the 0-1 km, but increases in
the 0-6 km layer. DCAPEs also exceed 1,000 J/kg across portions of
our area. Therefore, a few marginally severe storms with damaging
winds and/or large hail are possible. Locally heavy rainfall is also
possible. The strongest convection will dissipate around sunset. But
remnant showers and thunderstorms should persist most of the evening
and overnight. Lows will generally be in the 60s.

Sunday: Mid-level troughing will start to develop over the Southeast
U.S. as the day progresses. A surface front will be located to our
south and southeast during the day, possibly with a trough situated
across our area. Lots of moisture will remain in place around the
vicinity of the front, and into our area. An impulse of energy is
forecasted to move along the front during the day, tapping into lift
from the front, the afternoon sea breeze, and the moisture to
generate numerous convection in the afternoon. The details will
still need to be refined with future forecasts. But it`s certainly
looking more wet than dry, with locally heavy rainfall a concern,
especially if there`s lots of rainfall the previous two days.
Temperatures will be cooler than the previous two days, generally
within a few degrees of normal.
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&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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Mid-level troughing will persist over the Southeast U.S. into
Monday, then shift offshore Monday night. Zonal flow returns on
Tuesday, followed by weak longwave troughing over the East Coast on
Wednesday. A surface front located just off our coast Sunday night
will bring numerous showers to our area. Showers will end from west
to east on Monday, as drier air moves in from the west. High
pressure will then bring dry conditions through Wednesday.
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&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
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VFR conditions will prevail at CHS/JZI/SAV terminals through 06Z
Friday.

Extended Aviation Outlook: A slow moving front should bring
occasional flight restrictions Friday through Sunday. Flight
restrictions are looking most likely late Sunday.
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&&

.MARINE...
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Today and Tonight: High pressure will remain the dominant weather
feature across local waters while a weak trough exits further
offshore across the western Atlantic to our north. A slightly
enhanced gradient between these two features should continue to
promote the strongest winds (around 15 kt) across nearshore waters
along the Charleston County coast and across the Charleston Harbor
early morning, but winds should diminish a bit by late morning until
a seabreeze circulation takes shape and eventually shifts inland
during the afternoon. The seabreeze could result in southerly winds
gusting up to 20 kt along the Charleston County coast and across the
Charleston Harbor for a few hours this afternoon, before winds
decrease late afternoon into early evening. Elsewhere, south-
southwest winds should range between 10-15 kt, gradually turning
south this afternoon, then tipping back south-southwest overnight
while high pressure prevails. Seas will range between 2-3 ft through
tonight.

Friday: Surface High pressure located to our Southeast in the
morning will move away into the afternoon. Meanwhile, a cold front
will approach from the northwest, reaching our land areas around
daybreak Saturday. In the morning, expect backing winds, followed by
gusty winds along the land/sea interface in the afternoon due to the
formation of the sea breeze. Gusts should be around 20 kt in the
Charleston Harbor with its passage. In the evening, winds will veer
and increase as some coastal jetting develops overnight.

Weekend into next week: A cold front located across our inland zones
at daybreak Saturday will slowly move southeast across our area
Saturday. It`ll be spread across our waters Saturday night, then
shift further offshore by Sunday night or Monday morning. Winds and
seas don`t appear to be high enough to prompt Small Craft
Advisories. Expect southerly/southwesterly flow ahead of the front
and northerly/northeasterly flow behind it. High pressure will build
in behind the front.
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&&

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

&&

$$

NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...DPB
MARINE...DPB