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000
FXUS62 KCHS 210738
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
338 AM EDT Sun Apr 21 2024

.SYNOPSIS...
An area of low pressure and associated front will push through
the area and offshore today. High pressure will then return to
the region and prevail through much of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: 21/07z mesoanalysis placed a wavy cold front to the west
and north with a decaying outflow boundary moving south of the
Edisto River. A few showers are percolating behind the outflow
boundary, but these should be fairly short-lived as convergence
near the boundary weakens as it becomes increasingly more
diffuse. Conditions are rather warm and humid across Southeast
South Carolina and Southeast Georgia early this morning with the
region still fully embedded within the warm sector. A large
area of showers/tstms moving across central Georgia will
continue to propagate to the east/northeast, but its southern
flank should largely weaken as it brushes interior portions of
Southeast South Carolina and Southeast Georgia over the next few
hours.

The forecast for today remains extremely complex with an
unusually high bust potential, especially with respect to the
high temperature forecast. The front has moved very little over
the past few hours, but should begin to move to south and
southeast soon as rain begins to fall over the Midlands. Weak,
mainly channeled vorticity embedded in the zonal flow across the
Southeast U.S. will be gradually replaced by a somewhat
enhanced shortwave that is moving across the lower Mississippi
Valley and western Deep South this morning. This feature will
sharpen a bit this afternoon as the right entrance region of a
southwest-northeast oriented jet extending south out of the
Mid-Atlantic and New England pushes through. Increasing forcing
for ascent associated with these two features will support a
broad area of showers/tstms later this morning and afternoon
across the Southeast U.S. with most of the activity pushing
offshore of the South Carolina and Georgia coasts by early this
evening. Pops 70-90% were maintained for most areas today with
the highest rain chances centered across interior Southeast
South Carolina adjacent to the Southern Midlands and CSRA (the
area closest to the corridor of stronger forcing aloft) as well
as the lower South Carolina and upper Georgia coasts (area most
likely to see deeper convection along the front itself).

Pinning down high temperatures is proving difficult this morning
as much will depend on southward progression of the cold front
today. Highs will likely peak across the interior by mid-
morning before temperatures fall with FROPA. Highs will occur
later in the day closer to the coast, but even here, temperatures
will steadily fall as heavier showers/tstms develop and the
surface cold front moves through. Highs look to peak in the
upper 60s across the far interior to the lower-mid 80s extending
from far southern Charleston County through Beaufort/Hilton
Head and into coastal Georgia. Further adjustments in high
temperatures will likely be needed later today as short term
radar and temperature trends become more apparent. A strong tstm
or two could occur along parts of the Georgia and far southern
South Carolina coast prior to FROPA. DCAPE value are not overly
high per modified soundings at both KSAV and KHXD, but there is
a somewhat higher risk for gusty winds given the dry mid-level
air noted.

Tonight: The front will be offshore by sunset. Shower activity
should end during the evening hours. High pressure will steadily
build into the area overnight. Lows will range from the upper
40s well inland and across the Francis Marion National Forest to
the lower-mid 50s elsewhere, warmest at the coast.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
High pressure will build inland on Monday in wake of a departing
front, before shifting overhead and eventually offshore through
mid week. Aloft, trough axis passes across the area with
building heights thereafter. Aside from possibly a few showers
right near the coast on Monday morning, the forecast is dry.
Temperatures will be warming with time as highs initially
unseasonably cool in the mid/upper 60s increase back to around
80 by Wednesday. Low temperatures spanning the 40s away from
Monday night gain a few degrees for Tuesday night.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
A cold front is expected to drop into the area Wednesday night
into Thursday with little impact. Otherwise, high pressure will
prevail, building from the north and then transitioning
offshore as we head into the weekend. Forecast remains dry
through the period, but its worth noting a couple models
indicate a few showers shifting onshore with a coastal trough on
Friday. Temperatures will be within a few degrees of normal.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
21/06z TAF Discussion:
KCHS/KJZI: Southward moving outflow boundary will cross the
terminals around 06z, resulting in either a variable or
northerly wind direction. This feature could produce a few
showers/tstms through about 08z, but the atmosphere is capping
off pretty quick ahead of the boundary. The risk for low clouds
appears to be delayed with the front still well to the north and
expected to progress much slower than expected. MVFR cigs are
anticipated by mid-morning with the risk for showers increasing
by early afternoon. IFR cigs with showers impacts will be
possible 20-23z, so TEMPO groups were utilized to account for
this at both sites. Widespread IFR cigs are expected from late
afternoon through the remainder of the 06z TAF period.

KSAV: VFR will dominate through late morning with the
approaching cold front expected to remain to the north through
then. Showers/tstms will increase ahead of the front, which
could impact the terminal 19-22z. A TEMPO group for MVFR
vsbys/cigs in TSRA was utilized to account for this. Showers
may linger near the terminal through about 00z which should end
as the front passes through. Widespread IFR cigs are expected
from roughly sunset through the remainder of the 06z TAF period.

Extended Aviation Outlook: Flight restrictions will likely
linger into the first part of Monday before improving. VFR
thereafter.

&&

.MARINE...
Today: Winds have tipped northeast across the northern waters
early this morning behind weak outflow boundary. South of the
boundary, winds are largely southwest. Winds will tip to the
west and northwest later today as a cold front approaches.
Northwest winds will surge to 15-20 kt by late this afternoon
as cold front moves into the coastal waters. Seas will average
2-3 ft.

Tonight: North winds 15-20 kt will be common behind the front.
Gusts to 25 kt will be possible, but the frequency will not
increase until closer to daybreak Monday as the pressure
gradient begins to tighten. Seas will build 3-4 ft nearshore
waters with 20 NM and 4-5 ft over the Georgia offshore waters.

Monday through Friday: Main time period of concern is on Monday
when gusty northeast winds and elevated seas are forecast over
the coastal waters. Confidence was high enough to hoist a Small
Craft Advisory for the outer Georgia waters, but this could
eventually be expanded to include at least portions of the
nearshore waters as well. Conditions should fall below advisory
criteria Monday night, with the exception of the outer Georgia
waters where 6 ft seas will linger a bit longer. Winds will
gradually turn to become more southerly by mid week as high
pressure shifts overhead then offshore, before the next front
drops into the area. Winds and seas are forecast to stay below
advisory levels through the end of the week.

Rip Currents: Gusty northeast winds and building seas will lead to
an elevated risk of rip currents on Monday. A Moderate risk is
currently forecast at all beaches.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from 6 AM Monday to 2 PM EDT Tuesday for
     AMZ374.

&&

$$