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000
FXUS62 KCHS 211827
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
227 PM 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: Surface cold front remains held up along coastal
Charleston, Colleton and Jasper counties. Convective initiation
has begun near KJZI with showers and thunderstorms igniting up
and down the convergence line from coastal Jasper to coastal
Charleston. The surface front has continued to ooze south today
though, even with the weak coastal low forming near Hilton Head.
The front should slow and come to a brief halt due to the weak
surface cyclogenesis. At the same time, multiple cold pools from
the showers and thunderstorms should provide some resistance to
the southward pushing front.

The duration of the existence of the thunderstorms does appear
rather limited though to this afternoon. MLCAPE values are only
around 1000 J/kg (even though some weak synoptic scale lift
might help to modify capping slightly), with the cold front then
finally clearing the coastline by late this afternoon into early
evening. The main threat appears to be some potential for heavy
rainfall across Downtown Charleston (a quick 1" to 2") which
could result in some street closures.

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 /18Z SUNDAY THROUGH FRIDAY/...
21/18z TAF Discussion:
KCHS/KJZI: Both terminals were VFR early this morning, but are
now both impacted by restrictions. At KCHS, the cold front has
since oozed south with borderline IFR/ MVFR cigs in place. This
will likely hold in place through the evening hours. At KJZI,
the cold front has stayed just north of the terminal, but since
then showers and thunderstorms have formed and moved across the
terminal restricting the cigs and vsbys. A few more rounds of
showers and thunderstorms are forecast for the Charleston
terminals through 22z. By 00z, showers and thunderstorms will
come to an end as the surface cold front clears the area. A
return of the IFR/ MVFR cigs is then forecast on the backside of
the cold front. After midnight, cigs will slowly start to
recover.

KSAV: Prevailing MVFR cigs will then settle in as convection
pushes offshore and a cold front moves through. The risk for IFR
cigs looks to hold north of the terminal. VFR will return
overnight as high pressure builds in.

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

&&

.MARINE...
Today: South to 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.

&&

$$

NEAR TERM...Haines
SHORT TERM...
LONG TERM...
AVIATION...Haines
MARINE...