530
FXUS62 KCHS 211129
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
729 AM EDT Wed May 21 2025

.SYNOPSIS...
A cold front will arrive today and push offshore early evening,
followed by high pressure through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early Morning: Ongoing convection will shift across western zones
during the next hour, likely in a weakening/eroding trend due to
encountering dry air. Activity could very well diminish near the I-
95 corridor across Southeast South Carolina, but has a higher chance
of making a run towards coastal areas south of the Tri-County Area
through mid morning hours. Activity likely remains sub-severe in an
outflow dominant state, but gusty winds are possible with a few
thunderstorms. Attention then carries over to afternoon hours in
regards to shower and thunderstorm potential with an arriving cold
front.

Late Morning and Afternoon: Aloft, a primarily zonal flow will be in
place across the Southeast United States between weak mid-lvl
ridging sliding further away from the Southeast Coast and a trough
progressing eastward across the Great Lakes/Ohio River Valley region
towards the Northeast this afternoon. A cold front associated with
this trough will be forced east, approaching the region by late
morning hours and quickly traversing the local area this afternoon.
Latest guidance suggests a fair amount of dry air in place as the
front arrives, and with a west-northwest downslope flow also in
place, a drier solution than previous models runs have indicated.
This would suggest convection that is able to develop ahead/along
the front to be limited in coverage while traversing the local area
this afternoon, with the bulk of convection pressed more south of I-
16 across Southeast Georgia and mostly closer to the Altamaha River.
Although the severe weather risk remains low for the local area
today, an axis of SBCAPE around 1500-2500 J/kg and 0-6 km Bulk Shear
around 25-30 kt will be in place prior to the arriving front. Should
convection develop in this environment, unidirectional wind
profiles, low-lvl lapse rates around 8.5 C/km and DCAPE around 1000
J/kg depicted on soundings suggest a few strong and/or severe
thunderstorms capable of producing damaging wind gusts. Coastal
locations along far southern Southeast South Carolina and mostly
coastal areas across Southeast Georgia appear to have the highest
potential for a severe thunderstorm mid-late afternoon, until the
cold front quickly advances offshore by early evening.

Outside of shower/thunderstorm, ample sfc heating will lead to a
well mixed profile, contributing to gusty southwest to west winds
upwards to 20-25 mph and warm temps. In general, highs should peak
in the low-mid 90s, with peak temps generally along the I-95
corridor ahead of the arriving front.

Tonight: Any showers and/or thunderstorms that are able to develop
during the day will quickly shift offshore with a cold front by
early evening, putting an end to any strong and/or severe
thunderstorm concerns. A substantial amount of dry air depicted on
water vapor imagery will arrive post fropa, quickly ending any
precip across the local area for the remainder of the night once the
front shifts offshore. Lows will be noticeably cooler than the
previous night, generally in the low-mid 60s, although upper 60s
should remain along the beaches.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
Cyclonic flow aloft will remain to the north, with the Southeast
U.S. virtually positioned within the base of a stubborn trough. Dry
conditions are forecast during the period as a reinforcing cold
front is progged to push across the area Thursday into Thursday
night. Little moisture present due to the sweeping of Wednesday`s
cold front will maintain a rain-free FROPA. Other than a few
high/cirrus clouds, skies will be mostly clear. High pressure across
the Central U.S. will gradually filter into the area Friday, with
additional building into Saturday. It should feel pleasantly drier
as dew points drop to around 50 degrees or lower, along with nearly
full sun both Friday and Saturday.

Thursday will be rather warm with highs reaching the upper 80s to
lower 90s away from the immediate coast. Overnight lows will drop
into the low to mid 60s most locations and upper 60s along the
beaches. Friday and Saturday will be cooler in the wake of the
reinforcing cold front with highs only in the low to mid 80s,
although some spots across extreme southeast Georgia could peak in
the upper 80s. Friday night will be cool with lows in the mid to
upper 50s inland and mid 60s at the beaches and Downtown
Charleston.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A weak warm front will develop across the southern local CWA Sunday
and lift north Sunday night into Monday night ahead of a developing
system to the west. Slight rain chances will return as a few
showers/tstms could develop near the front. Then an associated cold
front is progged to sweep across the area Tuesday into Wednesday,
increasing rain chances. Temperatures will return to near or
slightly above normal early next week prior to the FROPA.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions will prevail at CHS/JZI/SAV terminals through 12Z
Thursday. However, a few showers could impact the SAV terminal this
morning, producing TEMPO MVFR conditions between 13-15Z. Otherwise,
a cold front arriving to the area could produce a isolated
showers/thunderstorms that impact any terminal, producing brief
periods of flight restrictions. At this time, probabilities
remain too low to include SHRA/TSRA at the terminals later in
the day. However, warm conditions will create a well-mixed
layer, resulting in gusty westerly winds upwards to around 20-25
kt at times during and post fropa late Wednesday morning and
through the afternoon.

Extended Aviation Outlook: No concerns through the weekend.

&&

.MARINE...
Today and Tonight: The pressure gradient will gradually strengthen
across local waters today between high pressure shifting further
offshore and a cold front arriving to the coast late day/early
evening. Southwest winds generally between 15-20 kt will be in place
during the day as a result, but even a few gusts to 25 kt are
possible off the Charleston County Coast despite warm air advection
ahead of the arriving front. Should trends favor a stronger wind
scenario, a Small Craft Advisory will likely be needed across
nearshore waters off the Charleston County Coast and perhaps in the
Charleston Harbor mid to late afternoon. Seas will also build today,
approaching 2-4 ft, but could reach 5 ft beyond 10 nm off the
Charleston County Coast late day. Cold fropa will likely occur by
early evening and some guidance suggests the potential for cold air
advection to produce a secondary round of gusty winds across local
waters during the night. For now, the forecast calls for
west/northwest winds generally between 15-20 kt, with wind speeds
weakening late night. Seas should gradually subside with the
offshore flow in place, generally to 1-3 ft.

Thursday through Monday: Southwesterly winds could become somewhat
gusty Thursday evening as a reinforcing cold front pushes offshore,
but conditions are currently expected to remain shy of Small Craft
Advisory criteria. There are no major concerns through the remainder
of the period as high pressure slowly builds over the waters.

&&

.CLIMATE...
Record High Minimum Temperatures:

May 21:
KCHS: 74/2022
KCXM: 78/1998
KSAV: 74/2017

&&

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

&&

$$

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