175
FXUS62 KCHS 031908
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
308 PM EDT Thu Apr 3 2025

.SYNOPSIS...
Strong high pressure centered over the Atlantic will prevail
into this weekend. A cold front will push offshore Monday with
high pressure prevailing for much of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Afternoon composite analysis reveals a broad upper level ridge
axis extending from Bermuda southwestward across the Florida
Peninsula and southeast region. Large area of surface high
pressure sits off the US Atlantic coast providing S/SE flow
across the region as well as unseasonably warm and somewhat
humid conditions. Satellite imagery reveals a well developed
Cu/StCu field across the southeast although largely flat/capped.
There is a small area of StCu and spotty radar returns moving
through the SC coastal waters that might be producing a few
sprinkles.

Pattern changes very little through tonight with upper level
ridging further expanding into the southeast, while surface high
pressure dominates off the coast. Other than a few sprinkles
brushing the Charleston coast, larger scale subsidence and
capping aloft will maintain rain-free conditions. Within a
southerly low level flow, and moisture getting stuck beneath the
nocturnal inversion, low stratus development will again be a
possibility, along with a touch of fog in spots.

Otherwise, another warm night is on tap with dew points in the
60s, and winds never fully decoupling in many places. Thus lows
will only be able to drop to the middle 60s to near 70.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
An impressively strong, deep-layered subtropical anticyclone for
early Spring will maintain its influence on the Southeast U.S.
through the weekend as it remains nearly stationary well offshore.
Modified forecast soundings show a modest subsidence inversion
dominating for much of the period with any risk for a very brief
shower occurring ahead of the resultant sea breeze circulation each
afternoon. The risk for an isolated shower looks greatest Friday
afternoon where the subsidence inversion does not look nearly as
strong, mainly across the far interior where some of the various
CAMs are spitting out one or two showers across the Midlands, CSRA
and over the far interior zones. Other than a 5% pop across the far
interior Friday afternoon, rain chances will hold near zero into
Saturday. Rain chances do increase to 10-30% (highest in the Millen-
Allendale corridor) late Sunday afternoon as weak, mid-level theta-e
advection occurs ahead of an approaching cold front, but soundings
still suggest this activity will be encountering a lingering mid-
level subsidence inversion despite an slow eastward progression of
the subtropical anticyclone well offshore. Highs each day look to
peak in the upper 80s/near 90 inland with considerably cooler
conditions at the beaches. Lows will bottom out each morning in the
lower-mid 60s well inland to the mid-upper 60s at the coast and
barrier islands.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Sunday Night into Monday Night: A strong cold front will march
across the Deep South Sunday night and across the Southeast U.S.
Monday as powerful southern stream shortwave energy gradually
dampens while phasing a northern shortwave that is progged to dig
across the Great Lakes. Model cross section suggest DCVA with the
dampening southern stream shortwave will remain rather robust with a
corridor of deep-layered UVVs progged to advect west-east across the
area Monday with the cold front. Given the column is expected to be
nearly saturated up to 200 hPa while fully aligned with the corridor
of strongest forcing, expect a fairly widespread of rain with
embedded tstms to move through beginning late Sunday night and
ending Monday evening as the cold front clears the coast. Pops
Sunday night were raised to 30-70% (highest across the Millen-
Allendale corridor) to account for pre-frontal rains in the broad,
warm air advection regime. Pops 80-90% were highlighted all areas
Monday with rain chances diminishing Monday night as the front
clears the coast. Instability is not expected to be overly strong,
but given the degree of forcing noted, isolated to scattered tstms
appear likely. 0-6km bulk shear >50kt is noted, but given the net
lack of mixed-layer instability, organized severe tstms appear
unlikely at this time. However, one or two strong to severe tstms
could still occur. Lows Sunday night will range from the lower-mid
60s inland to the upper 60s at the coast. Highs Monday will warm
into the lower-mid 70s inland with upper 70s roughly along/east of
the I-95 corridor. Lows Monday night will drop into the mid-upper
40s inland to the mid 50s at the beaches.

Tuesday through Thursday: A reinforcing cold front will cross the
area Tuesday with Canadian high pressure dominating Tuesday night
through Thursday. Near to slightly below normal temperatures will
occurring during this time. There could be a little frost early
Wednesday morning, but most areas look to remain warm enough to keep
any frost limited to only the coldest, most sheltered locations.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
KCHS/KJZI/KSAV: SCT-BKN VFR cloud cover will persist through
the afternoon into tonight. Gusty southerly winds persist until
sunset with gusts 20 to 25 knots anticipated.

Later tonight: MVFR-IFR ceilings will again be possible later
this evening and overnight with the development of a decent
inversion.

Extended Aviation Outlook: Flight restrictions are likely Monday as
showers with a few tstms impact the area ahead of a cold front.

&&

.MARINE...
Today and tonight: Strong Atlantic high pressure covers the
local maritime community, with SE and S winds around 15 kt or
less. The exception will be in Charleston Harbor, where sea
breeze influences could generate some gusts around 20 kt at
times this afternoon. Spectral Density Plots from the nearby
buoys show that the bulk of the wave energy will be in the form
of 9-10 second period swells. The resulting seas reach 3-4 feet
within 20 nm, and up to 5 ft further offshore.

Friday through Tuesday: Southerly winds with afternoon/early evening
sea breeze enhancements in Charleston Harbor and along the land/sea
interface will prevail through Saturday Speeds will generally remain
15 kt or less except 15 kt with gusts to 20 kt in the Charleston
Harbor. For Saturday night and Sunday, breezy conditions will
develop as the low-level wind fields begin to increase ahead of an
approaching cold front. South winds will reach as high as 15-20 kt
with gusts approaching 25 kt at times. Southwest winds of 15-20 kt
will gradually turn offshore Monday night as a cold front sweeps
through. Northerly winds will prevail Tuesday in the wake of a
secondary cold front. Seas will reach 4-6 ft over the Georgia
offshore waters Saturday night with 4-6 ft reaching the nearshore
legs with 6-7 ft over the Georgia offshore legs Sunday into Monday.
Seas will subside below 6 ft Monday night as winds turn offshore
after FROPA. Small Craft Advisories are possible all legs Saturday
night into Sunday and lingering into Monday.

Rip Currents: Lingering 3 ft breakers coupled with easterly 8 sec
swells will support a moderate risk for rip currents for all beaches
both Friday and Saturday.


&&

.CLIMATE...
Record High Temperatures:

April 5:
KSAV: 90/1988

April 6:
KSAV: 90/1967


Record High Minimum Temperatures:

April 3:
KCHS: 67/2012
KCXM: 68/2012
KSAV: 68/2012

April 4:
KCHS: 70/1974
KCXM: 69/1974
KSAV: 69/1974

April 5:
KCHS: 65/2017
KCXM: 67/2023
KSAV: 66/1957

April 6:
KCHS: 68/2023 KSAV: 68/2023

&&

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

&&

$$

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