271
FXUS62 KCHS 211721
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1221 PM EST Fri Feb 21 2025

.SYNOPSIS...
Cold high pressure will build into the region through the start
of the weekend. A weak disturbance will pass to our south on
Monday, followed by more high pressure into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Early this afternoon: No change to the forecast for the
afternoon. Previous discussion continues below.

Late this morning: Cold and dry high pressure will prevail
today. We are certainly off to a very cold start, with many
places having dipped into the mid 20s last night. Most locations
are now rising above freezing with full sun underway. Clear
skies will prevail for most of the day until thin cirrus starts
to arrive from the west later this afternoon. Low-level
thickness off the 12z KCHS RAOB supports highs similar to what
we already have in the forecast. Look for temperatures to peak
in the mid to upper 40s across southeast SC and the upper 40s
and maybe even a few 50s across southeast GA.

Tonight, the pattern will feature zonal H5 flow as the center
of the sfc high builds east of the Appalachians across VA/NC.
Mid and high clouds should stream west to east across the
forecast area, keeping conditions mostly clear to partly cloudy.
Low temperatures are expected to range from the mid 20s inland
to the mid to upper 30s across the coastal counties. Given light
to calm winds tonight, no Cold Weather Advisory is anticipated
for tonight.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
Saturday: The mid-levels will consist of a shortwave over the
mid-MS Valley in the morning. It`ll shift east as time
progresses, passing just to our north in the evening, then
offshore overnight. There will be some lift associated with this
disturbance, but not a significant amount. At the surface, High
pressure will be centered just to our north in the morning.
It`ll shift offshore into the afternoon. At that time, weak
troughing is expected to form off our coast, then prevail into
the evening and overnight. A second area of High pressure will
then approach from the west late at night. Moisture is expected
to increase with the trough, with the highest values remaining
just off our coast. Likewise, both the synoptic models and long-
range CAMs point towards some showers offshore, mainly in the
late afternoon into the first part of the night. Land areas are
expected to remain dry, as the Highs win out. Low-level
thickness values and cold 850 mb temperatures support high
temperatures in the mid to maybe upper 50s. Though, this may be
lower as clouds increase during the day. Mostly cloudy skies in
the evening will clear overnight, leading to a large temperature
spread. Temperatures far inland should bottom out near
freezing, while near the immediate coast they should be in the
mid to upper 30s, and the low to mid 40s at the beaches.

Sunday: Weak mid-level troughing will be located off the East
Coast in the morning, leading to NW flow overhead. Additionally,
a shortwave will be located over the southern Plains. It`ll
shift east as time progresses, becoming located over the
Southeast U.S. late at night. Weak surface troughing located
just off our coast in the morning will be pushed away by High
pressure building in from the west. The High should pass to our
north late in the day, then weaken as it moves offshore
overnight. Meanwhile, a storm system will be impacting the
northern Gulf states during the day, shifting eastward with
time. It should start impacting the Southeast late at night. The
High will bring dry conditions during the day and into the
evening. Moisture will increase from the south after midnight.
Likewise, most of the models have isolated showers south of I-16
during that time period. Hence, we went with slight chance
POPs. With a decent amount of sun, high temperatures should
range from around 60 degrees to maybe the middle 60s, except
cooler at the beaches. Increasing clouds late at night should
limit low temperatures to the mid 30s inland to the mid 40s
along the beaches.

Monday: The mid-levels will consist of a shortwave over the
Southeast U.S. in the morning. It`ll slowly shift offshore by
late in the day. At the surface, a storm system will be
impacting the Southeast U.S. in the morning. Though, most of
it`s energy should pass just to our south. Likewise, models have
most of the moisture and shower activity in this location. The
NBM keeps our area fairly dry, but this may be underdone based
on some of the synoptic models. This portion of the forecast
will need to be adjusted. Highs may rise to near normal.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
High pressure will bring dry conditions through Wednesday. A
cold front should bring a round of showers on Thursday.
Temperatures should be above normal throughout the long term.

&&

.AVIATION /17Z FRIDAY THROUGH TUESDAY/...
VFR conditions will prevail at KCHS, KJZI, and KSAV through 18z
Saturday.

Extended Aviation Outlook: A weak disturbance will pass to our
south on Monday, bringing low probabilities of flight
restrictions, mainly to our GA counties. Otherwise, VFR should
prevail the rest of the time.

&&

.MARINE...
This afternoon: Conditions have improved significantly over the
last couple of hours as the gradient has relaxed. The Small
Craft Advisory for the nearshore waters has expired but remains
in effect for the outer waters through the afternoon, mainly for
seas. Through the rest of the day winds are expected to be 10-15
knots across the nearshore waters with seas up to 3-5 feet. The
outer GA waters could still see a few gusts up to 25 knots with
seas 4-6 feet.

A sfc ridge will develop over the marine zones tonight,
supporting northeast around 10 kts. Seas should generally range
between 2 to 3 ft.

Extended Marine: Lots of synoptic changes will occur. High
pressure will be centered just to our north Saturday morning.
It`ll shift offshore Saturday afternoon. At that time, weak
troughing is expected to form over the coastal waters, then
prevail Saturday evening and overnight. A second area of High
pressure will then approach from the west late Saturday night.
The trough will be pushed away by this High on Sunday. The High
should pass to our north late Sunday, then weaken as it moves
offshore Sunday night. A storm system should start impacting the
Southeast U.S. late Sunday night. Though, most of it`s energy
should pass just to our south on Monday. High pressure will then
build in from the west later Monday and prevail through the
middle of the week. Even with all of these changes, no marine
headlines are expected.

&&

.CLIMATE...
Record Low Maximum Temperatures:

February 21:
KCHS: 47/2020

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 5 PM EST this afternoon for AMZ374.

&&

$$

NEAR TERM...BSH/NED
SHORT TERM...
LONG TERM...
AVIATION...BSH
MARINE...NED