Coosaw, South Carolina Weather Forecast Discussion

030
FXUS62 KCHS 150942
AFDCHS
Area Forecast Discussion
National Weather Service Charleston SC
542 AM EDT Mon Sep 15 2025
.SYNOPSIS...
High pressure will extend across the region this week. Low
pressure well offshore will begin to slowly drift toward the
North Carolina Outer Banks today and meander through the middle
of the week. A cold front could then approach the area from the
north next weekend.
&&
.NEAR TERM /THROUGH TONIGHT/...
15/00z upper air analysis and early morning GOES-E water vapor
imagery showed a rex block trying to take shape over the eastern
third of the CONUS with an upper level anticyclone centered
over the Great Lakes and an upper level cyclone near the South
Carolina/Georgia coast. Surface low pressure with an estimated
pressure of 1008 mb was noted about 335 mi east-northeast of the
Charleston Harbor at 15/05z and appears to still be attached to
a broad coastal trough that extends south from the low into the
northern Bahamas. The low is forecast to meander closer to the
North Carolina Crystal Coast and southern Outer Banks through
tonight as the supporting upper low propagates a bit farther to
the north into Eastern North Carolina. The system appears to be
purely baroclinic in nature per the latest phase diagrams and
will likely remain so even as it traverses the warmer Gulf
Stream waters.
Locally, quiet and dry weather will persist as high pressure
continues to wedge south through the Carolinas and Georgia. In
fact, the wedge will likely become reinforced later today into
tonight in response to the strengthening low-level cyclonic
flow around the low offshore. This coupled with low PWATs and
a considerable mounts of mid-level dry air will keep conditions
rain-free through tonight. There are still some low-end signals
that a brief, isolated shower could pop near the Santee River
late this afternoon, but chances for any measurable are just
too low to mention at this time. Highs this afternoon will peak
in the mid-upper 80, except lower-mid 80s across the Charleston
Tri- County with upper 70s/lower 80s at the beaches. The
boundary layer will likely decouple by mid-evening away from
the coast, but lingering cirrus aloft may curtail radiational
cooling a bit. Lows will range from the upper 50s/lower 60s
inland to the upper 60s/near 70 at the beaches.
&&
.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
Tuesday: A pseudo rex block pattern will be in place Tuesday as
a mid- level ridge near the Great Lakes region along with an
area of low pressure near SC/ NC stalls. At the surface, low
pressure will be located near the Outer Banks of NC. On the
southwest flank of the low pressure (or across SC and GA), PWATs
will be around 1.25" with downslope flow over the region. As
such, no precipitation is expected. At 250 MB, a 80 kt jet
streak will be overhead with only high and mid clouds forecast.
Expect high temperatures in the lower 80s closer to the surface
low (e.g., the TriCounty) with upper 80s forecast over interior
GA.
Wednesday: The mid-level low will start to pull away from the
area with the 250 mb jet streak remaining across coastal GA and
SC. As such, another day with temperatures in the lower to upper
80s with no precipitation is forecast.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
The overall synoptic pattern for the extended looks more like a
winter pattern as numerous wave breaking continues across
Ontario and Quebec. Over coastal SC and GA, weak mid-level
ridging will be in place with the shortwaves from the western
United States ejecting north and east around the ridge. By late
this weekend into early next week, enough wave energy will have
occurred which should start to dislodge the mid-level ridge
resulting in a slow increase in rain chances.
Thursday - Saturday: Mostly dry conditions with temperatures in
the upper 80s to lower 90s each afternoon. Lows will generally
be in the mid 60s to lower 70s at area beaches.
Sunday - Monday: Southern stream jet energy and multiple rounds
of shortwaves from the western United States should begin to
approach SC and GA. If this were to occur, it would favor
slightly cooling temperatures and an increase in rain chances.
Taking a look at the latest WPC Cluster Analysis and global
ensembles though, this remains rather uncertain. Some ensemble
members show the ridge holding on through the weekend as the
shortwaves washout. For now, will keep with consensus of
slightly cooler temperatures and increasing rain chances, but
this will likely change over the coming days.
&&
.AVIATION /12Z MONDAY THROUGH FRIDAY/...
15/12z TAF Discussion:
KCHS/KJZI/KSAV: VFR will prevail through 16/06z.
Extended Aviation Forecast: There are no high confidence
concerns.
&&
.MARINE...
Through Tonight: North to northeast winds will persist with
speeds generally 10-15 kt, except 15 kt with gusts to 20 kt in
the South Santee-Edisto Beach nearshore leg. Seas will average
2-4 ft, except 3-5 ft over the Georgia offshore waters and the
South Santee-Edisto Beach nearshore leg.
Tuesday through Saturday: Surface low pressure will be located
near the Outer Banks on Tuesday with surface pressures slowly
rising. The SC and GA waters will be on the southwest flank of
the surface low allowing for the pressure gradient to relax
significantly from the past weekend. The low pressure will
slowly eject northeast by the second half of the work week with
wind gusts remaining around 20 kt or less. Seas will be 3 to 5
ft on Tuesday and slowly fall through the work week to 2 to 4
ft.
Rip Currents: A moderate risk for rip currents continue for all
beaches into this evening. For Tuesday and beyond, the rip
current risk looks low due to the slackening wind field and
decreasing wave heights.
&&
.TIDES/COASTAL FLOODING...
High tide could peak near 7.0 ft MLLW (minor) at the Charleston
Harbor tide gage later this afternoon. The situation looks
marginal, but a Coastal Flood Advisory may be needed for
Charleston and Coastal Colleton.
&&
.EQUIPMENT...
The KCLX radar will be down for maintenance from September
16-18th for component upgrades. Users are encouraged to use
adjacent WSR-88D radar sites. These radars include:
KCAE: Columbia, SC
KLTX: Wilmington, NC
KJAX: Jacksonville, FL
KVAX: Moody Air Force Base, GA
KJGX: Robbins Air Force Base, GA:
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$

NWS CHS Office Area Forecast Discussion