501
FXUS62 KCHS 031004
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
604 AM EDT Tue Jun 3 2025

.SYNOPSIS...
High pressure will prevail across the area today. A coastal low
will result in unsettled weather across the region late tonight
through late in the week. A cold front could approach the
region over the weekend into early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
No changes were needed for the sunrise update.

Today: A brief Rex Block will quickly mature across the Southeast
U.S. today. The local area be pinned between a sharpening
trough along the Florida east coast and high pressure centered
offshore of the North Carolina Outer Banks. Despite a
strengthening onshore flow, the thermodynamic environment will
remain hostile to the genesis of deep, moist convection with
ongoing mid-level dry air, subsidence aloft and a thick elevated
smoke layer helping to keep a pronounced capping inversion in
place. Pops at 0% were highlighted for all areas today.

H3R Vertically Integrated Smoke guidance shows a large plume of
thick smoke generated by Canadian fires remaining in place
through the day. This will give the sky a hazy/smoky appearance
at times with an orange hue to the sun, but no meaningful
surface-based issued are expected. As has been the case for the
past few days, the elevated smoke layer will likely shave a
degree or two off potential afternoon highs with temperatures
topping off in the mid-upper 80s, except near 80 at the beaches
and Downtown Charleston.

Tonight: The atmosphere will be in state of transition tonight
as the Rex Block breaks down and the upper low over the eastern
Gulf begins a slow trek to the north. The surface trough over
eastern Florida will strengthen overnight, possibly closing off
into a weak surface low along the northeast Florida/far southern
Georgia coast by daybreak Wednesday. Guidance is similar in
showing PWATs and moisture advection increasing through the
night owing to modest 850 hPa moisture transport vectors. This
coupled with both isentropically driven and dynamic forcing
aloft will support a steady increase in rain chances after
midnight, especially over the Georgia coastal counties. There
may be enough dry air lingering across far interior Southeast
Georgia and Southeast South Carolina to preclude measurable
rainfall from occurring prior to daybreak; however, it will be
wet early morning for much of coastal Georgia into far south
coastal South Carolina as the weak low approaches. Pops range
from 5-10% across far interior areas to as high as 50-70% along
the Georgia coast. Enhanced rainfall rates could be realized
within pockets of concentrated convection given PWATs are
forecast to exceed 2", but flash flooding is unlikely through
the night. Minor flooding of low-lying and poor drainage areas
could still occur. Lows will range from the upper 60s well
inland to the lower-mid 70s at the beaches and Downtown
Charleston.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Wednesday and Thursday`s weather will be heavily driven by a
coastal Low. There is still some uncertainty in the exact path,
strength, and timing of the Low. But this will ultimately
determine our final rainfall forecast and associated impacts.

Wednesday: Strong mid-level ridging will prevail over the East
Coast. Meanwhile, a weak mid-level Low initially in the Gulf
near FL will shift northeast and slowly dissipate as time
progresses. Surface High pressure will be off the Outer Banks of
NC in the morning, shifting a little further offshore as time
progresses. Meanwhile, the disturbance over FL and weak coastal
Low will slowly move to the north, over our area. Deep moisture
will be ushered into our area, with PWATs making a run for 2.25"
late in the day and overnight. These values are near records
per SPC Sounding Climatology for CHS. NAEFS doesn`t hit the
PWATs or IVT as hard, but it still indicates the potential is
there. All of the deterministic models have numerous to
widespread showers across our entire area most of the day and
night. While there will be embedded convection, it shouldn`t be
as widespread or intense due to less than ideal instability. But
it would lead to locally higher rainfall amounts. QPF will have
a large gradient, ranging from about 0.5" across far inland GA,
rapidly rising closer to the coast where 1-2" is possibly along
the immediate coast, with locally higher amounts. Highs will be
around 80 degrees, held down by all of the showers. Lows will
be mild, in the mid/upper 60s far inland, to the low/mid 70s
near the coast.

Thursday: At the mid-levels, ridging over the Southeast U.S.
will weaken. Meanwhile, an embedded weak mid-level Low will
continue to dissipate as it shifts to the northeast. At the
surface, Atlantic High pressure will steer a disturbance over
the Southeast U.S., along with a coastal Low. It`ll slowly
direct them north as time progresses, near and then off the
coastal Carolinas. Deep moisture will persist with PWATs above
2", which is well above normal. Likewise, the deterministic
models point towards numerous to widespread showers across our
area during the day. Again, there will be embedded convection.
But it shouldn`t be as widespread or intense due to less than
ideal instability. As the system moves offshore in the evening
and overnight, it`ll drag most of the rainfall with it. Showers
will dissipate from our far inland counties in the evening,
trending lower towards our coast well after midnight. But it`s
still too early to tell if any areas will be completely rain-
free overnight. QPF will still have a large gradient, ranging
from about 0.25" across far inland counties, rapidly rising
closer to the coast where up to 1" is possible, with locally
higher amounts. High temperatures will be around 80 degrees,
held down by all of the showers. Lows will be mild, in the
mid/upper 60s far inland, to the low/mid 70s near the coast.

Friday: Zonal flow will try to prevail in the mid-levels. The
coastal Low will be off the Carolina coast in the morning, and
quickly moving away as time progresses. Then, a cold front will
approach from the northwest late in the day. However, it won`t
make it to our area during this time period. Models point to
isolated showers in the morning, followed by scattered
convection in the afternoon, aided by the sea breeze. There are
hints that instability and the associated storms could be more
intense than previous days. But this aspect of the forecast will
need to be refined. Highs will be in the upper 80s to lower
90s, except cooler at the beaches due to the sea breeze.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
The mid-levels will consist of WNW flow Friday night. It`ll
transition to longwave troughing on Saturday, with the trough
becoming stronger and more amplified along the eastern half of
the U.S. Sunday and Monday. A cold front will slowly approach
from the northwest over the weekend, but pass to our north. All
of this will yield diurnal convection. High temperatures will be
above normal over the weekend, generally in the 90s.

&&

.AVIATION /10Z TUESDAY THROUGH SATURDAY/...
03/12z TAF Discussion:
KCHS/KJZI/KSAV: VFR will prevail for much of the 12z TAF period.
The risk for MVFR cigs and shower activity will increase after
08z at KSAV. VCSH was highlighted for now.

Extended Aviation Outlook: A disturbance and coastal Low will
bring flight restrictions through Thursday night. Diurnal
convection could bring brief flight restrictions Friday and
Saturday.

&&

.MARINE...
Through Tonight: Winds will begin to increase later this
afternoon into tonight as weak low pressure approaches from the
south. Winds 15-20 kt will be common with seas building to 3-5
ft tonight. It is unclear is frequent gusts to 25 kt will occur
as much will depend on how how quickly and how strong low
pressure becomes as it moves along the coast. A Small Craft
Advisory may eventually be needed.

Wednesday: High pressure will be off the Outer Banks of NC in the
morning, shifting a little further offshore as time progresses.
Meanwhile, the disturbance over FL and weak coastal Low will slowly
move to the north, over our area. E winds will be elevated during
the day, causing seas to build as well. We`ll need a Small Craft
Advisory for our GA waters beyond 20 nm and maybe even some of the
waters within 20 nm. Winds should ease overnight, but seas should
take a little longer to subside.

Thursday through Saturday: The coastal Low will shift north,
moving out of our area by Friday. A front will then pass to our
north over the weekend. Expect SW winds to ease, followed by a
more typical summertime wind pattern. Seas will also trend
lower.

Rip Currents:
Today: The combination of building seas and onshore flow should
favor the development of rip currents along the Georgia beaches
today

Wednesday: The combination of elevated onshore winds and a 3-4
ft wave near 7 seconds will generate building surf and a stronger
longshore current. This will lead to a Moderate Risk of rip
currents at all of our beaches.

Thursday: Given the aforementioned conditions, it`s possible we may
need a High Risk for our entire coast.

&&

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

&&

$$