Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 191507
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1107 AM EDT Thu Sep 19 2019

.SYNOPSIS...
High pressure will provide noticeably cooler and drier
conditions today, then prevail through early next week. A cold
front could push into the region around the middle of next
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, the area will remain between a weak ridge of high
pressure to the west and a trough of low pressure over the Atlantic.
At the sfc, high pressure centered north of the region will continue
to wedge south into the area, bringing noticeably cooler and drier
conditions across Southeast South Carolina and much of Southeast
Georgia. Latest guidance suggests a few showers could develop
across coastal waters late this morning and early afternoon,
potentially drifting onshore in Southeast Georgia within a
northeast wind. Any showers should be light as the bulk of
moisture, characterized by PWATs around 1.0 inch, remains confined
to coastal Georgia and most southern locations near the Altamaha
River. Any convection persisting late this afternoon should
dissipate during the evening with the loss of diurnal heating.
Despite abundant sunshine, cold air advection into the region
will likely limit high temps to the upper 70s across the Tri-
County area and low/mid 80s south into Southeast Georgia.

Tonight: Sfc high pressure will continue across the forecast area as
mid-level ridge gradually builds over the region. Deep high pressure
centered west of the forecast area should yield mostly clear
conditions inland. Lingering instability over the nearshore
waters could support a few showers and greater cloud cover. Using
a blend of MOS, low temps are expected to dip into the upper
50s inland to around 70 degrees across the beaches.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Deep layered ridging will build from the west on Friday and then
blanket the forecast area over the weekend.

During Friday, the only feature of interest will be a weak shallow
coastal trough early in the day; transitioning inland south of the
Savannah River in the afternoon. There will also be a fairly quick
progression of the sea breeze in South GA. Moisture over southeast
GA remains shallow (mostly below 850 MB with the mid levels still
very dry. We maintained a slight chance POP along the coast early on
and then all GA areas along/south of I-16 in the afternoon. If any
measurable rains manage to fall, we suspect amounts would only
amount to few hundreds of an inch. Elsewhere, sunshine mixing with
periods of cumulus and stratocu with highs around 80 north to the
lower/mid 80s across GA.

The weekend will be dry with abundant sunshine, while expansive
surface high pressure centers from North GA to the Carolinas.
Scattered cu and stratocu will be most prevalent along coastal zones
with the onshore flow. Temps should be in the mid 80s coastal half
of the area with some upper 80s possible inland each afternoon.
Radiational cooling at night will be decent, lows around 60 inland
to the mid 60s coastal corridor.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
Deep layered ridging will persist into early Monday and then tend to
break down thereafter, before returning again late week. A stronger
mid-level short wave will pass well north of our region Monday night
but dry weather will persist. A weak cold front will settle over the
southeast states by mid week and perhaps linger in Thursday. Models
continue to show no significant chances for rainfall during the
medium range. Temps are expected to run above climo with some 90
degree highs returning for inland areas over the weekend into early
next week.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
VFR conditions will prevail at both CHS and SAV terminals through
12Z Friday. However, northeast winds could gust to around 20 kts
at both terminals this afternoon.

Extended Aviation Outlook: VFR conditions will prevail.

&&

.MARINE...
Today and Tonight: High pressure centered north of the area will
continue to wedge south across coastal waters today into tonight. A
fairly tight pressure gradient along the southern periphery of this
feature will likely lead to gusty northeast winds across the waters.
In general, wind speeds should peak in the 20-25 kt range. Long
period swell in combination with these gusty winds should also
support seas as high as 5-7 ft in nearshore waters and 7-10 ft in
offshore Georgia waters. Small Craft Advisories will be ongoing for
all waters outside the Charleston Harbor today and tonight. However,
winds should still gust to the 20-23 kt range for a few hours this
afternoon near the Charleston Harbor entrance.

High pressure to the north will build closer to the SC waters on
Friday while a strong low level gradient persists over the GA
Waters. SCA conditions are forecast all waters on Friday. The CHS
Harbor will likely be below SCA criteria. Onshore flow will then
weaken this weekend with a much weaker surface pressure gradient
forecast. Seas should gradually subside over offshore waters with
sub-SCA conditions expected early next week with winds lighter and
variable at times. We will watch for any advancing swells from
distant Tropical Cyclone Jerry.

Rip Currents: High risk of rip currents on all beaches through
Thursday evening due to strong northeast winds and at least a
2-3 ft/11 second period swell created by offshore Hurricane
Humberto. An elevated risk for rip currents may continue through
the weekend.

&&

.TIDES/COASTAL FLOODING...
Low chances for minor salt water flooding along the South Carolina
coast today during the midday high tide cycle.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
SC...High Risk for Rip Currents until 8 PM EDT this evening for
     SCZ048>051.
MARINE...Small Craft Advisory until 8 PM EDT Friday for AMZ350-352-354.
     Small Craft Advisory until 6 AM EDT Sunday for AMZ374.

&&

$$
NEAR TERM...DPB
SHORT TERM...
LONG TERM...
AVIATION...DPB
MARINE...DPB
TIDES/COASTAL FLOODING...


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