National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 130537
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
137 AM EDT Thu May 13 2021

.SYNOPSIS...
High pressure will build into the area tonight as cold front
becomes nearly stationary near the northern shore of the Gulf
of Mexico. A series of weak low pressure areas will track along
the stationary front well south of the region through Thursday.
High pressure will expand into the region late in the week and
likely persist into early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
-- Changed Discussion --
As of 130 AM: KCLX detected a ragged band of light returns over
the CWA, associated with drizzle. Based on the radar trends,
drizzle should largely end over the next couple of hours. In
addition, wind observations near the lake have remain well below
Lake Wind Advisory (LWA) criteria, based on the forecast winds
the LWA has been cancelled. Otherwise, the forecast appears on
track with temperature expected to remain generally steady
through the rest of the night.

Previous Discussion:
Tonight: High pressure will spread across the region behind a cold
front now south of the area. As this process continues to unfold,
chances of precip will become considerably lower as the bulk of mid-
lvl moisture is scoured out of the area. However, a fair amount
of low-lvl moisture will linger through the night, helping produce
bouts of light rain and/or mainly drizzle. Low stratus and lower
vsbys should also accompany drizzle, but lowest vsbys should be
temporary. Cold air advection across the region associated with
a north-northeast sfc wind favors noticeably cooler sfc temps
than the previous night. In general, temps should dip into the
mid-upper 40s inland to low-mid 50s closer to the coast late
tonight. This is around 10-12 degrees below normal.

Lake winds: Gusty north-northeast winds will persist over Lake
Moultrie tonight as high pressure builds in from the northwest
behind a departing cold front. A Lake Wind Advisory remains in
effect through tonight.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/...
Thursday and Thursday night: a surface cold front is expected to be
stalled well south of the region as high pressure builds well to the
north over the OH River Valley. Models all show that the best deep
layer moisture will slowly move south of the region, and have
therefore continued to trend PoPs down from low chance to slight
chance through the morning and into the afternoon. Any precip. is
expected to be in the form of light showers, with little/no thunder.
Model guidance continues to indicate that high temperatures will be
cool for this time of year, in the mid to upper 60s, potentially
flirting with record low max values. For Thursday night, there could
still be enough deep layer moisture over the eastern third of the
area for a slight chance for showers, but precip. chances are
expected to drop off completely before midnight. Lows will be cool,
ranging from the upper 40s well inland, to the lower to mid 50s else
where.

Friday and Saturday: An upper level trough will still be centered
north of the area through Friday, then upper heights are expected to
begin rising slowly by Saturday. At the surface, high pressure will
be north of the region on Friday, shifting to off the mid Atlantic
coast by Saturday. This pattern will keep generally low level
northeast winds on Friday, becoming light and variable on Saturday
as the pressure gradient becomes very light. Temperatures are
expected to continue below normal, with a gradual warming through
the period. Highs in the lower to mid 70s on Friday, warming to the
mid to upper 70s on Saturday. Lows Friday night in the mid 40s to
around 50s inland, and the lower to mid 50s near the coast.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Through Monday, models continue to show a relatively dry/quiet
period. A broad upper ridge is expected to develop near or just to
the west of the region with surface high pressure situated well to
the northeast. Temperatures will start off below normal, likely
moderating back closer to normal by Monday.

By Tuesday and Wednesday, models begin to indicate that better deep
layer moisture will return as the mid/upper level ridge tries to
retrograde/build further west. Have kept slight chance PoPs for the
western zones for Tuesday and all zones by Wednesday as low level
southeast flow and some return of instability should allow for
the potential for mainly afternoon showers/thunderstorms.
Temperatures expected to be close to seasonal normals.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Prior to the 6Z TAfs, IR satellite indicated that the clearing
line was located generally over the Fall Line of SC and GA.
Based on the satellite trends, restrictive ceilings and patchy
drizzle may linger over the terminals until daybreak, possibly
into the early daylight hours at KSAV. The rest of the period
should feature steady NE winds and VFR conditions.

Extended Aviation Outlook: Friday through Monday: Expect VFR to
prevail.
-- End Changed Discussion --

&&

.MARINE...
Tonight: A tight pressure gradient between high pressure building
south behind a cold front and low pressure exiting further offshore
will favor gusty north-northeast winds and elevated seas across all
local waters through the night. Small Craft Advisories will remain
in place for all waters with winds gusting upwards to 25-30 kt and
seas building as high as 6-8 ft (highest seas across offshore
Georgia waters late).

Thursday and Friday: the waters will be between high pressure to the
north and a stalled front and lower pressure well to the south. This
pattern is expected to maintain a moderately strong pressure
gradient and SCA conditions. Expect northeast winds of 15 to 20 kts,
with gusts of 25+ kts, and seas generally 4 to 6 ft within 20 nm,
and 6 to 8 ft beyond 20 nm.

Later Friday through Monday: Winds and seas are expected to
gradually decrease, with no highlights expected after Saturday
evening. Northeast winds through Saturday, will likely veer to east
and then southeast Sunday and Monday.

Rip currents: An elevated risk of rip currents is possible through
late week due to gusty northeast winds.

&&

.CLIMATE...
An unseasonably cool air mass, accompanied by clouds and showers,
could challenge the following record low maximum temperatures
Thursday 5/13.

CHS
5/13 68 (1996)

CXM
5/13 68 (1996)

SAV
5/13 69 (1928)

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
GA...None.
SC...None.
MARINE...Small Craft Advisory until 5 PM EDT this afternoon for AMZ330.
     Small Craft Advisory until 10 PM EDT Friday for AMZ350-352-354.
     Small Craft Advisory until 10 PM EDT Saturday for AMZ374.
-- End Changed Discussion --

&&

$$

NEAR TERM...NED
SHORT TERM...RFM
LONG TERM...RFM
AVIATION...NED/RFM
MARINE...DPB/RFM
CLIMATE...