Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 110220
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1020 PM EDT Mon May 10 2021

.SYNOPSIS...
A cold front will advance into the area Tuesday then will
gradually settle south of the area and stall Wednesday. A
series of low pressure areas will track along the stationary
front until late week. High pressure will expand into the
region this weekend into early next week.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Late this evening: Convection has become increasingly confined
to the far most interior portion of the forecast area, Jenkins
County. The line of showers and thunderstorms was actually
training for a while and produced some decent rainfall amounts.
Case in point, the USGS gage at Midville on the Ogeechee River
measured 0.66 inches of rain from 845 pm to 1000 pm. We could
still see showers and thunderstorms in this area, but overall,
convective activity will continue to dwindle over the next few
hours. Update rain chances to capture recent radar trends.
Otherwise, no significant changes.

Early this evening: Radar imagery shows that showers and
thunderstorms remain isolated and mainly favoring interior
southeast Georgia and southeast South Carolina. While there were
a few lightning strikes noted, most of the convection has been
quite weak. MLCAPE has topped out in the 500-1,000 J/kg range,
and updrafts just have haven`t been strong enough to loft
significant reflectivity high enough to produce decent storms.
We will likely remain in an environment supportive of isolated
showers across the area into the early morning hours, but no
significant impacts are expected. Lows are forecast to range in
the mid 60s inland to the upper 60s at the coast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Tuesday: A cold front will gradually settle into the region
Tuesday. progged moisture remains unimpressive, but the
combination of the advancing cold front and associated shortwave
trough aloft should be sufficient to support isolated/scattered
showers and a few thunderstorms, especially during the
afternoon. Across southern counties, where 0-6 km shear should
increase to 30-40 kts and MLCape values could increase to around
1500 j/kg, multicell thunderstorms could produce brief/isolated
episodes of damaging wind gusts and large hail. Thus, a
Marginal Risk for severe thunderstorms remains in place for
areas along/south of Interstate 16. However,
widespread/significant severe weather is not expected.

Tuesday night through Thursday: This period will feature
periods of wet weather and a transition to much cooler
temperatures. The cold front will continue to gradually settle
south through the area and should become essentially stationary
just south of the area late Wednesday/Wednesday night. Within
the associated baroclinic zone, a series of surface lows and
associated shortwave troughs aloft will cross the southeast
CONUS and will produce episodes of forcing for ascent/enhanced
moisture. Accordingly, PoPs increase Tuesday night, and at least
likely PoPs are in order most areas Wednesday. After this
initial surge of ascent/moisture, deeper moisture and likely
PoPs could shift into southern counties Wednesday night into
Thursday. Rainfall through Thursday should remain mostly
beneficial in light of a persistent dry period this spring, and
the probability for excessive rainfall/flooding remains low.
Also through this period, isolated thunderstorms could occur,
especially where elevated instability appears a bit stronger
across southern counties. However, surface based instability
will be pushed south of the region, and severe weather is not
expected.

Also of note, an unusually cool wedge of high pressure will
press into the region from the north, especially aided by
precipitation later Tuesday night through Thursday. High
temperatures could still recover into the 70s across southeast
Georgia Wednesday, but many locations will remain in the 60s
Wednesday, and some inland/northern counties could even dip into
the chilly upper 50s in showers Wednesday afternoon. Thursday,
temperatures should remain in the 60s at most locations. Please
refer to the climate section of this discussion for record low
maximum temperature information for Wednesday and Thursday.

Lake winds: Strengthening low-level winds and unusually cool
air flowing over the warmer waters of Lake Moultrie could
promote vigorous mixing/occasional wind gusts as high as 20-25
knots Wednesday through Thursday. We will assess the need for a
Lake Wind Advisory.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The parent upper trough will advance though the eastern CONUS
Thursday night into Friday, so isolated/scattered showers will
persist through this period. Then, after another cool day
Friday, drier high pressure will build over the region with a
gradual warming trend through the weekend.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
VFR conditions will prevail for much of the overnight, before
the chance for lowering ceilings increases late. A cold front
will approach from the north late tonight and is expected to
help push an area of MVFR or even IFR ceilings in as sunrise
Tuesday approaches. We have kept the forecast in the low MVFR
range, but the IFR potential is certainly there. MVFR ceilings
are timed into KCHS by 10z, and could stick around for much of
the morning. Ceilings will arrive later at KSAV, and are timed
for 12z there. We could see isolated to scattered showers and
thunderstorms Tuesday afternoon, but chances are too low to
include in the TAFs.

Extended Aviation Outlook: Flight restrictions possible Tuesday
into Friday, especially in precipitation.

&&

.MARINE...
Decent southwest winds have been occurring across northern
portions due to a low-level jet moving through. Winds in
Charleston Harbor, enhanced by a sea breeze, have occasionally
been gusting above 20 kt. Winds will gradually decrease through
this evening and overnight.

Tuesday through Saturday night: The primary concern is for a
period of Small Craft Advisory conditions late Tuesday night
though late week. A wedge of high pressure is expected to push a
surge of unseasonably cool air over the coastal waters,
starting late Tuesday night across AMZ350 then spreading south
with time Wednesday/Wednesday night. Once this regime becomes
established, enhanced low-level winds and marine layer
instability/mixing should support an extended period of Small
Craft Advisory winds/seas which could persist through Thursday
night or Friday.

Rip currents: An elevated risk of rip currents is possible on
Wednesday and Thursday due to gusty northeast winds.

&&

.CLIMATE...
An unseasonably cool air mass, accompanied by clouds and
showers, could challenge the following record low maximum
temperatures Wednesday 5/12 and Thursday 5/13.

CHS
5/12 69 (1963)
5/13 68 (1996)

CXM
5/12 65 (1907)
5/13 68 (1996)

SAV
5/12 69 (1885)
5/13 69 (1928)

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...BSH/SPR
MARINE...JRL/SPR
CLIMATE...CPM


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