Severe Thunderstorm Warning 121, NWS Charleston, SC

Area Forecast Discussion
National Weather Service Charleston SC
408 PM EDT Fri Aug 19 2022

.SYNOPSIS...
A stalled front will linger in the vicinity through the middle
of next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A mid-level trough will be located to our northwest, with a low
just to the west of the Great Lakes. Additionally, there will
be embedded impulses rounding the base of the trough, passing
overhead or just to our north. Higher up, the right entrance of
a jet streak will be passing just to our north. At the surface,
a stationary front will meander just inland of our coast, with
hints of a weak low located along the front to our north. All of
these features will provide a lot of lift across our area,
especially this evening. Flow is generally from the southwest,
which is ushering abundant moisture into the region. PWATs have
risen to ~2.25", which is well above the 90% for CHS for this
time of year. Models indicate numerous to widespread showers
with some thunderstorms developing/moving across our area during
the evening hours. The HREF continues to have lots of
precipitation with high probabilities of locally higher
amounts. However, the HRRR seems less enthusiastic, with less
rainfall/coverage. Likewise, the synoptic models all lean
towards much less rainfall/coverage. We kept the POPs
categorical as most locations should get something. The amounts
will be highly dependent on whether it's light/moderate showers
or heavy rain in thunderstorms, and how long they stay over the
same location. Steering winds are elevated, which is causing
these cells to move. So while they should be very efficient
rain-makers, they shouldn't stay in the same spot for very long.
As for the severe potential, high temperatures made it well
into the 80s, and the 90 degree mark in some locations. Hence,
SPC Mesoscale Analysis indicates MLCAPES up to 2,000-2,500 J/kg.
Effective bulk shear is decent, generally 30-35 kt. So it's not
out of the question we could have a severe storm or two with
marginally severe wind gusts. But the bigger threat is the
rainfall and the potential for flooding in low- lying and poorly
drained areas, especially areas that flooded yesterday or this
morning. All of the models indicate it gradually drying out from
west to east late this evening and overnight. Lows will be
around 70 degrees.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
On Saturday, the forecast area will remain between an amplified
trough over the Mid-West and the SW to NE axis of a Bermuda High.
This pattern will keep a sfc boundary generally stalled over the
forecast area. Weak west flow will likely keep the sea breeze pinned
to the coast through mid-day Saturday. However, the sea breeze
should start to push inland during the afternoon, likely supporting
the formation of scattered showers and thunderstorms.

Sunday into Monday, the H5 pattern will gradually become dominated
by the approach of a trough. The environment across the forecast
will continue to feature deep moisture and moderate instability.
Forecast soundings from the GFS indicates that LFC will become
rather low on Sunday, lowering to around 3 kft on Monday. Given the
approach of synoptic scale forcing, moderate instability, and low
LFC, convection should easily develop each afternoon and evening.
The forecast will feature likely to categorical PoPs for both Sunday
and Monday. Given the high coverage of showers and thunderstorms, it
is possible that heavy downpours could lead to localized heavy
rainfall. High temperatures are forecast to range from the upper 80s
across the SC Lowcountry to the low 90s across SE GA on Sunday.
Temperatures will cool on Monday, ranging from the low 80s inland to
the upper 80s near the coast.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
The H5 pattern is expected to feature a broad trough across the
forecast area through much of the long term, heights may start to
gradually rise on Friday. The environment will continue to feature
PW values of 2 in or higher, moderate CAPE, little to no afternoon
CIN. Models indicate that numerous showers and thunderstorms are
possible during the afternoon and evening, decreasing to isolated to
scattered by daybreak each day. Temperatures will not change much
through the period given the thick cloud cover and active
convection, with low to mid 80s in the afternoon and low to mid 70s
at night. Locally heavy rainfall will remain possible through the
long term.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
18Z TAFs: Showers and some thunderstorms will develop this
afternoon, bringing impacts into this evening. The TAF sites
should be VFR a majority of the time. But we expect there to be
periods of flight restrictions, probably as low as IFR due to
visibilities in TSRA. The time period this is most likely is
covered by TEMPO groups. But amendments may be needed based on
future radar trends. Conditions are expected to improve
overnight. Though, we can't rule out some low stratus or ground
fog.

Extended Aviation Outlook: Mainly VFR. Short-lived flight
restrictions will be possible due to showers and thunderstorms
each day.

&&

.MARINE...
Tonight: Showers and some thunderstorms are expected this
evening, with gusty winds possible. Otherwise, a stationary
front will be located just inland. The surface pressure gradient
is expected to remain relatively weak (outside of thunderstorms).
Expect S winds around 10 kt this evening, veering to the SW by
daybreak Saturday. Seas will be around 2 ft.

Saturday through Wednesday: South to southwest flow will continue
through the middle of next week. No Small Craft Advisory concerns
with winds 15 knots or less and seas 2-3 feet on average. However,
higher winds possible in and around any showers/thunderstorms that
impact the coastal waters.

&&

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

&&

NEAR TERM...
SHORT TERM...NED
LONG TERM...NED
AVIATION...NED
MARINE...NED

Hazardous Weather Outlook
National Weather Service Charleston SC
926 AM EDT Fri Aug 19 2022

GAZ087-088-099>101-114>119-137>141-SCZ040-042>045-047>052-201330-
Jenkins-Screven-Candler-Bulloch-Effingham-Tattnall-Evans-
Inland Bryan-Coastal Bryan-Inland Chatham-Coastal Chatham-Long-
Inland Liberty-Coastal Liberty-Inland McIntosh-Coastal McIntosh-
Allendale-Hampton-Inland Colleton-Dorchester-Inland Berkeley-
Inland Jasper-Beaufort-Coastal Colleton-Charleston-Coastal Jasper-
Tidal Berkeley-
926 AM EDT Fri Aug 19 2022

This Hazardous Weather Outlook is for southeast Georgia and
southeast South Carolina.

.DAY ONE...Today and tonight.

Heavy Rainfall: Showers and thunderstorms will develop this
afternoon and persist into the evening hours, leading to locally
heavy rainfall. This may lead to some flooding, especially in low-
lying and poorly drained areas.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

Heavy Rainfall: Considerable moisture will persist across the area
through early next week, resulting in showers and thunderstorms.
Periods of heavy rainfall are expected and flooding could occur,
especially in low-lying and poorly drained areas.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.

AMZ330-350-352-354-374-201330-
Charleston Harbor-
Waters from South Santee River to Edisto Beach SC out 20 NM-
Waters from Edisto Beach SC to Savannah GA out 20 NM-
Waters from Savannah GA to Altamaha Sound GA out 20 NM, including
Grays Reef National Marine Sanctuary-
Waters from Savannah GA to Altamaha Sound GA from 20 to 60 NM-
926 AM EDT Fri Aug 19 2022

This Hazardous Weather Outlook is for Atlantic coastal waters.

.DAY ONE...Today and tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter assistance is not anticipated at this time.