605
FXUS62 KCHS 162013
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
413 PM EDT Tue Jul 16 2024

.SYNOPSIS...
High pressure will persist offshore, while a weak trough
resides inland through mid week. A cold front will approach the
region late week and likely stall nearby, before high pressure
returns next week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
19Z SPC mesoanalysis roughly 1500-2500K J/Kg MLCAPE across the
forecast, minimal CINH and DCAPE 800-1000 J/Kg. Decent coverage
of thunderstorms is underway a county or two west of the
forecast area from the Midlands down through east-central
Georgia. Finally getting congested Cu and some convection to go
roughly along a line from upper Berkeley and Dorchester counties
down into southeast Georgia within the last hour. Notable
outflow boundary from convection toward JAX is spreading
northward toward Long/McIntosh counties which might trigger some
additional convection shortly.

Tonight: Monitoring convective trends. It still appears that
most convection will be impacting areas along of the I-95
corridor through early evening as well as south of I-16 in
Georgia with that northward propagating outflow. Per LSR
reports/obs and office collaboration, upstream storms have been
overproducing to some extent and storms will need to be watched
for the next few hours. Thereafter, convection will gradually
diminish through the evening and rain-free conditions
prevailing after midnight. It will remain warm and humid with
lows from the mid 70s well inland to the lower 80s at the
beaches and Downtown Charleston.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Aloft, a ridge will extend across the western Atlantic mid-late week
while a broad trough shifts across the Great Lakes region and toward
the Northeast. Ahead of the mid-upper trough, the pattern will
remain more summerlike in nature, with an inland sfc trough across
the Midlands/Upstate and sfc high pressure extending across the
local area from the Atlantic. As a result, scattered to potentially
numerous showers and thunderstorms are possible Wednesday and
Thursday afternoons, initially with a sea breeze circulation that
shifts inland, then potentially followed by convection developing
inland and drifting toward western most zones, before waning after
sunset due to diurnal heat loss (instability) and a lack of stronger
shear in place. A few thunderstorms could become strong and/or
marginally severe each afternoon into early evening, but should
remain pulse type in nature with gusty winds and brief/localized
heavy rainfall as PWATs slowly nudge above 2.0 inches and storm
motion remains slow. By Friday, a cold front is progged to approach
the region from the west and potentially stall across the local area
to start off the weekend. The combination of moderate instability,
2+ inch PWATS and slightly stronger forcing locally with the nearby
front should result in an uptick of shower/thunderstorm coverage
across Southeast South Carolina and Southeast Georgia, with numerous
to widespread precip coverage now in place in the latest forecast.
Although shear remains weak, clusters of thunderstorms could become
strong and/or severe with gusty winds and isolated heavy rainfall
possible.

Outside shower and thunderstorm activity, conditions are expected to
remain hot and humid each afternoon. Heat Index values on Wednesday
and Thursday should reach 105-107 across many areas, while some
locations potentially reach at or above 108. Heat Advisories could
be required for portions of the local area either day, but
convection could hinder temperatures from reaching their full
potential. Friday high temperatures should peak in the low-mid 90s,
but higher surface dewpts ahead of the front could lead to higher
Heat Index values before more greater precip coverage arrives. A
Heat Advisory could eventually be needed this day as well for areas
that don`t see ample low-lvl mixing out of sfc dewpts, especially if
convection starts later than anticipated. Overnight low temperatures
will provide little relief, only dipping into the mid 70s inland and
upper 70s to around 80 along the coast. Record high minimum
temperatures could be challenged at all three of the climate sites,
see the Climate section for more details.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Broad troughing aloft will prevail this weekend, with high pressure
extending across the Southeast United States from the Atlantic early
next week. At the surface, a front will approach, then linger across
the Carolinas through the weekend, yielding higher PWATs and
unsettled weather conditions. Between lingering forcing from the
nearby front and an afternoon sea breeze circulation, scattered to
numerous showers/thunderstorms are possible each afternoon. Guidance
continues to be rather bullish with PoPs through the long term
period, so the current forecast maintains chance to likely PoPs
through Thursday, still above climatology. By the weekend, the
front/stalled boundary along with ample moisture justifies slightly
higher precip chances with numerous to potentially widespread
showers and thunderstorms this weekend. With above normal
precipitation chances and increased cloud cover through the period,
temperatures should return to near normal, or even slightly below
normal through the weekend.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
16/18z TAF Discussion:
KCHS/KJZI/KSAV: VFR for much of the period through 17/18z. There
remains is a risk for afternoon showers/storms this afternoon
although nothing has developed near the local terminals thus
far. KSAV may still have the best shot for direct impacts from
convection late in the afternoon with lower chances at
KCHS/KJZI. Forecast has maintained VCTS and TEMPO for TS at KSAV
afternoon 22Z. But confidence is on the lower side.

Extended Aviation Outlook: Scattered to numerous showers and
thunderstorms will likely produce at least TEMPO flight restrictions
at CHS/JZI/SAV terminals during afternoon/early evening hours mid to
late week, especially as a front potentially stalls nearby late week.

&&

.MARINE...
Tonight: Another modest noctural surge is expected, especially
for the South Carolina waters north of the Savannah River
Entrance. Winds will range from 15-20 kt in the South Santee-
Edisto nearshore leg to 10-15 kt with gusts to 20 kt over both
Georgia marine zones. Winds will remains somewhat tempered in
the Charleston Harbor, but should still hold in the 10-15 kt
range. Seas will average 2-4 ft.

Wednesday through Saturday: High pressure will prevail across the
western Atlantic while a cold front approaches the region from the
northwest late week, gradually pinching the pressure gradient
between these two features along the Southeast Coast. Latest
guidance suggests gusty south-southwest winds across local waters on
Wednesday as 1000 mb geostrophic winds near 40 kts traverses the
area during afternoon and evening hours. Overall, conditions are
expected to remain below Small Craft Advisory levels through late
week given the warm air advection regime, but winds could briefly
peak near 25 kt Wednesday afternoon and/or night, mainly across
South Carolina nearshore waters. Otherwise, southerly winds top out
near 10-15 kt each day with slightly higher gusts along the coast
where afternoon sea breeze circulations develop, then shift inland.
Seas should average between 3-4 ft.

Rip Currents: Gusty onshore winds along with 2 ft swell every 8
seconds should lead to an elevated risk of rip currents Wednesday
afternoon. Given recent reports of rip currents along southeast
Georgia beaches along with slightly more favorable conditions north
across southeast South Carolina beaches, a Moderate Risk for rip
currents will be in place for all beaches Wednesday.

&&

.CLIMATE...
Record High Minimum Temperatures:

July 16:
KCHS: 78/2023
KCXM: 82/2021
KSAV: 82/1883

July 17:
KCHS: 78/2023
KCXM: 82/2021
KSAV: 80/1883

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Heat Advisory until 7 PM EDT this evening for GAZ116>119-
     138>141.
SC...Heat Advisory until 7 PM EDT this evening for SCZ043>045-
     047>052.
MARINE...None.

&&

$$

NEAR TERM...Adam
SHORT TERM...DPB
LONG TERM...DPB
AVIATION...Adam/DPB
MARINE...Adam/DPB