815
FXUS62 KCHS 012235
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
635 PM EDT Mon Jul 1 2024

.SYNOPSIS...
A cold front will impact the area tonight into early Tuesday
before dissipating offshore. A hot and humid air mass will
build over the region during the latter half of the week. By
Monday, a weak cold front may reach coastal Georgia and South
Carolina.

&&

.NEAR TERM /THROUGH TUESDAY/...
A quick forecast update to remove Berkeley and Dorchester
Counties from the Flood Watch. In addition, based on radar
trends and latest runs of the HRRR, hourly PoPs and Wx were
adjusted to reflect the timing of the front and outflow
boundaries. Temperatures were also aligned with recent
observations.

Impressive deep-layer moisture and moderate mixed-layer
instability are in place along/south of the front. As surface
moisture convergence increases and the front begins to zipper
line down the weak sea breeze noted along the coast, expect
showers/tstms to expand in coverage with an increase in rainfall
rates. With PWATs nearing 2.50 at times, hourly rainfall rates
near 3 in/hr look reasonable. Earlier this afternoon,
showers/tstms produced about 2 inches of rain in less than 50
min at an unofficial mesonet site near Awendaw, SC. Storm totals
of 2-4 inches with localized amounts in excess of 6 inches look
on track. A Flood Watch remains in effect until 9 PM EDT.

The near term flash flood threat looks to concentrate into two
areas. The first being across eastern Berkeley and upper
Charleston counties south into the Charleston Metro Area
(including Downtown Charleston) where the latest WoFS Ens 90th%
of Accumulated Precip product shows pockets of 5-6".
Complicating things is heavy rain could falling as the 5 pm high
tide approaches. The second being near the Savannah Metro area
where convection developing near the city and working in from
the south could merge. Trends are being closely monitored in
both areas and Flood Advisories and/or Flash Flood Warnings
could eventually be needed.

Convection will wane this evening, but there are signals that
ana area of renewed convection could fire after midnight along
parts of the upper Georgia and far southern South Carolina coast
near the southward moving front. This scenario is well
supported by a number of the 01/12z CAMs. This activity could
pose a risk for additional flooding. Lows tonight will range
from around 70 well inland to the upper 70s and the beaches.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Tuesday: The surface pattern is expected to feature a stalled
boundary across SE GA with drier high pressure ridging across
the SC Lowcountry. The environment along and south of the front
should continue to feature deep instability and PW. The forecast
will feature scattered to numerous showers and thunderstorms
along and south of the front, keeping portions of inland SC dry.
Using a blend of MOS, high temperatures are forecast to range
in the mid to upper 80s.

Wednesday: Short term guidance indicates that a 595 dm ridge
will build over the Deep South and Southeast CONUS. At the sfc,
the center of high pressure will remain off the NE and middle
Atlantic states, resulting in ENE flow across the forecast area.
This pattern will support a sea breeze to develop, serving as a
focus for deep convection. Given the wide field of instability,
scattered to numerous showers and thunderstorms are forecast to
develop along the sea breeze. High temperatures are forecast to
range around 90 degrees. A few counties across extreme SE GA
may see heat index values peak between 100-105 degrees.

Independence Day: Mid-level ridge will build over the forecast
area on Thursday. Given high pressure over the western Atlantic,
a sea breeze may develop during the afternoon. However, GFS
forecast soundings indicate drier conditions compared to the
first half of the week. Forecast soundings indicate PW around
1.5 inches with an inversion centered at H65. This profile
indicates limited instability. The forecast will indicated
isolated showers and thunderstorms. High temperatures are
forecast to range between 90-95 degrees over dewpoints in the
low to mid 70s. Heat index values are forecast to peak between
100-105 degrees.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Friday through Sunday, the feature of concern will remain the
595 dm ridge over the region. The forecast area under the strong
ridge will feature high temperatures in the mid to upper 90s
each day. In addition, dewpoints will climb in the mid to upper
70s. The max heat index will range between 105 to 113 each
afternoon. This may result in either a Heat Advisory or a
Excessive Heat Warning late this week into early next week. The
forecast will indicate diurnal isolated to scattered showers and
thunderstorms each day.

On Monday, a weak front will approach from the west as the mid-
level ridge shifts over the western Atlantic. Conditions across
the forecast area will remain hot. However, storm coverage
should increase, bringing some relief from the heat.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
01/18z TAF Discussion:
KCHS/KJZI/KSAV: Showers/tstms are expected to expand in area
through the afternoon/evening as a cold front approaches.
Prevailing tstms will be highlighted from 20-23z at KCHS and
KJZI with TEMPO conditions as low as IFR at KCHS and LIFR at
KJZI. For KSAV, impacts may be a bit later, closer to 23-02z.
Amendments will be needed as convective trends become clearer.
The front should move south of KCHS/KJZI by 00z and KSAV by 05z
with VFR cigs filling in behind it. These will linger through
the night.

Extended Aviation Outlook: Brief flight restrictions are
possible in showers and thunderstorms, mainly in the afternoon
and evenings through the period.

&&

.MARINE...
Tonight: A cold front will work slowly south into the waters
tonight. Winds will shift to the northeast behind the front
with speeds reaching 15-20 kt in the South Santee-Edisto Beach
nearshore leg late. Otherwise, winds speeds will remain 15 kt or
less. Widespread showers/tstms could reduce vsbys to 1 NM or
less at times. A few strong convective wind gusts in excess of
35 kt could also occur. Seas will average 2-4 ft.

Tuesday through Saturday: Gusty ENE winds should develop across
the nearshore SC waters on Tuesday. The region will remain
between building high pressure and the front stalled to the
south. Gusts are forecast to remain around 20 kts with 3-4 ft
seas. Conditions are forecast to remain below Small Craft
Advisory criteria through the rest of the week. A weak pressure
gradient should support winds 15 knots or less and seas
averaging 2-3 ft.

&&

.CLIMATE...
Daily Rainfall Records for July 1:
KCHS: 2.66 set in 1948
KCXM: 1.64 set in 1966
KSAV: 2.76 set in 1871

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...Flood Watch until 9 PM EDT this evening for GAZ101-116>119-
     137>141.
SC...Flood Watch until 9 PM EDT this evening for SCZ042-043-047>052.
MARINE...None.

&&

$$

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