612
FXUS62 KCHS 011848
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
248 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 TONIGHT/...
A busy afternoon and evening is expected. KCLX reflectivity
data show showers/tstms continue to slowly expand in coverage
along the coast with the most concentrated area occurring
across Berkeley County into central and upper Charleston County.
01/18z mesoanalysis placed the southward moving cold front just
north of the Santee River which is on target to meander south into
the Charleston Tri-County over the next few hours. 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 for all but the Tattnall to Allendale corridor until 9 PM
EDT.

The near term flash flood threat looks to concentrate into two
areas through 6 PM. 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 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 SUNDAY/...
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 /18Z MONDAY 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:




&&

.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>045-047>052.
MARINE...None.

&&

$$