853
FXUS62 KCHS 071920
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
320 PM EDT Tue May 7 2024

.SYNOPSIS...
Atlantic high pressure will remain across the region through mid
week. A cold front will move through the area Friday bringing
cooler conditions heading into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Mid level short-wave ridge is poised just upstream this afternoon
with surface high pressure draped from the southeast CONUS/Florida
Peninsula into the Atlantic. Latest SPC mesoanalysis shows over 1500
to as much as in excess of 2000 J/kg MLCAPE across the forecast
area and minimal CINH. Despite that, Cu field across the region
is rather anemic...just a little congested along the sea breeze,
which shows up quite nicely on radar this afternoon.

Short-wave ridging will continue to build into the southeast
region this evening and overhead during the overnight hours.
Despite the rather flat Cu field, a few brief showers cannot be
completely ruled out late this afternoon/early evening and
nearly every HRRR run in recent hours continues to show something
kicking off along the sea breeze late day. Will see. Tempted to
totally remove precip chances for the remainder of the afternoon.
But given the decent instability and aforementioned CAM guidance,
we will leave the slight PoPs as-is at this juncture.

Otherwise, quiet conditions are anticipated tonight. Very mild
temperatures...by early May standards...with lows in the upper
60s to lower 70s and a little warmer near the coast.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Wednesday and Wednesday night: The upper ridge axis will shift
offshore and the upper pattern will flatten out a bit. At the
surface, subtropical high pressure will continue to extend westward
into the forecast area and drive southwest flow for much of the day.
Skies should remain mostly clear, with just a muted cumulus field
expected, and model soundings are definitely not supportive of any
diurnal convection. Therefore, we have kept the forecast dry. The
main story will be temperatures. Low-level thickness values will be
supportive of widespread low 90s, with a few mid 90s possible for
interior southeast Georgia. Daily record highs are definitely
in play (see Climate section below). Fortunately, dew points
should mix out pretty well which will keep heat index values
solidly below triple digits. Overnight, expect dry and mild
conditions with lows only falling into the upper 60s and low
70s.

Thursday through Friday: Forecast difficulty and potential impact
will increase for the Thursday and Friday time period. Thursday is
expected to begin with a cold front situated well upstream, back
across the mid Mississippi Valley and into the Southern Plains. The
first part of the day should be similar to the last few days with
high pressure still the main feature across the forecast area
leading to southwest flow and warm conditions. Some degree of
convection should be ongoing across east TN, western NC, north GA,
and northern AL. The forecast for the afternoon and evening will
hinge greatly on the strength, position, and timing of this upstream
convection and its possible downstream propagation to the
Southeast coast. This time period is now starting fall within
the hi-res model run window, and model solutions range from a
strong (likely severe) squall line progressing across the
forecast area in the afternoon and evening hours to little to no
convection at all (favoring timing more into Thursday night and
Friday). With temperatures warming again into the low to
possibly mid 90s, there could be moderate destabilization in the
presence of strengthening mid-level flow ahead of any potential
convective line Thursday afternoon and evening. Lapse rates
steepen and nearly unidirectional 0-6 km shear on the order of
40-50 knots could set the stage for a large hail and damaging
wind threat. The area remains within SPC`s Day 3 Slight Risk
area and we will continue to highlight the severe potential
despite the uncertainties discussed. The cold front isn`t
expected to clear the area until later on Friday, and until it
does we could see rounds of convection Thursday night and again
early Friday. Given increased cloud cover and the effects of
convection, Friday temperatures are expected to be cooler. Look
for highs in the low to mid 80s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
The cold front will push well offshore Friday night, followed by
high pressure for Saturday. A weak boundary will pass by Saturday
night, with more high pressure for Sunday. A nice airmass change is
expected Saturday, with dry conditions and highs right around
normal. A modest warm up for Sunday will bring temperatures back
above normal by a few degrees. The forecast becomes more uncertain
early next week as model guidance suggests that southern stream
energy could move across the Deep South along a residual boundary.
Conditions could end up becoming quite unsettled, or the bulk of the
rainfall and convection could slide south of the area.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Solid VFR conditions anticipated through Wednesday morning. A
few "heating of the day" showers are possible near KCHS/KJZI
this afternoon although chances are not high enough to warrant
inclusion in the forecast. Otherwise, southwest winds this
afternoon will trend southerly this afternoon as the sea breeze
slowly moves inland. Winds around 10 knots anticipated with a
few higher gusts.

Extended Aviation Outlook: Primarily VFR. Chances of showers and
thunderstorms will increase late Thursday through Friday.

&&

.MARINE...
South to southwest winds will remain locally enhanced along the
coast into early evening but will weaken some this evening as
the sea breeze circulation diminishes. Winds and seas will
remain below Small Craft Advisory criteria through tonight.

Wednesday through Sunday: High pressure positioned to the east of
the local waters will maintain moderate south to southwest flow on
Wednesday. Winds and seas will then start to pick up later on
Thursday as a cold front approaches from the west. The front will
then shift offshore Friday and Friday night. Portions of the waters
could experience marginal Small Craft Advisory conditions ahead of,
and immediately behind, the passing front. Conditions will then
improve through the weekend with winds and seas both remaining well
below advisory thresholds. Another forecast issue for the local
waters will be the potential for strong thunderstorms Thursday
evening through Friday afternoon. The timing of thunderstorms
remains unclear for this time, but any storms that do develop and
move across the waters will be capable of producing strong wind
gusts.

&&

.TIDES/COASTAL FLOODING...
The upcoming New Moon (May 8) and recent Perigee (May 5) will lead
to elevated astronomical tides over the next few days. Minor
coastal flooding is possible along Charleston and coastal
Colleton Counties, including Downtown Charleston, during the
evening high tides Tuesday through Thursday.

&&

.CLIMATE...

Record High Temperatures:
May 8:
KCHS: 93/1986
KSAV: 96/1986

May 9:
KCHS: 95/1963
KSAV: 95/1962

&&

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

&&

$$

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