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000
FXUS62 KCHS 261958
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
358 PM EDT Mon Jul 26 2021

.SYNOPSIS...
Weak low pressure will move onshore across southeast Georgia
this evening. A trough will then bring unsettled weather
through midweek. A weak front could drop into the region late
week and stall over the weekend.


&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Tonight: The surface low to our south will move onto land over
southeast Georgia this evening and begin to dissipate, leaving
us within a southeast to south flow around the far western
portion of the sub-tropical Atlantic ridge. Diurnally driven
convection will fade early on, before some nocturnal convection
that forms over the ocean makes a run for the shore overnight.
Coverage will wane from north to south with 40-50% PoPs
decreasing to 15-25% by the evening. Isolated showers and
thunderstorms will continue over the waters and across the
extreme southeast GA counties tonight, given that it`ll remain
unstable offshore. Southerly flow will begin to push convection
onshore once again after midnight when low-level convergence
strengthens. Coverage will increase toward daybreak as land
areas begin to destabilize fairly quickly, which is when we
have slight chance PoPs over the coastal counties.

There will be areas of low stratus and perhaps even some
isolated areas of patchy fog well west of I-95 early morning.
Models are showing the greatest potential just outside our
forecast area, and given that yesterday`s models over-
forecasted fog probabilities for last night, mention of fog has
been left out of the forecast.

Given the southeast synoptic flow and elevated dew points,
it`ll be a relatively warm and humid night. Lows will only
reach the mid to upper 70s, and around 80F in Downtown
Charleston/immediate coastline.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
A surface trough of low pressure will linger over the region through
midweek. Aloft, a broad trough will persist over the Northeast with
a large ridge over the Central U.S. Models indicate PWats will surge
to near or over 2.25 inches Tuesday into Wednesday, before gradually
decreasing Wednesday evening. These values are well above late July
climatology. With aid from weak shortwave energy, scattered to
numerous showers and thunderstorms are expected to develop. Coverage
will peak in the afternoons when instability is greatest, but
activity will be possible just about any time including overnight.

Given the deep moisture and fairly weak storm motions, there will be
a threat for locally heavy rainfall which is backed up by some
probabilistic guidance including the HREF. Slow moving storms could
lead to minor flooding in low-lying and poor drainage areas. The
severe threat looks to be low overall, but a couple stronger to
possibly severe storms can`t be ruled out, with the main hazard
being isolated damaging wind gusts.

Moisture levels will be much lower on Thursday and with lack of
large scale forcing, shower/thunderstorm coverage is expected to be
less than previous days. Perhaps the more interesting forecast note
of the day will be the temperatures. Highs are expected to average
in the low to mid 90s, highest inland, with heat indices around
105.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Surface troughing will linger inland on Friday before a weak front
drops into the region and possibly stalls in the vicinity over the
weekend. Mainly diurnally driven showers and thunderstorms are
possible each day. Hot temperatures and higher relative humidity
values could lead to heat indices of 105-110. Given our heat
advisory criteria of 110, we will need to monitor the potential for
Heat Advisories, especially on Friday.

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
The approach of a weak surface low from the south and an associated
inverted trough will continue to impact the terminals through the
evening. Scattered showers with perhaps some thunder will be within
the vicinity of the terminals at times, keeping VCSH/VCTS through
the evening. Should any direct impacts occur, brief and sporadic
flight restrictions would take place, potentially dropping as low as
IFR with brief, low vsbys. Low stratus will begin to move in near
the end of the TAF period, along with isolated showers. Flight
restrictions will again be likely within showers, but details have
left out of the current TAF issuance.

KJZI has been reporting sky conditions since this morning`s outage
and AMD NOT SKED has been removed from the 18Z TAF.

Extended Aviation Outlook: Flight restrictions are possible in
showers and thunderstorms through Wednesday.

&&

.MARINE...
Tonight: The weak surface low that is just to our south will
move onshore southeast Georgia this evening. The marine
community will be situated on the western periphery of the sub-
tropical ridge, producing south to southeast winds of 15 kt or
less. Seas will average 2 to 4 feet, with isolated to scattered
thunderstorms continuing over the waters through the night.

Tuesday through Saturday: Generally south to southwest winds
expected through late week. Winds are expected to remain below Small
Craft Advisory criteria, although speeds on Friday could be in the
15-20 knot range as the pressure gradient tightens. Seas will
average 2-4 feet.

&&

.TIDES/COASTAL FLOODING...
The chances for minor salt water inundation in the Downtown
Charleston area during tonight`s high tide has diminished. As
winds become more unfavorable and astronomical tides continue to
decrease, the recent series of Coastal Flood Advisories has
ended, at least for the near future.

&&

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

&&

$$

NEAR TERM...BRM
SHORT TERM...ETM
LONG TERM...ETM
AVIATION...BRM/ETM
MARINE...BRM/ETM
TIDES/COASTAL FLOODING...