Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 261801
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
201 PM EDT Wed Jul 26 2017

.SYNOPSIS...
Broad low pressure will remain across far southern Southeast
Georgia through tonight. A weak cold front will stall over or
near Southeast South Carolina through Thursday. Another cold
front will move into the area this weekend, then likely stall
just offshore into early next week.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Wednesday afternoon: An upper low centered centered over
southern GA, associated weak forcing for ascent, deep layered
moisture and various boundaries will continue to support
showers/thunderstorms in many areas for the next few hours.
Across far northern counties, POPs will actually decrease as the
afternoon progresses, while likely/categorical POPs will prevail
elsewhere. best coverage of showers/thunderstorms will reside
along/south of I-16, closest to the upper low. Across far
southern counties, especially Liberty, Long and McIntosh, slow
thunderstorm movement and PWATs well over 2 inches could support
localized flooding.

Later this afternoon, POPs will generally diminish from north to
south, although showers/thunderstorms could persist into tonight
well south of I-16.

Meanwhile, we adjusted afternoon temperatures downward in most
locations to account for precipitation and cloud cover.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
Tonight: Convection will quickly diminish this evening with the
loss of insolation. However, the risk for isolated convection
will linger through the night given the warm, moist airmass that
will remain in place. Increasing coastal convergence along the
coastal waters and beaches could support more scattered activity
early Sunday morning, but he bulk of this convection should
remain over the coastal waters. Lows will range from the lower
70s inland to the upper 70s at the beaches.

Thursday: What`s left of a stationary front will slowly drift
offshore during the day. However, lingering moisture and the
position of the mid-lvl low should support chances of showers and
thunderstorms over much of the area. The bulk of precip activity
should trend toward the coast of Southeast Georgia late in the day,
where numerous showers/thunderstorms are possible while the mid-lvl
low slowly meanders and weakens near the Southeast coast. Cloud
cover will limit max temps to around 90 degrees, warmest inland.
Showers and thunderstorms are expected to taper off during the
overnight period. Low temps should range in the mid 70s.

Friday: Conditions should be slightly drier to start off the weekend
while the area sees a transition of low pressure weakening/shifting
offshore and stronger low pressure developing inland. However, a
southwest flow will likely begin to advect deep moisture into the
region well ahead of a cold front approaching from the north and
northwest late. Deepening moisture along with temps returning to the
lower 90s support chances of showers/thunderstorms during the
afternoon/evening hours. Shower/thunderstorm coverage could very
well increase from the northwest Friday night as the cold front
quickly shifts toward the Southeast United States. Wind fields also
suggest upstream convection could be more organized than previous
days, making a run toward the area late. Given the timing of the
event during overnight hours, the overall severe weather risk
remains low. Overnight lows should remain mild under clouds, ranging
in the mid/upper 70s.

Saturday: A cold front will shift over the region this weekend,
supporting numerous showers/thunderstorms within deep moisture
characterized by PWATs near 2.5 inches and moderate instability.
Isentropic lift ahead of the front could produce a fair amount of
clouds and showers before peak heating, limiting stronger afternoon
convection. However, wind fields will be slightly enhanced ahead of
cold fropa, suggesting the possibility of a few stronger
thunderstorms should sufficient sfc heating occur. Given the setup,
the greater threat for stronger thunderstorms would be over parts of
Southeast Georgia where sfc heating is greatest before the arrival
of the cold front. High PWATs also suggest the potential for heavy
rainfall with afternoon/evening thunderstorms.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Deep moisture characterized by PWATS up to 2.0 inches will persist
over the Southeast United States Saturday night into Sunday while a
cold front slowly progresses south and eventually stalls just
offshore and/or south of the region. The pattern becomes more
difficult to predict early next week with some guidance suggesting
that the stationary front drifts back near the Southeast coast or
low pressure develops along it and lifts northeast along/near the
Southeast coast. Regardless of the outcome, it appears chances of
showers/thunderstorms will be possible early next week with greatest
precip coverage anticipated near coastal areas.

Temps will generally be a few degrees below normal this weekend and
early next week given extensive cloud cover and precip activity. In
general, temps should peak in the mid/upper 80s. Overnight lows will
range in the low/mid 70s.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Thunderstorms will occasionally produce flight restrictions and
local hazards at KSAV this afternoon. VFR conditions are then
forecast for the balance of the 18Z TAF period. However, lower
ceilings could occur due to rich low level moisture especially
at KSAV. Thunderstorms are expected to redevelop over/near KSAV
Thursday morning.

Extended Aviation Outlook: Brief flight restrictions are possible
into Thursday as low pressure shifts offshore. VFR conditions should
prevail late Thursday into Friday. Higher chances of flight
restrictions should return late Friday through Sunday as showers and
thunderstorms occur with a cold front that slowly progresses over
the region.

&&

.MARINE...
This afternoon: A weak pressure pattern and thunderstorms will
promote variable winds. Eventually, a weak surface boundary
should push south of the waters, producing more uniform E/SE
winds 10 kt or less later this afternoon. Seas of 1-2 ft will
prevail. Locally heavy rains will produce vsbys less than 1/2 nm
at times through this afternoon.

Tonight: East winds 10 kt or less will prevail, accompanied
by seas 1-3 ft. Thunderstorms could produce locally hazardous
conditions tonight.

Thursday through Monday: A mid-lvl low will gradually shift over the
coastal waters and weaken Thursday. The waters should then remain
between high pressure well offshore and a strengthening trough of
low pressure inland through Friday. A cold front will approach from
the north/northwest Friday night and shift over the coastal waters
Saturday and Sunday before stalling over or just south of Georgia
waters. At least chances of showers and thunderstorms are forecast
over the waters through late week, while numerous showers and
thunderstorms are possible with cold fropa Saturday and Sunday. The
front could drift back over coastal waters early next week,
producing additional showers and thunderstorms. Wind/sea conditions
are expected to remain below Small Craft Advisory levels through the
period. However, a southwest/south flow could gust around 20 kts
Friday afternoon into early Saturday until cold fropa occurs. Seas
will gradually build from 2-3 ft to 3-4 ft this weekend and early
next week.

&&

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

&&

$$
NEAR TERM...SPR
SHORT TERM...
LONG TERM...
AVIATION...SPR
MARINE...SPR



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