Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 190528
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
128 AM EDT Sat Aug 19 2017

.SYNOPSIS...
Atlantic high pressure will remain in control through early
next week. A cold front may affect the area during the middle
of next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Very subtle isentropic ascent plus the proximity to a
deformation zone near the coast will produce scattered
stratocumulus clouds around 6-7K ft through the rest of the
night. Nocturnal convection could form closer to daybreak, but
the best convergence/instability will stay offshore, so only 10%
PoP`s or less over land areas through 6 am. temps will struggle
to dip below 870F in many places, and in fact some of the
barrier islands and downtown Charleston (unless they receive
isolated convection) will only reach 80-82F with breezy winds
from off to ocean to persist.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH MONDAY/...
A broad upper ridge will remain across the southeast United
States through the weekend, maintaining hot and muggy
conditions. A decent mid-level cap and weak afternoon sea
breeze will only allow isolated afternoon showers and tstms to
develop. Slightly higher high temps will be inland while the
highest dewpoints will be closer to the coast. The result will
be heat index values topping out 103-107F both days.

On Monday, the broad 500 mb ridge will persist across the
southeast United States and into the western and central
Atlantic. However, both the GFS and ECMWF now feature a weak
tropical wave (currently north of the Bahamas) drifting slowly
WNW toward the area. There are no signs of tropical development
of this wave, though it is expected to spread increasing
Atlantic moisture into the area Monday afternoon. This may yield
a modest increase in potential afternoon showers and tstms.
Additionally, sky cover may be somewhat greater Monday due to
greater mid and high level moisture. Highs will be in the lower
90s with heat indices 100-103F.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Very strong upper ridging will prevail into Tuesday before a trough
and cold front move in for the middle to latter portion of the week.
This will lead to increasingly unsettled weather toward mid week,
especially Thursday as the front moves into the area. Temperatures
should remain above normal through the period, except possibly
Thursday depending on the location of the front.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR with no concerns through about 16-18Z Saturday, before
isolated to scattered SHRA/TSRA develops on the sea breeze. This
boundary will be near both KCHS and KSAV from around 19-23Z,
and it is during this time that brief flight restrictions can
occur. For now VCTS with CB clouds will suffice at both
terminals during the mid afternoon through early evening.

Extended Aviation Outlook: Main concern through Wednesday is
showers and thunderstorms, mainly each afternoon/early evening.

&&

.MARINE...
Tonight: Winds/seas are expected to remain below Small Craft
Advisory levels, but there should be a fair pressure gradient and
nocturnal surge over the waters between a trough of low pressure
inland and high pressure offshore. In general, south-southwest winds
will peak near 15-20 kts, highest in South Carolina waters where
a few gusts to 25 kt can occur. Seas will average 2-4 ft.


Saturday through Wednesday: The coastal waters will remain
between an inland trough and offshore high pressure through
Saturday night which will keep a tighter than normal pressure
gradient in place. Winds could push 20 knots at times but this
is just below Advisory levels. A weakening cold front will then
approach early next week but likely stall out and never make it
through the area with winds generally remaining 15 knots or
less. Seas will mostly be 4 feet or less, highest near the Gulf
Stream.

&&

.TIDES/COASTAL FLOODING...
Astronomical influences will lead to a round of elevated tides
into early next week. Only small tidal departures are necessary
and we could approach shallow coastal flooding levels with the
evening high tides, mainly Sunday through Tuesday along the SC
coast.

&&

.CLIMATE...
Record high minimums for 18 August...
KCHS 78/2010...preliminary low for Friday was 80.
KCXM 82/1998
KSAV 78/2010

Record High minimums for 19 August...
KCHS 79/2010
KCXM 81/2009
KSAV 79/1878

&&

.EQUIPMENT...
The temperature and dew point sensors at the Downtown Charleston
observation site (KCXM) could periodically fail. Technicians
are working to resolve the problem.

&&

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

&&

$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
CLIMATE...
EQUIPMENT...


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