Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 230822
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
422 AM EDT Wed May 23 2018

.SYNOPSIS...
High pressure will remain to the east through Friday while a
trough of low pressure lingers to the west. Developing low
pressure over the Gulf of Mexico will slowly move north toward
the central Gulf Coast this weekend, possibly lingering through
early next week. This pattern will maintain higher than normal
rain chances across southeast South Carolina and southeast
Georgia.

&&

.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: Patchy low clouds and a few pockets of light fog were
developing inland areas on the edge of some deeper moisture across
central GA and the CSRA region. We think fog will be no more
than a localized issue as we near dawn. A few light showers may
develop to the west of I-95 close to sunrise but coverage also
on the spotty side. Temps will range from the upper 60s northern
inland areas to the lower 70s southern and coastal areas.

Today: A moist and unsettled weather pattern on tap today as
slightly deeper moisture nudges into the region while a warm
season surface ridge persists offshore close to 30N. Atlantic
ridging will maintain a modest feed of Atlantic moisture in the
lower levels. The forecast area can expect another round of
convective rains today, scattered to numerous showers with a
chance of diurnal tstms. Model soundings suggest a convective
temp around 80 degrees with some areas in the lower 80s. Deep
moisture between 850-500 MB along with a weak mid level vort and
some faint upper difluence look best along and west of I-95
this afternoon and this continues to be the region where we
maintained likely POPs. Sea breeze convergence and mid level
instability also appear to favor the area from Walterboro to
Moncks Corner but differential heating and mesoscale boundaries
should go a long way as to where concentrated pockets of
convective rains develop. With very low DCAPEs and warm mid
levels, we believe the risk of strong tstms is quite low. The
more pressing concern would have to be locally heavy downpours
due to slow cell motions and potential for clusters of multicell.

Tonight: Deeper moisture tends to linger overnight with little
overall change in the pattern. We maintained some 20-30 POPs
into the overnight with somewhat higher chances adjacent to the
CSRA and midlands and perhaps some of inland GA zones. Clouds
may thin later tonight but there could be more stratus once
again with some patchy fog where clouds become thinner. Lows
will be in the upper 60s to around 70 near the coast.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
A cold front near the Santee River should stall out Thursday morning
with Atlantic high pressure then prevailing through the end of the
week. By Saturday low pressure over the Gulf of Mexico should begin
moving north toward the central Gulf Coast. This pattern will keep a
tropical air mass in place with rain chances staying above normal,
mostly during the afternoon and evening each day. In general we
think the highest chances will be inland near the better moisture,
instability and forcing. Some spots will likely pick up over an inch
through the period. No significant flooding or severe weather is
anticipated at this time. Temperatures will generally be near to
above normal, especially lows.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
Not much pattern change late this week into early next week with
high pressure remaining to the east and low pressure over the Gulf
of Mexico moving north, most likely toward the north-central Gulf
Coast. The low could stall out near the Gulf Coast into early next
week. This pattern will mean the tropical air mass will remain in
place across southeast SC/GA leading to the continuation of higher
than normal rain chances, especially each afternoon/evening.
Temperatures should generally stay near to above normal.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
KCHS and KSAV should remain VFR through most of the 06Z cycle.
However, there is some risk for low stratus and/or ground fog at
both sites between 09Z and 12Z, and a chance for SHRA/TSRA in
the afternoon. Any potential for prolonged flight restrictions
remains too limited at this time to show in the forecast.

Extended Aviation Outlook: A persistent tropical air mass will lead
to higher than normal rain chances into early next week, mainly each
afternoon. Thunder chances will be low however given the limited
instability. Some restrictions will also be possible from morning
low clouds and/or fog as well.

&&

.MARINE...
Broad Atlantic high pressure will nose into the waters from
the western Atlantic through tonight. The forecast remains on
track with south to southwest flow northern waters and south to
southeast flow GA legs. Speeds mainly less than 15 kt with seas
in the 2-4 ft range, highest beyond 20 NM.

Thursday through Monday: The area will remain between low pressure
to the west and high pressure to the east. A tropical cyclone may
develop in the Gulf of Mexico later this week and track north toward
the north-central Gulf Coast and this should lead to an increasing
pressure gradient locally so we think winds and seas will be on an
upward trend as a result. Advisory conditions will be possible this
weekend into early next week, especially near the Gulf Stream.


&&

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

&&

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


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