Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240123
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
923 PM EDT Mon Oct 23 2017

.SYNOPSIS...
A cold front will push offshore tonight, then will be followed
by a stronger cold front late Tuesday and Tuesday night. High
pressure will then prevail into late week before another cold
front possibly affects the area this weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A cold front is located just west of the forecast area this
evening with the main band of showers and thunderstorms well
ahead of it around the SC Lowcountry/Pee Dee and extending south
into the Atlantic off the GA coast. The threat for severe storms
with damaging winds and/or tornadoes continues with this line,
mainly in Berkeley and Charleston Counties until 10 pm where a
Tornado Watch will remain in effect. Rain chances will
significantly diminish from west to east behind this main line
as much drier air filters in but some mainly light showers will
still be possible for several more hours mainly closer to the
coast until the front moves offshore later tonight. Strong cold
air advection behind the front will push temperatures into the
mid to upper 50s inland with lower to mid 60s at the coast.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
The initial cold front will be offshore by daybreak Tuesday,
with significantly drier air filtering in from the west.
However, with the lack of appreciable cold air advection and
downslope flow off the surface, high temps will still climb into
the mid/upper 70s.

The deep upper trough will push toward the Southeast late
Tuesday, pushing a secondary dry cold front through the region
Tuesday night. This will yield low temps Wednesday and Thursday
morning in the 40s with daytime highs in the mid/upper 60s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
After another unseasonably cool start on Friday, temperatures will
moderate back closer to normal Friday afternoon into the mid 70s as
high pressure centered to the north moves offshore. A coastal trough
could develop Friday night and bring some light showers to the area.
Some uncertainty exists however beyond that time as the models
differ with respect to another cold front approaching from the west
and low pressure to the south and east. For now we stayed pretty
close to the WPC`s guidance which has a cold frontal passage
Saturday night into Sunday. Temperatures will likely be near normal
through Saturday before falling below normal early next week,
possibly well below normal by Monday when some 30s are possible.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
Gusty southwest winds near 25 kt will be possible at KCHS until
about 02Z. The main band of showers and thunderstorms has pushed
east of the terms but some showers and MVFR or IFR ceilings are
still possible until about 05Z until drier air takes hold
behind a cold front. VFR conditions will then prevail late
tonight at both terminals as winds become westerly.

Extended Aviation Outlook: No significant concerns Tue-Sat.

&&

.MARINE...
This Evening and Tonight: South/southeast winds will remain elevated
within a tight pressure gradient ahead of a cold front approaching
from the west early tonight. In general, southeast/south winds will
gust near 25-30 kt, highest in nearshore South Carolina waters
and offshore Georgia waters. Seas will also range between 4-7
ft, highest in nearshore South Carolina waters and offshore
Georgia waters. For these reasons, Small Craft Advisories will
continue for nearshore South Carolina waters and offshore
Georgia waters through much of tonight. Otherwise showers/thunderstorms
will move through the waters ahead of an approaching cold front
this evening. The environment could support strong wind gusts
and/or isolated waterspouts. The passage of the front will
result in winds becoming west-northwest late. Despite some cold
air advection behind the front, winds will decrease to around
10-15 kt late as the pressure gradient and low-level winds
diminish.

Marine conditions will temporarily improve on Tuesday, allowing
the Small Craft Advisory for the offshore GA waters to drop
midday. However, a period of marginal SCA conditions is possible
late Tuesday night through Wednesday morning after a secondary
cold front and more significant blast of cold air advection. We
show gusts approaching 25 kt mainly over the GA waters during
this time.

Much improved conditions will return by Thursday as high pressure
builds back in and persists through Friday. Another cold front
could approach the waters Saturday but much uncertainty remains
with the forecast this weekend.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 5 AM EDT Tuesday for AMZ352.
     Small Craft Advisory until 11 AM EDT Tuesday for AMZ350-374.

&&

$$
NEAR TERM...RJB
SHORT TERM...JRL
LONG TERM...RJB
AVIATION...JRL/RJB
MARINE...DPB/JRL


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