Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240531
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
131 AM EDT Fri Mar 24 2017

.SYNOPSIS...
High pressure will build in from the north tonight before shifting
over the Atlantic Friday into the weekend. The high will weaken
early next week, then a cold front could possibly affect the
area around mid week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
As of 130 AM: The center of a 1035+mb sfc high will remain off the
DelMarVa coast, ridging sough across the Carolinas and Georgia
this morning. By early to mid afternoon, the center of the high
will shift off the Carolina coast. Winds will remain steady from
the NE through early this morning, veering from the SE by late
morning. High temperatures over land in the low to mid 70s and
SE flow around 10 kts should bring a sea breeze inland by mid
afternoon.

Previous Discussion:
Tonight: A modified Canadian high near the Delmarva will slip
east tonight, as a strengthening low pressure system occurs east
of the Colorado Rockies. A very subtle inverted trough will form
closer to the local area, out near the western wall of the Gulf
Stream during this transition.

We begin the night with mainly clear skies most places, except
for patches of mid and high level clouds west of US-301 in
Georgia. With a continued onshore fetch in the boundary layer
and isentropic ascent on the 290K surface, these conditions will
support the development of some lower stratus/stratocumulus
overnight, especially across the region south of I-16 in
Georgia.

Comparing temps tonight with those 24 hours ago, we see most
places about 5-9F cooler tonight. However, with weak low level
warm advection, minimum temps tonight won`t be much different
than last night, and actually not too different than what is
normal for the last part of March.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
Friday: Deep layered ridging is forecast to prevail with the surface
high center building north of Bermuda and the low level ridge axis
across the Carolinas. No significant risk of rain anywhere as
the mid level ridge builds atop the forecast area with dry
mid/upper levels. The synoptic flow is onshore and the sea
breeze should progress inland fairly quickly with coastal areas
likely to run a good bit cooler than inland areas by late
afternoon. Highs should average in the mid 70s for much of the
region.

Saturday: Model consensus indicates that upper level ridging
extending from Florida to Coastal GA and the eastern Carolinas will
hold strong, maintaining dry and warm weather. Mid levels remain
stable and dry overall with continued gradual moderation of temps.
On Saturday night, despite the approach of a short wave late, models
remain mainly dry. We continued to show slight chances for a few
showers nearing daybreak Sunday to maintain persistence. It will be
milder with increasing clouds on Saturday night.

Sunday: A dampening short wave will lift northeast from GA early,
through the Carolinas during the afternoon. Deep layered moisture
will increase a bit with PWATs up to 1.25 inches. Upper difluence
will occur early in the day followed by general subsidence in the
afternoon when instability looks to peak. We were comfortable
keeping POPs low-end and mainly inland. Temps will continue to climb
to the lower 80s in many and southern areas.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Conditions appear unsettled across the CWA Sunday night through late
Tuesday. Medium range guidance indicates that a axis of a longwave
trough will ripple across the southeast CONUS early next week. The
forecast area will remain within the warm sector, with weak to
moderate instability developing each afternoon and evening. The
environment appears the most supportive for deep convection late
Tuesday with the passage of the mid level trough and sfc boundary.
Temperatures early next week should start the day around 60 degrees
and peak around 80 by mid afternoon. Thursday and Friday, the
leading edge of a Canadian air mass is expected to spread across the
CWA. Conditions should feature dry wx with slightly above normal
temperatures.

&&

.AVIATION /05Z FRIDAY THROUGH TUESDAY/...
VFR. The center of a 1035+mb sfc high will remain off the
DelMarVa coast, ridging sough across the Carolinas and Georgia
this morning. By early to mid afternoon, the center of the high
will shift off the Carolina coast. Winds will remain steady from
the NE through early this morning, veering from the SE by late
morning. High temperatures over land in the low to mid 70s and
SE flow around 10 kts should bring a sea breeze inland by mid
afternoon. I will indicate SCT040 along and ahead of the sea
breeze this afternoon. Winds should settle to around 5 kts this
evening.

Extended Aviation Outlook: A few showers and thunderstorms could
develop each afternoon and evening Sunday through Tuesday, but
chances for any lengthy restrictions look low. Patchy early morning
fog is possible each day.

&&

.MARINE...
Tonight: A tight pinching of the E-NE gradient between a cold
front across southern Florida and high pressure near the
Delmarva will be slow in relaxing. Thus we have SCA`s on the
South Carolina waters through 1 am, and the Georgia waters out
20 nm til 4 am. The SCA on the outer Georgia waters goes well
beyond the tonight period. Winds have finally dipped below
advisory conditions in Charleston Harbor, so that advisory is no
longer in effect.

Seas are exceptionally large to begin with, averaging 5-7 ft
within 20 nm and 7-9 ft further out, and with the favorable long
duration onshore fetch, they will be slow in subsiding overnight.

Friday through Tuesday: The center of high pressure will shift over
the western Atlantic Friday and Friday night, allowing seas to
decrease to 2 to 4 ft near shore on Friday. The SCA for AMZ374 is
expected to linger through most of Friday. South to southeast winds
are forecast to remain over the marine zones through the weekend.
Wave guidance suggests some 6 FT seas could linger near the Gulf
Stream but overall, conditions will be below SCA criteria.

The flow will veer south to southwest early next week with seas
3-4 ft near shore and 4-5 ft offshore, perhaps still a risk for 6
FT seas out near the Gulf Stream.

Rip Currents: A strong northeast wind and a 7-8 second northeast
swell will produce a moderate risk for rip currents through this
evening.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 6 PM EDT this evening for AMZ374.
     Small Craft Advisory until 4 AM EDT early this morning for
     AMZ354.

&&

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



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