Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 230758
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
358 AM EDT Thu Mar 23 2017

.SYNOPSIS...
High pressure will build in from the north through tonight before
shifting over the Atlantic through the weekend. A cold front is
expected to affect the area early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Cool dry high pressure will wedge down the Eastern Seaboard
today. The column will be quite dry across southern SC where
only some high clouds will drift through today. Greater moisture
below 800 mb across southeast GA will support partly to mostly
cloudy skies there today. Quite a bit of sunshine in most
locations will allow temperatures to reach thickness values,
which required us to raise high temps 1-3 degrees.

The surface high starts to shift east tonight, allowing a
stronger onshore flow to develop and increase low-level
moisture. Some maritime stratus may move into coastal areas
late tonight though most areas will see no greater than partly
cloudy skies.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Friday, the center of sfc high pressure is forecast to shift over
the western Atlantic as low pressure deepens over the southern Great
Plains. This pattern will support steady SE winds across the
forecast area. Given partly sunny conditions and the passage of the
H5 ridge axis overhead, conditions should warm considerably from
Thursday. Using a blend of guidance, high temperatures are forecast
to range in the low to mid 70s.

Saturday, a low pressure system is expected to track from the
southern Great Plains to the Mid West as high pressure remains over
the Atlantic. Onshore winds from the SE through continue through the
period. High temperatures may warm two to four degrees warmer than
values reached on Friday.

Sunday, the base of a H5 trough is expected to rotate on the SE side
of a closed low centered over the Mid West. The occluded sfc low
will slowly move north toward Lake Michigan through the day. The
region will remain within the warm sector, highs reaching into the
upper 70s to the low 80s with dewpoints in the upper 50s. GFS
indicates that afternoon values of SBCAPEs are forecast to range
from 500 J/kg near the coast to over 1000 J/kg inland. I will
increase afternoon and evening PoPs to chc inland to schc over the
marine zones, mentioning both showers and thunderstorms.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
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 /08Z THURSDAY THROUGH MONDAY/...
VFR through tonight. Gusty winds today.

Extended Aviation Outlook: Showers and thunderstorms could develop
each afternoon and evening Sunday through Tuesday. Patchy early
morning fog is possible over wet soil.

&&

.MARINE...
The strongest NE gradient will continue through mid-morning over
the SC nearshore waters as the high pressure wedge builds south.
It still looks as though conditions will remain just below Gale
force this morning. Winds will slowly decrease this afternoon
through tonight though seas will be slower to subside.

The center of high pressure will gradually shift over the western
Atlantic Friday and Friday night, allowing seas to decrease to
around 5 feet for most areas by sunset Friday. SCAs are scheduled to
expire Thursday night,  expect AMZ374 remaining through most of
Friday. Steady South to Southwest winds are forecast to remain over
the zones through the weekend into early next week. Seas could
increase to six feet across eastern AMZ374 during the weekend.
Scattered showers and thunderstorms are forecast to develop Sunday
through Tuesday, especially during the daylight hours.

Rip Currents: A strong NE wind and a 7-8 second NE swell today
will produce a moderate risk for rip currents.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until midnight EDT tonight for AMZ350-352-
     354.
     Small Craft Advisory until 6 PM EDT Friday for AMZ374.

&&

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



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