Area Forecast Discussion
Issued by NWS Charleston, SC

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517
FXUS62 KCHS 251922
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
322 PM EDT Sat Mar 25 2017

.SYNOPSIS...
Atlantic high pressure will weaken into early next week. A weak
cold front should then stall over the area during the middle of
next week, then shift back north as a warm front late in the
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Quiet conditions will persist tonight as weakening Atlantic
high pressure holds firm. A broken line of showers associated
with a decaying cold front could approach far interior Southeast
Georgia just before sunrise, but most of the measurable rainfall,
if any, looks to remain to the west. Scattered, diurnal cumulus
will quickly dissipate after sunset with only thin cirrus
poised to traverse Southeast South Carolina and Southeast
Georgia this evening. The only exception will be across the
Charleston Tri-county area and portions of the far southern
South Carolina coast where extensive closed-cell stratocumulus
will continue to stream inland from off the Atlantic. Expect
most locations will be mostly cloudy by daybreak Sunday as
thicker cirrus steadily overtakes the area from west-east after
midnight ahead of negatively tilted shortwave energy trailing
south of the upper low over the Mid-Mississippi Valley. Adjusted
sky cover grids to reflect this thinking. Lows will range from
the mid-upper 50s inland with upper 50s-lower 60s at the
beaches.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
A weakening shortwave trough will cross the region from west to east
Sunday, supporting isolated/scattered showers and even a couple of
thunderstorms during the afternoon/early evening especially away
from the immediate coast as the sea breeze pushes through inland
counties. Shortwave ridging will prevail Monday, but isolated-
scattered showers/thunderstorms could still develop along the
sea breeze mainly during the afternoon/early evening. A somewhat
deeper but weakening shortwave trough aloft will push into the
region later Monday night through Tuesday. This trough should
produce isolated/scattered showers/thunderstorms, especially
Tuesday afternoon. Due to westerly steering flow and a sea
breeze pinned near the coast, a few thunderstorms could push to
the beaches.

Guidance advertises limited instability through this period, so the
potential for severe weather remains low. Limited coverage of
showers/thunderstorms should also reduce the potential for
significant rainfall.

Despite the fact that we can expect more clouds than sunshine
through this period, above-normal temperatures will prevail, with
inland high temps around 80F Sunday increasing to the lower 80s
Monday and even mid 80s min some areas Tuesday. With onshore flow,
temperatures will remain much cooler, mainly in the 60s, on the
beaches Sunday and Monday. Tuesday, warmer temps in the 70s could
migrate to the beaches before the sea breeze develops in the
afternoon. Above-normal overnight low temperatures in the upper 50s
to lower 60s will remain common, with many areas not falling below
60F Tuesday overnight/early Wednesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
A weakening cold front looks to approach the area mid week before
stalling and eventually shifting back northward as a warm front. By
Friday forecast uncertainty grows as the 00Z/25 GFS is showing a
potent upper low moving through the region which would make for more
unsettled weather than the preferred ECMWF solution which is more in
line with WPC. At this point we think some showers and thunderstorms
will be possible, mainly each afternoon starting Thursday, with
temperatures running above normal.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR. There are some signs that a brief period of MVFR cigs could
develop at KSAV overnight, but statistical guidance and RAP
soundings suggest otherwise. Will keep conditions VFR for now.

Extended Aviation Outlook: Mainly VFR. Brief flight restrictions
possible in any showers/thunderstorms. Low probability of flight
restrictions, mainly early morning low clouds and/or fog Monday
through Wednesday.

&&

.MARINE...
Tonight: East to Southeast winds will continue tonight with the
center of Atlantic high pressure centered well offshore. Speeds
look to remain 15 kt or less through sunrise with seas averaging
2-4 ft nearshore waters and 4-5 over the Georgia offshore leg.

Sunday through Thursday: Winds should remain below Small Craft
Advisory levels through this period. However, swell energy will
maintain elevated seas, and 6 foot seas could push into the waters
especially beyond 20 nm early to mid week, enhanced by offshore low
pressure through the first half of the week. Wave watch guidance
advertises even high seas as high pressure builds from the north
later this week.

&&

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

&&

$$



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