Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 221431

Area Forecast Discussion
National Weather Service Charleston SC
931 AM EST Wed Feb 22 2017

Weak low pressure will pass to the south through Thursday. A cold
front will cross the region early Saturday, followed by cooler
high pressure through Monday. The high will then shift offshore
bringing unseasonably warm temperatures back to the area for mid


Numerous showers are poised to push onshore along the Georgia
coast over the next several hours. This activity is associated
with an area of enhanced surface moisture convergence juxtaposed
with a northwest-southeast oriented ribbon of higher pwats
advecting northwest along the eastern flank of a large upper
level low. The ribbon of enhanced moisture will remain anchored
to Southeast Georgia this afternoon as the upper low digs into
the eastern Gulf of Mexico and Florida.

Pops have been increased to 50-90% for areas south of the I-16
corridor, highest along the coasts of McIntosh and Liberty
Counties. Very little rainfall is expected across Southeast
South Carolina this afternoon where slightly drier air and a bit
more subsidence will persist. Pops there will range from 10%
across the Charleston Tri-county area to 20-30% closer the
Georgia state line, except as high as 40% for parts of Jasper

Cooler temperatures are expected over Southeast Georgia this
afternoon where showers and thicker cloud cover will persist.
Lowered highs by several degrees there to reflect this. Highs
will range from the mid 70s across Southeast South Carolina to
the lower 70s across Southeast Georgia, cooler at the beaches.
Would not be surprised to see a few upper 70s occur in the
Walterboro-Moncks Corner corridor.


Tonight: The upper low will pass over south Florida late and
this will shift rain chances further southward and gradually
offshore. Skies could begin to clear well inland late as a mid
level vort nears the coast and this could result in stratus and
fog development. We have introduced patchy fog along and inland
from I-95 late as a trend. Layered clouds along coastal zones
may temper fog development but confidence in late night sky
cover is not good at this point. Another mild night on tap with
lows in the mid to upper 50s many areas.

Thursday through Saturday: Low pressure near the Bahamas will
slowly shift northeast farther into the Atlantic late the week
as high pressure lingers inland through Friday, then gives way
to a passing cold front Saturday morning. Could see a few
showers Thursday with Friday remaining dry and then a few more
showers mainly early Saturday. Also, some dense fog possible
Friday and Saturday mornings. Temperatures look to be well above
normal through the period, with record highs/high mins possible
Friday/Saturday (see Climate section below).


High pressure will move into the area for the end of the weekend
into early next week bringing much cooler temperatures with it, at
least back closer to normal. Could even be some 30s well inland
Sun/Mon mornings. Temperatures will increase starting Monday as high
pressure shifts offshore and the air mass modifies, possibly nearing
record levels again Wednesday. Some showers possible Monday/Tuesday
as an upper disturbance moves through but chances too low to mention
at this time given the GFS/ECMWF disagreement.


Much of the moisture in the mid and upper levels today but forecast
soundings at KSAV suggest a potential for MVFR cigs as well as
an uptick in showers as low level moisture convergence builds
under difluent upper levels. We maintained VFR today at both
terminals but at least a short window of lower cigs are possible
at KSAV.

Tonight: The low level moisture flux will continue in the
boundary layer but upper levels will tend to dry. There is a
potential for MVFR or lower cigs and vsbys along the coastal
corridor, but the chances appear best toward the end of the 12Z
cycle and quite dependent on whether skies tend to clear.

Extended Aviation Outlook: Mainly VFR with best chance of
restrictions due to fog/low clouds early each morning through


Today and Tonight: Onshore flow today will begin to tip more
northeast by early Thursday morning as surface low pres
translates from the western Gulf into south Florida. Wind speeds
today will mainly be in the 15 KT range with some speeds
nearing 20 KT beyond 20 NM. Seas will range from 3-4 near shore
to 5 ft offshore. By later today and tonight, marginal SCA
conditions for seas to 6 feet are possible for outer GA waters,
closer to the Gulf Stream. We have noted that seas were running
higher than guidance already at Grays Reef, thus a SCA may be
needed at some point later today and tonight for AMZ374.

Thursday through Monday: High pressure to the north and east will
shift farther offshore late this week with a cold front moving
through early Saturday. Cooler high pressure will then move in
through early next week. Persistent northeast winds could lead to
Advisory conditions Thursday beyond 20 nm as seas build, possibly
reaching the SC nearshore waters Thursday night into Friday before
some improvement occurs until the cold front passes Saturday.
Improving conditions then expected early next week with no
headlines likely beyond Sunday morning


Record Highs for Feb 24:
KCHS: 81 set in 2012/1996.
KCXM: 81 set in 1930.
KSAV: 86 set in 2012.

Record Highs for Feb 25:
KCHS: 80 set in 1949.
KCXM: 80 set in 1930.
KSAV: 82 set in 1985/1930.

Record High Minimums for Feb 24:
KCHS: 60 set in 1992.
KCXM: 61 set in 1901.
KSAV: 64 set in 1980.

Record High Minimums for Feb 25:
KCHS: 62 set in 1992.
KCXM: 59 set in 2011.
KSAV: 63 set in 1992.




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