Area Forecast Discussion
Issued by NWS Charleston, SC

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KCHS 210532
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1232 AM EST Wed Feb 21 2018

.SYNOPSIS...
A large area of high pressure will remain across the region for
much of the week. A cold front will likely impact the area
early next week.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
The fog potential remains highly uncertain given the amount of
wind noted within the mixed layer. The boundary layer is having
a hard time decoupling early this morning with warm temperatures
holding in place. Have increased overnight lows per going
trends, but not quite as much as some guidance would suggest.
Webcams show some sea fog is beginning to develop and move
inland along the coast. The fog should transition to stratus has
it moves farther way away from the marine layer. However, some
of this will likely build-down through daybreak resulting in
some varying degrees of visibility restrictions. Again, it is
unclear how widespread any dense fog will be at this time.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
A pattern more typical of summer will prevail this period with
deep high pressure centered near Bermuda. This will lead to
unseasonable warmth with highs near 80 each day away from the
locally cooler coastal areas and lows closer to typical highs
for this time of year near 60. Such temperatures could lead to
record highs, especially at Charleston/Savannah Airports.
Although low-level moisture will be fairly abundant we do not
expect any significant rainfall, although cannot rule out some
mainly afternoon brief light showers/sprinkles due to some low-
level isentropic ascent and a weak coastal trough. More likely
though will be late night/early morning fog each day, some of
which could be dense. At some point sea fog could develop over
the nearby Atlantic and move onshore, possibly affect coastal
areas with foggy/cloudy conditions lasting beyond the morning
hours.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A large ridge of high pressure centered over the western
Atlantic will be the primary contributor to the weather over the
Southeast United States, maintaining warm conditions through
the weekend. In general, temps will be well above normal,
peaking into the upper 70s/lower 80s Saturday and Sunday.
Overnight lows will be mild, ranging in the upper 50s to lower
60s. The next substantial precip chances should arrive late
Sunday into Monday as a mid/upper trough passes to the north
with a southward extending cold front moving through the
Southeast. PWATs near 1.5 to 1.75 inches will be possible
along/near the front, suggesting chances of showers over most
areas as fropa occurs. Temps should be slightly cooler on Monday
with showers and fropa, peaking in the mid/upper 70s. On
Tuesday, temps will remain cooler under a zonal flow aloft,
peaking in the low/mid 70s.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Low confidence on vsbys and cigs overnight. KCLX shows quite a
bit of wind holding in the boundary layer early this morning.
This is keeping the fog and stratus at bay for now. Low-level
flow is more southeast compared to southerly over the past few
nights which is not ideal for sea fog developing and spreading
inland from the beaches. However, any coastal fog that develops
will transition to low-stratus as it moves west away from the
marine layer. The degree of cigs and vsbys remains highly
uncertain with short term guidance showing a number of
possibilities from widespread dense fog to VFR at both KCHS and
KSAV. Given current trends, will opt for slightly more
optimistic conditions limiting conditions to MVFR at KCHS and a
brief period of IFR at KSAV. Amendments will have to be issued
as confidence in shorter term trends increase.

Extended Aviation Outlook: Flight restrictions are likely each
night/morning due to low clouds/fog through the weekend,
possibly lingering into the afternoon hours as it will take
longer for any ceiling heights to rise above MVFR levels.

&&

.MARINE...
Tonight: Winds are expected to trend southeast as a weak
coastal trough dampens with speeds generally remaining less than
15 knots and seas ranging 2-4 feet. Fog will be a concern
especially close to shore later tonight. The low level
southeasterly flow isn`t particularly supportive of sea fog
development and would likely push most of it onshore. Patchy to
areas of fog is forecast, and dense fog is still a potential.

Wednesday through Sunday: High pressure will prevail across the
area this period with no significant pressure gradient
expected, resulting in winds/seas remaining below Advisory
levels. However, increasing southeast swells could push
significant wave heights to near Advisory levels later this
week. The main concern will be the potential for sea fog across
the nearshore waters, mostly late this week.

&&

.CLIMATE...
Record highs for February 21:
KCHS: 82/1991
KSAV: 83/1991
KCXM: 80/2001

Record highs for February 22:
KCHS: 82/1991
KSAV: 83/1991 and previous
KCXM: 77/2011

Record highs for February 23:
KCHS: 81/2012 and previous
KSAV: 84/2012
KCXM: 81/1930

&&

.EQUIPMENT...
The Downtown Charleston observation site (KCXM) is reporting
intermittently. Please use the data with caution.

&&

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

&&

$$



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.