Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 211446

Area Forecast Discussion
National Weather Service Charleston SC
946 AM EST Sun Jan 21 2018

High pressure will prevail into Monday. A cold front will move
through the region Tuesday morning, followed by high pressure
for the rest of the work week.


Late Sunday morning: Ongoing forecasts remained in decent shape
and required only minor adjustments to hourly parameters
through early afternoon.

High clouds will gradually diminish through early afternoon
this morning as a well-developed shortwave advances offshore.
Decreasing clouds and 850 hPa temperatures forecast to rise to
10-11C and 1000-850 hPa thicknesses peaking 1355-1360M this
afternoon will support highs within a degree or two of 70F for
most areas away from the beaches. A light onshore flow will
develop by early afternoon as surface high pressure shifts
offshore and a sea breeze circulation develops. This will keep
the beaches and barrier islands a few degrees cooler where
influences from the cooler Atlantic will be more prevalent.


Tonight: A return flow regime will setup tonight as high
pressure shifts farther out to sea and a cold front approaches
the lower Mississippi Valley. Another bout of cirrus will likely
overspread the region after midnight as another powerful
subtropical jet spreads high-level moisture across the Deep
South ahead of a developing winter storm across the Central
Plains. Could see a little stratus and possibly some shallow
ground fog develop closer to sunrise as isentropic assent atop
a weak coastal trough offshore impacts the coastal areas.
However, no measurable rainfall or major stratus/fog problems
are expected. It will be another warm night despite a decoupled
boundary layer with lows ranging from the lower 40s across
interior Southeast South Carolina to the upper 40s/near 50 near
the immediate coast and beaches.

Monday: High pressure will prevail over the Southeast the first part
of Monday, then quickly move offshore as a cold front approaches
from the west. Weak coastal troughing will also form at this time.
The result will be an increasing threat of showers along the coast
into the Tri-County during the day, with the threat increasing
inland overnight with the front. A few hundredths of an inch of QPF
are expected across the area, mainly late at night. Temperatures
will be well above normal.

Tuesday and Wednesday: Remnant showers may linger along the coast in
the morning as the front moves offshore. High pressure will build in
from the west during the afternoon and prevail into Wednesday,
bringing dry conditions. Temperatures will be above normal Tuesday
and near normal Wednesday.


High pressure will prevail into Friday, bringing dry conditions and
seasonal temperatures. The threat of showers returns with a
disturbance on Saturday.


VFR through this evening. Probability for MVFR cigs increases closer
to daybreak Monday.

Extended Aviation Outlook: Flight restrictions are likely with a
cold front Monday night into Tuesday morning.


Today: A weak pressure patter will support light offshore flow
followed by onshore winds less than 10 knots as high pressure
shifts offshore and a sea breeze circulation develops. Seas of
1-2 ft, dominated by a 9-10 second period easterly swell, will

Tonight: Weak onshore flow will persist as a weak coastal trough
develops offshore. The trough will remain rather ill-defined
with only a subtle wind shift confined mainly to the Georgia
offshore waters. Winds will remain <10 kt with seas 1 ft or
less nearshore and 1-2 ft offshore.

Monday through Thursday: High pressure will prevail Monday. A cold
front will move through the region Tuesday morning, bringing a brief
increase in winds/seas and maybe some sea fog. Seas might approach 6
ft for a few hours across the outer portion of AMZ350 Tuesday
morning, so a Small Craft Advisory is not out of the question.
High pressure will build towards the Southeast late Tuesday and
prevail into Thursday.


The KCLX radar remains out of service until further notice.
Repairs are ongoing. Adjacent radars include: KLTX, KCAE, KJGX,

The Downtown Charleston observation site (CHLS1/KCXM) remains
out of service until further notice.




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