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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 162249
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
549 PM EST Wed Jan 16 2019

.SYNOPSIS...
Dry high pressure will build from the west and prevail into
Thursday. A weak upper level disturbance will move through
Thursday night. A stronger storm system will then impact the
area Saturday night and Sunday. 

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
For the early evening update we have expanded the range of
minimum temps a little bit more, based on excellent radiational
cooling inland and just enough mixing along the coast to occur.
This will produce some lows at or below freezing along parts of
the coldest rural locations of our northwest tier. Otherwise
very few changes required at this time.

Previous discussion...
Aloft, semi-zonal flow will persist over the area. At the
surface, broad high pressure will spread across the East Coast,
with its center becoming located over the Great Lakes Region 
late. Dry weather will prevail. Skies should be mostly clear
with some thin cirrus possible late. This combined with calm 
winds overnight will allow good radiational cooling. Lows should
fall into the mid 30s inland and near 40 degrees at the 
immediate coast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Surface high pressure over the eastern United States will
gradually shift to the east through Saturday. A weak upper level
disturbance will bring a cold front through the area Thursday
night. Moisture return ahead of this wave will be quite limited
and the quasi-zonal flow aloft will limit upward vertical
motion. Therefore we only show isolated showers moving through
far northern SC zones Thursday night. Strengthening southerly
flow Thursday into Friday will bring warming temperatures with
highs reaching the middle 60s by Friday.

An upper trough will move out of the central United States on
Saturday with a strong cold front approaching the area late in
the day Saturday. Most of the associated precipitation will
remain west of the area through sunset. However, despite
extensive cloud cover, continued warm advection will result in
high temps in the low to middle 70s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Moderate forecast confidence most of the period. There is more model 
agreement now that a cold front will likely move through from the 
west Saturday night into early Sunday, with much colder high 
pressure building in thereafter through early next week. By the end 
of the period a coastal trough and a possible low pressure system 
could bring some rain back into the forecast but confidence is much 
lower toward the middle of next week. Most locales should see a half 
inch to maybe 1 inch of rain through the period, with most of the 
rain coming over the weekend. Although deep layer shear is strong we 
don't see a lot of instability so not overly concerned about the 
severe thunderstorm threat at this point and in fact we don't even 
have any mention of thunderstorms. It will also be breezy Sunday 
into early Monday and a Lake Wind Advisory may be needed for Lake 
Moultrie. 

Most, if not all, locales should be below freezing Monday morning 
with inland areas in the mid to upper 20s and wind chills near 20 
degrees. It's not out of the question that coastal areas reach Wind 
Chill Advisory levels of 15 degrees. Highs Monday should only range 
from around 40 near the Santee River to 50 near the Altamaha River. 
Temperatures Monday night are a bit tricky as much depends on how 
much a coastal trough and high clouds come into play but inland 
areas should get back below freezing again. Thereafter temperatures 
will modify into mid week to near or above normal levels.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
00Z TAFs: VFR.

Extended Aviation Outlook: Restrictions expected Saturday night
into early Sunday, likely IFR or worse at times. Also, 
breezy/gusty conditions are expected later Saturday through at 
least Sunday night.

&&

.MARINE...
Tonight: High pressure over the region will support varying winds
around 5 kt. Seas will be no more than 1 or 2 ft, except for
some 3 footers beyond 50 nm offshore. 

Extended Marine: No significant concerns through Saturday but 
conditions will be deteriorating significantly Saturday night 
and Sunday as a strong cold front affects the area with some 
heavy showers and possible thunderstorms (mainly near the Gulf 
Stream). Winds could even gust near gale force across the GA 
waters beyond 20 nm. Otherwise, Small Craft Advisories are 
likely for the entire area. Should see improving conditions 
Monday as winds turn offshore and diminish with the weakening 
cold air advection.

&&

.TIDES/COASTAL FLOODING...
Coastal Flooding: Astronomical tide levels will be high early next
week and strong north/northeast winds will help contribute to even
higher levels which could lead to minor saltwater flooding 
around high tide. Thus, Coastal Flood Advisories will be 
possible.

&&

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

&&

$$
NEAR TERM...
SHORT TERM...JRL
LONG TERM...RJB
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...