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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 231947
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
347 PM EDT Sat Mar 23 2019

.SYNOPSIS...
High pressure will persist through early Monday. Low pressure
will cross the region Monday night followed by a strong cold
front Tuesday. Another low pressure will develop off the
Southeast coast and will gradually move away through midweek.
As the low departs, high pressure will build into the area and
will prevail into next weekend. 

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 340 PM: The center of sfc high pressure will build over 
the eastern Carolinas late tonight. At the mid levels, the axis 
of a H5 ridge will ripple over the area by 9Z Sunday. Sky will 
remain clear through late tonight, a few thin cirrus should 
arrive during the pre- dawn hours Sunday. The combination little
to no cloud cover, calm winds, and wide dewpoint depressions 
will provide excellent radiational cooling conditions tonight. I
will favor the cooler guidance for low temperatures, expecting 
temperatures between 40 to 45 degrees. 

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: High pressure will provide another dry day. Onshore flow 
will hold temps in the 60s on the beaches, but high in the mid/upper 
70s will be common away from the immediate coast. High level clouds
will stream into the region from the west. 

Sunday night: Atlantic high pressure will maintain rain-free 
conditions. By early Monday temperatures will bottom out around 50F 
inland and in the mid-upper 50s on the coast. 

Monday:  Atlantic high pressure will retreat from the region, and 
low pressure will approach the region from the west. The morning 
should remain rain-free. Then, ahead of the advancing shortwave 
trough aloft and associated surface low, warm conveyor belt moisture 
should spread into the region during the afternoon. Latest afternoon 
PoPs are graduated from chance inland to slight chance closer to the 
coast, with lowest PoPs across far southern counties. 

Monday night: The lead shortwave trough aloft and associated surface 
low will translate east across the region. Deep-layered forcing for 
ascent/associated moisture will support scattered to numerous 
showers, with best precip coverage during the first half of the 
night. To address this scenario, evening PoPs range from likely 
north to chance south, then overnight PoPs settle back to 30-50 
percent across the region. 

Also of note, Monday afternoon and Monday evening, showers could 
also be accompanied by isolated thunderstorms. However, model 
instability remains weak and appears unfavorable for any severe 
weather. 

Tuesday, the low pressure will push offshore, and a strong cold 
front will push through the region from north to south. This front 
will bring an abrupt wind shift to the northeast and will signal a 
rapid change to a below-normal temperature regime that will persist 
until late week. Also, persistent moisture within the associated 
baroclinic zone could support isolated/scattered showers through 
Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Low pressure will develop off the coast Tuesday night/Wednesday and 
will only gradually move away from the coast through Thursday. As a 
result, showers could remain over or close to the coast through 
midweek, and elevated northeast winds/below-normal temps could 
persist through Thursday. The, building high pressure will help push 
temps into the upper 70s/around 80 late next week into at least 
early next weekend. 

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
VFR conditions will prevail at KCHS and KSAV through 18Z 
Sunday.

Extended Aviation Outlook: Flight restrictions possible Monday 
night through Tuesday night.

&&

.MARINE...
Building high pressure will result in light east winds across the 
marine zones tonight. Seas will range from around 1 foot near shore 
to 3 feet across the outer GA waters.

Sunday through Thursday night: On the periphery of Atlantic high 
pressure, southeast winds will be enhanced by the sea breeze Sunday. 
Then, ahead of approaching low pressure, winds will turn to the 
south/southwest Sunday night and Monday, and a few gusts could 
exceed 20 kt Monday/Monday evening. Then, a strong cold front will 
cross the waters from north to south late Monday night into Tuesday, 
and winds will shift sharply to the northeast and will intensify. 
Then, due to the tightening gradient between high pressure building 
from the north and low pressure developing offshore, winds/seas 
could easily reach Small Craft Advisory levels most areas Tuesday 
through midweek, and gale force gusts could occur, especially beyond 
20 nm. 

&&

.TIDES/COASTAL FLOODING...
Between strong high pressure building from the north and low 
pressure developing off the coast, strong northeast winds will 
create elevated tide levels along the coast Tuesday through 
Thursday. While astronomical factors do not favor tidal flooding, 
probabilistic guidance depicts a low chance for minor salt water 
flooding, especially Wednesday. We will continue to assess this 
scenario during the next several days. 

&&

.EQUIPMENT...
The KCLX radar remains out of service. Repairs are expected to occur 
Monday.

&&

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

&&

$$
NEAR TERM...NED
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...NED/SPR
MARINE...NED/SPR
TIDES/COASTAL FLOODING...SPR
EQUIPMENT...SPR