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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 210141
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
941 PM EDT Sat Apr 20 2019

.SYNOPSIS...
A weak surface trough will prevail to the west through tonight
then will gradually lift out of the region Sunday. High
pressure will then dominate the weather through Thursday. Low
pressure and a cold front could impact the region late week
into next weekend. 

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Late this evening: Cloud coverage has remained fairly widespread
over the forecast area as a vigorous mid level vort lobe shifts 
from southwest GA into northeast FL. Most of the clouds were 
altocumulus with flat bases and little to no vertical extent. 
Clouds should begin to decrease as the southern-most mid level 
trough axis moves offshore overnight. Winds have diminished 
since sunset and some sheltered inland areas may decouple 
overnight over inland GA zones, however a light offshore wind 
will prevail at many observation sites for much of the night as 
a decent low level gradient prevails. We did not make much 
change to our forecast curve overnight as the forecast remains 
on track. 

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: The upper trough/associated thermal trough will begin to 
lift northeast of the region but will still support a decent field 
of shallow/diurnal cumulus/stratocumulus and should hold max temps 
in the lower to middle 70s, 3 to 6 degrees cooler than normal for 
April 21. A tranquil night will follow with mainly clear skies and 
excellent radiational cooling allowing temps to fall into the mid to 
upper 40s inland and into at least the lower to middle 50s near the 
coast.

Monday and Tuesday: High pressure will build at the surface and 
aloft and will promote a warming trend. High temps in the upper 70s 
to lower 80s Monday will transition to above-normal highs in the 
lower/mid 80s inland from the beaches Tuesday. Monday night, low 
temps should range from the lower to middle 50s inland to the upper 
50s/around 60F near the coast. Also, mainly sunny skies are expected 
Monday, although some mid/high level clouds could occasionally push 
into the region due to the persistent upper low to our northeast. 
Tuesday, more high clouds could stream into the region from the 
west.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
High pressure will prevail along the Southeast Tuesday night into 
Wednesday, then shift further offshore Wednesday night into 
Thursday. The result will be dry conditions and above normal 
temperatures. By Thursday night and Friday a trough or cold front is 
expected to move over the region, bringing showers and cooler 
temperatures. Though, models differ on the strength, timing, and 
potential impacts. Hence, we went with a blend for the forecast.

&&

.AVIATION /01Z SUNDAY THROUGH THURSDAY/...
VFR at KSAV/KCHS through 00Z through 00Z Monday.

Extended Aviation Outlook: VFR.

&&

.MARINE...
Tonight: We have lowered SCA on all SC waters this evening as
Pilot Boat reports suggest 6 ft seas are now beyond 20 NM and 
winds in the harbor have lessened. We have the SCA coming down 
after midnight over outer GA waters as seas will slowly subside 
to less than 6 ft over the Gulf Stream overnight. Wind speeds 
within 20 NM mainly 15 kt or less with seas 2 to 4 ft. 

Sunday through Thursday: Small Craft Advisory conditions are not 
expected. Offshore winds should average 10 to 15 knots Sunday, 
significantly lighter than the past couple of days. Seas of 3 to 5 
feet early should gradually subside to 2 to 4 feet, highest beyond 
20 nm, as the day progresses. The, high pressure will build over the 
waters and will prevail for the remainder of this forecast period. A 
weak pressure pattern will allow local winds including the afternoon 
sea breeze to dominate into midweek, and winds mainly less than 15 
knots will be accompanied by seas no higher than 2 to 4 feet, 
highest beyond 20 nm. By Thursday, the high pressure will shift 
offshore, and south/southwest winds will strengthen somewhat.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 1 AM EDT Sunday for AMZ374.

&&

$$
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...