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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 161706
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
106 PM EDT Mon Sep 16 2019

.SYNOPSIS...
Hurricane Humberto will move away from the coast through mid 
week. A cold front will advance through the area Wednesday, 
followed by high pressure into next weekend. 

&&

.NEAR TERM /THROUGH TONIGHT/...
Early Monday afternoon: As expected, large scale
drying/subsidence enhanced on western periphery of Hurricane
Humberto will support mostly sunny, breezy and very warm
conditions this afternoon. Temperatures will top out in the
lower/middle 90s at most locations away from the beaches. 

Tonight: Humberto will continue to move away from the coast,
and dry conditions will prevail over our region. Expect low
temperatures ranging from 65-70F inland to the middle 70s 
on the beaches.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Tuesday: Hurricane Humberto is forecast to pick up some speed 
on a east northeast track away from coast. A weaker pressure 
pattern will develop across the area with deep layered dry air 
aloft and dry weather conditions expected to persist. We 
anticipate abundant sunshine allowing temps to warm into the 
lower and middle 90s across then forecast area. 

Tuesday night: Clouds should begin to increase as we see 
moisture building ahead of a cold front which is expected to 
backdoor into SC from the north late. Models suggest a few 
showers may break out before daybreak on Wednesday north of the 
Savannah River, but any coverage should be spotty. 

Wednesday: Showers and perhaps isolated tstms over GA are 
expected to press southwest and perhaps better diurnal 
instability by late afternoon from east central GA into far 
southeast GA near the FL/GA border. Since these areas look to be
removed from our inland GA zones, we capped POPs at slight 
chance since PWATS will be decreasing during the afternoon for 
all but zones adjacent to the Altamaha River. Cooler air will 
advect into the area from the north into SC and high temps 
should range from 80-85 across SC to around 90 far southwest and
to the south of I-16.

Thursday: The change in temps will be evident across the entire
forecast area, as highs will range from a few upper 70s along 
the South Santee River to the mid 80s to the west of I-95. Since
all the moisture is below 850 MB, we suspect scattered and 
shallow diurnal cumulus for the most part with plenty of 
sunshine otherwise. Breezy conditions are likely coastal areas, 
especially beaches and barrier islands.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Deep layered ridging will persist over the region late week 
into early next week, bringing near climo temps and dry weather 
for the forecast area.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
VFR through the 18Z TAF period. N/NE winds could gust around 20
knots at times this afternoon. 

Extended Aviation Outlook: Patchy fog is possible around the 
terminals around daybreak Wednesday, flight restrictions appear 
unlikely at this time. Otherwise, VFR.

&&

.MARINE...
Today through Tonight: The setup will remain unchanged and the 
local waters will continue to be situated between high pressure 
to the north and Hurricane Humberto to the southeast. North/
northeast flow today will be followed by northerly flow overnight.
Wind speeds will peak through the afternoon as the pressure 
gradient will be tightest. Then overnight, wind speeds will back
off as Humberto moves to the east and the gradient relaxes. 
Seas will remain quite high thanks to the combination of swell 
energy from Humberto and wind wave driven by the tight pressure 
gradient. Small Craft Advisories remain in effect for all waters
outside the Charleston Harbor through today. Then, as winds 
weaken overnight conditions should improve enough to allow for 
first dropping the Advisory for the nearshore Georgia waters 
around midnight. Then closer to sunrise Tuesday we should be 
able to remove the advisory for the southern South Carolina 
waters. 

TC Humberto is forecast to gain some progress exiting the 
southeast coast on Tuesday. Weak high pressure will linger over 
our waters with winds on the lighter side, generally 15 kt or 
less. We will maintain a Small Craft Advisory for Charleston 
waters as well as GA waters beyond 20 NM as seas 6 ft or greater
persist.

Late Tuesday night into Wednesday, a cold front will move south
through the waters while cooler high pressure settles to the 
north through late week. Small Craft Advisory conditions will 
redevelop across all near shore waters in the wake of the front 
as high pressure builds in. Northeast winds are expected to 
reach 20-25 kt with seas 5-6 ft near shore and 7-10 ft beyond 20
NM. The gradient and overall winds and seas should gradually 
subside this weekend as broad high pressure blankets the 
southeast states.

Rip Currents: We maintained a high risk for rip currents at all
beaches today due strong northeast winds and long period swell 
emanating from Hurricane Humberto. The rip current risk will 
then remain elevated throughout much of the week as northeast 
winds and the longshore currents strengthen and elevated (mixed)
swell waves persist.

&&

.TIDES/COASTAL FLOODING...
Low chances for minor coastal flooding around the times of high
tide through late week, especially along the South Carolina 
coast.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117-
     119-139-141.
SC...High Risk for Rip Currents until 8 PM EDT this evening for 
     SCZ048>051.
MARINE...Small Craft Advisory until 6 AM EDT Tuesday for AMZ352.
     Small Craft Advisory until 6 PM EDT Friday for AMZ350.
     Small Craft Advisory until midnight EDT tonight for AMZ354.
     Small Craft Advisory until 8 PM EDT Saturday for AMZ374.

&&

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