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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 161509
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1109 AM EDT Tue Jul 16 2019

.SYNOPSIS...
The area will remain situated between an area of weak low
pressure inland and high pressure offshore into early next
week. Hot and humid conditions will prevail through late week. 

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Aloft, a fairly strong mid-lvl ridge of high pressure will 
extend across the area, helping set up strong sfc heating under 
mostly sunny skies. 1000-850mb thickness values along with a light 
downsloping wind aloft will likely support afternoon temps in the 
mid/upper 90s, highest across inland areas. These temps along with 
moist conditions should support heat index values upwards to 105-109 
degrees, highest along/near the I-95 corridor in Southeast Georgia 
and along/near Highway 17 in Southeast South Carolina where moisture 
convergence is enhanced by a seabreeze. The only relief from the 
heat will come in the form of showers/thunderstorms this afternoon. 
Strong ridging aloft will likely suppress most convection until 
early afternoon hours. Thereafter, warm temps and deep moisture 
should support a few to perhaps scattered showers/thunderstorms near 
the seabreeze circulation extending along Southeast South Carolina 
initially, then across parts of Southeast Georgia where a weak sfc 
trough axis extends north/south into the region. Greatest coverage 
of precip should occur across southern most locations of Southeast 
Georgia where the trough axis and seabreeze circulation coincide 
with MLCAPE around 2500 J/kg and PWATs upwards to 2.0 inches. 
Although shear is weak, a few thunderstorms could be strong with 
gusty winds and brief downpours given DCAPE values near 1100 J/kg 
during the time of maximum heating and greatest low-lvl moisture in 
place. However, the overall threat of severe weather is low 
late afternoon into early evening. Convective activity should 
begin to diminish across northern areas by early evening, but 
could persist a few hours longer across Southeast Georgia.

Tonight: Convection should dissipate within 1-2 hours following 
sunset. Low temps should range from the mid 70s inland to the upper 
70s over the beaches. It is noteworthy to indicate that heat index 
values near the beaches will remain in the upper 80s through
tonight.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
Moderate to high confidence this period. Inland troughing will 
prevail mainly north and west of the area while ridging prevails to 
the southeast. The pattern will favor a few showers near the coast 
each morning with showers and thunderstorms inland during the 
afternoon/evening. No significant risk for severe storms is expected 
due to the mostly pulse nature of the convection but certainly can't 
completely rule out isolated severe storms each day. Temperatures 
will remain above normal through the period (mainly mid-upper 90s 
inland each afternoon) with heat indices generally peaking close to 
110 degrees away from the immediate coast. Not enough confidence 
though to mention possible Heat Advisories in the Hazardous Weather 
Outlook but will need to consider this later. Overnight lows could 
also be near record high levels in the upper 70s, especially at KCHS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
Moderate confidence this period. The low-level lee-side trough looks 
to persist through the period while some upper ridging tries to give 
way to more troughing, especially by Tuesday. For now we have 
maintained a climatology and persistence forecast as far as rain 
chances (mostly around 30 percent) with temperatures remaining above 
normal. Heat indices will remain high, but mainly below the Advisory 
threshold of 110 degrees.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
VFR conditions are expected at both CHS and SAV terminals into early 
afternoon. Isolated showers and thunderstorms will develop across 
the region this afternoon, potentially impacting either terminal.
VCTS has been added to both sites, (18-21Z at CHS and 19-22Z at
SAV). Flight restrictions are possible this afternoon, but 
confidence remains too low to include in the latest taf issuance.
Otherwise, conditions should feature south winds during the daylight
hours and calm to light winds at night.

Extended Aviation Outlook: Low risk of flight restrictions from 
mainly afternoon/evening showers and thunderstorms through 
the weekend.

&&

.MARINE...
Today and Tonight: The coastal waters will remain situated between 
high pressure over the western Atlantic and a weak trough of low 
pressure over land. The pattern will favor a weak pressure gradient 
across all waters, supporting mainly southwest to southeast 
winds around 10 kts or less. Seas will generally range between 
1-2 ft, but could build as high as 3 ft beyond 50 nm in offshore
Georgia waters tonight. 

Wednesday through Sunday: Inland low pressure and offshore high 
pressure will lead to mainly south/southwest winds through the 
period, generally highest near the coast during the afternoon from 
the sea breeze. However, conditions should stay below Small Craft 
Advisory levels as significant wave heights will be 4 feet or
less.

&&

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

&&

$$
NEAR TERM...DPB
SHORT TERM...RJB
LONG TERM...RJB
AVIATION...NED/RAD/RJB
MARINE...DPB/RJB