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Area Forecast Discussion (AFD)

Issued by Charleston, SC (CHS)

                            
000
FXUS62 KCHS 170510
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
110 AM EDT Wed Jul 17 2019

.SYNOPSIS...
The area will remain situated between an area of weak low
pressure inland and high pressure offshore into early next
week. 

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
A couple of stray t-storms near the savannah River and outside
the forecast region will not impact any our counties overnight,
thus keeping a forecast that is free of any rainfall. Other than
few-scattered cirrus clouds and maybe a little stratus in spots
close to daybreak, skies will be clear to partly cloudy. Temps
will not be able to fall any more than another 3-5F given the
elevated dew points and light south-southwest synoptic flow.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
The mid-levels will consist of high pressure over the Southeast
Wednesday morning while a shortwave stretches from the Great 
Lakes Region southwards into the TN Valley. The high will 
dissipate into Wednesday night as the shortwave passes to our 
north. The northern extent of the shortwave is expected to move 
off the coast of the Northeastern U.S. Thursday. Though, it's 
southern half should be slower to move off the Southeastern 
U.S., lingering into Thursday night, then dissipating early 
Friday. Heights should build later Friday. At the surface, our 
area will be sandwiched between high pressure in the Atlantic 
and troughing inland. Plenty of moisture will be in place 
throughout the short term. PWATs will be ~1.75 Wednesday, 
creeping up to ~2" Thursday and Friday. The typical instability 
for July will be in place each afternoon. Convection is expected
to initiate along the sea breeze and spread inland each 
afternoon, dissipating around sunset. Then, more convection 
should develop over the coastal waters overnight. Given the 
pulse nature of the storms, a marginally severe thunderstorm 
with damaging wind gusts will be possible each day. But the more
noticeable impact will probably be the locally heavy rainfall 
from these storms. Temperatures will be above normal. Heat 
indices will peak close to 110 degrees each afternoon, mainly 
along the coast and across parts of SC. The potential for heat 
advisories will need to be evaluated each day.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
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 /06Z WEDNESDAY THROUGH SUNDAY/...
Due to the wet grounds from convection on Tuesday, there could 
be some ground fog around daybreak at KCHS. Otherwise, VFR much
of the time through 06Z Thursday at KCHS and KSAV. The exception
would be for possible temporary flight restrictions in TSRA at 
both sites from about 19-23Z as activity develops along the sea 
breeze. 

Extended Aviation Outlook: Brief flight restrictions are 
possible during afternoon/evening showers/thunderstorms.

&&

.MARINE...
Rest of 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 S-SW 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 late tonight. We'll need to maintain a close
watch for a possible waterspouts risk close to daybreak and into
the morning daylight hours given the light wind fields within a
somewhat favorable environment. 

Extended Marine: The area will remain situated between an area 
of weak low pressure inland and high pressure offshore into 
early next week. This synoptic pattern will lead to winds mainly
from the south/southwest. Aside from the typical afternoon 
increase with the sea breeze, sustained winds should stay below 
15 kt. No Small Craft Advisories are expected.

&&

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

&&

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