Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 251941
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
341 PM EDT Tue Jul 25 2017

.SYNOPSIS...
Broad low pressure will remain across the Carolinas and Georgia
through tonight. A weak cold front will then stall over or near
southeast South Carolina through Thursday. Another cold front
will move into the area this weekend and stall into early next
week.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
To start, ahead of an upper low advancing east across southern
GA, thunderstorm coverage will range from numerous/widespread
across SE GA to isolated/scattered across SE SC into early
evening. Primary concerns focus on the threat for locally
excessive rainfall within an environment featuring PWATs
exceeding 2 inches and weak steering flow, especially where
coverage is maximized across SE GA. MLCapes exceeding 2000 j/kg
could translate to an isolated/brief pulse severe event with
damaging wind gusts, but the probability for severe weather will
remain low.

Thunderstorms should undergo diurnal weakening/dissipation later
this evening. Then, as the upper low continues to roll toward
the region, isolated/scattered showers/thunderstorms could
redevelop later tonight. Locally heavy rain could again occur,
especially along the coast.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Troughing will linger through the period, although it will be
strongest through Thursday. The deepest moisture is also likely
through Thursday so through this time is when we expect the highest
rain chances, especially Wednesday. Although cannot rule out isolated
severe storms, the bigger risk will be heavy rainfall/flooding given
weak wind fields and very deep moisture. This wetter than normal
pattern will lead to lower than normal high temperatures and
generally above normal low temperatures. By Friday temperatures
could reach above normal in the mid 90s with heat index values
peaking in the lower 100s.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
Deep moisture will advect to the Southeast United States ahead of a
cold front that is expected to move into the area Saturday. PWATs
between 2.25 to 2.5 inches and forcing associated with the front
support numerous showers and thunderstorms Saturday into Sunday
while the front slowly progresses south and eventually stalls over
or near southern areas of Southeast Georgia. A few thunderstorms
could become more organized than previous days given greater wind
fields aloft, but the overall threat of stronger thunderstorms could
be limited due to the timing of fropa during earlier hours on
Saturday. At least chances of showers and thunderstorms could linger
into early next week while moisture continues to lift over or near
the stationary front.

Temps will generally be a few degrees below normal this weekend and
early next week given extensive cloud cover and precip activity. In
general, temps should peak in the mid/upper 80s. Overnight lows will
range in the low/mid 70s.

&&

.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
Thunderstorms are expected this afternoon at both terminals,
with most significant impacts at KSAV. Then, VFR conditions are
forecast at both terminals through the 18Z TAF cycle. However,
low-level moisture could support MVFR/IFR ceilings later
tonight. Then, as an upper level low advances east and deep-
layered moisture spreads north across the region, showers could
redevelop late tonight, and thunderstorms could develop before
the end of the 18Z TAF period. Any showers/ thunderstorms could
produce flight restrictions.

Extended Aviation Outlook: Brief flight restrictions are possible
with showers and thunderstorms, especially Wednesday into Thursday
as weak low pressure approaches the region. VFR conditions should
prevail late Thursday and Friday before flight restrictions return
with showers and thunderstorms along/near another cold front
Saturday.

&&

.MARINE...
Seas of 2-3 feet will persist through tonight. The sea breeze
and synoptic winds will combine to produce S/SW winds 10-15
knots into early evening, then synoptic SW winds mainly 15 kt
or less will prevail for the remainder of tonight.
Thunderstorms could produce locally hazardous conditions over GA
waters this afternoon/evening and anywhere across the coastal
waters later tonight.

Wednesday through Sunday: A cold front looks to stall near the SC
waters through Thursday before dissipating before another cold front
moves into the area this weekend. Conditions are expected to remain
below Small Craft Advisory levels through the period. However, a
southwest/south flow could gust around 20 knots Friday night into
early Saturday until cold fropa occurs. Seas will gradually build
from 2-3 ft up to 4 ft at times later this week as the pressure
gradient tightens a bit ahead of the front.

&&

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

&&

$$
NEAR TERM...SPR
SHORT TERM...RJB
LONG TERM...DPB
AVIATION...RJB/SPR
MARINE...RJB/SPR



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