Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 260457
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
1257 AM EDT Wed Jul 26 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 THIS MORNING/...
MSAS shows surface moisture convergence steadily increasing over
the coastal waters as weak low pressure meanders across interior
Southeast Georgia. Low-level convergence looks to increase the
most along the lower South Carolina coastal waters so expect
activity to initiate there later this morning. Increasing
reflectivity returns east of Hilton Head and Edisto Beach are
not precipitation given latest KCLX correlation coefficient
data. Pops 20-40% look reasonable through daybreak, highest
lower South Carolina coast.

&&

.SHORT TERM /6 AM THIS 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 /06Z WEDNESDAY THROUGH SUNDAY/...
Main concern is for tstm impacts at both terminals.

KCHS: Early morning activity looks to organize along the lower
South Carolina around daybreak, which could impact KCHS mid/late
morning before pushing inland. Will carry TEMPO group roughly
16-19z for marginal MVFR conditions in TSRA to cover for now.
Activity should push west of the terminal by early afternoon
with dry conditions prevailing for the rest of the TAF period.

KSAV: Guidance is in pretty good agreement in showing a cluster
of showers/tstms impacting the terminal later this morning and
lingering into the early afternoon hours. High PWAT values
support low vsbys at times in heavy rain. Window for the
greatest impacts looks to center roughly 15-18z. Will carry
prevailing MVFR with a TEMPO group with vsbys within IFR and
approaching alternate minimums. However, briefly lower
conditions, possibly to airfield minimums, will be possible at
times. Activity will push south of the terminal by early/mid-
afternoon with dry conditions prevailing thereafter.

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...
Tonight: 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.

&&

$$



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