Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 231953
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
353 PM EDT Wed Aug 23 2017

.SYNOPSIS...
A cold front will move into the area tonight and linger nearby
through the end of the week. A wave of low pressure could form
along the front offshore Friday, as high pressure builds from
the north through the weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A cold front near the Appalachians will move southeast toward
the coast overnight. Deeper moisture along with some upper
shortwave/jet forcing is also anticipated and this will help
keep some showers and thunderstorms around. Probably the best
chances will be across SC closer to the front and better
forcing. We cannot rule out a few stronger storms through early
evening during peak heating as moderate instability and high
DCAPE values around 1000 J/kg are expected which could result
in damaging wind gusts. Lows will mainly range from the mid 70s
inland to near 80 at the coast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
A weak cold front will very slowly migrate southeast through
the area Thursday through Saturday. On Thursday we expect the
day to begin with scattered showers and tstms moving offshore
with a shortwave, followed by a relative lull until the
afternoon when another shortwave moves in from the west. A
moderate sea breeze will also develop and provide a focus for
convection.

Drier, cooler high pressure will steadily build from the north
Thursday night through Saturday while a relatively zonal flow
develops aloft. The greatest chance for showers and tstms will
shift to coastal SC and southeast GA along and south of the
advancing front. High temps will be down to the mid/upper 80s by
Saturday.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
Surface high pressure will continue to reach into the area from
Canada. Fairly reasonable model agreement depicts a coastal low
developing off the GA/SC coast by late this weekend. In addition,
guidance suggests that the remnants of Harvey will track towards the
forecast area from south Texas. At least some degree of wedging of
the high pressure over the Carolinas seems probable with low
pressure to the east and west, resulting in a cloudy and potentially
unsettled period. Daytime warming would be tempered in this regime,
with highs averaging in the mid-80s appearing reasonable at this
time. By Tuesday, deeper moisture may provide greater coverage of
convection, but model solutions diverge considerably by this time,
increasing forecast uncertainty.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
We kept the 18Z TAFs VFR but there will be a low-moderate chance
for showers/tstms from late afternoon through the end of the
period as a cold front approaches from the northwest. However,
confidence in timing/significance is too low to warrant any
mention at this time.

Extended Aviation Outlook: Brief flight restrictions will be
possible in mainly daytime showers/tstms Thursday through
Saturday. Greater potential at KSAV.

&&

.MARINE...
Tonight: Southerly winds will shift southwest as a cold front
approaches. The gradient will continue to tighten through this
evening and winds will peak between 15 and 20 knots for a
period into the early morning, unless any convection or
convective boundaries moving offshore disrupt the synoptic wind
flow. Winds will gradually diminish late tonight as the cold
front nears from the NW and N. Seas will mainly range from 2 to
4 ft, highest near the Gulf Stream.

Thursday through Sunday: Southwest winds less than 15 kt will
continue through Thursday night before shifting to northeast on
Friday as a cold front slowly drops into the area. A fairly
tight pinched northeast gradient is expected to develop Saturday
and persist through at least Monday as a wave of low pressure
develops along the stalled front while high pressure builds from
the northwest. Small Craft Advisories are likely for most if
not all waters starting at some point Saturday. The low pressure
system is currently forecast to make its closest approach next
Monday into Tuesday, potentially as a tropical cyclone.

Rip Currents: A 2-3 ft swell every 9-10 seconds along with
moderately strong onshore winds will keep an elevated risk of
rip currents along the Charleston County coast into this evening.

&&

.EQUIPMENT...
The KCLX radar has been restored to operational status.

The temperature and dew point sensors at the Downtown Charleston
observation site (KCXM) could periodically fail. Parts are on
order and technicians will attempt to resolve the problem once
they arrive.

&&

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

&&

$$
NEAR TERM...RJB
SHORT TERM...JRL
LONG TERM...JMC
AVIATION...JRL/RJB
MARINE...JRL/RJB
EQUIPMENT...



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