Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 281702
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
102 PM EDT Sun May 28 2017

.SYNOPSIS...
High pressure will linger over the region today. A weak cold
front will gradually sag south through the area Monday through
Wednesday, then lift back north late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Today: Still seeing decent coverage of mid/high clouds
across the area this afternoon mainly near/north of the Savannah
River with cumulus south of this area across southeast GA.
Models suggest mid-level capping will remain in tact across
southeast SC/GA today but we cannot completely rule out
showers/thunderstorms later this afternoon, mainly toward the
Pee Dee/Midlands/CSRA, as shortwave energy rides by to the north
closer to a weak surface low/cold front. It is possible that
mesoscale boundaries such as differential heating, convective
outflows, the sea breeze and Lake Marion/Moultrie lake breezes
could eventually serve as initiation mechanisms. The modified
12Z CHS sounding and forecast model soundings suggest that
isolated severe thunderstorms will be possible given abundant
instability /CAPE over 3000 J/kg and LI near -9 deg C/ and
downdraft CAPE /1000+ J/kg/ and sufficient deep layer shear /30+
kt/ supportive of rotating storms. Damaging downburst winds
will be the main hazard but large hail is also possible. We
continue to think that the overall threat is low enough to not
mention in the Hazardous Weather Outlook.

Tonight: If any storms develop in the afternoon, they should
diminish quickly in the evening with the loss of heating.
Through the remainder of the overnight, dry and mild conditions
should prevail. Lows will likely not fall below 70 for most
areas.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
The upper ridge will gradually weaken and shift east Monday
into Tuesday, allowing more shortwave energy to push into the
area. A weak cold front will move into northern GA and far
western NC/SC Monday afternoon, then approach the local area
Tuesday afternoon.

Monday looks rather toasty as warm low-level thicknesses reside
over the area, ample sunshine occurs, and low-level flow is
westerly. Highs expected to be in the mid 90s away from the
coast. Model soundings show a decent mid-level cap until the
afternoon which will probably preclude convective development
until later in the day. There won`t be much forcing for
convection on Monday though it`s possible that some activity
will develop over the SC Midlands and push east-southeast late
in the afternoon. Convective parameters would be conducive for
some severe thunderstorms given extensive dry air off the
surface and CAPEs of 1500-2000 J/kg.

Tuesday is looking more active than Monday given the continued
breakdown of the upper ridge and shortwave energy making its way
into our inland zones during the day. The surface front pushing
in late in the day will also provide a trigger for convection.
We increased pops a bit during the afternoon. Convective
parameters looks similar to Monday except the cap is weaker in
the morning. There would be enough 0-6 km shear to support some
multicellular organization, and the dry air aloft will be
conducive for damaging winds.

Slightly cooler temps expected Wednesday as the front remains
stalled over the area and more cloud cover is present. There
will be enough forcing for isolated to scattered convection
mainly in the afternoon, though instability and shear will be a
little lower than Mon-Tue.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
A fairly active period is in store as a quasi-zonal flow exists
aloft and weak shortwave perturbations continually traverse the
area. With increasing moisture through late in the week and
daytime temps in the upper 80s or low 90s, scattered to numerous
showers and tstms expected to develop mainly during the
afternoon and evenings.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR conditions expected to prevail at KCHS/KSAV through 18Z
Monday. Very low risk of showers/tstms at KCHS later this
afternoon into early evening.

Extended Aviation Outlook: Mainly VFR conditions. Brief flight
restrictions possible in mainly afternoon/evening showers/tstms
starting Monday.

&&

.MARINE...
Today through tonight: Overall the setup is quite similar to
the last couple of afternoons. Morning westerly flow will shift
to more southwesterly in the afternoon as the sea breeze
develops. We will see enhanced flow mainly along the land/sea
interface with a solid 15-20 knots along the Charleston County
coast. Elsewhere 10-15 or a solid 15 knots is expected. The
thinking is again that conditions in Charleston Harbor will stay
just below Small Craft Advisory thresholds. Seas are expected
to be 2-3 feet.

A slightly stronger gradient will persist into Monday with a
decent 15 kt sea breeze possible in the afternoon. Thereafter,
fairly weak winds and small seas are expected as a front drops
into the area and lingers through the week.

&&

.TIDES/COASTAL FLOODING...
High tide will again be elevated this evening due to the new
moon and perigee. Fortunately the wind directions are not very
conducive for surge, but we could see very marginal coastal
flooding along the South Carolina coast and a Coastal Flood
Advisory may eventually be issued.

&&

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

&&

$$
NEAR TERM...RJB
SHORT TERM...JRL
LONG TERM...JRL
AVIATION...JRL/RJB
MARINE...BSH/JRL
TIDES/COASTAL FLOODING...


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