Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 260802
Area Forecast Discussion
National Weather Service Charleston SC
402 AM EDT SUN JUN 26 2016
A cold front will shift slowly south of the region today before
dissipating. Another cold front will impact the area beginning
Tuesday, becoming nearly stationary into Wednesday, then
dissipating through the end of the week.
.NEAR TERM /THROUGH TONIGHT/...
Today: A change in air mass has arrived, and the heat and humidity
won`t be as intolerable for many people as it was the past couple
of days. This is courtesy of a cold front that is pushing through
our Georgia counties early this morning, and gradually heads south
of the Altamaha thereafter. A 1024 mb high hugging the coast from
the Delmarva to southeast New England has actually wedged in
behind the front, and will supply the area with an easterly flow
from off the ocean. This will cut down on max temps, as 850 mb
temps are closer to where they should be this time of year, around
16-18C. The end result is for afternoon highs in the upper 80s and
lower 90s for most communities, with mid 90s across interior
southeast Georgia. The beaches will receive the most benefit from
the onshore flow, as highs will hold in the mid or upper 80s. Our
dew points never really change too much despite the passage of the
cold front, as they`ll generally remain in the 70-75 degree range.
The resulting heat indices will reach as high as 100-104F over our
Georgia zones. A few places could peak around 105F south of I-16,
but duration and spatial coverage is too small to raise a Heat
We start the day with an expanding area of low stratus behind the
cold front, which initially will cut down on the insolation. But
during the mid and late morning the wedge inversion relaxes and
climbs and these clouds will transition into a decent diurnal
cumulus field. The onshore trajectories in the boundary layer
between the departing front and around the inland high will
generate sufficient low level convergence, enough to negate the
lack of any short waves aloft as we`re under the influence of the
eastern side of an amplified mid and upper ridge centered in the
lower MS valley. With the sea breeze boundary to get an early
start and sufficient instability and moisture, we anticipate
isolated to scattered showers and t-storms. Warm mid level air
will result in poor mid level lapse rates, so the vertical growth
of convection will be limited overall. But with DCAPE on the order
of 1200-1600 J/kg a few of the tallest storms can produce strong
winds, especially south of I-16 where the better thermodynamic
environment will be situated.
Tonight: Mid and upper level ridging will continue as the cold
front stalls near the Florida-Georgia border and becomes more
diffuse or dissipates. Most of the convection is diurnally driven
and will fade this evening, but there is still enough coastal
convergence in the boundary layer from around the inland wedge.
This results in at least small Pops during the overnight along the
coastal counties. Again there could be some areas of low stratus
after midnight with just enough moisture trapped beneath a weak
nocturnal inversion. Temps will fall to near or slightly above
late June norms.
.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
Monday and Monday night: The large ridge aloft centered near the
Four Corners region will continue to extend eastward and across
the southeast for Monday. The ridge will then begin to break down
and retreat Monday night. A rather nebulous surface pattern will
prevail across the forecast area well in advance of a front
shifting towards the southern Appalachians and the deep south.
Monday looks like a rather generic summertime day with highs
rising into the low 90s for most locations and lows falling into
the low to mid 70s overnight. Thunderstorm chances will be quite
limited thanks to warm mid levels and very dry mid and upper
levels. Have maintained a slight chance pop, but any showers and
thunderstorms that develop are expected to be on the weaker end of
the spectrum. The overnight is forecast to be dry as the
aforementioned upstream front begins to approach from the
Tuesday through Wednesday: The pattern will begin to shift as the
ridge aloft completely weakens and is gradually replaced by
increasingly cyclonic flow. A weak front will slowly push into the
area from the west/northwest Tuesday afternoon and the increased
moisture will result in increased convective activity. This uptick in
coverage of showers and thunderstorms will continue through
Wednesday as the front becomes stationary and aligned near or just
upstream of the forecast area. High end chance pops are in place for
now, and we may end up needing higher pops with subsequent forecast
.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
The pattern aloft in the long term will feature a large ridge in the
west and a broad trough in the east. The southern extent of the
trough will brush the forecast area through late weekend and into
the weekend, while the surface front continues to linger in the
vicinity as well. This should result in a more active regime which
will favor at least mid to high end chance pops each period through
the start of the weekend. Temperature will remain in the near normal
range with highs in the low 90s and lows in the mid 70s.
.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
KCHS: Low stratus spreading in from the northeast behind a cold
front will at least occasionally cause MVFR ceilings at the
terminal through 12z. VFR conditions will return thereafter, with
only a small potential for SHRA/TSRA and associated flight
restrictions in the afternoon due to the sea breeze and coastal
convergence between high pressure to the north and a cold front to
KSAV: VFR through 06z Monday, with only a low end possibility of
SHRA/TSRA and flight restrictions this afternoon due to the
proximity of a nearby cold front to the south and the sea breeze.
Extended Aviation Outlook: Chance for direct impacts from
afternoon/evening thunderstorms Tuesday through Thursday.
Today: Somewhat of an abnormal pattern for summer, an inland wedge
with it`s parent high not far from long Island, with a cold front
pushing south into the Georgia waters early this morning, before
clearing the entire marine area by afternoon. There is a decent
pinching of the resulting NE-E gradient behind the front to
generate winds upwards of 15 or perhaps locally 20 kt, ands
although the Georgia waters start the day with mostly some sort
of southerly wind component at or below 15 kt, they too will
experience the NE-E winds. Seas will build as high as 3 or 4 ft.
Tonight: High pressure to the southeast of New England will weaken
a few millibars as the cold front to the south stalls and becomes
diffuse. The pressure gradient will ease off enough where mostly
easterly winds will fall to less than 10 or 15 kt. Seas will
average 2-3 ft in height.
Monday through Friday: Overall the pattern will favor relatively
quiet conditions across the local waters for much of the upcoming
week. Winds will start off more northeast or easterly on Monday as
a weak surface trough lingers to the east. The flow will then
become more south to southwest through late week as a front
approaches from the west and then lingers in the vicinity. Winds
are expected to be 15 knots or less, strongest along the land/sea
interface each afternoon with the development of the sea breeze.
Seas will generally range 1-3 feet, highest beyond 20 nm.
Rip Currents: We`ll be very close to a moderate risk of rip
currents today given modest NE-E winds. But with some uncertainty
in regards to the amount of swell energy reaching the beaches we
have held onto a low risk. Even so, the longshore current will be
stronger than normal, running from N-NE to S-SW or "down" the
coast. Be safe if at the beach and swim only near a life guard.
Charleston Airport /KCHS/ tied the record high temperature of 99
degrees Saturday set in 1977.