Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
445 am EDT Sat may 30 2015
a weak trough of low pressure off the southeast coast will move
inland later this morning and this afternoon. High pressure will
then return Sunday and persist until a cold front moves into the
area and stalls middle week. Low pressure could move northward along
or near the coast later next week.
Near term /through tonight/...
today...middle and upper level ridging will continue to extend across
the region. At the surface...a weak coastal trough is positioned
just offshore early this morning. This trough will begin to shift
onshore late this morning...then progress inland along with the
sea breeze this afternoon.
Low level convergence associated with the coastal trough has
resulted in the development of scattered showers over portions of the
coastal waters early this morning. These showers will begin to
advect onshore around daybreak...then steadily progress inland
with the westward advance of the trough/sea breeze through this
afternoon. The showers should be scattered in coverage across
most areas...except more isolated north of the I-26 corridor where
low level convergence will be weaker. Isolated thunderstorms are
certainly possible as well today...but with poor middle level lapse
rates and strong subsidence aloft limiting vertical growth...the
potential for any strong/severe thunderstorms appears very low.
Temperatures will once again warm to highs in the middle and upper
80s across most inland areas...with an onshore flow off the Atlantic
limiting the beaches/barrier islands to highs around 80 or in the
lower 80s. Easterly winds will veer a bit more to the southeast
behind the sea breeze...and could become gusty at times closer to
Tonight...Atlantic high pressure will build into the region. There
is some indication that weak low level convergence could develop
along and/or just off the Georgia coast later tonight.
Isolated showers/thunderstorms could linger west of the I-95
corridor into early evening...then dissipate as the sea breeze
shifts west of the area and with the loss of diurnal heating.
Isolated showers and thunderstorms could then develop within the
area of low level convergence late tonight and affect portions of
the upper Georgia coast. Low temperatures should be in the middle and
upper 60s inland...with lower 70s near the immediate coast.
Short term /Sunday through Tuesday/...
high pressure weakens through the period as an upper trough deepens
over the Gulf Coast region. Meanwhile...a cold front will move
toward the area from the north and west with deep moisture advecting
northward from Florida. This will result in slightly higher than
normal rain chances much of the period with temperatures a bit above
normal. Increasing instability by Monday and Tuesday could yield a
few stronger to possibly severe storms.
Long term /Tuesday night through Friday/...
unsettled weather on tap through most of the rest of the week with a
stalling front over the area and possible low pressure somewhere
around the southeast U.S. Coast. Thus...rain chances should be above
normal with temperatures likely cooling off a bit toward the end of
the week...especially if low pressure tracks close to the local
Aviation /08z Saturday through Wednesday/...
patchy smoke caught beneath a low level inversion could briefly
reduce visibilities to around 6sm through daybreak at kchs.
Otherwise...VFR conditions are generally expected to prevail at
kchs and ksav through 06z Sunday. The inland progression of a
weak coastal trough could allow isolated to scattered showers to
develop toward daybreak...before shifting inland of the terminals
by middle-afternoon with the sea breeze. Have maintained mention of
vicinity showers at both terminals...but with a greater coverage
of showers expected near ksav have also included a tempo group
there for showers with MVFR ceilings/visibilities from 15-19z.
Gusty southeast winds are then expected at the terminals from middle-
afternoon to early evening behind the sea breeze.
Extended aviation outlook...mainly VFR. Small chance for flight
restrictions within mostly late morning/early afternoon rain showers and
thunderstorms and rain through Wednesday.
today...an inverted trough over the coastal waters will retrograde
and eventually shift inland late this morning into this afternoon.
As this occurs...easterly winds will veer a bit more to the
southeast this afternoon. Wind speeds will generally be less than
15 knots over the open Atlantic waters...but become enhanced upwards
of 15-17 knots near the land/sea interface as the sea breeze
circulation develops this afternoon. The majority of the wave
energy will be a 9-11 second swell around 3 or 4 feet...atop a short
period wind wave. Significant wave heights will average 3-4 feet
across the near shore waters and 4-5 feet across the outer Georgia
waters through the day. Isolated to scattered showers will
Tonight...Atlantic high pressure will maintain southeast winds
generally around 10 knots or less. Wind speeds should diminish a bit
as the night progresses due to a weakening surface pressure
gradient. Seas should also gradually subside by about a foot or so
by late tonight.
Sunday through Thursday...Atlantic high pressure in control into
Tuesday before a cold front likely pushes south into the area
Wednesday and then stalls into Thursday. Meanwhile a trough of low
pressure over the western carribbean/near Florida could strengthen
into a low and begin to move north toward the end of the period.
Conditions could be worse than currently depicted Thursday depending
on the strength and position of the low.
Rip currents...persistent onshore flow will result in an elevated
risk of rip currents. A moderate risk of rip currents will be in
effect for all beaches today.