Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
929 PM EDT Monday may 25 2015
high pressure will extend across the region through early next
Near term /until 6 am Tuesday morning/...
no significant changes were made for the late evening update.
High pressure will remain across the area tonight. Isolated shower
activity has dissipated and expect dry conditions to prevail
overnight. A few light sprinkles could approach the South Carolina
coast after 3-4 am, but the risk for measurable rainfall is just
too low to justify mentionable probability of precipitation. Skies will clear this evening
with low clouds redeveloping after midnight as a rich/moist low-
level flow advects stratocumulus from off the Atlantic. The last
few usable visible satellite images Show Low clouds already
redeveloping over the Gulf Stream southeast of the Charleston
Harbor. Adjusted the sky forecast to show mostly clear conditions
this evening for most locations with clouds increasing overnight.
Lows will range from the upper 60s inland to the Lower-Middle 70s at
the coast--warmest along the beaches and downtown Charleston.
Short term /6 am Tuesday morning through Thursday/...
Tuesday...the weather pattern will remain nearly unchanged...with
surface high pressure centered over the Atlantic and upper ridge
sitting just east of the forecast area. Negative vorticity advection aloft will keep rain
chances pretty limited...with forecast only featuring slight
chance/low end chance far inland in the afternoon where better
moisture resides. Some models show a few showers moving onshore
Charleston County in the morning but currently think probabilities
are too low to include mention in the forecast. High temperatures
will be a couple degrees higher than normal...mainly in the upper
80s away from the coast where highs will only be in the low/middle
80s. Lows Tuesday night expected to be in the upper 60s/around 70.
Wednesday into Thursday...the upper ridge will weaken as shortwave
energy approaches the region. At the same time...a weak surface
trough is expected to develop west of the area. Increasing moisture
and aid from passing shortwaves will support slightly better chances
for afternoon showers/thunderstorms...especially inland. Convection
will die off after sunset. Highs will be in the middle/upper 80s...lows
in in the middle/upper 60s.
Long term /Thursday night through Monday/...
a broad upper ridge regime persists over the eastern United States
while Atlantic high pressure sits off the coast. Friday and Saturday
with the surface high farther north...slightly drier air will be in
place which will minimize precipitation potential. Sunday into
Monday as the high shifts south...low-level moisture increases and
slightly better coverage of daytime showers/storms expected. Highs
will be in the upper 80s to around 90.
Aviation /02z Tuesday through Saturday/...
VFR this evening with increasing probability for MVFR ceilings
overnight. Stratocumulus will move inland from off the Atlantic
later this evening with ceilings becoming established 07-09z at both
terminals. MVFR ceilings appear likely roughly 09-13z with conditions
improving to VFR thereafter. There is a low probability of IFR
ceilings at mainly kchs...but values are too low to justify mentioning
in the 00z taf cycle. Trends will be watched carefully, however.
Extended aviation outlook...mainly VFR through the period. Slight
chance for brief MVFR ceilings late morning into early afternoon
tonight...Atlantic high pressure remains in control with generally
southeast winds 10-15 knots. Seas will average 2-3 feet nearshore
waters and 3-4 feet offshore waters.
Tuesday through Saturday...Atlantic high pressure is expected to
prevail through the period. Onshore flow will generally be 15 knots or
less with seas 2-4 feet...highest in the outer waters.
Rip currents...local rip current calculations support a very
marginal low-end moderate rip current risk along the Charleston
County beaches with a low risk elsewhere. Per collaboration with
weather forecast office Wilmington...will hold the Charleston County beaches in a low
risk for now and reevaluate conditions after the 00z model suite
is received later tonight.