Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Charleston SC
400 PM EDT Monday Aug 31 2015
on the periphery of Atlantic high pressure...a weak trough of low
pressure will meander over the southeast most of this week. Late
this week into next weekend...low pressure will develop over the
Atlantic while weak inland high pressure expands south and east
into the region.
Near term /until 6 am Tuesday morning/...
a much quieter night is expected with partly cloudy skies for
most areas and low temperatures ranging from low 70s inland to
high 70s near the coast. Low stratus/fog could be a concern...so
have included patchy fog for inland zones from 8 to 11z. Over
land zones...probability of precipitation generally capped at low- to- middle 20s...highest
to the south and nearest the coast to account for isolated
convection early due to any seabreeze activity. Highest chances
for precipitation should remain over the waters as deep moisture
increases and a middle level vorticity axis slides north from Florida.
Because of uncertainties with timing...probability of precipitation over water through the
period are capped at low-to- middle 30s.
Short term /6 am Tuesday morning through Thursday/...
Tuesday...surface high pressure will remain over the eastern U.S.
While a weak trough of low pressure lingers in the local vicinity.
Aloft...an upper ridge will sit atop the local area...however a
channel of vorticity will lift northeast out of the eastern
Gulf/Florida Peninsula towards the area. There are still a few
timing discrepancies between models on the evolution of this
feature...however it will result in higher chances of showers and
thunderstorms...with best chances across southeast Georgia where the
deepest moisture resides. High temperatures will be near
normal...ranging from the upper 80s/around 90. Tuesday
night...precipitation over land will largely diminish and rain
chances will shift to the coastal waters. Low temperatures will
mainly be in the low to middle 70s.
Wednesday into Thursday...the surface pattern will not drastically
change. The upper ridge will be suppressed from the north as a vorticity
maximum traverses Indiana/Ohio and moves into the Middle-Atlantic States.
More typical afternoon/evening precipitation coverage is expected
with lack of any prominent large scale forcing. Highest probability of precipitation will be
maintained over southeast Georgia where moisture is greatest.
Temperatures will be around normal.
Long term /Thursday night through Monday/...
a longwave upper trough is prognosticated to advance into the region from
the west late this week. Then...this feature could become cut-off
over the southeast as a blocking pattern develops next weekend
through early next week. Meanwhile...high pressure will gradually
build into the region from the north...producing a persistent/long
fetch onshore flow. By late weekend/early next week...a coastal
trough could develop. This pattern should support unsettled
conditions...justifying at least chance probability of precipitation during the day and
persistent nighttime probability of precipitation especially near the coast and across
adjacent coastal waters...as well slightly cooler high temperatures
in the middle to upper 80s.
Aviation /20z Monday through Saturday/...
both terminals have returned to VFR conditions. Some MVFR ceilings
could develop at either terminal prior to sunrise and persisting
into tomorrow morning due to lowering stratus. Light and variable
winds expected overnight at both terminals.
Extended aviation outlook through Friday...mainly VFR. Brief flight
restrictions could occur mainly within showers/thunderstorms.
flow remains offshore behind the wave that passed through the area
earlier today...but there are signs that a weak and/or short-lived
seabreeze could develop before sunset. Seas are capped at 5 feet
and windflow will become S or SW this evening. Seas expected to
diminish tonight as the gradient slackens and flow becomes
somewhat variable from north to south.
Tuesday through Saturday...surface high pressure will generally
maintain control of the weather pattern...however a trough of low
pressure will linger in the vicinity. Weak pressure gradient will
allow conditions to stay well below Small Craft Advisory criteria.
On average winds will be less than 15 kts with seas 3 feet or less.
Rip currents... an elevated risk for rip currents exists today and could
persist Tuesday. An elevated risk for rip currents could develop
again next weekend.
a coastal Flood Advisory may be needed this evening to account
for higher than normal tides...but early indications suggest that
The Tides may not reach required levels. Tide levels would be
impacted by a seabreeze...but there are no significant signs of
such a circulation at this time.