Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 240736

Area Forecast Discussion
National Weather Service Charleston SC
336 AM EDT Mon Oct 24 2016

A cold front will move through the region tonight and be followed
by another area of high pressure prevailing into the middle of the
week. A weakening cold front should approach late in the week
followed by more high pressure for the weekend.


The area will remain well embedded within a warm sector ahead of
an approaching cold front today. Despite a relatively chilly
start, temperatures are poised to rise quickly mid-late morning
once the nocturnal inversion mixes out, maxing out in the lower
80s for most locations away from the beaches. Extensive cirrus
moving across Texas and the lower Mississippi Valley early this
morning is forecast to move east, but should thin with time as it
propagates closer owing to lower RH in the 200-400 hPA layer this
far east. Still expect some patches of cirrus to pass through at
times, but skies should remain mostly sunny.


Tonight: The boundary layer will decouple quickly after sunset
resulting in mostly calm conditions away from the coast.
Temperatures will fall quickly owing to calm winds and mostly
clear skies, but thermal falls shouldn`t be as quick as the past
several nights given some cirrus will be present aloft, especially
central and southern zones. The boundary layer will gradually
recouple from north to south as a cold front drops through the
region. The front is on target to clear the Altamaha River just
before sunrise Tuesday. Favored the cooler side of guidance owing
to solid radiational conditions for much of the night, especially
central and southern areas. Lows will range from the upper 40s
across interior Southeast Georgia to the upper 50s/near 60 at the

Tuesday: A long wave trough will be off the east coast. A cold front
will be dissipating to our south in the morning while high pressure
builds across the Great Lakes, stretching into the Southeast. These
features will cause a pinching of the gradient, which will lead to
breezy NE winds along the coast. Gusts could reach 25-30 mph.
Despite the NE winds, mostly sunny skies and thickness values
support temperatures near normal in our SC counties and a few
degrees above normal in our GA counties. Low temperatures will be at
or slightly below normal due to clear skies and easing winds as the
gradient weakens.

Wednesday: The long wave trough will shift slightly offshore and
weak ridging will spread across the east coast during the day.
Surface high pressure generally east of the Appalachians should
gradually be pushed offshore due to a system in the upper MS Valley
moving eastward. As the flow become more onshore during the day, the
models hint that a few light showers could form across the Gulf
Stream and reach the GA coast late in the day. We kept POPs low here
due to the dry air mass in place, but this may need to be bumped up
if moisture increases with the changing synoptic flow. Daytime
temperatures will be near normal, but night time temperatures should
be above normal due to increasing clouds ahead of the aforementioned
MS Valley system.

Thursday: The ridge will weaken and get pushed offshore in the
morning as a trough stretches from the Great Lakes down to the
Southeast. A surface low over the Great Lakes will move into the
Northeastern states, helping push the remnants of surface high
pressure further offshore. A weakening cold front approaching from
the west should reach the southern Appalachians in the evening. Most
of the moisture in advance of this front is forecasted to remain
north of our area. The mountains will only help to limit the
precipitation potential for our area. Right now we`re only going
with a slight chance of light showers across the Charleston Tri-
County at night. This might be a stretch as the model trend has been
drier. But a few sprinkles are not out of the question. Warm air
advection ahead of the front will lead to temperatures several
degrees above normal.


The strongest portion of the trough along with the surface low will
pass well to our north, with the remnants of the cold front perhaps
reaching our area Thursday night. POPS are low given the dry air in
place and the system weakening as it reaches our area. A ridge and
surface high pressure are forecasted to build across the Southeast
Friday and Friday night. By Saturday the ridge and high will be
pushed offshore as another trough and associated surface low move
across the Great Lakes, reaching down into the TN Valley. Once again
most of the activity will remain to our north and POPs are low. High
pressure returns on Sunday.



Extended Aviation Outlook: VFR.


Today: Westerly flow will dominate the local marine area today
with the area positioned between a surface ridge extending across
northern Florida an a weak lee-side trough over the North
Carolina Foothills and South Carolina Upstate. Winds will average
10 kt, except 10-15 kt for the Charleston County waters where the
pressure gradient will be a bit tighter. Seas will average 1-2 ft.

Tonight: West winds will veer to the north overnight as a cold
front drops south through the marine area. Winds will average
10-15 kt, but will increase to 15-20 kt closer to sunrise for the
Charleston County waters. Seas will average 1-2 ft for much of the
night, but build to 3-5 ft over the Charleston County waters just
before sunrise.

Tuesday: A cold front will be dissipating to our south in the
morning while high pressure builds across the Great Lakes, reaching
into the Southeast during the day. These features will cause a
pinching of the gradient, which will lead to a fresh to strong NE
breeze, especially beyond 15 NM. Seas could build to 6 ft in the
evening, especially beyond 15 nm. Small Craft Advisories may be
needed for at least AMZ350 and 374 through the evening.

Wednesday through Friday: The gradient won`t be as strong as we go
from high pressure prevailing on Wednesday to a weakening cold front
passing to our north Thursday Night or Friday. Winds and seas are
forecast to remain below any Small Craft Advisory levels.




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