Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 242238
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
638 PM EDT WED AUG 24 2016

.SYNOPSIS...
High pressure will prevail into the weekend. A weak surface trough
will push into the region by late weekend, then persist through the
middle of next week.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
For the 64th day in a row the temperature at Savannah (KSAV)
reached at least 90F, it`s longest stretch in recorded history.

Aside from a brief stray shower on the sea breeze front near and
west of US-301 in GA this evening, conditions look to be rainfree
tonight as deep layered ridging prevails. Some low level
convergence will arrive overnight across the Atlantic waters, what
can be seen generating isolated-scattered showers off the cost of
NC this evening. This activity is currently forecast to stay over
the ocean, although it will approach the coastline closer to
daybreak.

Considerable dry air, especially in the layer from about 850-400
mb, where mean RH is as low as 15-25% will prevail. Associated
PWat is down near 70 or 80 percent of normal for late August, and
with dew points in most sections in the 60s and winds to decouple
quickly away from the coast this evening, we`re looking at the
coolest night for many of us in about 2 months.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
Thursday and Friday: A large mid/upper lvl ridge of high pressure
will prevail over the Southeast late week, generally favoring a dry
forecast over most locations. However, we can not rule out a few
showers and/or isolated thunderstorm drifting onshore in Southeast
Georgia or well inland where a weak sfc trough approaches the region
from the northwest late week. At this time, the front should have
minimal impact to the forecast area while temps continue to modify a
few degrees under the persistent ridge aloft. In general, high
temps should peak in the upper 80s to lower 90s on Thursday,
followed by low/mid 90s on Friday. Overnight lows will also show a
warming trend, ranging in the upper 60s to lower 70s Thursday
night, then lower 70s inland to mid/upper 70s near the coast
Friday night.

Saturday: Very little change is anticipated in the overall pattern
this weekend. However, models generally agree that the mid/upper
ridge of high pressure over the Southeast will nudge further
north/northeast, allowing an east/northeast flow to become more
directly onshore. The setup will favor some moisture advection from
the Atlantic while afternoon temps peak in the low/mid 90s. Given
the moisture and heating, slight chances of showers/thunderstorms
will remain in the forecast with greatest chances occurring in
Southeast Georgia where a seabreeze should be slightly more active.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
The eastern CONUS upper ridge and associated surface high are
expected to weaken this period. Details regarding this process
differ, but a reasonable scenario includes general weakening of
subsidence/capping aloft and a trend toward surface troughing.
This should, in turn, support an increasing chance of
showers/thunderstorms as onshore flow/moisture transport persist.
Latest forecasts include a transition from slight chance POPs
north/chance POPS south Sunday-Monday to greater coverage of chance
POPS Tuesday-Wednesday, especially during the daytime hours.
Meanwhile, odds favor slightly above normal temperatures through
much of the period.

Guidance generally agrees that a tropical cyclone could be
approaching south FL by later this weekend. However, solutions
diverge greatly thereafter, so this feature does not directly
factor into our forecasts through the middle of next week.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
VFR will prevail.

Extended Aviation Outlook: VFR conditions are expected at both CHS
and SAV terminals.

&&

.MARINE...
Tonight: A huge anticyclone centered near 40N and 65W and
extending across the SE and into the Gulf of Mexico will be the
dominant weather feature. There exists a fairly decent packing of
the isobars between it and lower pressures in the Caribbean,
enough to produce E and NE winds as high as 15 or 20 kt this
evening, before they back slightly and diminish to 15 kt or less
after midnight. While there will be an occasional small swell that
moves in, the bulk of the wave energy will be in the form of short
period wind waves averaging 3-4 ft.

Thursday through Monday: High pressure will dominate the coastal
waters through Saturday, before giving way to a weak trough of low
pressure which will advance into or develop over the waters this
weekend. With occasional/minor variations, east/northeast winds
should average between 10-15 kt with gusts as high as 20 kt through
this period. Through late week, seas will range between 2-4 feet,
although seas as high as 5 feet will occasionally push into the
outer Georgia waters. Then, the long fetch/duration onshore flow and
the possible arrival of larger, long period swell emanating from TC
Gaston will increase the chance for Small Craft Advisory conditions
beyond 20 nm this weekend into early next week.

Rip currents: Onshore winds and a small long period swell will
persist this week, perhaps elevating the risk of rip currents by
late week. There is a chance that a larger, long period swell
created by TC Gaston swell could reach the beaches as early as this
weekend. If this occurs, the chance for rip currents will increase
significantly this weekend into next week.

&&

.TIDES/COASTAL FLOODING...
A long duration of E/NE winds will support elevated high tides
through at least this weekend. Extratropical surge guidance has
consistently held tides at least one-half foot below Coastal Flood
Advisory levels through the period. However, there remains a low
probability that afternoon high tide levels could slightly exceed
forecasts and approach Coastal Flood Advisory thresholds especially
along the SC coast.

&&

.EQUIPMENT...
The Metter NOAA Weather Radio All Hazards station, WWH-25 will be
off the air until further notice.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...SPR
AVIATION...
MARINE...
TIDES/COASTAL FLOODING...
EQUIPMENT...



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