Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 250442
Area Forecast Discussion
National Weather Service Charleston SC
1242 AM EDT WED MAY 25 2016
Atlantic high pressure will prevail through Friday. A wave of low
pressure could develop offshore over the weekend before
dissipating or moving away early next week.
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Dry conditions persist overnight as high pressure strengthens
across the area. Winds will diminish and cloud cover will remain
thin, allowing temperatures to drop into the lower/mid 60s inland
and near 70 at the coast, several degrees milder than last night.
.SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/...
Wednesday and Thursday: Quiet, dry and warm conditions will
prevail during this period as the area remains positioned between
building subtropical ridge to the west and the formation of a
weakness near the Bahamas. Point soundings off the various global
models all depict a dry, subsident pattern holding for much of the
week with a pronounced mid-level capping inversion remaining in
tact, despite temperatures warming into the mid-upper 80s away
from the beaches. A rain-free forecast will be maintained both
days with only a shallow, diurnally driven cumulus field forming
during the afternoon ahead of the sea breeze. Lows both Wednesday
and Thursday Nights will range from the mid 60s inland to around
70 at the beaches.
Friday: Subsidence is poised to intensify further Friday as a
large tropical wave moves north of the Greater Antilles to a
position near the Bahamas Friday Night. Although an isolated
shower could certainly occur along/ahead of the sea breeze during
peak heating, the development of deep, moist convection should be
curtailed by increasing mid-level subsidence. Pops will be kept
below mentionable thresholds. Highs will be tempered somewhat by
the deepening onshore flow ahead of the approaching tropical wave.
Highs should only top out in the mid 80s for most locations away
from the beaches with a few upper 80s possible across far interior
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
There is considerable uncertainty this weekend and into early
next week as much will depend on the timing and strength of an
approaching tropical wave. There are signs that a weak surface
low could form somewhere off the Southeast U.S. coast as an upper
low over the Bahamas becomes a bit better defined, but there is a
lot of uncertainty on exactly how this scenario will play out. The
only clear signal right now is that the area could see a modest
increase in moisture and shower activity as the holiday weekend
unfolds. A conservative approach to this portion of the forecast
remains the best option this far out. Pops will be limited to
20-40% through the period with the highest rain chances confined
to the coastal regions.
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR through 06Z Thu. Very low probability for ground fog around
daybreak this morning.
Extended Aviation Outlook: mainly vfr.
Tonight...the sea breeze circulation will give way to synoptic
scale southerly flow as high pressure consolidates offshore.
Winds should remain below 15 kt, accompanied by seas 1-2 feet
within near shore waters and 2-3 feet beyond 20 nm.
Wednesday through Friday: A typical summer wind regime will
dominate through the period with a general South to Southeast wind
regime prevailing. Sea breeze influences are likely each
afternoon, especially near the land-sea interface, but the wind
fields do not look especially strong during any one period. Some
tightening of the pressure is likely by Friday as influences from
an approaching tropical wave intensify, but speeds look to go no
higher than 15 kt at this time. Seas will average 1-2 ft nearshore
with 2-3 ft offshore...building to 2-3 ft nearshore and 3-4 ft
offshore by Friday.
Saturday through Monday: A retreating Atlantic ridge and the
approach of a tropical wave/very weak low will produce more of an
east/northeast flow into the weekend. The gradient doesn`t appear
to be too strong at this time, with winds to remain below 15 kt or
so. However, seas will build some in response to the wave of low
pressure and some 6 footers might make it at least into the outer
Georgia waters at some point. Small Craft Advisory conditions may
occur at some point over the weekend.
Rip Currents: There could be increased risk of rip currents at
area beaches over the holiday weekend as an onshore flow
strengthens a bit ahead of a tropical wave coincident with a
slight uptick in swell energy.
Grays Reef Buoy /41008/ has returned to service.