Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 280812
Area Forecast Discussion
National Weather Service Charleston SC
412 AM EDT THU JUL 28 2016
Atlantic high pressure along with an inland trough will prevail into
early next week. This high will migrate further out to sea and a
cold front may approach from the north by the middle part of next
.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: Warm and humid conditions will persist through daybreak as
expansive high pressure holds firm and skies remain mostly clear.
Lows will range from mid-upper 70s inland to the lower 80s at the
The synoptic pattern does not change much through tonight with the
center of strong mid level subtropical high just off the coast and
extensive deep layered ridging forecast to persist. Slightly lower
pwats are expected to move into the area today suggesting mid levels
will dry even more and 1000-850 mb rh progs show plenty of drying
as the day goes on. On a positive note, this will keep dew points
from pooling inland from the slow late day sea breeze. In fact,
forecast soundings show inverted-v profiles and even suggest surface
dew points could fall to the mid 60s inland from I-95 in some areas.
We have solid upper 90s high temps today and would not be surprised
to see a few spots touch 100 degrees as diurnal cumulus fields
expected to be sparse given forecast cloud progs and soundings. We
do not show heat indices touching our criteria values of 110 anywhere
today but will have to watch for a brief period of 106-109 apparent
temps along the typical sea breeze corridor from Mid-town Savannah
to Beaufort and Charleston as dew points surge before it can cool
much. All signs point to dry weather today but as is typical, we
cannot completely discount a couple brief showers or a tstm along
the sea breeze where the only decent surface moisture convergence
will occur. The low level gradient looks strong enough to incite
some decent breezes along coastal areas this afternoon with 15 to
20 mph gusts at times since the mixed layer looks to be unusually
deep for this time of year.
Tonight, another carbon copy of warm humid conditions and mainly
clear skies with lows ranging from some mid 70s inland to lower
80s right along the coast.
.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Stubborn ridging aloft is expected to persist across the Southeast
through the weekend as a shortwave trough moving across the Great
Lakes shifts over the Northeast. A series of mainly weak
disturbances will ride along the southern periphery of the trough,
which should reside across the Mid-Appalachians and Mid-Atlantic,
providing convective enhancement focused mainly to our north Friday
night through Sunday.
While Atlantic high pressure should remain in control
locally, suppressing most convection away from the sea-breeze each
afternoon, the proximity of more defined disturbances to the north
of the area will justify the highest POPs across the Charleston Tri-
County through most of the weekend to account for the possibility of
intruding boundaries initiating additional storms. Along and south
of the Savannah River should see close to climo (30-40%) afternoon
thunderstorm chances Saturday and Sunday thanks to increasing deep
layer moisture. Modest instability will keep the severe threat low.
Temps will remain above normal through the period given the west-
southwesterly low and mid-level flow and subsidence aloft. Highs in
the mid to upper-90s can be expected each day away from the coast,
with dew points mixing out to near 70 each afternoon resulting in
heat indices topping out in the mid-100s (though values near 110
immediately along the sea breeze may briefly appear each afternoon).
A few places could hit triple digit highs Friday if low-level winds
veer a bit more westerly than currently expected.
.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
The upper level ridge will gradually slide off the coast early next
week as the base of a broad upper level trough dips closer to our
area, resulting in a more unsettled period. At the surface: Atlantic
high pressure slides further out to sea, allowing troughing that has
been confined well inland over the past week to gradually spread
toward the coast. A weak cold front may approach, and possibly fully
cross, the area Tuesday, providing at least a temporary break from
the above normal temps for the middle portion of next week.
.AVIATION /08Z THURSDAY THROUGH MONDAY/...
VFR at KSAV/KCHS through 06Z Friday. A few surface wind gusts in
the 15 to 20 kt range are possible this afternoon along parts of
the coastal corridor.
Extended Aviation Outlook: VFR will prevail at both sites. Brief
flight restrictions possible, especially in the afternoon, with
isolated showers/thunderstorms Saturday through early next week.
No changes to the diurnal fluctuations we have seen the past few
days. Noctural surging early this morning will ebb later this
morning and surge again after mid afternoon into much of tonight.
The low level jet looks similar to the past couple of days but
perhaps just a bit stronger this evening and a few spots may reach
near 20 kt. Seas will average 2 to 3 ft within 20 nm and should
reach 4 ft during surges beyond 20 nm again tonight. Both the risk
for waterspouts and significant convection look quite low the next
Friday through Tuesday: Atlantic high pressure will prevail along
with an inland trough. This pattern will favor south to southwest
winds at 10 to 15 knots, with gusts that may approach Advisory
levels (25 knots) mainly along/off the Charleston County coast
during late afternoon/evening due to the sea breeze. Seas will be 2
to 4 feet, primarily winds waves.
Record high minimums for 28 July possible:
KCHS: 80 set in 2014...
KCXM: 83 set in 1999...