Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 281342
AFDCHS

Area Forecast Discussion
National Weather Service Charleston SC
942 AM EDT THU JUL 28 2016

.SYNOPSIS...
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
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
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 /14Z THURSDAY THROUGH MONDAY/...
VFR at KSAV/KCHS through 12Z Friday. A few surface wind gusts in
the 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.

&&

.MARINE...
No changes to the diurnal fluctuations we have seen the past few
days. Noctural surging currently ebbing will 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 with sustained
flow. 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
24-30 hours.

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.

&&

.CLIMATE...
Record high minimums for 28 July possible:
KCHS: 80 set in 2014...
KCXM: 83 set in 1999...

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...CEB
AVIATION...
MARINE...
CLIMATE...



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