Area Forecast Discussion
Issued by NWS Charleston, SC
FXUS62 KCHS 250815
Area Forecast Discussion
National Weather Service Charleston SC
415 AM EDT MON JUL 25 2016
Atlantic high pressure will prevail through much of the week while
a weak trough persists inland.
.NEAR TERM /THROUGH TONIGHT/...
Pre-dawn: Tranquil weather overnight as deep layered subtropical
high pres remains locked in over the region. A few high thin
cirrus and patchy altocumulus can be expected as dawn approaches.
There may be a few showers developing off the beaches with weak
speed convergence offshore. Temps are in the mid 70s inland to
upper 70s coast.
Today the pattern favors slowly building mid level heights over
southeast Georgia and the Carolinas as a weak upper low moves over
the Gulf of Mexico while an upper trough pulls away from Canadian
Maritimes. Warm temps of -3C to -4C at 500 mb and a slot of drier
and more stable air easing in off the Atlantic will enhance
subsidence over the forecast area this afternoon. Yesterday we saw
isolated diurnal convection mainly along the sea breeze corridor
and today we expect that shower/tstm coverage will be even less as
building subsidence aloft acts to quell updraft potential. We have
some slight chance pops along the South Carolina sea breeze and
well inland this afternoon but pops mainly less than 20 percent at
any given location. Despite good downdraft capes and steep low
level lapse rates again, risk for any strong tstms looks very low
given the proximity soundings around the area from both the
Rap/Nam models. High temps will average mid 90s but there could be
a few upper 90s closer to the CSRA and SC midlands. Low level dew
points are expected to mix out fairly good for this time of year
and heat indices should not be close to advisory levels this
afternoon, mostly below 105 degrees.
Tonight will be mostly clear most areas with lows again in the mid
70s many areas.
.SHORT TERM /TUESDAY THROUGH THURSDAY/...
Impressive and persistent mid/upper-level ridging extending across
the Carolinas and Georgia will remain in place into the second half
of the week. Model guidance is consistence with showing below-
normal precip through this period, due largely to the lack of
substantial deep layer moisture and CAPE values mainly 1500 J/kg or
less through peak afternoon heating each day. Have removed
mentionable POPs from the forecast for the Charleston Metro for
Tuesday, with only slight chance maintained across most of Southeast
Georgia where models indicated that convection across Northern
Florida could creep a bit north Tuesday afternoon. Slight chance
POPs will remain in the forecast mainly along the sea breeze
corridor and inland Wednesday and Thursday as confidence is lower in
convective personality at this point. Early morning land-breeze
formation will likely result in some convergence along and off the
coast each morning, but and storms forming along this boundary
should remain isolated and weak with a couple of waterspouts the
Temps will remain above normal through the period given the warm
airmass already in place, WSW flow through the low/mid levels and
subsidence aloft allowing for plenty of sunshine through midday each
day. Heat indices will top out in the mid to upper 100s each day,
with a few areas possibly near the 110 briefly in the afternoons,
though not likely long or widespread enough to solicit a heat
.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
Hot and humid conditions will continue through the weekend as
ridging persists overhead and Atlantic high pressure remains at the
surface. A weak cold front may approach from the north Friday or
Saturday, but will likely dissipate before reaching the area.
Afternoon thunder chances across land areas, and morning thunder
chances over the waters, trend closer to climo in the long range,
with dry air/subsidence aloft gradually moderating through the
weekend. High temps will continue to reach the mid-to- upper 90s
away from the immediate coast through the weekend assuming minimal
debris clouds and convection abates until mid-to- late afternoon
A pattern change could come as early as Monday as weak upper level
troughing begins working into the eastern U.S.
.AVIATION /08Z MONDAY THROUGH FRIDAY/...
VFR conditions expected to prevail at KCHS/KSAV through 06Z Tue.
Very low chance for isolated convection this afternoon along
the sea breeze.
Extended Aviation Outlook: VFR will prevail at both sites. Brief
flight restrictions possible with isolated afternoon
showers/thunderstorms mainly late week.
Persistence forecast through tonight as the pattern holds with
the Atlantic ridge axis. Wind speeds will increase later today as
the sea breeze rolls inland and reach 15 kt tonight as the nocturnal
boundary layer jet peaks and then veers more westerly nearing
daybreak on tuesday. Seas will average 2 to 3 ft much of the time.
Tuesday through Saturday: Atlantic high pressure will prevail
through the period with south-southwest winds through Thursday.
Expect winds mainly 10 to 15 knots and seas generally 2 to 3 feet,
with gusts to 20 kt and seas to 4 feet across the outer Georgia
waters during the early morning hours. Any early morning showers and
thunderstorms will remain isolated.