Area Forecast Discussion
Issued by NWS Columbia, SC

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FXUS62 KCAE 252334

Area Forecast Discussion
National Weather Service Columbia SC
734 PM EDT Sun Jun 25 2017

A slow moving cold front will stall along the coast tonight
while high pressure builds in from the northwest. Cooler and
drier air with lower humidity is expected through mid week.
Moisture will return by the end of the week with increasing
temperatures and chances of rain through the weekend.


UPDATE: Showers developing along an outflow boundary over the
central Midlands from Bishopville through Rembert to just south
of Columbia to Gaston. MesoAnalysis indicated moisture
convergence with CAPES 2000-3000 J/kg and LI minus 3C to minus
5C. HRRR model has this area of convection drifting slowly
southeast through 06Z. Have adjusted pops across the Midlands

Previous Discussion: An upper level trough will continue over
the eastern CONUS. An upper level disturbance moving through the
base of the trough combined with slow moving frontal boundary
will continue showers and thunderstorms from the eastern
Midlands to the coast early this evening. The front will move to
the coast by daybreak Monday.

Convection should gradually move east of the Midlands during the
evening as drier air continues to filter into the region from
the north. Dewpoints will lower to lower 60s by Monday morning.
Patchy fog will be possible from the southern Midlands to the
CSRA tonight. Have forecasted overnight lows from the mid 60s
north and west to the lower 70s southeast.


The surface frontal boundary will be stalled along the coastal
plain on Monday with weak north to northwesterly flow across the
forecast area. The deeper moisture will still be lingering over
the southeastern Midlands and lower CSRA with precipitable
water values around 1.5 inches through the morning but lowering
through the day as high pressure continues to build into the
area. Forecast instability is expected to be minimal with lifted
index values around -2C through early afternoon and diminishing
after that with daytime mixing.

Given the very weak instability and diminishing deep moisture during
peak heating and frontal boundary southeast of the forecast area,
will carry a dry forecast although cannot rule out an isolated
shower in the far eastern Midlands.  Temperatures will be slightly
below normal with highs in the mid to upper 80s and lows Monday
night in the lower to mid 60s.


A digging upper trough will move across the Ohio Valley and Mid-
Atlantic on Tuesday bringing colder 500mb temps around -12C to the
region.  The deeper moisture and surface boundary that pushed
through the forecast area will remain stalled along the coast with
precipitable water values over the forecast area generally in the 1
to 1.3 inch range with the higher values in the southeastern
Midlands. The limited moisture is a limiting factor for convection
and forecast instability is expected to remain weak in our area so
will continue to carry slight chance pops mainly east of I-77 and
south of I-20 corridors.

Another shot of drier air will filter into the area behind the
trough Tuesday night and settle over the area Wed/Thu with surface
high pressure becoming centered over the Carolinas.  This seasonably
cooler and drier air mass will provide stable conditions and prevent
diurnal convection while providing a more comfortable less humid
environment for outdoor activities.

Moisture will be on the increase Friday through the weekend as the
surface ridge shifts offshore and return southerly flow develops.
The upper level pattern Fri-Sun becomes more zonal at 500mb with
some weak troughiness moving into the area Sat/Sun which will
provide an increased chance of diurnal convection supported by
precipitable water values back close to 2 inches.

Temperatures through this period will be slightly below normal
Tuesday then near normal the remainder of the week into weekend.


Area of dissipating convection across the extreme southern forecast
area (FA) expected to continue dissipating and pushing south. A
few new showers developing near CUB along an outflow boundary
may affect CUB and possibly CAE in the near term.

Otherwise, drier air will push into the FA from the north late
tonight behind a secondary front/trough. Veil of mid and high
level cloudiness appears will continue streaming across the FA,
though it may push south of the FA late tonight/early Monday
morning. These factors appear to preclude fog/stratus concerns
over most of the FA. However, at fog prone OGB where
precipitation occurred this evening and where dewpoints are
higher, some possibilities of MVFR fog exist, with some
potential at fog prone AGS if cloudiness clears late tonight.
Will include tempo groups at both locations. Otherwise, VFR.
Drier air will continue pushing into the FA Monday under NE
surface winds.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation




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