Area Forecast Discussion
Issued by NWS Columbia, SC-- Highlight Changed Discussion --
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FXUS62 KCAE 232159
Area Forecast Discussion
National Weather Service Columbia SC
559 PM EDT Sun Apr 23 2017
An approaching low pressure system will slowly cross the region
tonight through Monday night bringing showers and thunderstorms.
Dry weather and above normal temperatures will return by Wednesday
as high pressure takes control.
.NEAR TERM /THROUGH TONIGHT/...
Latest analysis continues to show a nearly stationary front
extending from joust south of Augusta to Orangeburg to just
south of Myrtle Beach. Closed upper low has developed over
northern Alabama with surface lows over northern and east
central Georgia. Scattered showers and thunderstorms have
developed across the Midlands, and will increase in coverage
this evening. There is the possibility of isolated supercells
tonight with moderate instability and strong mid level cooling.
A squall line type feature is expected push across the region
between 10 PM and 5 AM. A small tornado threat also exists
given the increased helicity values in vicinity of the frontal
boundary. SPC has the area outlooked in a slight risk for severe
Precipitable water values peak overnight with anomalously high
values close to 1.7 inches and with the slow movement of the
convection and orientation which may favor some training there
is the threat of heavy rainfall and possible isolated flooding,
certainly in the urban areas and other typical low lying
locations. SREF and GFS ensemble guidance suggest 48hr mean
total rainfall 2-2.5 inches with some higher totals as high as
4 inches possible. A flash flood watch has been issued for the
entire area from this evening through the day Monday. WPC has
part of the area outlooked in a slight risk of excessive rainfall.
There continues to be a great contrast in temperatures on
either side of the stationary front this evening. North of the
front, temperatures range from the upper 50s over the extreme
north to the lower 70s in the central Midlands, while south of
the front, temperatures have warmed into the mid 80s.
Overnight lows tonight will remain above normal but will
feature a gradient from the mid 50s western Midlands and upper
CSRA to mid 60s eastern Midlands.
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
The closed upper low to the west will shift eastward across
Georgia to off the southeast coast Monday into Monday night
bringing the coldest 500mb temperatures (as low as -18C) over
the forecast area creating steep lapse rates. Moderate
instability is forecast on Monday and the axis of highest
moisture will pivot over the Midlands and keep chances of rain
high. Heavy rain will remain a threat across the northern and
eastern Midlands with training convection likely. Could see
strong storms once again. SPC has the central and eastern
Midlands outlooked in a marginal risk. Extensive clouds and rain
will hold temperatures in the mid 60s northwest to mid 70s
southeast. The surface low and upper low will lift northeast of
the area Monday night and allow for cool advection resulting in
overnight lows in the mid 50s.
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Generally fair weather and a return to well above normal
temperatures expected by the middle of the week.
An upper level ridge will traverse the forecast area on
Wednesday with southerly low level flow which will support warm
advection. A weakening upper trough lifting northeast from the
Mississippi Valley into the Ohio Valley Wednesday night into
Thursday will push a weak cold front into the area by Thursday
night into Friday morning bringing a low chance for rain. The
front will become diffuse Friday into the weekend as the upper
ridge builds back over the southeastern states. Increasing
moisture and instability will bring another chance for diurnal
Temperatures during this period will be well above normal with
highs in the mid 80s to around 90 degrees with lows in the 60s.
.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
A nearly stationary front is currently draped across the CSRA
and southern Midlands. Scattered showers and thunderstorms have
developed across the area and coverage will increase this
evening. A squall line is expected to cross from west to east
between 02Z and 08Z with heavy rain and strong wind gusts. MVFR
ceilings in between showers, with IFR restrictions likely in
rain through Monday.
EXTENDED AVIATION OUTLOOK...CIG restrictions continuing Monday
GA...Flash Flood Watch through Monday evening for GAZ040-063>065-
SC...Flash Flood Watch through Monday evening for SCZ015-016-018-