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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCAE 202130
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
530 PM EDT Sat Apr 20 2024

.SYNOPSIS...
A cold front moves slowly southward and through the area
tonight. The front becomes stationary near or slightly south of
the area Sunday. Deep moisture and lift across the area will
result in numerous showers Sunday and Sunday night. Temperatures
Sunday and Monday are expected to be well below normal. Drier
conditions return on Monday, with a gradual warming trend
through the week.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
21z Update. SPC has issued a severe thunderstorm watch until
1000 pm for the Pee Dee and east Midlands. Thunderstorms have
developed in the north Midlands near surface frontal
boundary/trough where moisture is pooling/convergence quite
enhanced. Meso-analysis indicates moderate to strong
instability downstream. Moderately strong deep layer shear near
40 kts. Strongest shear near the NC/SC border. Storm mode has
been supercell with large hail and damaging winds the main
threats. CAMS suggest a threat to the east-southeast this
evening as the boundary sags south.

Previous discussion...

A weak surface trough and slow moving moisture-thermal boundary
continue to linger across the Southeast with westerly flow
aloft nearly parallel to the boundary. Only some scattered
strato-cu is pushing across the area as relatively dry air at
low levels is keeping any deeper convection from developing
early this afternoon. HREF members have trended slightly more
aggressive with potential convection later this evening as some
surface convergence and pressure falls occur along the surface
boundary in NC and SC. Forecast soundings generally develop
between 1000-1500 ML CAPE between 21z and 00z, generally along
I-20 and southeast; however, the HRRR and other HREF members are
extremely consistent showing a cluster of stronger storms near
the NC-SC border during this time, thanks to enhanced moisture
pooling due to stronger pressure falls and low development which
is line with current obs. Organized severe potential remains
fairly low in any convection that does develop as shear is
relatively weak and pulse severe is also limited as theta-e
depressions aloft are minimal thanks to relatively moist mid-
levels. Some an isolated severe storms remains possible later
this evening and SPC slightly expanded their marginal risk
accordingly.

The boundary will finally push south and east later tonight with
strengthening northerly, dry low level flow and corresponding
increasing 850-700mb moisture advection and isentropic lift. So
shower activity will increase as the boundary sags south
overnight into Sunday morning with wedge conditions beginning to
develop.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Sunday and Sunday night: Surface cold front will be situated
south of the forecast area. Weak high pressure off to the north
will push cooler air into the region on northeasterly winds,
allowing a low-level wedge to develop. Aloft, shortwave energy
moves out of the central Gulf Coast States to start off the day,
then traverses the southeastern U.S. into Sunday night. Ahead
of the upper wave, a good deal of isentropic lift is expected as
warm moist air lifts and overrides the surface wedge in place
across the forecast area. This will lead to periods of light to
moderate rainfall for a good portion of the daytime hours
Sunday. Temperatures will be much colder as the wedge develops
and rainfall re-enforces it through the day. High temperatures
may actually occur early in the day in many areas, with
temperatures either holding steady or slowly falling through the
day. Max temperatures are expected to range from the upper 50s
north to mid 60s south. Sunday night will see the rain begin to
end from west to east as upper energy moves east and towards the
coast. Lows Sunday night in the lower 40s north, to the upper
40s south.

Monday and Monday night: As deeper moisture moves east with both
the exiting shortwave and surface front, drier air will be
settling back into the area through the day. Can not rule out a
brief period of light rain across the extreme east early Monday
morning as the system moves out. In addition, an isolated shower
can not be completely ruled out as the main upper trough moves
through. For the majority of the forecast area, it will remain
dry though. Clouds may still hang around behind the low through
a good portion of the day, which will still help to keep cooler
temperatures in the area, but still a little warmer than
Sunday as highs do reach into the middle 60s. Skies should begin
to clear out some by Monday night. Overnight lows in the low to
mid 40s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Period will be mostly on the dry side, with only a slight chance
for rain entering late in the period. Two frontal boundaries
are forecast through the period. The first comes through
Wednesday night/Thursday, but with limited moisture to work with
it should push through mostly dry. Better chance for rain may
occur with the second front toward next weekend. Temperatures
will slowly continue to moderate each day through the week.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
VFR conditions are expected through this afternoon. Evening
showers-storms possible, with deteriorating conditions Sunday
morning.

Some mid-level strato-cu likely this afternoon with light west
winds less than 10 knots. Showers and storms are possible later
this evening, after 21z, primarily at CAE-CUB-OGB but confidence
is too low for direct TAF mention for now; included VCSH from
this evening onward. Low VFR ceilings will push in behind the
boundary overnight into Sunday morning, but should remain VFR
through 09z Sunday at AGS-DNL and 12z at CAE-CUB-OGB before
dropping to MVFR. Widespread showers and some isolated
thunderstorms are also expected overnight starting after 06z at
all sites through the end of the TAF period. IFR cigs will then
likely develop by late Sunday morning for all sites and remain
down through the end of the period.


EXTENDED AVIATION OUTLOOK...High confidence in ceiling and
visibility restrictions Sunday night into Monday with wedge
conditions expected.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...None.
GA...None.

&&

$$

SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...