134
FXUS62 KCAE 172337
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
737 PM EDT Sat Aug 17 2024

.SYNOPSIS...
A cold front approaches the Southeast US this weekend along with
increasing moisture and rain/thunderstorm chances. A few strong to
severe storms will be possible, with better chances on Sunday. Drier
air and cooler temperatures are then on tap for early to mid next
week. The next chance for rain arrives late in the work week

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Message(s):

- Thunderstorms likely in the western Midlands this evening,
  some damaging wind and hail possible.

As the primary mid-level trough continues to dig towards the
area, a shortwave and associated forcing is helping fire some
convection across northern GA and Upstate SC. Given the synoptic
scale trough pushing towards the area, we actually have some
notable effective and deep layer shear across eastern GA and
central SC, generally between 30-40 knots. Instability
additionally is fairly impressive with a broad swath of
1500-2500 ML CAPE over the forecast area thanks to abundant low
level moisture and falling mid-level lapse rates. These
thunderstorms are expected to push into the Midlands before
diurnal cooling helps stabilize things a bit, and diminishes
any severe threat. So some scattered damaging winds, especially
in Fairfield and Newberry counties, are possible through 11pm
and in general, anyone along the I-20 corridor should be
prepared for some potentially strong-severe thunderstorms from
8pm through 11pm. The threat after 8pm should transition to
more of primary wind threat, rather than hail, as the line grows
upscale and becomes more linear.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Message(s):

- Scattered afternoon thunderstorms expected, a few of which
  could produce damaging wind gusts.

A bit of a tricky forecast for Sunday. Upper trough over the Great
Lakes region is expected to amplify and eject a rather robust mid-
level shortwave around its base. This disturbance is progged to
move through GA and the Carolinas Sunday afternoon and evening
in conjunction with a surface front. Adequate moisture will be
available, with PWATs around 1.5"-1.7". Convergence along the
approaching surface boundary is expected to be sufficient enough
for convective initiation. Given forecast temperatures in the
low 90s and dewpoints in the low 70s, SBCAPE between 1500 and
2500 J/kg should generate a broken line of storms along the
front. Potential for mainly severe wind gusts will exist, given
DCAPE values in excess of 1200 J/kg and 0-6km bulk shear of
25-35 kts aiding in organization. Some model discrepancies exist
with the timing of the frontal passage, and the extent of
thunderstorm coverage will likely depend on sufficient heating
as it moves through. Current thinking is that the eastern half
of the CWA is at greatest risk, or mainly east of I-20. This
area should have convective elements lining up the best in time
and location. HREF members are generally showing initiation in
this region, though its possible the strongest storms will be
reserved for the Coastal Plain. As the forecast stands now, SPC
has placed almost all of the Midlands and CSRA in a Slight Risk
for severe thunderstorms. Thunderstorms that do develop will
push southeastward along with the front. Behind it, drier air
will begin to filter into the area with falling PWAT values and
lows around 70.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Key Message(s):

- Dry through midweek before rain chances return for the end of
  the week.

Next week is relatively quiet compared to the first half of the
month. Upper level troughing will remain in place over the eastern
CONUS through midweek with drying northwest flow aloft. We`ll still
have some lingering moisture near the surface, but dewpoints will be
lower, generally in the 60s or perhaps upper 50s, while PWATS will
linger between 1" and 1.25". With this stagnant pattern, the front
that pushes through Sunday and Sunday night will linger just
offshore, with showers and thunderstorms south and east of our area
through midweek. Late in the period, deterministic and ensemble
solutions are in good agreement that surface high pressure will
strengthen over the Great Lakes and move eastward before ridging
down the coast. The breakdown of the upper trough is then expected
to assist in allowing the offshore front to move back toward the
coast. As such, there will be a slight increase in shower and
thunderstorm chances at the end of the week, particularly for the
eastern Midlands. Overall moisture will still be on the lower side
though, so maintained only slight chances for these areas.
Temperatures this week will be quite pleasant for August, in the mid
to upper 80s with lows in the mid to upper 60s.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR outside of any convection.

Broken line of showers and thunderstorms is better organized
across much of upstate SC and GA this evening. This activity is
forecast to hold together and remain quite organized over the
next several hours. Latest guidance does show the thunderstorms
approaching the central Midlands and CSRA after 02z this
evening, lasting through about 06z. Have gone ahead and
introduced vcts between 02z-03z, with a 2-3 hour tempo window
for thunderstorm activity with mvfr restrictions at
ags/dnl/cae/cub. Not as confident in any of these storms holding
together into ogb, so not mention of any thunderstorms in that
location. After 06z, remainder of the overnight into Sunday will
be dry. Additional convection possible across the eastern
Midlands on Sunday, but low confidence at this time.

Outside of convection, vfr conditions are expected to prevail
through the entire 24 hour taf period. Winds remain gusty this
evening before becoming lighter late tonight. Additional wind
gusts will pick back up late morning on Sunday.


EXTENDED AVIATION OUTLOOK...Scattered showers and thunderstorms
are expected Sunday afternoon and evening, possibly strong to
severe with restrictions possible.

&&

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

&&

$$