036
FXUS62 KCAE 170757
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
357 AM 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
storms are possible each day this weekend, with higher chances
on Sunday. Drier air and cooler temperatures are then on tap
for early to mid next week. The next chance of rain arrives for
late week.

&&

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

- Scattered thunderstorms late this afternoon and evening
  focused in the west and north Midlands/CSRA. A few storms may
  be severe.

Deep upper trough over the Great Lakes region will be moving
slowly east today and amplifying across the Tennessee river
valley. The upper ridge that has been in place across the area
will retrograde and resulting heights aloft will be falling
although short wave energy moving thru the trough appear to be
weak and mainly north of the area. Upper divergence does
increase across the area, especially north and west late in the
day. At the surface, expect Piedmont trough to set up and
strongest low-level convergence will be in the Upstate.
Moisture flux increases this afternoon with southwest low-level
flow with an axis of 2.00 inch or slightly higher precipitable
water values across the area around 00z Sunday. Weak warm
advection/some downslope flow so forecast high temps in the low
90s, a little higher than guidance. Model soundings show
moderate instability with surface based CAPE 1000-2000 J/kg.
CAPE appears "long and thin". HRRR model shows moderately strong
deep layer shear approaching 30 kts. The GFS shows stronger
shear. So, some potential for organized strong convection late
in the afternoon and evening especially across the Piedmont into
the north Midlands. Soundings do not show inverted V, but some
precip loading/wet microburst potential. CAMS show scattered
convection moving southeast out of the Upstate into the
west/north Midlands during the late afternoon/evening period
then weakening late in the evening. Other storms may develop in
the CSRA from north Ga. So a few strong to severe thunderstorms
possible given possible higher CAPE than models indicating as
temperatures rise into the low 90s and clouds delayed. A few
lingering showers overnight, low temps in the low 70s.

&&

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

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

Upper trough over the Great Lakes region continues to trek
eastward through the day, amplifying as it does. An embedded
shortwave is forecast to move through the area during the
afternoon timeframe. Meanwhile at the surface, a cold front is
expected to pass through the forecast area during the day. Ahead
of the front, southerly flow reinforces low-level moisture flux
into the area, particularly the eastern half of the state.
Behind the front, drier air begins pushing into the western
portions of the state, causing a fairly tight moisture gradient
across our area. Latest guidance suggests the front and
associated moisture gradient sets up along I-20. Some of this
location is dependent exactly where the front and moisture
gradient set up. Expect thunderstorms to develop along area and
push southeastward as the front progresses in that direction.
Hi-res guidance indicates that areas in the eastern Midlands are
forecast to see mixed layer CAPE values over 2000 J/kg along
with 0-6 km bulk shear values in the 25-35 kt range. In
addition, low-level lapse rates are forecast to be high, around
9.0 degrees C/km. These parameters suggest there is a risk for
severe weather with some of the activity Sunday afternoon into
the evening, with damaging winds being the primary threat.

&&

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

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

Upper level trough remains over the Atlantic seaboard through
midweek while the surface front is forecast to remain offshore.
This is expected to allow cooler and drier air to settle into
the area for the first half of the week. Ensembles then indicate
a surface high building over the Mid-Atlantic to Northeast,
which could aid in pushing the surface front back toward the
area, leading to slight chances for rain to end the week.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
VFR Conditions expected through at least 18z. Scattered
thunderstorms in the late afternoon and evening may result in
brief restrictions, but confidence low at this time.

Mid level clouds spreading into the region this evening as
convection upstream dissipates. Guidance indicating a low fog
threat early this morning. High pressure has shifted to the
coast. The upper ridge over the area will be weakening today as
an upper trough over the Great Lakes region amplifies. At the
surface a Piedmont trough will set up and provide some weak low
level convergence. The air mass is expected to become moderately
unstable in the afternoon and moisture appears high. The high
resolution models suggest scattered convection will develop in
the afternoon, after 18z. A few storms may impact terminals
primarily during the 18z Saturday to 04z Sunday, but confidence
low at this time. So, scattered to broken VFR cumulus expected
especially during this period. Winds will be southwest 5 to 10
knots with a few higher gusts in the afternoon.

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

&&

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

&&

$$