131
FXUS62 KCAE 110912
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
512 AM EDT Sun Aug 11 2024

.SYNOPSIS...
Hot temperatures and high humidity are likely to lead to triple
digit heat indices again today. Scattered afternoon and evening
thunderstorms are also likely this afternoon. River flooding is
expected to continue over the next several days. Temperatures then
cool off slightly early this week with daily chances of afternoon
showers and thunderstorms continuing.

&&

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

- Patchy fog possible around daybreak.
- Isolated flash flooding and severe thunderstorm potential
  this afternoon.

High clouds are moving off to the east this morning as seen on
satellite imagery. The low levels remain quite saturated, with
temperatures in the mid 70s and dewpoint depressions of only 1 or 2
degrees. With that in mind, as the clouds move off to the east,
areas of patchy fog and low stratus will have a chance to develop in
the hours before dawn, particularly with calm or nearly calm winds
at many observation sites. Some locations are already reporting
visibilities down to 4 or 5 miles, but would not be surprised to see
further reductions over the next couple of hours.

For the remainder of today, much of our weather will be similar to
Saturday. Upper level winds will be relatively zonal with a weak and
diffuse surface boundary nearly stationary across the area.
Temperatures are expected to rise into the mid 90s, with dewpoints
steady in the mid to upper 70s. We will still have some minor
concerns around the heat index values, but they should remain at or
below 105 degrees for the most part, and no headlines have been
issued. This robust heating combined with copious moisture (PW
values of 1.8" to 2.2") is expected to generate moderate to strong
instability, with SBCAPE values over 2000 J/kg. Despite the moist
atmosphere, we are also expecting some mid level dry air to filter
in, and DCAPE values at or greater than 1000 J/kg will raise
concerns for strong to severe thunderstorm winds. Some additional
organization is possible for any storms which develop across the
northern Midlands, as forecast shear values in that area are
slightly higher. The surface boundary and perhaps sea breeze will
likely serve as the main areas for convective initiation, and PoPs
are generally lower in the western Midlands and slightly higher in
the eastern Midlands. Additionally, WPC has maintained a slight risk
of excessive rainfall for the eastern Midlands and a marginal risk
in the western Midlands due to saturated antecedent conditions. So
we will be on the lookout for any slow moving and/or training storms
which could pose an elevated Flash Flooding threat this afternoon
into this evening. HREF members are generally in good agreement
regarding this scenario.

The boundary should sink to our south tonight, and convection is
expected to diminish after sunset. Some lingering clouds tonight
could inhibit cooling, but generally we can expect overnight lows in
the mid 70s once again.


&&

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

- Showers and storms expected across the eastern half of the forecast
  area on Monday, with chances decreasing on Tuesday.

Nearly zonal flow aloft will develop throughout Monday as deep
ridging builds to our west and the trough over the Mid-Atlantic
slides east. The diffuse surface trough that has lingered over the
Southeast since the departure of Debby will remain in place for
another day, with a broad moisture gradient across SC. PWAT`s will
remain above 2.0" for our forecast area and dew points will float
around in the mid-70`s. Instability will be a bit weaker on Monday
compared to the weekend, primarily due to relatively "cool" surface
temps around 90; generally lower heights, weak northeasterly flow at
low levels, and some persistent cloud cover are the primary
cause for the cooler temps. PoP`s and convective potential in
general in the GEFS, EC, and HREF are mostly consolidated to the
eastern Midlands and coastal plain, which makes sense given the
weaker instability inland and lack of true forcing outside of
sea breeze convergence.

The pattern begins to amplify on Tuesday as ridging builds further
in the south-central US, positioning the fa under northwest flow
from 700-250 mb. Drier air will then filter in aloft and help drop
PWAT`s a bit by the afternoon. Overall, the convective potential
looks to be the lowest on Tuesday since Debby thanks to weaker
instability, lower PWAT`s, and no trigger of note. High temps like
Monday will struggle to get much above 90 as surface high pressure
to our north drives north-northeast flow.


&&

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

- Relatively "cool" but seasonably dry weather expected
  throughout the middle part of the week.

Deepening of the trough across the northeastern US on Wednesday and
Thursday will help strengthening the associated surface high and
drive stronger northwest flow over our area. These will both combine
to yield relatively dry air, both aloft and near the surface, and
cooler temps for much of next week; NAEFS and EC ensemble output
shows consistently unremarkable heights, moisture, and temps
Wednesday through Saturday with anomalously strong northwesterly flow.
This in turn will yield slightly below average temps and PoP`s,
thanks to the positioning the surface high to our north in
conjunction with the northwest flow aloft. High temps should
therefore run a few degrees below average and dew points should drop
down into the 60`s consistently.

&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
IFR/LIFR conditions possible early this morning in fog and stratus,
especially near the CAE/CUB/OGB terminals.

Expect mainly mid and high level clouds this morning, with near calm
winds. However, persistent low-level moisture across the area and
clearing aloft over the next several hours will lead to some fog and
stratus concerns toward sunrise. Fog and stratus may be slow to
erode, but by 11/16z expect VFR conditions with scattered cumulus at
4-6k ft MSL. The air mass should become moderately to strongly
unstable in the afternoon, with scattered thunderstorms expected
after 11/18z. Confidence is still a bit low for TEMPO groups at the
terminals, so used VCSH for now. Winds generally light and variable
increasing S/SE this afternoon around 8 kts or less. Thunderstorms
may produce erratic and gusty winds to 40 kts. Convection clears
late this evening with winds returning to light and variable.

EXTENDED AVIATION OUTLOOK...Afternoon and evening convection
and associate restrictions will be possible through Thursday.
Early morning fog and stratus could occur, especially at fog-
prone AGS/OGB.

&&

.HYDROLOGY...
Key Message(s):
- Area rivers have crested and are falling. The Pee Dee at Cheraw
and the Wateree River at Camden are currently at moderate flooding
levels, but will fall into the minor category shortly. Minor
flooding will continue on the Congaree River south of Columbia in
the Congaree National Park through tomorrow morning.

&&

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

&&

$$