343
FXUS62 KCAE 181032
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
632 AM EDT Mon Aug 18 2025

.SYNOPSIS...
Another hot and humid day is expected today before wedge-like
conditions develop on Tuesday and Wednesday. Showers and
thunderstorms are possible early this week, but coverage should
be limited. A retreating upper ridge breaks down on Wednesday
and allows Major Hurricane Erin to pass offshore of the United
States. More typical rain chances should return by the end of
week with cooling temperatures due to developing upper
troughing.

&&

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

- Patchy fog in spots this morning.

- Warm and muggy day with heat indices between 100F and 105F

- Isolated showers/storms possible during the late afternoon
  and into the evening.

Strong radiational cooling and nearly calm winds into the
morning hours should allow patchy fog to develop by daybreak,
mainly toward the southern CSRA and eastern Midlands where low
level moisture is greatest. Once this fog burns off, mostly
clear skies are expected today outside of some cumulus
development in the afternoon as the upper ridge over the Ozarks
continues to control our sensible weather with this shot of
drier air (PWAT`s between 1.4-1.5") remaining overhead. The
ridge will begin to slowly retreat westward throughout the day
with flow turning a bit more easterly to southeasterly, allowing
moisture to start increasing through the afternoon and evening
with PWAT`s quickly rebounding to just under 2". Strong
isolation and increasing moisture should bring a muggy day with
temperatures in the low to mid 90s and heat indices that remain
under Heat Advisory criteria, but still top out between
100-105F.

CAMs and the recent 00z HREF run continue to suggest isolated
to scattered convection should develop toward the northern
Midlands and into the Pee Dee region during the afternoon with
the retreating ridge and perhaps a weak ribbon of vorticity near
the area. Some of this activity may spread south into the rest
of the Midlands during the late afternoon and into the evening,
but with the loss of heating, much of this is expected diminish
overnight. The risk for strong storms is low but locally heavy
rainfall could be possible where convection trains as these
showers and storms should be efficient rainfall producers.
Overnight, some scattered to broken cloud cover is expected from
lingering debris cloudiness and the maintenance of high low
level moisture as flow remains out of the east to southeast with
Hurricane Erin expected to be positioned east of the Bahamas
and some weak surface ridging extending down into the FA from
high pressure up in the New England region.

&&

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

- Not as hot Tuesday and Wednesday as a wedge-like pattern sets
  up in response to north to northeasterly flow around the
  western edge of Major Hurricane Erin.

- Erin will pass offshore of the United States on Wednesday and
  should further suppress convection from developing locally.

Upper ridging will continue to retreat westward during the short
term. This allows for a weakness to develop in the upper
pattern, pulling Major Hurricane Erin northward and eventually
northeastward well to our east. Latest NBM has come down
significantly on daytime temperatures on Tuesday compared with
yesterday, likely in response to the development of a wedge-
like pattern as surface winds shift toward the north and
northeast. Would expect this trend to continue into Wednesday
with temperatures lower than currently shown in the NBM once hi-
res guidance goes out that far. The CAMs on Tuesday show a
drier scenario as this more stable air mass comes in. Rain
chances should be generally low, less than 30 percent, on
Tuesday and even lower on Wednesday when Erin makes its closest
approach to the United States.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
Key Message(s):

- Greater coverage of diurnal convection through the period.

- Near normal temperatures on Thursday fall below normal as an
  upper trough sets up over the Eastern CONUS.

Major Hurricane Erin will be moving out to sea and away from the
United States at the start of the extended. Weak upper flow will
be over the region on Thursday and Friday before the next trough
sets up over the Eastern CONUS. Rain chances should ramp up and
return to a more typical summer pattern with daily afternoon and
evening convection. Temperatures start the period with near
normal values but should fall below normal this weekend as the
upper trough becomes established.

&&

.AVIATION /10Z MONDAY THROUGH FRIDAY/...
Periods of IFR to MVFR visibilities at OGB/AGS this morning
before VFR conditions are expected the remainder of the day.
Another round of patchy fog and stratus will be possible tonight
and into Tuesday morning.

Satellite imagery and observations show fog development across
much of the southern CSRA and into the eastern Midlands, mainly
along river valleys, but due to this, AGS and OGB have been
seeing IFR restrictions with periods of LIFR restrictions. This
is expected to continue the next couple of hours, possibly
improving some shortly after sunrise toward MVFR, before
finally starting to burn of after 13z. After this, VFR
conditions are expected to prevail this afternoon with FEW to
SCT cumulus as winds remain light out of southeast, but they
could be bit squirrely at times. Model guidance continues to
show isolated showers/storms developing north of the TAF sites
this afternoon where some of this may eventually drift south
mainly toward CAE/CUB/OGB. Confidence in restrictions is still a
bit limited and thus I have left the PROB30 group in. This
activity should diminish to end the period with lingering debris
cloudiness expected and winds that become light and variable
before more patchy fog and stratus could be possible tonight,
mainly at AGS/OGB again.

&&

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

&&

$$