338
FXUS62 KCAE 190604
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
204 AM EDT Tue Aug 19 2025

.SYNOPSIS...
Isolated to scattered convection expected today favoring the
eastern Midlands and CSRA with a warm and moist air mass in
place. 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):

- Another morning with some patchy fog possible.

- Isolated to scattered showers/storms during the afternoon and
  evening, mainly south of I-20 corridor.

A batch of showers and a couple weak storms are pushing out of
the northern Midlands as a diffuse boundary is swinging in from
the north, currently positioned near the SC/NC border. This
should help usher in some stratus that is currently seen pushing
through NC for the morning hours where some patchy fog could be
possible as well. For the remainder of the day, the upper ridge
will continue to retreat towards the Four Corners region and
flow will become progressively more out of the northeast with
weak surface high pressure in New England ridging down into the
FA, though PWAT`s should remain high with the sinking frontal
boundary (around 2-2.1"). This northeast flow and some cloud
cover likely keep temperatures a bit lower during the afternoon,
in the upper 80s to near 90. For shower/storm chances, high
PWAT`s coupled with the diffuse boundary and the inland pushing
sea breeze should allow isolated to scattered showers and storms
to develop mainly south of the I-20 corridor during the
afternoon and into the evening before diminishing into the
overnight period. No strong storms are expected with marginal
instability, but locally heavy rain could be possible. Weak high
pressure in New England slowly pushes out overnight with
Hurricane Erin making it`s approach toward the western Atlantic,
though no direct impacts are expected to the CWA.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
Key Messages:

- Tropical Cyclone Erin will remain offshore with no direct
  impacts expected

- Drier with increased northeasterly winds developing on
  Wednesday

- Near normal temperatures and Less Humid

Tropical cyclone Erin is expected to make a northward and
eventually northeastward turn away from the Carolinas coast on
Wednesday. Erin should remain well offshore to prevent any
direct impacts to our forecast area. Stronger subsidence is
expected around Erin and that is noted in forecast soundings
showing a subsidence inversion between 850mb/700mb with deep
mixing expected and associated drop in PWATs to around 1.5
inches. Temperatures should be near normal in the upper 80s to
lower 90s but the deeper mixing should allow for dewpoints to
drop into the upper 60s and feel a bit less humid, if only for
a day. No convection is expected with the subsidence outside of
a possible stray shower along the sea breeze. Winds should be
up a bit more with a slightly increased pressure gradient and
the deeper mixing but gusts appear to stay below 20 mph.

Thursday features a transition back to a more typical summer
pattern with PWATs rising back over 2 inches by afternoon as
Erin continues to lift northeastward away from the East Coast
and deep layer moisture returns as noted on forecast soundings.
The humidity will return and be noticeable with dewpoints back
in the 70s and temperatures remaining near normal in the lower
90s. Some weak upper trough will fill the void left behind
departing Erin and this should be enough combined with
increased deep moisture to support scattered mainly diurnal
convection. The high PWATs should support efficient rain in a
generally weak shear environment so locally heavy rain is
possible and WPC has the western Midlands and CSRA outlooked in
a marginal risk of excessive rainfall.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Key Messages:

- Cooling trend expected Friday into Saturday with upper level
  troughing then gradual warming trend returns Sunday into
  Monday

- Shower and Thunderstorm Chances increase into the Weekend

LREF guidance suggests a weak upper trough trapped over the
deep south and southeast with upper ridging over the Great Lakes
and Northeast on Friday and Saturday with a stalled frontal
boundary across central and southern GA. Ensemble mean PWATs
Fri/Sat are forecast to be around 110-120 percent of normal with
values around 2 inches and expect scattered to numerous showers
and thunderstorms each day diurnally favored in the afternoon
and evening given the weak upper troughing and boundary nearby.
The highest chances should be along and south of the I-26
corridor. Temperature should be noticeably cooler with highs in
the lower to mid 80s Fri/Sat with plenty of cloud cover.

Another front is expected to approach the forecast area on
Sunday and push east of the area to the coast by Monday as a
stronger upper trough digs into the Great Lakes region and down
the east coast. This should result in higher chances of rain on
Sunday across the eastern half of the forecast area and confine
them to the Coastal Plain on Monday as drier air builds in
behind the front with lower dewpoints and PWATs dropping
significantly on Monday. Below normal temperatures are expected
Sun/Mon although they will be warmer than previous days.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Lingering showers pushing out near CAE/CUB before stratus and
some patchy fog possible toward the early morning hours.

A batch of lingering showers is pushing northwest of the
Columbia terminals at this time, but there remains some debris
cloudiness here and down toward OGB. Winds are nearly calm as a
diffuse boundary is pushing south and with it a stratus deck is
seen forming across NC, continuing to push south. the HRRR, NBM,
and LAMP guidance continue to show that MVFR to potential IFR
ceilings push into the Columbia terminals and possibly OGB
between 09-11z, but there is a bit less confidence toward
AGS/DNL. A period of MVFR ceilings at AGS/DNL seems reasonable
closer to 10-11z with the current suite of model guidance. Some
fog could also be possible at the typical prone sites of
AGS/OGB, similar to last night. Ceilings appear that they will
be a bit slow to raise and thus MVFR ceilings could linger until
16-18z before scattered cumulus develops with 5-7 kt winds out
of the northeast. Isolated to scattered convection should
develop toward the eastern Midlands after 18-20z but confidence
in this impacting the TAF sites is fairly low at the moment. OGB
and the Augusta sites would have the best chance for seeing
this activity and thus I have added a PROB30 group at this time
to account for this. These showers/storms then diminish toward
the end of the period with light winds and some high clouds
moving in.


EXTENDED AVIATION OUTLOOK...Drier weather continues to be
expected for Wednesday and Thursday. Late this week and into the
weekend moisture increases opening up the potential for early
morning restrictions and diurnal convection.

&&

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

&&

$$