565
FXUS62 KCAE 221444
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
1044 AM EDT Tue Apr 22 2025

.SYNOPSIS...
Showers and thunderstorms approach the area today as a cold
front edges closer to the region. This front is expected to
stall out across the area for the mid to late week period,
bringing possible rain chances each day for the remainder of the
week.

&&

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

- Thunderstorms possible late afternoon and evening

This afternoon, a cold front will slowly work its way into the
Deep South where it will stall. Southwest flow will allow low-
level moisture to increase supporting convective development to
our west during the afternoon along with a potent shortwave
trough. As this shortwave and convective outflow moves east in
the late afternoon, storms may enter the western FA. Another
source of convective initiation (CI) may be the sea-breeze as
it moves further inland in the late afternoon/evening, however
ridging just offshore may hinder development along the sea-
breeze. If CI occurs then outflow collisions between sea-
breeze convection and the shortwave-driven convection may
support thunderstorm activity well into the evening.

While multiple surface boundaries and a strong upper shortwave
would typically favor widespread thunderstorms for our FA, a
dry air mass will limit the overall threat of severe weather.
PWAT values from GOES and forecast soundings are around 1 inch.
There is also a large difference between RH values in the 500
and 700 mb layer. GFS 600 mb Td values are near -65 deg C while
the HRRR is closer to -35. Overall this dry layer will work to
hinder convective development through entrainment and may partly
explain why CAMs generally show convection diminishing as it
moves in from the west (where PWAts are 1.25"+) and runs into
the ridge.

If deep, moist convection can develop there may be an isolated
threat of damaging winds. A deep inverted V sounding will lead
to DCAPE values near or over 1000 J/kg. The greatest threat may
be along the NC/SC border where moisture is deeper and PWAT
values are around 1.25 inches.

Convection may continue into the overnight period if storms
develop during the day as outflow boundaries interact and
shortwave activity continues. Look for another mild night with
lows in the low to mid 60s.

&&

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

- Diurnal shower/storm chances continue Wednesday afternoon and
  evening with the front stalling out near the CWA.

- These chances continue Thursday afternoon and evening as well
  with the diffuse front lingering.

Wednesday and Wednesday Night: Wednesday likely brings another
afternoon and evening where diurnal showers and storms are
expected in the FA as the cold front begins to stall out toward
the northern FA and a couple more weak embedded shortwaves move
into the area in the southwest flow regime. Depending on the
timing of convective initiation, temperatures could be kept more
in check, but afternoon highs into the low to mid 80s are
forecast across the FA. Now for thunderstorm chances/intensity.
The aforementioned frontal boundary should be stalled more
toward the northern FA but southwesterly flow will bring PWATs
between 1.3- 1.45". This increasing moisture looks to yield
fairly strong instability as high-res model guidance shows
MLCAPE generally between 1500-2000 J/kg, highest in the eastern
Midlands. 3km CAPE is also fairly high, up to 100-130 J/kg. Deep
layer shear continues to be the lacking ingredient in this
setup, but between 20-30 kts is being shown in forecast
soundings and ensemble guidance. Forecast soundings also show
that by 2-4pm locations will likely be nearing the convective
temperature and due to this, scattered to numerous storms
should fire during the afternoon with the aid of possible
embedded upper shortwaves and any lingering outflow boundaries
from Tuesday and collapsing downdrafts with this activity
Wednesday. This all leads to a primarily strong pulse
environment but shear may be enough for a couple more organized
multicell clusters. The main hazards continue to be heavy rain
and frequent lightning, but some modest DCAPE values could bring
strong winds in the more robust updrafts. The activity then
likely dies off into Wednesday night with overnight lows into
the low 60s.

Thursday and Thursday Night: Thursday continues the trend of
these diurnal showers and thunderstorms as PWAT`s remain near
1.4" and the diffuse front remains in the FA before finally
lifting north into Friday. A similar story to Wednesday is
expected with possible more muted afternoon high temperatures in
the lower 80s depending on convective initiation timing. The
environment for these afternoon and evening storms remains
largely unchanged from Wednesday, though NBM guidance does
suggest slightly less instability maybe seen with mean CAPE
values being around 800-900 J/kg. Another shortwave is noted
moving into the region in each of the recent operational runs of
the NAM/ECMWF/GFS and forecast soundings tell a similar story
to Wednesday with a general lack of organizing shear and a
continuing mainly strong pulse environment where the primary
threats are heavy rain and frequent lightning.

&&

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

- The lingering frontal boundary is expected to move north
  Friday, but some more diurnal showers/storms may be possible.

- Stronger cold front moves in Saturday with another chance of
  showers and possible thunderstorms.

- Temperatures look to remain above normal into the weekend
  before possibly cooling slightly Sunday and Monday.

The frontal boundary that will have been lingering in the FA
for multiple days is expected to start lifting north Friday but
global model guidance shows another potential shortwave
entering the FA by the afternoon/evening with above normal
temperatures continuing and PWAT`s near 160% of normal. This
brings another afternoon/evening with a chance of showers and
thunderstorms but the signal for any potential strong/severe
storms in ML guidance is weak to non existent and ensemble
guidance for probabilities of MUCAPE over 600 J/kg is near
40-60 percent. Heading into Saturday, above normal temperatures
continue but an upper trough and associated surface low will be
moving through the Ohio Valley, bringing a cold front into the
CWA. Right now GEFS and EC ensemble guidance is in decent
agreement that the front will enter from the NW in the afternoon
into an environment with near 150-170% of normal PWAT`s and
decent instability (probabilities around 50-70% for MUCAPE over
1000 J/kg). The current lacking ingredient for organized
convection is strong deep layer shear but this will be worth
keeping an eye on as ML guidance like CIPS and CSU have picked
up on this potential signal. Drier air then begins to move in
Sunday and Monday behind the front where slightly cooler
temperatures are possible but greater uncertainty in this exists
as seen in NBM box and whisker plots.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
Scattered showers and thunderstorms associated with a slow
moving front will move into the forecast area this evening.
Most of the convection should remain north of the terminals, so
confidence is only high enough to include a PROB30 group for
showers. With the potential for outflow boundary collisions and
shortwave activity to continue into the night, there will be at
least a chance for showers and thunderstorms from 00Z through
the remainder of the TAF period. Winds today generally out of
the southwest at less than 12 kts. Winds return to light and
variable tonight, continuing into Wednesday.

EXTENDED AVIATION OUTLOOK...A front will stall over the region
leading this week leading to convection and restrictions for
periods through Saturday.

&&

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

&&

$$