-- Discussion containing changed information from previous version are highlighted. --
955
FXUS62 KCAE 231848
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
248 PM EDT Thu May 23 2024

.SYNOPSIS...
-- Changed Discussion --
A frontal boundary will approach the region Friday and is
expected to stall near the area resulting in chances of showers
and thunderstorms through the weekend. Another more organized
system is expected to be crossing the eastern US Monday and
Tuesday with additional chances for thunderstorms. Drier
weather is expected to return Wednesday.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
This afternoon: Daytime heating with dewpoints in the mid to
upper 60s has resulted in widespread cumulus clouds across the
region. Despite the clouds, temperatures have pushed into the
upper 80s to lower 90s with warm southwesterly flow at the
surface. No signs of convection across the forecast area despite
mesoanalysis showing MLCAPE values 1000-1500 J/kg and strong low
level lapse rates in place, likely due to the lack of upper
forcing and any low level convergence boundaries. Regional radar
is showing some convection along the higher terrain of NC and
norther GA.

Tonight: Hi-res guidance is highlighting the evening and
overnight hours as the best chances for convection to impact our
area moving in from the west around 00z and crossing the
northern Midlands with sufficient instability to maintain some
scattered convection after midnight. Chances of severe weather
appear to be low but nonzero with relatively high DCAPE values
around 800-1000 J/kg supporting an isolated damaging wind threat
and large hail. Expect convection to diminish after 06z but
leaving an outflow boundary across the region as a possible
focus area for Friday convection. Overnight lows expected to be
mild in the upper 60s to around 70 degrees with limited
radiational cooling due to convective debris cloud cover and a
20-25 knot low level jet.
-- End Changed Discussion --

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
The first shortwave trough in a series of disturbances will push
across the area Friday with some distinct height falls and broad
upper level diffluence developing. Deep moisture with PWAT`s over
1.5" and sufficient surface heating during the day will produce
moderate-high instability throughout the afternoon; HREF and GEFS
members prog somewhere between 1000-1500 j/kg ML CAPE developing in
the afternoon and evening with a deep mixed boundary layer. The
shortwave aloft will produce some impetus for some weak shear but
generally less than 30 knots in 0-6km layer. HREF and MPAS ensemble
members are consistent in producing widespread convection by roughly
21z, but the storm features depicted are representative of the
environment with somewhat weak updraft velocities and UH. So the
severe potential Friday looks to be more of quantity over quality
event with numerous weak convective cells and a few isolated severe
cells; damaging winds will be the primary threat given the modest
dry air aloft driving up DCAPE and hail a secondary threat given the
lack of storm organization.

As we move into Saturday, the shortwave and larger scale trough to
our north will move east and on the backside, force some northwest
flow below 500mb over our area. This will help drop PWAT`s slightly
and increase dry air aloft as weak ridging also builds in. Moderate-
high instability however is expected to develop despite this, with
between 1500-2000 j/kg ML CAPE developing in afternoon; GEFS and ECE
probs of greater than 1000 j/kg are 80-90%. Convection will
generally struggle to initiate in this environment based the forecast
soundings and model depictions, but any storms that are able to get
established would have a high probability of producing damaging winds
given the aggressive entrainment aloft and deep boundary layer
mixing. So relative to Friday, convective coverage will be less
widespread but each individual storm will have a higher likelihood of
producing severe weather and the upper ceiling on wind speeds-
damage is higher.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
A deep mid-level trough will slide eastward and strengthen over
the Great Lakes as we move into Sunday, helping weaken our
ridging aloft as heights begin to steadily fall. Moisture is
progged to return in the GEFS and ECE members with nearly
unaminous agreement in PWAT`s bumping back above 1.5".
Consequently the GEFS and ECE members then show sufficient
instability developing into the afternoon and evening thanks to
strong heating and the weak height falls aloft. There will be
not a strong synoptic mechanism for initiating convection on
Sunday however, so much like the previous few days, some
isolated-scattered thunderstorms will pop by the evening. By
Monday however, a secondary shortwave will force the primary
upper level trough axis eastward and help push an associated
cold front towards our area. Heights falls aloft and moderate-
high instability will likely develop ahead of any surface front
in the afternoon and the potential exists for a scattered-
widespread severe threat; the combination of synoptic forcing,
strong mid-deep layer shear, and robust instability all could
line up Monday afternoon but there are some potential issues
related to the diurnal timing of the front. Beyond Monday, drier
air should steadily fill in behind Monday`s trough and reduce
diurnal convective activity chances for the middle of next week.
-- End Changed Discussion --

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --
VFR conditions generally expected during this forecast period.

Strong heating has led to widespread cumulus development with
VFR cigs around 5kft to 7kft with some higher clouds passing
overhead. Convection is developing along a frontal boundary over
the TN Valley and along the higher terrain of NC and is expected
to eventually shift eastward toward the northern Midlands early
evening but should remain north of the terminals. Southwesterly
winds around 5 to 8 knots should diminish with sunset but stay
up a bit overnight with a 20-25 knot low level jet which should
mitigate a fog threat along with the expected cloud cover. Some
guidance, mainly the NBM suggesting some stratus may develop
across the northern Midlands but SREF and HRRR do not show much
so decided to just include a mention of MVFR cigs in a tempo
group CAE/CUB only during the 09-13z time frame. Otherwise,
winds pick up from the southwest to around 7 to 10 knots after
14z Friday. Some convection is expected to develop but likely
at the end of this forecast period.

EXTENDED AVIATION OUTLOOK...Low probability of restrictions
during the late week period into the weekend from afternoon and
evening convection.
-- End Changed Discussion --

&&

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

&&

$$