283
FXUS62 KCAE 270014
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
814 PM EDT Sun May 26 2024

.SYNOPSIS...
A cold front will move through the area late Monday. Scattered
strong thunderstorms are expected ahead of the front with
temperatures remaining above normal. More seasonable
temperatures and drier conditions are expected behind the front
through mid to late week as a high pressure area builds in from
the upper Mississippi Valley.

&&

.NEAR TERM /UNTIL 7 AM MONDAY MORNING/...
8:00pm Update: A Severe Thunderstorm Watch has been issued for
Fairfield, Lancaster, and Newberry counties until 11pm this
evening. Thunderstorms have rapidly developed across the Upstate
of South Carolina and are on an eastward trajectory towards
portions of the northern Midlands. Profiler data from GSP
indicates strong mid to upper level flow and effective shear in
excess of 40 knots, which is sufficient to maintain this
convection as it heads eastward. While all severe hazards will
possible, modeled soundings from both CAE and CLT show ample
mid-level dry air and a well-defined inverted-V signature
indicating that damaging winds will be the primary threat. Large
hail will be the secondary threat with modeled soundings in
Lancaster County showing a SHIP in excess of 1. There is also
speed and directional shear being noted indicating a non-zero
tornado risk as well. Convection is likely to be maintained this
evening as it moves across the northern Midlands but should be
winding down around midnight. The threat of showers and
thunderstorms is lower for locations south of the Columbia area.

Previous Discussion: A series of shortwave troughs and
associated MCS`s will push through the area over next 18 hours
or so ahead of the deepening low over the central US. Ridging
aloft remains in place over much of the eastern US, with the
primary axis sitting just to our northwest, so northwest mid-
level flow is present over SC and GA. The first of these MCS`s
that will come at least close to our area is developing over TN
as 18z and will steadily slide east before turning southeasterly
this evening as it rounds the ridge axis. Ahead of this, a
generally unstable airmass will develop with somewhere between
1500-2500 j/kg MU CAPE will develop, but only around 1000 j/kg
ML CAPE thanks to pervasive dry air at low-mid levels. The
tightening height gradient aloft as the primary trough axis
pushes southeast will increase mid- level flow (40-50 knots at
500mb) enough to provide modest deep layer shear this afternoon
and into the evening. But given the lack of forcing, mid-level
entrainment, and noticeable dry air below 700mb, airmass
thunderstorms this afternoon will remain very isolated with only
a few expected to initiate prior to 22-23z; however, any deep
convection that does develop and become established will have a
fairly high probability of producing severe weather given the
dry mid-levels and modest shear. Convective coverage will likely
increase somewhat, especially across northern SC, this evening
as the first of the MCS`s moves it way southeast out of the
Appalachians. The environment will still remain favorable for
severe thunderstorms given the diurnal timing and any organized
cold pool should be plenty to trigger convection until diurnal
instability wanes. Hi-res guidance is mixed on exactly how far
south the convection will make it (mostly staying over NC) but
most of the HREF members have any at least some thunderstorm
activity moving across northern SC between 23-02z. So PoP`s
increase, mainly from Columbia north into the northern Midlands,
during this timeframe.

The next MCS in the series is progged to push towards the region
late tonight into Monday morning. Again most of the HREF members
develop this MCS within the prefrontal trough of the primary trough
and then send it southeast over the Appalachians between 06-10z. The
severe threat with this MCS would be very limited given the diurnal
timing, but some gusty winds and heavy rain would remain possible.
This MCS however will play a role in complicating the severe threat
for the rest of the day Monday.

&&

.SHORT TERM /7 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
The active weather pattern will continue Monday into Monday
night as low pressure tracks through the central Great Lakes and
pushes a cold front through the SE US. Although there is high
confidence the front will be moving through the region
confidence is currently low as to storm development and
coverage with much surrounding the convection and movement of
the MCS tonight. The MCS is expected to be moving toward Upstate
SC tonight however models continue to weaken the remains as it
crosses the mountains. Model soundings indicate some CIN in the
area Monday morning along with low level lapse rates under 5.5
C/Km and 850 mb winds turning more westerly. Even though
thunderstorms may not form in the morning and early afternoon
hours the front will still be west of the area and act as a
focusing mechanism for convection during the late afternoon and
evening hours as it crosses the region. CAPE during the
afternoon and early evening ahead of the front will be around
2000 J/Kg or higher with pwat values aoa 1.75 inches and DCAPE
around 1000 J/Kg. Divergence aloft during the late afternoon and
evening will be weak with winds at 35 kft expected to be a
maximum of 60 knots. With the potential for damaging winds and
hail SPC has expanded the slight risk to include the entire
forecast area tomorrow. High temperatures tomorrow will be in
the upper 80s to low 90s with lows Monday night in the mid 60s
to around 70.

Tuesday and Tuesday night are expected to be convection free as
the front will be offshore and high pressure along with drier
air will be building into the region. The upper level trough
will remain over the eastern US however with pwat values
dropping to under 1 inch by midday and 850-500 mb lapse rates
under 6.0 C/Km do not expect much in the way cloudiness and any
cumulus which develop will be vertically limited. Highs Tuesday
afternoon will be in the upper 80s to low 90s with lows in the
low to mid 60s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
The upper level pattern will remain highly amplified and
progressive through the long term with changing conditions
across the region. Upper level trough will remain over the
eastern US through Friday while the surface will be controlled
by high pressure and drier air. This will keep partly clear
skies over the area with increasing clouds Thursday as a mid
level disturbance moves through the region. This feature will be
quickly ushered offshore as the upper level trough axis swings
through the region Friday afternoon. High pressure will be
moving across the region Saturday with increasing moisture
Saturday afternoon as return flow from the Gulf begins. By
Sunday the high will be east of the region with a trough of low
pressure moving into the area and possibly becoming a focusing
mechanism for convection. Temperatures through the long term
will be near to slightly below normal.

&&

.AVIATION /23Z SUNDAY THROUGH FRIDAY/...
VFR conditions expected outside of any shower-storm activity
this evening and overnight.

Ridge offshore with south-southwest flow across the area. The
cumulus field has diminished across the area during the past
hour due to subsidence/loss of diurnal heating, drier air in the
central midlands. There may be some mid level capping as
suggested by RAP/HRRR soundings. However, the air mass remains
moderately unstable, deep layer shear is increasing across the
area ahead of an upper trough and upper heights will fall a bit
this evening. Thunderstorms have develop in the Upstate SC and
are tracking to the northeast. Based on radar trends think most
of the convection will stay north of the terminals this evening.
So expect mid level ceilings with southwest winds 5 to 10
knots. The boundary layer remains well mixed overnight so fog is
not expected. The HRRR is suggesting some stratus may develop
near the AGS/DNL terminals around daybreak but other guidance
remains VFR. Expect scattered cumulus to develop by mid to late
morning with mid level ceilings. Thunderstorm threat increases
in the afternoon as a cold front approaches from the Carolina
Mountains. The air mass is expected to be moderately to strongly
unstable and strongly sheared. Scattered strong thunderstorms
are possible mainly in the afternoon. The pressure gradient will
strengthen and expect southwest winds to gust to around 20
knots in the afternoon.

EXTENDED AVIATION OUTLOOK...Restrictions possible Monday evening
in scattered thunderstorms as a cold front moves through the
area. Otherwise, significant restrictions not expected.

&&

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

&&

$$