337
FXUS62 KCAE 081918
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
318 PM EDT Wed May 8 2024

.SYNOPSIS...
Potential for strong to severe storms Wednesday through
Thursday night ahead of an approaching cold front. Drier
conditions return for the weekend. Expect generally above
average temperatures through the latter half of the week before
transitioning to near or slightly below average during the
weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Convection associated with a shortwave is progged to move
through the northern forecast area this afternoon into this
evening. Storms have already initiated well to our northwest,
and continue to be stronger than initial guidance suggested.
Strong heating with temperatures in the upper 80s and low 90s
combined with dewpoints in the upper 60s and low 70s have
yielded SBCAPE values over 3000 J/kg. CAMs are in decent
agreement that the storms across the Upstate and western NC will
continue east/southeastward over the next several hours with a
very favorable environment (0-6 km shear increasing to 30-40
kts) helping to sustain organization. Main threat will be for
strong winds (DCAPE >1000 J/kg) across the northern half of the
forecast area, but large hail is also possible with many of the
storms to our west/northwest producing hail between 1 and 2
inches in diameter given low WBZ heights. The tornado threat is
low given the lack of helicity and weaker 0-1km shear, but can`t
be ruled out.

Additional convection is likely late tonight into early
Thursday, primarily after about 09/08z. A MCS is expected to
develop across portions of TN and push through the area with the
severe threat continuing. However, there is lower confidence in
the evolution of this system and it will depend on how things
evolve with this first go around. Overnight lows mild in the
70s.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Very complex forecast expected to unfold in this time period, with
multiple rounds of severe thunderstorms (some severe) possible. Much
of what actually occurs tomorrow is actually dependent on how much
convection gets going tonight and subsequently pushes into and
through the FA. HREF members are quite confident in convection
initiating upstream in the TN Valley and pushing the doorstep of the
FA between midnight and 8a Thursday...which is a large time period.
Confidence has increased in this scenario but the primary question
is where the convection tracks and how widespread it will be. Some
guidance shows an initial wave developing and pushing into the
northern FA overnight with a secondary line of storms developing
over northern AL/MS by early Thursday morning and progressing into
the western and southern FA by late morning or early afternoon. To
be honest, this is one of the tougher forecast periods I can
remember simply due to the amount of model spread that remains.
Looking at current radar, HRRR/ARW/NSSL CAMs are doing well and will
be leaned upon with early Thursday morning`s forecast...and each of
these have different solutions. Bottom line is that the
thermodynamic and shear environments present across the area and to
our southwest will be favorable for severe convection, even early in
the morning hours Thursday. I think the most likely outcome is that
a line of storms pushes along a weak boundary that is laid up across
the northern FA right now (the focus for potentially severe
convection this afternoon), with another line of storms across
the southern TN valley pushing southeastward into the CSRA.
Primary threat is for wind with all of this activity, but an
isolated tornado cannot be ruled out. SPC has placed the entire
area in a Slight Risk with an Enhanced Risk across the southern
FA. It is important not to get hung up on exactly where the risk
lines run as the majority of the area is under the threat of
severe weather at some point over the next 24 hours.

Confidence is fairly high that we will see a break in convection
tomorrow afternoon as the complex of thunderstorms moves
southeastward and leaves the atmosphere worked over by the afternoon
hours. Highs should be somewhere in the 80s across the FA, with
confidence low and dependent on morning convective evolution. A
stronger and more substantial shortwave trough is expected to rotate
around the large scale trough and approach the FA from the west by
Thursday night, with another complex of thunderstorms likely pushing
through by Friday morning. Not quite as confident that this will
produce severe weather as there will be little time for the
atmosphere to recover. So (for now) just expecting rain and
thunderstorms to arrive across the FA from west to east after
midnight Friday, progressing through the area by early Friday
afternoon. The front should finally push through thereafter and
decrease our threat for severe weather altogether.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Operational and ensemble guidance is in good agreement with respect
to the overall synoptic evolution in this period. 500 hPa troughing
is expected to finally swing eastward by Saturday, setting the area
up within convergence aloft as a 250 hPa jet streak pushes eastward
and across the area. High pressure is forecast to begin settling
into the southern plains, and will likely push eastward as upper
level convergence shifts eastward. A 500 hPa vort max is likely to
shift into the Mid-Atlantic, shifting another reinforcing cold front
through during the afternoon hours. Probabilities are low, but
wouldn`t be surprised to see a stray shower along and ahead of that
feature Saturday afternoon. Aside from that, things looks quite nice
Sat/Sun/Mon as the progressive pattern keeps high pressure
translating towards and through the FA. Temps look much more
seasonal - in the upper 70s and lower 80s. As we get into early next
week, shortwave ridging shifts over the region by Monday night. This
will be ahead of a slow moving, closed mid/upper level low progged
to push into the eastern CONUS by the middle of next week.
Confidence is low on the details of this as operational models and
LREF members diverge on speed and amplitude of this feature. But
moisture return ahead of it and southwesterly flow aloft favor the
potential for showers and thunderstorms Mon Night through Wednesday,
and that will be reflected in the grids.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Mainly VFR conditions this evening. SCT-BKN clouds AOA 4k ft MSL. SW
winds 10-12 knots with gusts up to 20 kts through the afternoon.
Gusts diminish overnight but speeds remain around 4-7 kts. Strong
thunderstorms may develop this afternoon but should remain north of
the terminals. Tonight, thunderstorms may move through the terminals
mainly after 09/08z with gusty winds and brief CIG/VSBY restrictions.
There continues to be more uncertainty Thursday regarding the exact
timing and location, but multiple rounds of showers and
thunderstorms are possible through at least the morning hours.
Storms will continue to be capable of gusty winds in excess of 40
kts.

EXTENDED AVIATION OUTLOOK...Then expect another day of convection
and associated restrictions on Friday. Drier weather with no
restrictions likely for this weekend.

&&

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

&&

$$