River Flood Warning 15, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
509 PM EDT Wed Apr 6 2022

.SYNOPSIS...
Chance for showers and thunderstorms including some severe
thunderstorms across the region once again into tonight. Dry,
cool weather will return for late this week and into the
weekend. Temperatures and shallow moisture will increase through
early next week but the next chance for showers should hold off
until late Tuesday or Wednesday.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

Tornado Watch 102 has been issued for areas along and south of
I-26 excluding Newberry county.

Previus discussion follows:

Mostly cloudy across much of the area this afternoon.
Temperatures have struggled to warm, but dewpoints remain quite
juicy with values in the mid to upper 60s. Remnant boundary
which started south of the CWA this morning is still expected to
become the focus for another round of shower and thunderstorm
development this afternoon into tonight. Some breaks in the
clouds are noted along that boundary, with storms in western GA
beginning to develop. As this boundary continues to lift north,
we'll be keeping a close eye for shower and thunderstorm
development. Upper dynamics appear favorable for severe
weather, generally in the form of damaging wind gusts and some
large hail. This is due to sufficient CAPE in the hail growth
zone, strong mid-level lapse rates and drier air aloft leading
to high DCAPE values. All said, model solutions suggest MLCAPE
values between 1000 and 2000 are possible into this evening.
While there remains a low-end tornado threat, wind shear, SRH
and EHI values are not as significant as Tuesday, and so current
thinking is that this threat will generally remain south of our
area. However, short-lived and quickly developing spinups are
possible with any severe storms which develop. Best coverage should
be across the southern half of the CWA through this evening.

Hi-res CAMs are not in as good of agreement regarding the
evolution of convection compared to Tuesday. However, the
majority of them do highlight the 06/20Z through 07/04Z time
period. There looks to be a bit of a break before a secondary
round of showers and thunderstorms is possible ahead of a cold
front somewhere around 07/07 to 07/10Z tonight. The severe
threat with the subsequent push of showers and storms seems to
be lower at this time.

Temperatures this afternoon could warm up an additional few
degrees into the mid 70s, except to the south where breaks in
the clouds may allow for some additional warming. Overnight the
rain, cloud cover and background wind field will limit cooling
and lows should remain warm, in the mid 60s. Slightly lower
values are possible in the western CSRA if clearing occurs late
in the near term period.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Cold front will push through the forecast area Thursday morning
with the potential for some shower activity along and ahead of
the boundary. However westerly 850 mb winds and modest moisture
advection suggest only scattered or isolated convective
coverage. Confidence in thunderstorm development is
low however due to unfavorable diurnal timing and a lack of deep
moisture. Think the bulk of any precip will be east of the
area by midday as PWATS decrease rapidly below one inch and
dewpoints crash into the 40s. It will be breezy behind the
front with westerly gusts up to 25 mph, just below Lake Wind
Advisory criteria for now but will have the midnight shift
reevaluate. Highs will be in the low to mid 70s for most
locations - cooler in the western FA and CSRA. Cold advection
will strengthen overnight with temperatures dropping into the
mid to upper 40s. Winds will remain elevated preventing ideal
radiational cooling conditions despite dewpoints settling in the
upper 30s and mostly clear skies.

A deep upper level trough will settle over the eastern CONUS
Friday. At the surface, dry high pressure will ridge into the
forecast area with below normal temperatures expected Friday
afternoon. Temperatures will peak in the upper 60s and breezy
conditions continue due to a tight pressure gradient. Lows
Friday night a bit cooler with values in the upper 30s to low
40s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Troughing persists through Saturday and finally swings through
on Sunday with ridging building in behind. Dry conditions
continue this weekend with below normal temperatures and breezy
conditions. Winds die off a bit Saturday night with lows falling
into the 30s. We'll have to watch for a potential frost threat.
Surface high pressure is in control Sunday night into Monday
with dry low levels and weak winds, and another cool night is
expected. Current NBM guidance has temperatures a bit warmer
than Saturday night, but will continue to monitor trends. The
aforementioned upper ridging will help induce a warming temperature
trend with increasing shallow moisture on Monday. Mean PWAT
values from global ensembles rise above 1 inch late Tuesday or
Wednesday. A few passing upper level disturbances moving through
the flow may increase rain chances during this period, but there
remains some uncertainty in the forecast this far out in the
period.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
Restrictions through tomorrow morning, then slowly improving as
the cold front moves east.

Deep cloud coverage remains over the area and all TAF sites
remain in IFR/LIFR. Looking at current satellite, drier air is
beginning to advect into the southern Midlands and CSRA.
Ceilings will lift, however this will preclude convection
initiation. Scattered thunderstorms will move into Augusta then
Orangeburg terminals, at times possibly widespread as we head
into the early evening. Showers and storms will likely reduce
visibilities to IFR/LIFR considering the available moisture in
the atmosphere. After the initial evening convection, another
round of showers will move through as the cold front enters the
area around 05-08z. Gusts outside of storms will be from the
SSW around 5-10kt, veering west as the front pushes through in
the early morning hours. Mixing will ramp up shortly after
sunrise and skies will quickly clear before noon, but before
that, expect intermittent MVFR/IFR cigs/vis through most of the
forecast period.

EXTENDED AVIATION OUTLOOK...Dry air moves in behind the cold
front. No widespread restrictions expected.

&&

.HYDROLOGY...
Heavy rainfall on the order of 2 to 4 inches across the region
on Tuesday has lead to considerable rises on many area mainstem
rivers. Multiple Flood Warnings and Flood Advisories are
currently in effect. With heavy rainfall possible this
afternoon into this evening, additional flooding and subsequent
warnings and advisories may be issued.

&&

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

&&