Special Weather Statement, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
711 PM EDT Thu May 4 2017

.SYNOPSIS...
A warm front will linger in the forecast area this evening
ahead of an approaching cold front. The cold front will cross
the area tonight. Associated strong low pressure moving into the
Ohio River Valley today will reach the Mid-Atlantic States
Friday. The low will be farther north of the area Saturday.
Cooler and drier air will dominate over the weekend into early
next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Main concern remains possible severe weather potential this
evening and overnight.

Latest surface analysis at 23z indicates warm front in the
southeast Midlands and the CSRA region with strong
thunderstorms confined to southeast coastal Ga and the low
country SC. Thunderstorms moving across the Midlands are
shallow and further development appears unlikely in the short
term with air mass north of warm front stable. Stronger Deep
layer effective shear over Ga and higher precipitable water will
likely shift into SC this evening. Limiting factor for severe
weather appears to be lack of instability at the moment.

Later this evening...As shear increases the threat for rotating
storms will be possible and cannot rule out an isolated brief
weak tornado threat in addition to damaging wind gusts if
instability increases and is realized as forecast through the
evening hours. Greatest region for threat appears to be
southeast Midlands/CSRA. Note that the latest HRRR model appears
less threatening with convection later this evening.

Later tonight as the upper low and attendant surface low slowly
move eastward through tonight the cold front will shift east
across the forecast area. Increasing upper dynamics with
diffluent 500mb flow will overspread the region overnight and
could enhance convection along and ahead of the front with
the best shear and instability (albeit weak) in place. The one
potential limiting factor may be decreasing deep moisture.
Hi-Res ARW/NMM WRF models show most of the convection shifting
east of the forecast area around 06z-08z with cooler and drier
air moving in behind the front. SPC continues to outlook the
area in a marginal risk through tonight.

Temperatures will be limited by mixing and clouds overnight and
have raised temps a bit from previous forecast in the
northeastern portions of the forecast area where the cooler air
is slower to arrive.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
Cold front will be east of the area early in the day Friday,
with much of the rainfall also pushing east during the morning.
The main upper low will still be west of the region through the
day, and we should see some dry slotting across the cwa during
the morning. By the afternoon hours, as the cold pool aloft
slowly nears, there may be some redevelopment of some scattered
low topped showers. Models also showing stronger winds aloft
through the day mixing down the surface. Sustained winds 15 to
20, with the momentum transport from soundings showing gusts
around 25 knots. Although conditions appear to remain below
criteria at this time, a Lake Wind Advisory may still be
needed through the day Friday if winds are stronger.
Temperatures through the day Friday will be noticeably cooler,
with highs mainly in the 60s. Dry conditions return by Friday
night, with overnight lows cooling down into the upper 40s to
around 50.

Saturday into Saturday night, Temperatures begin to slowly
rebound during the afternoon under plenty of sunshine. Highs
should be able to climb into the lower 70s for many areas. The
models do show another shortwave moving southward on the
backside of the eastern low late in the day Saturday, with the
system still bringing enough moisture with it to passably eek
out a shower or two late in the day or into the evening hours
across the extreme western/northern counties. Will have low end
slight chance pops for that period, with very light qpf amounts.
Dry after midnight Saturday, with lows still falling down to
around 50 degrees.

Sunday through Sunday night, region remains under northwesterly
flow aloft. Dry weather expected to continue, along with the
slowly moderating temperature trend. Temperatures in the middle
to possibly upper 70s. A reinforcing shot of dry air during the
day possible, which will bring slightly cooler overnight lows
for Sunday night. Readings back into the middle to upper 40s.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Dry weather from Monday through Wednesday, with temperatures
continuing to warm slightly each day and night. The next chance
for any measurable rainfall may not occur until Wednesday
evening through Thursday as the models show a stronger shortwave
moving through the region at that time.

&&

.AVIATION /23Z THURSDAY THROUGH TUESDAY/...
Radar indicates heavier shower activity and a few thunderstorms will
push east of CAE/CUB/OGB after 00Z. Main cold front, still to our
west near the GA/AL line, will come through our forecast area (FA)
late tonight. Shower and thunderstorms activity currently along the
front may weaken as it approaches our FA. Ahead of the front,
periods of light to moderate shower activity possible. At this
point, based on radar trends and latest high resolution guidance,
confidence of thunder affecting our TAF sites insufficient to
include TS in the TAFs at this time. Combination of rain-cooled air,
and currently existing CIG restrictions to our west advecting
into our FA, suggests MVFR CIGS for our TAF sites tonight into
Friday morning. Though CIG heights could gradually lift Friday,
high end MVFR CIGs could linger into Friday afternoon. Despite
cooler and some drier air filtering into our FA Friday behind
the cold front, main upper low still over our FA could provide
some brief light scattered showers Friday afternoon. Will handle
with VCSH. Breezy conditions expected through Friday, with a
strong low level jet tonight. Will indicate LLWS.

EXTENDED AVIATION OUTLOOK...Breezy conditions at times through
Saturday, possibly into Sunday.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Columbia SC
855 PM EDT Thu May 4 2017

GAZ040-063>065-077-SCZ015-016-018-020>022-025>028-030-035-037-041-
060100-
Lincoln-McDuffie-Columbia-Richmond-Burke-Lancaster-Chesterfield-
McCormick-Newberry-Fairfield-Kershaw-Edgefield-Saluda-Lexington-
Richland-Aiken-Barnwell-Calhoun-Bamberg-
855 PM EDT Thu May 4 2017

This Hazardous Weather Outlook is for the Midlands of South Carolina
and the Central Savannah River area of Georgia.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

SCZ029-031-036-038-060100-
Lee-Sumter-Orangeburg-Clarendon-
855 PM EDT Thu May 4 2017

...TORNADO WATCH 194 IN EFFECT UNTIL 3 AM EDT FRIDAY...

This Hazardous Weather Outlook is for the Midlands of South Carolina
and the Central Savannah River area of Georgia.

.DAY ONE...Tonight.

Please listen to NOAA Weather Radio or go to weather.gov on the
Internet for more information about the following hazards.

   Tornado Watch.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is requested.

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