Severe Thunderstorm Warning 166, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
202 PM EDT Sun Jul 23 2017

.SYNOPSIS...
Upper level ridging will weaken across the area today as the
upper level trough digs over the eastern US. A bermuda high will
provide very warm and humid conditions through Monday with
scattered afternoon and evening showers and thunderstorms. A
weak cool front will stall over the area Tuesday, then move
southward into southern Georgia on Wednesday before dissipating,
providing somewhat cooler weather and a continued threat for
scattered thunderstorms. High pressure will become re-
established for the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Satellite imagery shows remains of an MCS over KY with the
outflows from it continue moving through TN and into the NC
mountains. Around the forecast area cumulus have begun to
develop...however currently remain vertically limited. PWAT
values have increased over the area with a minimum currently
over the eastern Midlands and Pee Dee. Through the afternoon
hours expect thunderstorms to develop as moisture continues
increasing and thunderstorms/outflows move into the area from
the Upstate and NC. Although instability is strong the potential
for hail is low and shear is weak...leaving the main potential
for severe thunderstorms to damaging wind gusts. PWAT values
over two inches later this afternoon will also provide the
potential for locally heavy rainfall and with storm motion
relatively slow will monitor for possibility of localized
flooding. Temperatures have risen into the low to mid 90s
across the area and with dewpoints in the low to mid 70s heat
index values currently range between 100 and 105. Expect these
values to increase slightly through the afternoon but remain
short of 110.

Convection will diminish with sunset...however with outflow
boundaries intersecting and generating new cells expect a few to
linger into the late evening/early overnight hours. This will
keep some mid and upper level debris cloudiness over the area
with low temperatures in the mid to upper 70s for most
locations.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
The forecast area will remain on the western edge of the Bermuda
high through Tuesday night, while heights aloft slowly drop as a
longwave trof becomes established over eastern North America.
This combination will lead to hot afternoons with max temps
generally in the lower to mid 90s, and maximum heat indices a
little above 100. The combination of developing steep low level
lapse rates each afternoon and weak vorticity aloft will lead
to scattered afternoon and evening convection. PWs will range
from 1.8 inches to 2.2 inches across the CWA, so any slow moving
convection could dump some locally heavy rain in spots.

Min temps will remain quite warm with lows in the mid to upper
70s most places.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...On Wednesday, a weak
front will slowly slide through the CWA as a small area of low
pressure develops off of the South Carolina coast and moves to
the northeast. It's main impact will be to dry the air out a
little bit Wednesday night and Thursday, but max temps on
Thursday afternoon will still be in the 90s as an increase in
sunshine will offset any weak cool advection that tries to set
up. Thursday will also see the lowest chance for afternoon and
evening convection for the week.

By Friday, the main global models begin to diverge with details,
but the overall pattern indicates a digging shortwave will move
into the southeastern states on Friday. This will cause an
increase in the deep southwesterly flow, allowing moisture to
quickly return in the form of clouds and scattered convection,
especially during the second half of the day. The weekend
contains a lot of uncertainty as the GFS shows a rather strongly
amplified pattern for july with a significantly deep trough
carving out over the southeastern states, while the ECMWF is
much more progressive with the digging shortwave on Saturday and
instead is more focused on the next shortwave, which is in the
7-10 day period and not part of this package. I have gone for
generally unsettled weather due to the mean trof, without
concentrating too much on the individual shortwaves. This means
slightly above normal chances for rain and slightly below
normal afternoon temps due to increased cloud cover.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Mainly VFR conditions expected through the TAF period...with
convection possible this afternoon and evening.

Cumulus have begun developing across the area with a few showers
to the southwest of AGS/DNL. Expect further cumulus development
over the next couple of hours with thunderstorms around the
terminals from mid afternoon through the evening hours. Have
remained with VCTS for all sites as confidence in timing of
arrival at terminals remains low. Main concern with
thunderstorms will be potential for wind gusts and locally heavy
rainfall. Early morning fog and stratus potential will depend
on afternoon rain so no mention attm.

EXTENDED AVIATION OUTLOOK...Increasing confidence in
restrictions in mainly afternoon/evening thunderstorms through
Wednesday. We could also see some morning cig restrictions from
stratus by Tuesday and Wednesday. The convection looks to
decrease on Thursday, but should pick right back up again by
Friday.

&&

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

&&

SYNOPSIS...Alsheimer
NEAR TERM...99
SHORT TERM...Alsheimer
LONG TERM...Alsheimer
AVIATION...99

Hazardous Weather Outlook
National Weather Service Columbia SC
352 AM EDT Sun Jul 23 2017

GAZ040-063>065-077-SCZ015-016-018-020>022-025>031-035>038-041-240800-
Lincoln-McDuffie-Columbia-Richmond-Burke-Lancaster-Chesterfield-
McCormick-Newberry-Fairfield-Kershaw-Edgefield-Saluda-Lexington-
Richland-Lee-Aiken-Sumter-Barnwell-Orangeburg-Calhoun-Clarendon-
Bamberg-
352 AM EDT Sun Jul 23 2017

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

.DAY ONE...Today and Tonight.

The probability for widespread hazardous weather is low.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.