Severe Thunderstorm Warning 107, NWS Columbia, SC

Area Forecast Discussion
National Weather Service Columbia SC
209 PM EDT Wed Jul 17 2024

.SYNOPSIS...
A stalled frontal bounday will lead to increased shower and
thunderstorm chances over the next few days, resulting in a
wetter than normal 7-day period. After Thursday, temperatures
are expected to drop to near or slightly below normal levels
through early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Message(s):

- Scattered showers and thunderstorms with locally heavy
  rainfall develop this afternoon, with some gusty to damaging
  winds in stronger thunderstorms.
- Hot with heat index values 100 to 105.

Upper level trough centered over the Great Lakes region will be
moving to the east while amplifying a bit. A cold front ahead of
the trough will remain well northwest of the Carolinas through
tonight. At the surface, a Piedmont trough remains in place
across the area to provide some at least weak convergence. The
air mass is moist with precipitable water near or above 2
inches. With strong diabatic heating, temperatures will again
rise into the mid to upper 90s this afternoon. Low to mid level
lapse rates are a little steeper than yesterday as upper heights
fall just a tad. The resulting instability appears moderate to
strong with surface CAPE around 2500 J/kg, a little lower in the
west due to slightly drier air mixing down. Deep layer shear
remains weak, although the boundary layer winds are a little
stronger. Model soundings suggest a continued microburst threat
with inverted V soundings, DCAPE near 800 J/kg, water vapor low
level appears dry. Although heavy rain possible, storms should
be moving due to the slightly stronger low to mid level flow.
The latest HREF supports scattered thunderstorms. Convection
early this morning in northwest GA has temporarily dissipated.
These showers were forced by a weak mid level short wave. The
models suggest convection will re-develop in east central GA and
move into the Midlands late afternoon/evening. Convection should
diminish by mid to late evening and becoming isolated. Muggy
again tonight with lows in the mid 70s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
Key Message(s):

- Scattered to numerous afternoon and evening showers and
  thunderstorms with the potential for gusty winds and flash
  flooding
- Daytime temperatures expected to be near normal by Friday
  behind the passage of a cold front

Upper trough continues to take shape over the eastern half of
the country during the short term as the upper ridge in the
west builds. At the surface, a weakening cold front will slowly
sink southeast towards the FA on Thursday, stalling across the
region on Friday. The frontal boundary, combined with passing
short waves, will increase the risk for showers and
thunderstorms during the period, especially on Friday. CSU
severe probabilities continue to highlight the potential for
strong to severe thunderstorms on Thursday and Friday with gusty
winds as the most likely hazard. At the moment, only the Pee
Dee is highlighted on the Day 2 SPC Severe Weather Outlook but
would not be surprised if the severe threat is more widespread
than what we saw the previous few days given the ample moisture
(PWATS in excess of 2 inches), instability (modeled CAPE in
excess of 1000 J/Kg), and lift. Conditions appear to be more
favorable for severe weather on Thursday but the threat could
linger into Friday as well. The risk of heavy rainfall and
localized flooding also continues with a Marginal (1/4) risk for
excessive rainfall across the CWA on Thursday and Marginal to
Slight (2/4) risk on Friday. Thursday will be another hot day
though Heat Index values are likely to remain below criteria.
Temperatures are expected to be near to below normal values on
Friday due to the increased cloudiness and expected rainfall.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Key Message(s):

-The pattern remains favorable for daily chances of afternoon
 and evening showers and thunderstorms

PWATs remain elevated through the extended as moisture continues
to advect into the region around the Bermuda High. While the
stalled frontal boundary will eventually dissipate, the upper
level pattern remains largely unchanged with troughing over the
eastern CONUS sending a series of short waves through the CWA.
Expect scattered to numerous showers and thunderstorms to
develop each day during the afternoon and evening hours with
gradually decreasing convective chances early next week. This
comes with the continued risk for localized heavy rainfall and
flash flooding in addition to gusty winds from any stronger
thunderstorms. Daytime temperatures through the period will be
near to below normal.

&&

.AVIATION /16Z WEDNESDAY THROUGH SUNDAY/...
Generally VFR conditions expected through the TAF period.

Scattered cumulus developing at 17z across the area in area of
weak convergence/surface trough. The air mass is moist and
moderately unstable. The high resolution models suggest
scattered thunderstorms will develop over east central GA and
spread into central SC this afternoon and early evening.
Confidence is high enough that thunderstorms will be near
terminals mainly 19z-23z. Mainly mid level clouds after
convection dissipates in the evening. Fog not expected tonight
as the boundary layer remains well mixed. Winds will be
southwest 10 to 15 knots through the afternoon then diminish
after 00z.

EXTENDED AVIATION OUTLOOK...Typical summertime afternoon
showers and thunderstorms may cause periodic restrictions each
day with abundant moisture causing possible, brief early morning
restrictions around sunrise.

&&

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

&&

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