Area Forecast Discussion
Issued by NWS Columbia, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS62 KCAE 171750

Area Forecast Discussion
National Weather Service Columbia SC
150 PM EDT Wed Jul 17 2019

A mid level ridge over the southeastern states will weaken and
move south of the area this afternoon as a trough approaches
from the west. Moisture increases Thursday as a lee-side trough
becomes more prominent. This pattern supports typical
summertime convection each day. Models suggest an upper-level
trough will dig into the eastern US early next week with a
frontal boundary approaching the region near the end of the
forecast period.


The mid and upper level ridge has shifted slightly south as
trough approaches from the Tennessee River Valley. Surface
trough across the area to provide some weak convergence. The
air mass is becoming moderately to strongly unstable due to
steep low to mid level lapse rates/strong insolation. Mixed
layer CAPE 2000 to 2500 J/kg and likely to increase. Cumulus,
some moderate spreading northeast across the area. Radar
indicating showers and thunderstorms in north Ga into the
Upstate SC. The high resolution models suggest these showers and
thunderstorms will move east into the western CWA later this
afternoon and evening but weaken, although some short wave
support noted. A few storms may develop in the east associated
with a possible sea breeze. Will increase pops slightly in the
west CWA otherwise mainly widely scattered through the early
evening. The storms may linger late mainly to the north. One
concern is the elevated DCAPE due to dry mid level air. So can`t
rule out a pulse severe storm. Precipitable water remains high
near 1.7 inches. Temperatures in the mid to upper 90s. Even with
some drier air mixing down, heat index near 105. Any convection
should diminish after 04z as short wave moves east of the area.


Temperatures will again be in the mid to upper 90s with maximum Heat
Index values from 100 to around 105.

The upper level ridge will weaken over the area Thursday as a lee-
side surface trough becomes more pronounced. Atmospheric moisture
will increase Thursday with PWAT values exceeding 2 inches. Given
the increase in moisture and convergence into the surface trough we
expect scattered thunderstorms to develop in the afternoon. High
PWAT values and moderate instability from a tall, skinny CAPE
profile supports localized heavy rainfall. Though, mean wind values
of 10 to 15 kts limits the threat of flash flooding outside of flood
prone areas. Thunderstorm activity will diminish after sunset, with
overnight lows in the lower to middle 70s.


An upper level ridge shifts north of the forecast area late this
week. Surface high pressure will ridge into the region from the east
feeding low level moisture to the area. This synoptic pattern
supports an increase in diurnal convective activity through much of
the long term. Above normal temperatures are likely through the
weekend. Over the past week or so, model guidance has shown a cool
bias in high temperatures compared to URMA verification. Therefore
we leaned towards the upper end of the guidance spectrum for daytime

Early next week, the ECMWF and GFS continue to show an upper level
trough pushing into the eastern US. The associated surface boundary
will near the forecast area Tuesday or Wednesday bringing a higher
chance of rainfall, higher cloud coverage and cooler high
temperatures. The models suggest the upper level trough will stall
over the eastern US towards mid-week which would continue the trend
of near normal temperatures and higher than normal rainfall


Expect mainly VFR conditions although widely scattered
thunderstorms late this afternoon and evening. Patchy fog
possible late tonight mainly at AGS.

Scattered cumulus across the area this afternoon into the
evening. Air mass becoming moderately to strongly unstable. A
few thunderstorms are possible but confidence low on any impact
to terminals...expect widely scattered coverage mainly to the
west of the terminals across the SC Piedmont. Winds will be
southwest around 10 to 15 knots with a few higher gusts then
light and variable after 00z. Thunderstorms should diminish
after 04z with scattered to broken mid level clouds. Based on
persistence, included the possibility of MVFR at AGS toward

EXTENDED AVIATION OUTLOOK...Ridging extending from the Atlantic
is forecast to dominate. Thunderstorms mainly associated with
strong heating will be scattered. Some locations may experience
early morning fog.




AVIATION...99 is the U.S. government's official web portal to all federal, state and local government web resources and services.