St. Andrews, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

398
FXUS62 KCAE 201711
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
111 PM EDT Sun Jul 20 2025

.SYNOPSIS...
The high heat and humidity continues again on Monday, with Heat
Advisory conditions expected across much of the region. Isolated
showers and thunderstorms possible this afternoon and evening,
followed by increased convective coverage Monday and Tuesday.
Temperatures return to normal for mid-week followed by another wave
of heat to end the week.

&&

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

- Heat continues into this evening, then warm and muggy
  conditions are expected again tonight.
- Isolated storm or two possible through this afternoon and
  into this evening.

Upper ridging will continue to slowly retrograde westward into
Monday. Pwat values between 2 to 2.3 inches this afternoon and
evening, with high moisture values expected through the
overnight hours. Heat index values currently climbing above 100
for many areas, but still expected to remain just below advisory
for the day. Deeper moisture and higher Pwat readings are being
indicated across the southern Midlands and much of the CSRA
this afternoon, and this shows up on regional satellite images
with enhance cumulus fields developing. Radar does show an
isolated shower or storm developing in this deeper moisture west
of the CSRA, along with some of the higher elevations of the
central Appalachians. Should continue to see development this
afternoon and evening, with coverage remaining isolated for the
most part. Highest confidence in rainfall is over the CSRA along
the moisture axis, with lower confidence in any activity moving
out of the mountains holding together into the Midlands this
evening.

For tonight, with dewpoints remaining in the low to middle 70s, and
overnight lows expected in the middle 70s, it will be another warm
and muggy night across the area.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
Key message(s):

- Potential for dangerously high heat index values on Monday,
  especially across the Southern Midlands and CSRA.
- Higher threat for showers and thunderstorms both days with
  isolated severe weather possible on Monday.

Upper ridge axis and surface high pressure will be centered over
the North-Central Gulf at the start of the period, shifting west
on Tuesday. This should promote northwest flow aloft while the
FA sees another day of high heat and humidity. Daytime
temperatures in the mid to upper 90s will combine with dewpoints
in the lower to mid 70s to produce heat index values of 105 to
110 degrees, prompting the issuance of a Heat Advisory with this
forecast package. Confidence in criteria being met is highest
across the southern half of the forecast area, roughly from the
Columbia Metro area and points south, but will ultimately be
determined by the timing and coverage of showers and
thunderstorms. Regardless of formal criteria being met, tomorrow
is expected to have the most oppressive conditions of this
stretch of summer heat and typical precautions should be taken
while outdoors on Monday. With added moisture in place, and a
backdoor front sliding in from the north, scattered showers and
thunderstorms should develop during the afternoon hours. SPC
maintains a Marginal (1/5) risk for severe weather across the
CWA on Monday with damaging wind gusts as the primary severe
hazard.

Temperatures are expected to be noticeably cooler on Tuesday as
the aforementioned frontal boundary sags south into the FA.
Expect more clouds around during the day with numerous to
widespread showers and thunderstorms. Given the potential for
slow moving thunderstorms, there is the potential for localized
flash flooding, especially on Tuesday. The WPC outlines the
entire CWA in a Marginal (1/4) risk for Excessive Rainfall on
both Monday and Tuesday. The severe potential appears to be
lower on Tuesday but a stronger thunderstorm or two cannot be
completely ruled out, especially in the southern half of the
forecast area.

&&

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

- Temperatures start off around normal values, warming as the
  week goes on and upper ridging builds back in.

Latest model guidance suggests that the front will stall just
south of the forecast area, preventing a cooler, drier air mass
associated with high pressure over New England from fully
reaching the region. There may be a gradient set up across
South Carolina, with the north enjoying lower dewpoints and
rain chances while the south remains more humid with higher
rainfall potential. Any gradient should becoming less defined
towards the weekend, as the frontal boundary becomes diffuse.
Meanwhile, strong upper ridging should move back over the region
with surface high pressure just off the coast. If this pans
out, then the CWA can expect a return to the high heat and
humidity with isolated afternoon showers and thunderstorms.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
VFR Conditions Likely the Next 24 Hours.

Afternoon cumulus field has developed in the deeper moisture across
the CSRA region early this afternoon, with additional cumulus
expected to develop across the Midlands. Bases with any of these
clouds will remain above 3kft, with vfr conditions expected at all
taf locations through the period. An isolated shower or storm
will be possible through this afternoon and evening, especially
closer to AGS/DNL where the deeper moisture resides. Some
activity already being shown on regional radars west of the
CSRA. If any convection can make it into AGS/DNL, a brief period
of mvfr ceilings and/or visibilities can not be ruled out. Due
to limited coverage, plan on keeping tafs dry at this time, and
will monitor radars and amend as necessary if any activity
approaches terminals. Additional rain chances will become
possible near the very end of the 18z taf forecast period as a
weak surface front approaches from the north. Westerly winds
around 10 kts, with gusts of 15-18 kts through the afternoon,
then diminishing after 00z. Westerly winds on Monday not
expected to be quite as strong, with most speeds between 5 and
10 knots, and limited gusts.

EXTENDED AVIATION OUTLOOK... Patchy early morning fog/stratus
through the extended. Rain chances increase early for the first half
of the week ahead of an approaching surface boundary, then become
more seasonal the remainder of the period.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Heat Advisory from noon to 8 PM EDT Monday for SCZ016-018-
     020>022-025>031-035-037-038-041-115-116-135>137.
GA...Heat Advisory from noon to 8 PM EDT Monday for GAZ040-063>065-
     077.

&&

$$