St. Andrews, South Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

755
FXUS62 KCAE 040742
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
342 AM EDT Mon May 4 2026

.WHAT HAS CHANGED...
Confidence increasing in periods of moderate to heavy rain late
Wednesday and Thursday. Aviation discussion updated for 00Z
TAFs.

&&

.KEY MESSAGES...
- 1. Periods of moderate to heavy rainfall are expected during
  the mid week with the potential severe weather.

- 2. Rain chances pick back up late week and into the weekend

&&

.DISCUSSION...
Key Message 1: Periods of moderate to heavy rainfall are
expected during the mid week with the potential severe weather.

Summary: The rainfall forecast remains on track for mid-week as
an upper level trough digs into the central US, phases with
southern stream energy, and shifts eastward. The associated
surface cold front will work into the Southeast on Thursday.
Models continue to show agreement in overall synoptic pattern
despite differences in the timing of the front and other
details. This increases confidence in periods of moderate to
heavy rainfall but leaves the threat of severe weather
uncertain.

Rainfall: Robust moisture transport is expected ahead of this
front with PWAT values reaching the NAEFS 99th percentile by
Thursday morning and IVT at the climatological maximum. As
synoptic scale lift moves over the region late Wednesday into
early Thursday, scattered showers and storms should develop.
Coverage will likely increase Thursday morning as moisture
transport and surface convergence ahead of the front peaks. This
activity could bring periods of moderate to heavy rain as
forecast soundings Thursday morning depict deep moisture, a
long/skinny CAPE profile, and a 30- 40 kt LLJ. With the
antecedent dry conditions, the overall flash flooding risk is
expected to be on the low side. The front will shift east late
Thursday bringing an end to rain from west to east. Gusty winds
will also be possible Thursday and a Lake Wind Advisory may be
needed.

Severe Threat: The threat of severe weather will be largely
dependent on the timing of the front. Some of the timing
differences stem from the progression of the upper trough and
the interaction with a cut-off low to the west. There is also
some uncertainty in the degree of destabilization through the
day with widespread rain and cloud cover anticipated. That said,
ECMWF EFI values for CAPE- Shear combo still range from 0.6 to
0.8 indicating some potential for deep shear to line up with
moderate instability. NCAR ML/AI severe probabilities have
remained consistent indicating a potential threat of severe
weather, particularly to our east where instability may be
higher and to the north in the Mid-Atlantic states where the
dynamics will be stronger as the trough lifts.

Key Message 2: Rain chances pick back up late week and into the
weekend

Global ensembles tend to favor a somewhat persistent synoptic
pattern through the weekend with another trough digging into the
central US then shifting east. However a large spread in 500 mb
heights indicate much more uncertainty in the forecast compared
to the mid- week system. Mean PWAT values from the GEFS and
ECMWF ensemble rise back above 1 inch by early next week. Near
normal moisture and upper level troughing over the region
supports a chance of rain near the end of the forecast period.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
VFR conditions will prevail through 06Z Tuesday.

Clear skies and light/calm winds will persist through the
overnight hours. An overall dry airmass should limit fog
potential, but some river valley fog cannot be completely ruled
out at AGS/OGB.

Winds along the back side of Atlantic high pressure will
increase from the southwest to 5-10 kt during the late morning
and afternoon hours today. While they should diminish with the
loss of daytime heating this evening, they may not fully
decouple. Thin cirrus should begin spreading over the area this
afternoon, potentially increasing in thickness/coverage toward
the end of the forecast period, but will have no impact to
aviation interests.

EXTENDED AVIATION OUTLOOK...Drier conditions are expected
through Tuesday, then a midweek system brings a chance for
restrictions once again.

&&

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

&&

$$

DISCUSSION...CJR
AVIATION...JAQ