920
FXUS62 KCAE 220745
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
345 AM EDT Sat Jun 22 2024

.SYNOPSIS...
Above normal temperatures are expected today through the middle
of next week. Heat Advisories may be possible from Monday
through Wednesday. Expect scattered diurnally driven showers and
thunderstorms for much of the short and long term forecast.

&&

.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:

- Hot and humid with scattered showers and thunderstorms
  possible in the SE portion of the forecast area.

Upper level ridge centered over the Southern Plains with high
pressure aloft and at the surface continuing to hang on over the
area. Low pressure has moved onshore from the Atlantic along the
coast of southern Georgia which will continue to allow moisture to
stream into the area with onshore flow leading to increasing
humidity. With little change in the overall synoptic pattern, high
temperatures expected to be similar to yesterday, in the low to mid-
90s. Forecast soundings indicate broad subsidence over the area but
there will likely be some surface convergence with an inverted
trough near the Coastal Plain. With PWATs around 1.6 inches in the
northern portion of the area to near 2 inches in the southern area,
scattered showers and thunderstorms develop this afternoon, favoring
the southeastern area where the highest moisture overlaps with low
level convergence. Lingering high moisture with the surface low to
the south expected to track near the SC coast will lead to at least
slight chance of showers overnight in the southeastern portion of
the forecast area.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
KEY MESSAGES:

- Increasing moisture will lead to a chance for afternoon and
evening thunderstorms.
-Heat Advisory criteria possible Monday.

Sunday and Sunday night...Upper level ridge weakens slightly
and the center retrogrades to the southern Plains to the Gulf
coast. However, upper heights remain higher than normal.
Moisture appears to increase across the area with precipitable
water rising into the 1.75 to 2.00 inch range. Slightly drier
air in the Piedmont as 850mb flow becomes more westerly. At the
surface, weak Piedmont trough in place. Tropical remnant low
near the lower Savannah River. Air mass expected to become
conditionally unstable due to strong diabatic heating. Low level
lapse rates should be quite steep. Strong mid level capping
expected due to continued warm temperatures aloft with NAEFS
indicating 1 to 2 standard deviations above normal. The cap is
weaker in the southeast Midlands. Moisture higher in the east
along with low- level convergence associated with sea breeze
front. So have chance pops favoring the southeast Midlands with
mainly diurnally driven convection. With stronger subsidence in
the central and west areas, confidence high for heat index
values in the 100-105 degree range in those areas with highs in
the mid 90s. This is based on the blended temperature guidance.
Muggy at night with lows in the low to mid 70s.

Monday and Monday night...Although heights aloft fall a bit,
they still remain above normal. With short wave trough moving
across the northeast and Mid Atlantic, a weak "cold" front will
approach and maybe move into the area late Monday. Weaker short
waves may slide around ridge across the area with maybe stronger
lift. Airmass appears weakly to moderately unstable with
continued steep low level lapse rates. Mid level capping should
continue to limit convection in the west, but weaker in the
east. Downslope flow noted and this leads to lower chance
showers in the west but more importantly, higher temperatures.
Heat index values near 105 or a little higher, so approaching
heat advisory criteria. Continued chance of afternoon and
evening showers and thunderstorms. Continued muggy conditions at
night with lows in the low to mid 70s.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
KEY MESSAGES:

- Temperatures rise late this weekend into mid-week.
- Heat Advisory criteria possible Tuesday and Wednesday but
  confidence low.

Daytime temperatures from Monday through Wednesday may be near 100
degrees. Varying levels of moisture during this period limit
confidence in reaching Heat Index values above 105. Daily showers
and thunderstorms could also hinder heating.

The weak frontal boundary may shift to the south and drier air
advects into the area, especially north of Columbia. The
ensembles probability of precipitable water > 1.5 inches are
below 50 percent across much of the region during the afternoon.
Stronger subsidence expected Tuesday which should limit
convection. This should limit heat index values although
ambient temperatures could be near 100 degrees. Moisture
increases again Wednesday and Thursday as low level flow
becomes southerly ahead of a more amplified upper trough moving
east from the Tennessee Valley along with surface front.
Stronger convection possible during this period as deep shear
increases. The front may hang up near the area Friday or move
southeast of the area, confidence low. Temperatures cool
slightly with trough moving into the area and higher moisture,
temperatures cool slightly late week but remain near or above
normal.

&&

.AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
Low clouds beginning to move over the terminals early this
morning. Restrictions have moved over OGB and should move over
the Columbia terminals over the next hour or so. Highest
confidence in IFR ceilings at OGB so have left prevailing IFR
ceilings in there but have put IFR ceilings in a TEMPO group for
Columbia terminals with guidance trending more optimistic in
restrictions this morning. Restrictions should dissipate shortly
after sunrise with a cumulus field developing around 4kft.
Chances for showers and thunderstorms mainly for OGB and
possibly the Augusta terminals but confidence is a bit limited
to include in this TAF update.

Winds will generally be out of the ESE this morning, although
will likely become mostly light and variable in the pre-dawn
hours. Winds increase again late this morning, shifting out of
the SSE between 5 to 10 knots.

EXTENDED AVIATION OUTLOOK...Increasing chances for afternoon scattered
showers and thunderstorms and associated restrictions Sunday
through Wednesday.

&&

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

&&

$$