-- Discussion containing changed information from previous version are highlighted. --
015
FXUS62 KCAE 212337
AFDCAE

Area Forecast Discussion
National Weather Service Columbia SC
737 PM EDT Sat Sep 21 2024

.SYNOPSIS...
-- Changed Discussion --
High pressure building over the SE US will keep warm and dry
conditions in place through Sunday. A return to more seasonable
conditions is expected early to mid week along with chances for
showers.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 7 AM SUNDAY MORNING/...
-- Changed Discussion --
Key Message(s):

- Partly cloudy with near normal low temperatures

Weak high pressure will remain over the area overnight. Some
moisture increase in the mid and upper levels as remains of
convection well northwest of the area moves through the region.
Expect the bulk of the clouds associated with the convection to
move north of the area and with current weakening of the
convection and the mountains yet to cross do not expect any
showers through daybreak. Overnight lows will be in the mid to
upper 60s.
-- End Changed Discussion --

&&

.SHORT TERM /7 AM SUNDAY MORNING THROUGH MONDAY NIGHT/...
Key Message(s):

- Upper ridge dominates over the area with above temps

The upper ridge axis will build over the forecast area this
period while shortwave energy dives southeastward through the
Mid-Atlantic region on Sunday and shifts the upper trough off
the Mid-Atlantic coast. A series of shortwaves will continue to
spill over the ridge Sunday and Monday before the ridge axis
shifts off the southeast coast. Surface high pressure centered
over New England will extend southward and along the coast of
the Carolinas into early next week. Forecast soundings continue
to show a capping subsidence inversion and this should limit
convection on Sunday but this feature weakens Monday and
Tuesday. PW values remain around 1.5 inches on Sunday, but do
increase along the SC/NC border on Monday/Monday night to around
2.0 inches. The atmosphere appears to be too capped on Sunday,
but by late Monday afternoon/evening there could be a few
isolated showers/thunderstorms across the northern Midlands.
The rising 500mb heights should support continued above normal
temperatures with highs expected in the lower to possibly mid
90s on Sunday. Monday high temperatures may be a bit cooler
across the northern Midlands due to slightly cooler 850mb temps
but highs should range from the mid 80s north to lower 90s
south. Overnight lows will also continue above normal with
temperatures upper 60s to lower 70s.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Key Message(s):

- Chances of rain increase by midweek with limited confidence
- Continued above normal temperatures

The extended forecast features a lot of uncertainty regarding
the evolution of the upper level pattern and possible tropical
development near the Yucatan Peninsula. Medium range ensembles
diverge on the 500mb pattern evolution beyond Thursday after
being in reasonable agreement earlier in the week. The upper
ridge axis shifts east of the forecast area Tuesday afternoon
allowing for increasing chances of rain with deeper
southwesterly flow and PWATs rising to around 130-150 percent of
normal. The GEFS/CMC/ECMWF all try to bring a trough into the
central portion of the country then cut the system off by
mid/late week. However, the depth and location of this
development differs from model to model and run to run.
Additionally, the high pressure ridge along the southeast coast
settles differently depending on the model.

This leads to lower confidence in the forecast, especially the
probability of precipition through the period. It does seem
reasonable that chances of rain will increase later in the week
given increased moisture and may be reasonable to expect
isolated diurnal convection late in the week. The other
uncertainty in the forecast revolves around a possible
development of low pressure near the Yucatan Peninsula moving
into the Gulf of Mexico by mid/late week. The deterministic and
ensemble forecasts indicate something over the eastern half of
the Gulf of Mexico during the period, but timing and location
still very uncertain. It will most likely take the system to
actually begin forming for the models to have a better handle on
timing and location along with the developing mid/upper level
pattern across the eastern portion of the country.

Temperatures are expected to remain above normal and warm with
NBM probabilities of max temperatures above 85 degrees at 80% or
higher across most of the area through Thursday. Slightly cooler
temperatures expected by Friday and Saturday with increasing
clouds and possible rain.
-- End Changed Discussion --

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
Generally VFR conditions anticipated through the TAF period.

Afternoon cumulus should dissipate this evening as the sun sets,
leaving the area with just some patchy cirrus overnight. With
much less low level moisture around compared to the last few
days, I think fog will be tough to come by despite mostly clear
skies and light surface winds.

Sunday will be another day with no issues expected at the
terminals as high pressure remains in the area and partly cloudy
skies are expected, with all clouds above problem categories.

EXTENDED AVIATION OUTLOOK...No significant impacts to aviation
expected through Wednesday.
-- End Changed Discussion --

&&

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

&&

$$